reza doostan

This research evaluates the influence of climate change on precipitation, temperature, and evapotranspiration in Iran, a region with diverse climatic conditions, using UNEP and Demartonne climate classification systems to explore changes in Iran's climatic zones from the reference period (1961-1990) to the most recent normal period (1993-2022). The results show a decrease in the number of humid climate stations and an increase in semi-arid, dry, and desert stations under both classification methods. Mann-Kendall and Sen's slope analyses reveal significant decreases in precipitation, and increases in temperature and evapotranspiration in over 75% of the stations, with the highest annual precipitation decrease observed in Gorgan, and the highest temperature and evapotranspiration increases in Mashhad and Ahvaz, respectively. The findings suggest that Iran's climate is rapidly shifting towards drier conditions due to global warming, with approximately 13 stations having shifted to drier conditions and 29 stations experiencing increased aridity when comparing the two normal periods. These results align with previous studies, highlighting the urgent need to address the impacts of climate change in Iran and providing valuable insights for policymakers and stakeholders to develop effective strategies for climate change adaptation and mitigation in the region.

The position of Iran between extratropical and subtropical latitudes, the location of a major part of Iran on the desert belt of the world from North Africa to Central Asia, and the role of various geographical phenomena in Iran have caused all kinds of atmospheric hazards in this region. To have an accident (Alijani, 2018). Such risks are inherent in Iran's climate and have occurred regularly since the distant past, as the natural environment and human activities in different regions of Iran have adapted to these phenomena. As the behavior of these phenomena has been repeated somewhat regularly and the climatic changes and short-term atmospheric processes have been less. These phenomena include droughts and droughts, heavy rains and floods, floods and dust storms, frosts, heat and cold waves (Omidvar-Kamal 2013). But in recent decades, with the increase in the temperature of the earth after the industrial revolution (1850), and with the intensification and rapid trend of temperature in the recent decades from 1970 onwards, the atmospheric hazards in the world, including Iran, have become abnormal. Such heavy and short-term rains cause a lot of damage related to agriculture, severe soil erosion, and destruction of transportation infrastructure and flooding of cities and villages. In recent years, in connection with global warming and changes in the behavior and anomaly of rainfall in the world, the amount of rainfall has decreased in this region, but the rainfall has mainly changed its behavior to heavy and short-term rainfall. Therefore, knowing the patterns that lead to the occurrence of these precipitations will be useful in the first place for predicting and managing precipitations. The aim of this research is to identify and analyze the atmospheric circulation patterns leading to the occurrence of heavy rain and short-term flooding based on the data of the stability rain gauge in Khorasan.

in this study, the daily rainfall data and the rain logger of the stability station were used. Among the stations in the region, those that have a proper distribution in terms of spatial distribution and also have long-term statistics (1993-2017) were selected. The synoptic stations were chosen to cover all the regions of the province with different topography and climate diversity. In order to determine heavy rains, the 95th percentile index of daily rains in each station was used. In the following, days with heavy rainfall and more than 95th percentile were extracted in each of the stations using these indicators. The spatial distribution of these rainfalls in the whole province was determined by using the number of these rainfalls in the entire region. , heavy rain. In connection with the purpose of this study, determining the atmospheric patterns of heavy rainfall in Khorasan, after determining the days with heavy rainfall in the previous stage, the atmospheric patterns of rainfall were determined and synoptically analyzed. For this purpose, reanalyzed daily grid data with a resolution of 2.5 degrees were extracted from the National Center for Environmental Prediction and Atmospheric Research (NCEP/NCAR) for the above days. The selected window for receiving network data in this study is 15 to 70 degrees north and 15 to 80 degrees east, so that the patterns affecting Khorasan precipitation in this range can be identified.

On February 17, 2017, in the geopotential height map of the middle surface of the atmosphere, a trough is drawn over the entire western half of Iran and the western coast of the Caspian Sea, and the center of this trough is a closed cell with a height of 5280 geopotential meters over the northeast of the Caspian Sea and Kazakhstan. This deep trough extends to Saudi Arabia and passes through the center of Saudi Arabia at a height of 5750 meters and shows the penetration of cold air in the upper atmosphere to the warm southern sea of Iran. At the same time, in the east of the Mediterranean Sea, there is a Rex-type blocking. These atmospheric conditions caused persistence and slow movement of the circulation system in the synoptic scale in Southwest Asia. At the same time, there is a low pressure center with a pressure of 1010 HP in front of the curved ship in the east of Iran. The east of this trough extends from the southwest and the western half along the southwest to the northeast direction of Iran, which caused instability in the northeast of Iran. On April 1, 2016, the arrangement of westerly winds in the entire Eurasia area shows a large anomaly in the westerly wind waves, naturally in late winter and early spring, due to the reduction of temperature and pressure differences in the northern hemisphere, westerly winds move meridian. And the number of long waves also increases hemispherical. In this map, there are two meridional patterns of westerly winds in the north and south, the first pattern in the north with a deep and curved channel with a west-east direction and closed with two equal heights, cut off low respectively over Western Russia and Kazakhstan respectively with There are 5280 and 5440 meters, That on the surface of the earth in these two areas, two low pressures with a pressure of 1003 and 1011 HP, respectively, indicate a strong rotation and instability in these areas.

Heavy rains and floods are one of the most important weather hazards that cause great damage to nature and humans every year. This type of precipitation, which is an inherent feature of arid and semi-arid climates, has increased significantly in recent years due to global warming and the increase in climate extremes.

Climatic phenomena in different regions of the world are different in relation to the geographical characteristics of each region. Dust is one of the dominant atmospheric phenomena in desert and semi-desert regions of the world. This phenomenon is related to air pollution in most parts of Iran with dry climate, including Birjand in eastern Iran. The origin and direction of dust in this area are varied in the year, and knowing them helps urban risk management, forecasting and desertification. In this study, Landsat satellite images were used to determine the origin of dust in the period of 1955-2017. The dust day was defined based on the classification of Shao and Dong with code 06 and 07 with horizontal visibility of less than 10 km, and revealed with BTD and TDI index. To determine dust atmospheric patterns, grid data from NOAA was used, and dust trajectories were carried out with the HYSPLIT model. The results showed that the most dust days in 1963 and 2008 (45 years), with 148 and 128 days, respectively, which mainly occur in the warm season and July. The 120-day winds of Sistan in the east of Iran plays a major role in transporting dust particles and air pollution in Birjand from the east and northeast from the deserts of Central Asia, Turkmenistan, Afghanistan, Khorasan Razavi plains and interior plains. But in the cold period of the year, Siberian cold masses from the east, cold fronts (migrating anticyclone), occluded fronts and low pressures from the northwest, west and southwest by passing through the central plains of Iran and sometimes the deserts of Syria and Iraq causes dust in the upper levels of the atmosphere. In all these centers, the occurrence of particles and pollution of cities prevails during periods of drought.

The aim of the present study was to investigate the role of climatic conditions on the genesis and morphological diversity of karst rocks of carbonate formations in Kalat Basin in the east of Kopeh Dagh. For this purpose, the experimental method (geomorphometric overlap) based on climatic zoning model and laboratory studies (calcimetric and lime purity percentage) have been used. In the research process, first, the climatic zoning map of the basin was prepared through 25 stations with a statistical period of 35 years in the GIS environment and four climatic zones of the region were determined. Then, using geomorphometric techniques, ground samples were collected on 240 samples of three types of Karen with different morphology (linear, Pitcarn and Triticar). The results showed that the more humid the climate of the karst rock, the more not only the number of carnations per unit area will increase, but also the morphological diversity and evolution will increase. In fact, climate change has a very effective role in the genesis and development of surface karst Carns and there is a direct relationship between wetter climatic zones and morphological diversity and evolution of Carns in karst-forming formations, as in the climate zone (Q4). In humid climates, a variety of linear, depth and width of linear carnivores, triticarmens and peatcarns in temperate and humid climates (Q4.Q3) located at high altitudes to three to 10 times the size of carnivores Arises in arid and semi-arid climates (Q1, Q2).

To investigate the mechanism governing the formation of cyclones in Iran over a period of 18 years (2017-2000) using the National Geological Survey's Center for Environmental Prediction / Atmospheric Sciences (NCEP / NCAR) 2.5 Geographic Resolution And the European Center for Medium Term Forecasting (ECMWF), with a resolution of 0.125 °, identified the phenomenon in the Zagros Mountains. Two potential equilibrium parameters on the convective surfaces and relative equilibrium advection were also used to investigate the dynamic structure. The results showed that during this 18 year period, only three examples of the above mentioned phenomenon occurred in Iran. The major mechanism governing the formation of these cyclones in the windward part of the mountain with the formation of a high-pressure core and an increase in relative relative tropics at the ground level and the positioning of a quasi-stationary stack in the troposphere mid-level as a major condition of the mountainous winds and the presence of a dune. With the strong geopotential rotations over the mountainous altitudes that continue from the middle to upper troposphere, these conditions are accompanied by a positive torrential flow. Thus, the first and foremost condition for the occurrence of windsurfing is the existence of these two conditions on the windward and mountainous slopes. At the level of 500 hPa in central Iran, the relative tropical advection values ​​increase, indicating a positive relative tropical increase both in time and location in the region.

 Iran is located the spatial geographical position in the south of the temperate region and north of the tropical region between the northern latitudes 40 to 25 degrees north and 65-44 degrees eastern along the seas, oceans and warm and great desert, on the other hand, with complex topography in the Alpine- Himalayas mountain belt (the world's largest mountain belt). These conditions have caused the climate of Iran to experience a variety of the prevailing natural hazards (33 of 43 world-wide risks). One of the natural hazards is the drought that happens over the Iranian plateau since the distant past, with the name of Dave of Drought, and so far. The Iranian plateau has undergone various drought periods over the past decades and various civilizations have faced this risk, and some of the Iranian ingenuity and management have emerged about this risk of the Iran. These include qanats, reservoirs built on commuter routes and cities, historical gardens, and so on. Today, this risk is dominant over the Plateau of Iran every year, and with increasing population and growth in different sectors and, in some cases to mismanagement, followed by a larger crisis called the water crisis and the crisis Economic-social, immigration, and so on. So, given the importance of the subject, different researchers have studied different aspects of this hazard. The fact is that in the past few decades, with the advent of computers and software and data, research has become easier and more scientific, naturally, in Iran, with these tools and data, researchers has been done on different parts of the crisis. What was the achievement of these studies, and most importantly, did the researchers contemplate a practical solution to the crisis on the Iranian plateau? This study provides an overview of past studies of drought and their achievements over the last few years.
In this study, used Four hundred and three of scientific articles were published in various journals to termed "drought" in the article titled of scientific information database (SID), one of the most important sources of internal research in Iran. The distribution of the time of research and distribution of various scientific fields that investigated the drought was identified. By studying the articles and the results from them, we found that 384 scientific articles with a specific output. Based on these findings, the frequency of articles in different fields of study was determined and analyzed.
researches of drought in the past years (1379 to 1391) had increasing trend and since 1394 has been decreas in Iran. The most drought research has been done in agricultural sciences with 166 papers from 403 papers (41.2%), geographic sciences with 118 papers (29.3%) and Medical and basic sciences and engineering sciences have the least research, 0.2, 2 and 5% respectively. 78% of the studies have examined the drought in different parts of Iran And 11 percent of the articles  evaluated the consequences of this  phenomenon. 7% of drought studies have predicted this phenomenon with different statistical models and 2.5% and 2% are dedicated to drought management and zoning  in different regions of Iran respectively. Most drought studies hase been in Iran, Khorasan, Fars, Sistan and Baluchestan, Tehran, Isfahan and Kermanshah, but in other parts of Iran, studies have also been conducted in different regions. Therefore, the drought phenomenon has been studied in all regions of Iran and drought assessments have been carried out.
The reduction of drought researches in recent years suggests that quantitative and qualitative research has been carried out in this basin before 1395, and drought has been studied and evaluated with different indicators in different regions of Iran. The reality of Iran's climate and research shows that every part of Iran experiences a drought phenomenon, which is an Inherent characteristic of the climate of Iran, that given the geographical location and atmospheric patterns affecting these latitudes on the planet. The consequences of drought have also been reflected in different parts of the environment, social, economic, and so on. As part of the newspapers has indicative of the damage to this climatic phenomenon in recent years. It seems that the dominant section of the phenomenon is associated with the unconscious and real perception of managers and people of this phenomenon (which has a cultural root). At present, the consequence of severe and droughts in recent decades is the lack of proper planning and environmental degradation and crisis in various parts of Iran's environment. On the other hand, the negative consequences of global warming for the climate of Iran and similar climates are more and more worrying. Therefore, it is essential to take practical and practical solutions instead of evaluations and mere studies. The practical solutions and the production of technology and operational program in relation to these environmental crises require group research in the sub-sectors with together. While, for example, engineers play the most role in controlling superficial fluid (water and dam), But the smallest drought- research related in this area. Therefore, the separate study of each part of these hazards is merely an evaluation and is not a practical way of solving the risk for managers and planners; For example, a water crisis requires a team of researchers such as hydrology, climateology, meteorology, agriculture, urban management, rural, etc. Of course, it should be noted that our researchers have not been trained and not accustomed to group work, and the idea of teamwork is poor in our culture; But there is no way and should start from one point. Perhaps we should start with kindergartens and elementary schools in order to find suitable solutions for at least the next 20 years, researcher’s teams. Finally, it is necessary to address the sustainable development and drought, localization of indicators, operational and management plans based on the environmental capabilities and knowledge of the native area of each region.

Rainfall is the most significant phenomenon or feature of the environment. The factors causing rainfall have been the subject of numerous studies. Both the rainy or very dry years have considerable impact on the quality of humans’ living environments. Rainfall occurs when there is enough moisture as an effective factor. Both of these conditions are provided through circulation patterns of the atmosphere. The purpose of the present study is to identify the circulation patterns and factors causing rain showers in the mountainous regions of Iran (i.e. Southern Alborz and Eastern Zagros mountain range); moreover, it is attempted to explain how they are formed, during which period of the year they could evolve more significantly, and at what times they occur in the region, along with their similarities and differences. Given the breadth and considerable socioeconomic significance of the region being studied (i.e., Southern Alborz and Eastern Zagros mountain range) it is necessary to identify the circulation patterns causing such damaging rain showers. To this end, the occurrence of this phenomenon could be predicted by observing the commencement of the sequences of patterns leading to torrential rain showers at least one or two days beforehand. In this case, there would be enough time to make necessary preparations. In this study, the circulatory synoptic approach to environment was used; in this regard, first the statistics and data on the climate codes of past and present in stations including codes 80 to 99 related to showers or heavy rainfalls accompanied by lightning were extracted from 50 synoptic stations in the region of the study during a 30-year period (1985-2014). Next, the days of occurrence (code 80-99) were identified followed by the days with rain showers among the entire statistical data which had been observed in at least 50% of the stations of the region; ultimately, 80 days of rain showers were identified. Then, clustering approach was used on data in order to identify circulation patterns causing such showers based on Euclidean distances and integrate it with Ward’s method in SPSS. It was carried out according to the elevation data at 700 hectopascal level of these days, which is the best level for demonstrating how rain showers are formed. Furthermore, data on the vertical speed (omega) and components of orbital, meridional and vorticity winds obtained from clustering patterns at 10-80 E and 10-70 N with a spatial resolution of 2.5 2.5 degrees were provided. In the end, the related maps were drawn and analyzed in Surfer and GrADS softwares. According to the findings obtained from principal components analysis, seven primary components constituting 80% of total data diffraction were selected so as to indicate climate circulation patterns. Given 80 days representing the entire days being studied (19333 days) in 50 synoptic stations during a 30-year period (1985-2014), 7 clusters (circulation patterns) causing rain showers were identified through the aforementioned method as well as conducting cluster analysis with Euclidean distances based on data at the level of 700 hectopascal using Ward’s integration method. Drawing conclusions on the analysis of seven clusters at the region of the study showed the presence of drought in the western part of the region as well as blocking and cut-off low at the level of 700 hectopascals, low-pressure systems in Saudi Arabia and Eastern Iran and a high-pressure system at the northern part of the region, and dominant synoptic phenomena during days of rain showers at the region. Examining the patterns of climate’s upper levels in the region studied shows that the highest volume of rainfall occurs when systems are formed as blocking, while the high-altitude subtropical center moves toward more southern latitudes. Given the analysis of drawn synoptic patterns, according to the data of level 700 hectopascals, in general, it must be pointed out that among the obtained patterns from clustering the aforementioned level data, the highest number of days with rain shower occurrences in the region follows the cut-off low pattern of the Black Sea as well as the deep drought of North-Western Iran; these patterns have been formed mainly during Spring (March, April, and May). The highest amount of rainfall in this pattern has occurred in the Western and North Western of the region. The examination of this pattern demonstrated the presence of a deep and strong closed low-altitude center on the Black Sea. While this low altitude contour gradient center in the region moves, it paves the way for the formation and expansion of baroclinic waves in the eastern regions of the trough. As the low altitude center (cut-off low) is closed, the movement of Western systems over the Iranian mountainous region is slowed down and rainfall continues. On the other hand, the western and north-eastern parts of the region under investigation are influenced by the 1025 hectopascal high pressure of Western Europe in this pattern while the eastern parts of the region are affected by the low-pressure center. The presence of a strong ridge in the Northern Mediterranean Sea as well as a deep scot-off low in the Eastern Black Sea have strengthened baroclinic waves at the lower level of the atmosphere; consequently, considering the proper convergence in low levels, suitable conditions for ascension and positive vorticity, divergence at upper levels of the atmosphere, and desirable rain showers (more than 40 mm) have been observed, particularly, in the north-eastern parts of the region. In this pattern, humidity transfer has occurred in the north-eastern and eastern parts of the region over the Caspian Sea, through high-pressure tabs. In addition, the role of the cyclonic movement of south-eastern systems in transferring and enhancing the humidity of the Arabian Sea and the Persian Gulf cannot be overlooked. According to the 7 synoptic patterns formed in this clustering, the southern and south-western low-pressure systems are of substantial importance in offering convergence among low levels and rain showers. Rainfalls occur in high volumes when systems appear as cut-off low or deep and strong low-altitude centers in the upper layers of the atmosphere. Furthermore, the presence of a strong ridge in Western Europe and the subsidence of cold weather from high latitudes have enforced pass pression center at low levels while its tabs have led to the northern streams and the injection of Caspian humidity to the western parts of the region under investigation.

Teleconnection is defined as a meaningful relationship of time variations of two meteorological patterns that are far from each other and teleconnection is an important principle in climate for the explanation of meterologic phenomena. The term was used for the first time in climate studies by Angstrom (1935). Later Wallace and Gautzler (1981) defined the concept as a meaningful correlation between the time series of a month or longer of the climate parameters in distant locations. Teleconnections are associated with the anomaly of atmospheric large scale and hemisphere circulation. Therefore, it is important to recognize teleconnections affecting the regional climate. In this regard the question is: What are the most important global teleconnections for the cold seasons in Iran? To find an appropriate answer, the monthly time series of teleconnections close to Iran and the world from 1950 to 2010 were selected and the Pearson correlation method was used. The correlations indicated that global phenomena associated with regional teleconnection are established in the North Atlantic, Europe and Western Siberia, while the Pacific Oceanographic centers have a weak connection with the regional teleconnection in the cold period. The most important phenomena in the middle layers of the atmosphere are the North Sea - Caspian Pattern (NCP), and the North Atlantic Oscillation (NAO) associated with regional teleconnection of the Western Europe - North Caspian. In the positive phase of the North Atlantic Oscillation and the North Sea - Caspian Pattern, the precipitation increases and the temperature decreases while in the negative phase, the temperature increases and precipitation decreases in Iran. These two phenomena are important and reliable predictors in Iran. At ground level, the Arctic Oscillation (AO), Scandinavia (SCAND), Eastern Atlantic - Western Russia (EA-WR) and East Atlantic (EA) related to regional teleconnection of Northern Europe, Northern Siberia, and Central Asia are the most important phenomena on the surface for the climate of Iran. In the negative phase of the Arctic Oscillation, Scandinavia, the precipitation increases and temperature decreases for the climate of Iran, and in the positive phase of these two, the climate of Iran experiences dries conditions. Also in the positive phase of the Eastern Atlantic and Eastern Atlantic - western Russia, the temperature decreases and the precipitation increases, and in the negative phase, the temperature increases and the precipitation decreases. It appears the global and regional teleconnections in Eurasia and the Northern Atlantic are not completely separated. Therefore, the global teleconnection associated with the climate of Iran are: the North Atlantic Oscillation, the North Sea - Caspian Pattern, Arctic Oscillation, Scandinavia, Eastern Atlantic - Western Russia and Eastern Atlantic. Often, teleconnections of the cold seasons of Iran are related to meridional westerlies along the blocking and cut-off low that are established in Western Europe, Central and Western Siberia to lower and higher latitudes in the same geographic locations. In climate studies one should not ignore the role of geographic featues on the surface of the earth, while considering the above-mentioned issue.

The increase in the temperature of cities is the urbanization crisis of the present century. The purpose of this study was to identify surface temperature spatial variations in the city of Mashhad, which was characterized by the thermal bonding of 11 Landsat images for the period 2009-2013 and the digital land use map. In this equation, a separate window algorithm was used to calculate the surface temperature. The model of the spatial pattern of the surface temperature of the city of Mashhad during the year is the increase of surface temperatures from the center to the periphery of the city at the time of the passage of the satellite, so that the central and old parts of the city (Sanabad, Abkouh, Saadabad, Malekabad), have lower surface temperatures than The highest surface temperature in the southern margin of the city, in front of the Binalood Mountains from the west to the south-east of Mashhad, the railway, the airport, Shohada square, the border of Imam Ali Highway and the Hemmat ring way, Sheshsad Dastgah, the sugar factory and spinning mill, and the empty open spaces and and no urban use. Urban transportation usages, bare lands and altitudes throughout the year, maximum surface temperatures and minimum temperatures, are used for recreational and tourist use, agriculture and gardens, especially in hot months. The 12th district of the city is the warmest and district 1 is the coolest district in the city of Mashhad in terms of surface temperature. The maximum surface temperature of Mashhad is in the months of July and August, and the minimum temperature is in December, and the spatial extent of the surface temperature of the city is respectively September and the spring is the highest in October and the lowest in autumn.

An identity of dust atmospheric patterns and extreme dust in northeastern Iran is the aim of the study. This main was determined to using of daily visibility data in ten synoptic stations from its establishment until 2009 and digital data of geopotential height and wind components from NCEP- NCAR and to principle component analysis and clustering approach. In northeastern of Iran, respectively, the dust of cold half is related to western Asia trough, Iran eastern trough and low in the region to central Asia, whereas the cause of warm half dust is subtropical high, Iran-Pakistan low and Caspian high with maximum pressure gradient in the region. This condition intensified to 5900 meters of subtropical height in the region. In the cold half, Cutoff low in north and northwest of Caspian along strong low caused extreme dust and extreme dust of warm half is related to the establishment of blocking and cutoff low of Western Asia, Pakistan low and Caspian high. Thus, extreme dust, other similar climatic events is related to the cutoff low and blocking neighbor to Iran. According to the position of the atmospheric patterns above-mentioned, throughout the year, central Asia desert and eastern of the region to north and northeast flow, is a source of dust in warm half and dust course of cold half related to the position of fronts of the cyclone and unstable weather, are internal deserts.

The Central Zagros cold season with abundant snowfall that other event such as climate, influenced by the atmosphere circulation patterns and distribution of surface pressure of Earth. In this study, to determine weather patterns and dynamical conditions of heavy snowfall in the mountain roads, daily data of synoptic station: Borougen Branch, Koohrang and Lordegan for the year 1987- 2010 of Iran Meteorological Organization received. In the following, days of heavy snow to use of index measure rainfall more than 15 mm and below-freezing temperatures and check the monitor code 70-75 (Code scout snow), 136 days of heavy snow was determined. In order to determine weather patterns, principal component analysis matrix array S on 500 hPa geopotential height data was used. The results showed that heavy snowfall in the mountainous roads of Zagros cause to seven synoptic patterns. As trough of the east Mediterranean is west of Iran and study area is close to the region's extreme volatility. At the same time low pressure gradient in north and south of the study area Caucasus is severe, respectively, associated with strong positive vorticity in the study area, and strong negative vorticity on the East of Oman in the south and Caucasus area in north. However, low pressure center and the North East with strong positive vorticity and high pressure of Siberia to the eastern border of Iran is the continuation and sustainability under the dynamic conditions in the study area. During heavy snowfall strong high pressure of Siberia combined from the north of Iran and the Caspian Sea with high-pressure of Caucasus in relation to Polar vortex in the middle levels of the atmosphere Caucasus cold air streams in the study area. The humid currents from the Black Sea and the Mediterranean by the cyclone flow in the West of Iran through the Persian Gulf region flows to the Zagros Mountains. In all atmospheric patterns, the temperature of zero degrees in the south on the Persian Gulf region and the arrival of masses of cold and wet down to widths And heavy snowfall in the roof of Iran.

The proper study of atmospheric phenomena and reporting the weather in accordance with current standards and extracting the average of climatic elements in different periods in a region in order to recognize local climate and micro climate of a geographical units, requires building a network of enough weather stations. This problem is very important, due to creating exclusive conditions in urban areas that are created because of the physical difference between cities with their surrounding environment. Therefore in this research after studying effective parameters on urban weather stations site selection under mentioned circumstances and the qualities of the studied area, positioning indexes including: dispersion of climatic elements in the city, dispersion of physical qualities of the city (crossings and land uses) and dispersion of environmental jeopardies in relation with the climate of the city were selected and after gathering required information of each index such as: climatic data in reported form, matrix data related to physical qualities of the city and environmental jeopardies reports, required layers were extracted using GIS. Setting priorities of indexes related to each other was done using experts’ verdicts and analytical hierarchy process technique and binary comparison. Then, the obtained weights of layers normalized with Fuzzy membership function in AHP are compounded and overlapped using weighted average approach and the weight of the layers were determined and finally the most appropriate parts including 11 parts are prioritized and located with a suitable distance from the main station in order to expand Mashhad and replace urban weather stations .

IntroductionEvery year natural hazards damage various parts of the planet. One of the hazards of the desert margin with a dry and semi-arid climate, including the Middle East, is dust. Dust reduces horizontal visibility and cancellation of flights, causes crashes, pulmonary and ocular diseases, work closures, air pollution, reduced water quality and damage to the agricultural sector, etc. Today, air pollution with dust is reported in different cities of Iran, including the storm in the July 18, 2009 in 18 provinces, with particles suspended from the desert of Syria and Iraq to Tehran and the amount of suspended particles with 460 ppm showed the highest record of polluting (Ranjbar Saadat Abadi & Azizi, 2012). Estimated economic losses in the western Iran (Ilam, Khuzestan and Kermanshah) from 2006-2011 were 2227 million dollars in the first scenario to $ 13361 million in the fourth scenario (Khalidi, 2013). Every year, 108 tons of dust particles are imported into the atmosphere, with the largest share of Africa (Kutiel & Furman, 2003). The Arabian Rub' al Khali Desert, the Tigris and Euphrates suburbs of the Euphrates and the coasts of Oman are the main focus of Middle East dust production (Prospero, Ginoux, Torres, Nicholson & Gill,., 2002). In Iran, a significant dust storm trend was reported in the west (Rasouli, Sari Sarraf, & Mohammadi, 2011). Zabul with an average of 183 storms had the highest number, and Zahedan, Bushehr, Tabas, Bandar Abbas, Jask, Iranshahr, Hamadan and Ahvaz were the next, with the maximum number in July and minimum in December (Farajzadeh & Alizadeh, 2011). The two critical centers of dust in the southwest of Iran from 1979-2008, Dezful and Bushehr, have highest amount of dust in spring and lowest in December (Azizi, Miri, & Nabavi, 2012). The purpose of this study is to determine the pattern of spatial distribution, continuity, major sources and dust hour pattern in northeastern Iran.
MethodThe extensive spatial pattern of dust (roundness, continuity, major resources and hourly pattern) was performed with the following steps: Hourly data of horizontal view, wind speed and wind direction of the synoptic stations of Quchan, Golmakan, Sarakhs, Mashhad, Neyshabur, Sabzevar, Kashmar, Torbat Heydarieh, Torbat-e-Jam and Gonabad have been received from the Iranian Meteorological Organization since its inception by 2010. Day of dust was defined as the day when the horizontal view was less than 10 km and with the present weather of 06-07-08-09 and 30-31-32-33-34-35, in one of 8 watches per day. Subsequently, the annual, seasonal and monthly frequencies were calculated. The data of wind speed in the dust dates of windrose during the year, the season and the month were illustrated. The speed and direction of the windrose were determined for estimation of dust hour with a 12-hour GMT basis with a maximum recorded dust concentration. The dust accumulation was determined in 2, 3, 4 and more days. In the next step, in order to determine the dust hour pattern, the frequency of occurrence of dust in the eight hours of data recording for each station was calculated and maps were drawn.
FindingsSarakhs with the average 24 -40 days a year experience the largest dust, and the least dust was in Quchan and Kashmar with 9 days a year. Most of the winds run from Turkmenistan in the north, northwest, north east, and east directions. Dust days fluctuate around an average of 18 days a year. The highest winter dust is in Sarakhs, Sabzevar and Gonabad, and the lowest in Quchan, Golmakan, Neyshabur and Kashmar. The dust from the west and southwest is related to western winds, cyclones and the position of cold fronts in the Dasht Kavir and the Bajestan Desert. The region's largest dusting occurs in spring. In spring, Sarakhs and Sabzevar have the highest level of dust, and Ghouchan, Golmakan, Kashmar and Torbat Heidariyah have the least amount of dust. In this season, winds in the north, northwest, east, and southeast blow from Turkmenistan deserts. The peak of the April dust volumes is in Sabzevar, Mashhad and Sarakhs; in June, it is in Sarakhs and Sabzevar, and the lowest is in Quchan, Torbat Heydarieh and Kashmar. After spring, summer is the most dusty, with winds from north, northeast, east, and southeast. The source of spring and summer dust is Turkmenistan's desert and east of the region. The peak of the July dust is in Sarakhs, Sabzevar, Mashhad and Gonabad, with winds blowing from north, northeast, and east. In summer, Kashmar and Quchan are not dusty. The greatest continuous duration of dust is two days and more in Sarakhs, Mashhad, Gonabad, Golmakan and Sabzevar and the least continuous dust is in Kashmar, Quchan. From 1983 onwards, the continuity of dust has a positive trend. In 2008, the highest dust accumulation was recorded. The highest level of dust was recorded at 12 and 15 GMT, except for Sarakhs that recorded the highest dust at 6 GMT. Maximum recorded winter dust was at 12 and 9 oclock, in autumn at 12 GMT, except for Sarakhs which was at 9 GMT. The maximum in spring was at 12 and 15 except for Sarakhs which was at 6 GMT, and the pattern of this season is similar to the annual pattern, the highest summer dust was at 15 and 12. In all seasons, the lowest dust incidence occurred at 0 and 21 GMT.
ConclusionThe dust spatial trend of the region is northeastern-southeast, indicating the arrival of dust from the desert of Turkmenistan and the eastern dry plains. The mountain direction, position of the station and the station's height affect channeling wind and dust from dry lands. Sarakhs has the lowest station that experienced the highest level of dust. The peak is in spring, summer, and the lowest levels occurred in December and January. This trend is also evident in other parts of Iran. In the cold period, with the arrival of the wet system, the soil is stabilized. Summer dust is more homogeneous with stable atmospheres and surface heating, and it is heterogeneous in the semi-cold with unstable system. Most of the persistence of dust is in Sarakhs, Gonabad, Mashhad and Sabzevar, which is associated with a 120-day wind in the summer. Maximum dust is at 12 and 15 GMT, except for Sarakhs, which is similar to Zabul that experiences the highest level at 6 oclock in the afternoon. Decrease in the dust of Kashmar confirms that the northeastern dusts of Iran are mainly from the Karakum desert and the northeastern postal areas of the region, and deserts of the Dashte Kavir in the east and the desert of the southwest of Bajestan play a less role. Therefore, recognition of atmospheric patterns and control of dust cores in the northeast of the region are useful for risk and crisis management in the northeast of Iran.

Identifying the climatic indices and study of teleconnection is an important method in association with the purpose of synoptic climatology science. What are the most important indicators for Iran's climate? For this aim, digital data of daily height for important atmospheric levels from the National Centers for environmental prediction and Atmospheric research for a period of 63 years (1948-2010) and daily temperature and precipitation data for 43 synoptic stations was received in 30years (since 1977-2008). from meteorological organization of Iran. By using the analysis method of main component the important atmospheric indices in the geographical limit of northern latitude of 10 to 70 degrees and 10 to 80 degrees of geographical east longitude for the cold half of year (fall and winter) were identified and through correlation method, the manner and importance of each one of these indices in Iran's climate were determined. The results showed that there are seven climatic indexes in the under study geographic area and the most important of them for Iran's climate from beginning of cold season up to the middle of March include the indices of Central Asia ,North Siberia, Western Europe, Anatolia and the Western Mediterranean respectively. Indicators have the greatest impacts on the temperature of Iran’s climate and their precipitation effect is zonal. Most of the precipitation relationship is between the Caspian Sea coastal area and the index of Central Asia and Scandinavia - Central Siberia respectively in autumn and winter and whole of Iran with western Mediterranean. Thus, according to tobler’s principal in geography, the centers and the most important indicators of Iran's climate are near Iran and their importance is more than the climatic indices located in far away distances.

Climate change refers to the increase or decrease in the average climatic factors over a long period of time (i.e. more than 30 years). Today, climate change has become a human concern and the scientific community are already aware of this fact. Global temperature has followed an unprecedented increase over the last hundred years. Based on synoptic climatology, climatic parameters and its changes are related to atmospheric patterns. In the atmospheric upper levels, the role of dynamic factors and atmospheric circulation is dominant (Alijani, 2006; Yarnal, 1993). ”Understanding climate change through atmospheric patterns is closer to reality. The surface pressure patterns affect the moisture and the heat of the earth's surface, and there is uncertainty in climate change” (Lolies, 2007, p. 361). The arrival of the wave of westerly winds follows the cold period and the instability of weather in Iran. The study of Iran’s climate change with synoptic patterns during the cold period is of great importance. Part of the studies in the literature include the investigation of climate change in the behaviors of climatic indices, the positive trend of North Atlantic Oscillation since 1979-1989 and northern hemisphere activity centers (Mote, 1998; Ostermeier &Wallace, 2003; Rauthe, Hense, & Paeth, 2004), the positive trend of the Mediterranean Oscillation Index, the negative trend of meridional circulation of Mediterranean and non-trend of the Eastern Atlantic Jet in the late 1980s (Dunkeloh, 2003), the shift of the East/West Center of Asian Summer index to the northwest and southeast and the reduction of their power after 1970 (Wu, 2002), the positive trend of East Atlantic Western Russia index, a reduction of pressure in high-pressure center of Siberia after 1970 (Panagiotopoulos, Shahgedanova, Hannachi, & Stephenson, 2005), the negative trends of North Atlantic Oscillation in winter, an increase in anticyclone and a decrease in cyclone in Europe since 1960 to the early 1990s related to the severity of zonal flow (positive index) from 1960s to early 1990s, and an increase in the maintenance of pressure patterns and the stronger blockings in the 1990s with the rising trend of Summer anti-cyclones (Kysely & Huth, 2006), the positive trend of North Atlantic Oscillation and the Azores center for the 500 Hp Europe is over the past 40 years in winter and spring (Casty, Raible, Stocker,Wanner, & Luterbacher, 2007). The aim of this study is thus to identify the climate change in Iran in relation to the atmospheric indices in the middle levels.
The climatic indices of the cold period (Alijani & Doostan, 2015) were determined through analyzing the daily data of the reconstructed geo-potential height of 500 Hp from 1948 to 2010 in fall (September, October, & November) and winter (December, January, & February) collected from the database of the National Centers for Environmental Prediction-National Center Atmospheric Research (NCEP-NCAR) with a resolution of 2.5 degrees for geographic areas of 10 to 70 degrees in north and 10 to 80 degrees in east (725 cells) using Principal Component Analysis. The changes of indices were investigated along with the factor scores or their time series in 500 Hp. This series was investigated on daily, o, monthly, yearly, and five-day average scales during the study period; however, according to the lack of trend at all scales, annual time series in autumn and winter were used to study the changes along with the selection of a prediction model. This series shows the changes of each of the indices during the study period. To examine the trends in time series, the Box Jenkins models were used. The changes of each of the series over time were determined and the appropriate model for the series was fitted. This statistical model predicts the future time series for each of the indices.
Climatic indices of autumn are located from Western Europe to Western Mediterranean, from Northern Siberia to the Balkans, and from Central Siberia to Central Asia. Given the order of climatic importance in Iran, indices of Northern Siberia, Western Europe, Anatolia, Central Asia and Central Siberia are in autumn. In winter, climate indicators are located on Central Asia, Western Mediterranean, the North Sea, Eastern Mediterranean, and Central Siberia. “These centers control the climate of Iran with special atmospheric patterns during the cold half of the year” (Alijani & Doostan, 2012, p. 255). The results showed that the time series of climate indices of the cold period lack a trend, and the index of Central Asia has a weak and insignificant trend. The time series of first order having a negative autocorrelation show the annual fluctuations (yearly changes). The time series of indices during autumn and winter with autoregressive model show distribution best fitting and validity. This model is the best predictor of changes in the time series; the predictive modeling of the time series of Northern Siberia index is the autoregressive sixth order (AR 1, 6). The time series of Western Europe is matched with the third-order autoregressive model (1, 3) AR. The time series of Anatolia index are in conformity with the sixth-order autoregressive model. The time series of Central Asia are totally in conformity with the fourth-order autoregressive model AR (1, 4). Of all the ARIMA models, the autoregressive model is the best model of predicting the climate changes in the winter time series of Central Asia, Western Mediterranean, and the North Sea indices in which the time series of indices are in conformity with the time series of predicting modeling.
Conclusion and Suggestion: Indices of the cold period are in conformity with the location of the frequent westerly winds pattern in atmospheric middle layers with trough, ridge, cutoff low, and the blocking of westerly wind arrangement. These geographic regions in the atmospheric middle layers with the stable and unstable atmosphere and the movement of air masses control the climate in their surrounding areas. The time-series of these indices do not show any significant positive or negative changes during the study period (63 years) in autumn and winter. The temporal behavior of these indices include the annual changes and variability. In addition, the negative first-order autocorrelation in relation to the whole time-series has confirmed the annual changes (yearly) of the indices. These results are in agreement with the previous studies in other regions of the planet, including the insignificant change of climatic indices in the Middle East, the Caspian Sea pattern (in accordance with the position of Western Europe-North-Sea Caspian Index in this study), the Eastern Mediterranean, and the Mediterranean Oscillation Index in 500 Hp level (Dunkeloh, 2003), the lack of trend of pressure patterns in 500 Hp in Europe and North Atlantic (Casty, Raible, Stocker, Wanner, & Luterbacher, 2007), and the insignificant changes in pressure patterns in 500 Hp level in Iran. Box-Jenkins models indicated these changes and fluctuations in each of the time series and confirmed the lack of a significant trend in this series. Fluctuations in each of the time series of climate indices in Iran are in conformity with autoregressive (AR) model. This model can predict future changes in the time series with different orders in each series.

In this study, using Land sat TM images of band 6 sensors were identified heat island of Mashhad city in 4 years (1371-1390) in hottest months(July and august). The results showed that in the city of Mashhad places such as parks, gardens ( Astan Quds Razavi , malek Abad ) to high vegetation index and humidity have low temperature and areas to low humidity and free of vegetation and open spaces with dominant non-users and users of transport transport of soil and rock, such as 12 urban areas have high land surface temperature and urban heat islands form.

The position of Iran in the subtropical region that has made its arid and semiarid climate and the topographic diversity changes this trend of climate. Therefore, climate hazards such as frost, flood, dust storm, drought, temperature anomalies, heavy rainfall, avalanches, snow, sleet, etc occur in Iran. The Northwest of Iran experiences the above conditions following the arrival of west winds, cool and humid polar air mass from the East Europe, and the complex topography (mountain nodes of Iran). The relationships among climate hazards, and the weather patterns and identifying climate anomaly patterns of activity can mitigate the effects of climate and forecasting atmospheric phenomena, which helps the planners and managers. Much research has been done in this regard, including the planetary-scale circulation anomalies compared with synopticscale anomalies associated with higher intensity of extreme weather events are in America (Konrad, 1995, p. 1067) and the atmospheric circulation patterns associated with heavy snowfall in Montana of America, with a deep trough in the west winds and the cold flow from northwest, and with temperatures below zero (Birkland & Mock, 1996, p. 281). The flow pattern in the Great Lakes Basin winter severity Lorentz in the period of 1950-1998 were shows to the prevailing winter circulation patterns in the three synoptic type associated with the winter cold, temperate and hot identified, each of them during the rule of a special circular pattern (Rodionov & Assel, 2000, p. 601). The daily circulation patterns causing heavy snowfall in Poland using principal component analysis are related to strong positive anomalies in the Nordic and North Atlantic sealevel pressure, with positive anomalies of Iceland and the Azores high pressure weak anomalies (Bednorz, 2008, p.133). The aim of this study is identified the atmospheric important index of heavy snow in the middle levels in Northwest of Iran.
Study Area : The Northwest of Iran locates in the East latitude of 36. 4 and 39. 2 and North longitude of 49. 2 and 44. 26. The mountains of Alborz and Zagros connected together and one of the largest lakes in the world is locate in this area. Also the cold and wet air masses from the Arctic, Northern Europe and Eastern Europe come to Iran from this area. With this feature the lowest temperatures throughout the year and most snow is falling in this region.
Material and In connect to aim of study, to determine of the Synoptic snow days, the daily data of precipitation and temperature since 1989-2010 of twelve synoptic stations received of Iran Meteorological Organization. The identify of heavy snowfall according to definition of the World Meteorological Organization, rainfall of 15 inches of snow in 24 hours, and considering that 15 inches of snow is equal to 12.5 mm of precipitation done (Alizadeh,1999). Because of the lack of long-term statistics height of fresh snow, the rain days with 12 mm of precipitation or more and the minimum temperature of zero or less is snow day. In order to more accurately in determination of snow day used snow coefficient (Bairoodain, 2003, p. 320). In order to determine of the activity centers associated with the heavy snowfall, first to receive of the digital data was selected the geographic window to the North latitude of 10-60 and East longitude of 15-80. Therefore the daily data for the height of 500 hPa, sea level pressure, Omega of 850 and temperature of 700 of the Centers for Environmental Prediction and Center for atmospheric research were received. The principal component analysis (PCA) was used to determine of the activity centers of heavy snow at level of 500 hPa.
The seven of action center was identified that account for 79% of the total variance in the original data. The first five Center of action are the most important, the first centers to 18% of the variance locate on the Arabian Sea and North Pole, this pattern shows westerly winds and the general circulation. The second center (14%) with two West- East of center represents meridional movements in Western Europe and Central Siberia. The third center (13%) locates on Eastern Europe and the northern Black Sea (Balkan). The fourth of action center (12%) is located on the central Asia. The fifth center (9%) is on the Anatolia area, Turkey and Northwest of Iran. The pattern of the atmosphere of first center is associated with the polar vortex from Western, Eastern Europe and the Mediterranean with height of 5480 m and the deep trough to cut off low locate on Turkey with height of 5450 meters. The pressure pattern of the surface is Siberian high pressure and southern Europe that combined in the region. The pattern of the second center is the deep trough in the northern Siberia. The strong blocking is located on the Mediterranean and Europe. The surface pattern is low pressure in the Arctic, North Asia and the Caspian Sea and the high pressure center is locate on the southern Europe and the extension to Iran and South Asia. The pattern of the third center is associated to ridge on the central Mediterranean, at the same time, cutoff low in the Caspian is caused deep trough in East Mediterranean. The cutoff low in Caucasus and ridge of European caused flows from northern Europe and Scandinavia to the Black Sea and Iran. Also at ground level, extreme high pressure on Europe combined to Siberian high pressure. In this pattern, isobar of 1035 hPa in Black Sea and isobar of 1023 and 1026 pass of the Northwest of Iran. The pattern of the fourth of action is connected to the west winds in southern Europe, the Middle East, Northern Europe and northern Asia. The ridge of Southern Europe and cutoff low locate on the Caucasus, caused deep trough in the westerly winds in the East Mediterranean. At the same time, Siberian high pressure andEurope to 1020 hPa is evident. The pattern of the fifth of action center is related to meridional flow and the ridge on Europe and height of 5700 meters is located on the north of the Mediterranean and southern Europe. In surface, the deep trough of westerly winds of the north-western Russia continues to southern Egypt. In this pattern, the polar vortex is located on the Scandinavia, Black Sea, Turkey, Iraq, north and Northwest of Iran. The pattern of the Earth's surface is connect to high pressure of western Mediterranean and high pressure of Siberia in East Iran and low pressure in northern Europe to Iran.
The climatic indices of heavy snow in the Northwest of Iran is locate in northern Siberia, Central Siberia, Balkan, Central Asia and the Anatolia. The of upper atmospheric patterns of these indicators are associate with meridional westerly winds, blocking of southern Europe, ridges in central Asia, eastern Europe, east Mediterranean sea, central Asia and cutoff low on Turkey. The blocking and long ridges related to air masses of the north Atlantic over Europe by crossing of the Black Sea and persistence of the cutoff low on Balkans is caused heavy snowfall. At ground level are a combined high pressure of Siberia and Europe. So that the Isobaric 1017 and 1020 hPa passes through the Northwest of Iran to the cold air masses in heavy snowfall days. The Siberian high pressure in the East and Northeast of Iran causes continued rainfall in northwestern of Iran. the lowest temperature in the middle levels of atmosphere experience in the days of heavy snow with -10 ° C and isotherm of zero is on the Persian Gulf in southern of Iran, Therefore, fluctuations in temperature in Iran is above 15 degrees Celsius.. Also local and geography phenomena, including high elevation and local high pressure are affective.

Dust is the first Natural hazard in desert and semi-desert world and Iran. In order to identify the days of the dust of South KHorasan, the daily amount of horizontal visibility, wind speed and direction in the spring and summer of 1991 -2008 were received from Meteorological Organization. Then, based on Shao and Dong index, the days were extracted with dust. In order to determine atmospheric pattern led to the dust, the daily Geopotential height 500 HP from the National Center for Environmental Prediction America/ National Center for Atmospheric Research (NCEP / NCAR), was prepared. In this study, to determine the pressure patterns were used the principle component analysis approach in the state S and hierarchical clustering (ward). Then the composite maps of vorticity, geopotential height, and sea pressure and flow pattern for each pattern produced and were analyzed. The results showed that the tow dominant synoptic patterns respectively are the summer pattern with a subtropical high on Iran and high low on Pakistan in the high levels of the atmosphere and the pressure difference between the South-East of Iran (low pressure) and the Caspian Sea (high pressure) on the land surface. In this pattern, the wind from the East of the Caspian Sea and Turkmenistan desert in the dry lands and deserts to eastern Iran flows and causing dust. This atmospheric conditions is this Connection with the 120-day winds of Sistan and Baluchestan in Iran's East. In the spring pattern, the trough of westerly winds in the center and east of Iran in the high level of atmosphere and low pressure on the ground in this area has led to unstable weather conditions in the central deserts of Iran and the West the province that these flows transfer dust particles and reduce visibility. As well as intense pressure difference between the centers lead to dust storms in the South Khorasan province.

Air pollution is one of the most important environmental issues in Megacities which is seriously threatening human health. High concentration of air pollution is frequently seen over large cities of Iran in recent years. It is difficult to estimate the exact loss of lives and properties resulting by air pollution because of the lack of data، however there are reports that show the vast destructive effects of this phenomenon over the polluted cities. Air quality over the cities is determined with respect to both the total air pollution in a given area as it interacts with meteorological conditions such as humidity، temperature، and wind characteristics to produce an overall atmospheric condition. Air quality is determined by emission sources and weather situations; however، serious pollution episodes in the urban environment mainly result from certain weather conditions which pose difficulty for pollutant dispersion. Air pollution is influenced by meteorological factors through transport، chemical transformations، and removal via wet and dry processes. In this research، the role of regional atmospheric circulation on the occurrence of critical air pollution episodes in the Mashhad metropolitan is investigated. Also the synoptic and thermodynamic mechanisms which are dominated during the most polluted days over the city is identified. Study Area: The study area is located in the valley of Kashaf-Rood River between two mountain ranges of Binalood and Hezar-masjed. Its geographical coordinates are 59º، 27''، 0«E to 59º، 40''، 30'' E and 36º، 22''، 0'' N. The city benefits from the proximity of the mountains، having cool winters، pleasant springs، rather hot summers، and beautiful autumns. It is only about 250 km (160 mi) from Ashgabat، Turkmenistan. Mashhad is 999 m higher than the sea level. According to meteorological records، the average maximum temperature for the four seasons in Mashhad are: winter 8. 3°C (52°F)، spring 21° C (88°F)، summer 33. 2°C (92°F)، and autumn 22. 2°C (72°F). The average minimum temperature for the four seasons also is: winter -3. 6°C (18. 9)، spring 7. 3°C (45. 2°F)، summer 13°C (61. 3°F)، and autumn 5. 7°C (42°F). Mashhad has a semi-arid climate with occasional rainfall in spring and autumn and light snow in the winter. The city only sees about 250 mm of precipitation per year، some of which occasionally falls in the form of snow. Mashhad also has wetter and drier periods with the bulk of the annual precipitation falling between the months of December and May. Summers are typically hot and dry، with high temperatures sometimes exceeding 35 °C (95 °F). Winters are typically cool to cold and somewhat damper، with overnight lows routinely dropping below freezing. Mashhad enjoys on average just less than 2900 hours of sunshine per year. Its population was 2،772،287 at the 2011 population census; so، the city is ranked as the second most populous city of Iran (http: //en. wikipedia. org/ wiki/Mashhad).

In this study، a combined synoptic analysis approach is employed to identify the role of regional atmospheric circulation pattern on the occurrence of high-polluted days over Mashhad. Four types of dataset including air-quality monitoring station data، reanalysis gridded data، upper air soundings data and a lograngian backward trajectory model (HYSPLIT) outputs are used to do this research. The air-quality monitoring station data is obtained from Khorasan-e-Razavi Environmental Protection Administration، while the upper air soundings data and reanalysis gridded data are obtained from National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR). and Wyoming Weather Web، respectively. Also، the Hybrid Single-Particle lograngian integrated Trajectory (HYSPLIT) model is employed to determine the main sources of air parcels by using a backward trajectory approach. Using the Pollutant Standards Index (PSI). daily، seasonal and annual variations of Mashhad air quality is investigated for a 7-year (2005-2011) time period. Using PSI index، we first detected and extracted all very high-polluted days (PSI>200) over Mashhad. Then، a combined synoptic classification approach has been applied by using a set of manual synoptic classification، lograngian backward trajectory model outputs and thermodynamic diagrams.

Investigating the temporal variations of five air pollutants over Mashhad، it is seen that Carbon monoxide is apparently shown a decreasing trend among all air pollutants. While Ozone and Sulfur dioxide experience an increasing trend during the study period. Also، it’s seen that the PM10 shows the most monthly، seasonal and annual values among the others. Moreover، it is revealed that those pollutants with low concentration are showing more seasonal variations in Mashhad. Using combined synoptic classification approach it is indicated that the days with highest level of air pollution in Mashhad can be classified into four main atmospheric circulation patterns including: combined Siberian high-subtropical high، migrating anticyclone، subtropical high and extra-tropical cyclone patterns. In combined Siberian high-subtropical high pattern، a simultaneous domination of Siberian high in lower atmosphere and subtropical high in middle troposphere has been caused an atmospheric stability and high levels of air pollution during cold period of the year. In this pattern، formation and coexistence of a shallow inversion layer in the lower atmosphere and another upper inversion layer in mid-troposphere show coincident roles of Siberian high and subtropical high in increasing the concentration of air pollution to higher level. In mitigating anticyclone pattern، by crossing a Rossby wave over the area، a strong mid-tropospheric ridge over the Oral Mountains and the Caspian Sea will dominate. The eastward inclination of this ridge has been caused an anticylonic circulation in a region from Caspian Sea to northern Khorasan in lower atmosphere. In this pattern، a few thin inversion layers form at the same time below 400hPa level. Rapid temperature drop between the inversion layers indicate the strength and weakness of air subsidence in this pattern. The subtropical high pattern has caused a high level of air pollution over Mashhad only in warm period of the year and it shows a distinct pattern of subsidence inversion type in the vertical profile of atmosphere. The Low-pressure pattern has identified by passing of a rather deep trough over the northern Iran in mid-troposphere and the formation and eastward movement of a cyclone in the lower atmosphere. In general، this pattern is not associated with a distinct and strong inversion layer in vertical profile of the atmosphere، while the thermodynamic diagrams show baroclinic instability through the atmosphere. In this pattern the days with very high levels of air pollution have been caused by lifting، transportation and distribution of dust and particles to the study area due to instability and vast ascend of air as well as lack of suitable moisture feeding into the low pressure.

The results indicate that the middle atmospheric circulations play the most important role in creating extremely high air pollution episodes in Mashhad. The results also demonstrate that the importance of each atmospheric circulation pattern differs from one season to another season. In other words، while in cold period of the year the occurrence of extremely high air pollution episodes has strongly related to extra-tropical atmospheric circulation patterns (i. e. mitigating anticyclone and low-pressure patterns). in warm period، all of high polluted days have mainly related to subtropical atmospheric circulation pattern. However، the subtropical ridge is the most important and also the most frequent pattern which should be consider among 4 main atmospheric circulation patterns. Implication of a combined synoptic classification approach by combining manual synoptic classification، backward trajectory analysis and investigating atmospheric thermodynamic conditions provide a better understanding of dominant mechanisms in extreme air pollution episodes over northeast of Iran. This approach was successful and effective and it has created reasonable and reliable results.

1- Introduction From the time human settlements has been formed as concentrated and fixed communities, air pollution on human life has become perceptible. Air pollution is one of the most important environmental crisis of Iran metropolises which has made life in these cities costly and even dangerous during recent four decades. An increase in urbanization and high consumption of fossil fuels on the one hand, and use changes and industrial development on the other hand, have led to an increase of the concentration of pollutants in the air of cities. Understanding Climate and Pollution is a prerequisite for any sustainable urban planning. Increased air pollution causes changes and disruption in the climatic patterns of the planet and the environment. 2- Theoretical framework The Association of Engineers of air pollution and its control have provided the following definition for air pollution: air pollution means the existence of one or more contaminants such as dust, fumes, gas, mist, smoke or vapor in the air backsets, features and time of remains which is dangerous for human, plant or animal life i.e. the unbearable ease of use of life and property. In general, any change in the physical and chemical components of air is called air pollution.3- Methodology In this study daily data of air pollution in Mashhad (Vahdat station) for a 4 year period (2007-2010), which was provided by the Environmental Protection Agency of Khorasan Razavi province is used. Standard contaminent threshold were determined using Air Quality Index (AQI). Afterwards, the days that were polluted by two pollutants of carbon monoxide (CO) and aerosols (PM10) were determined. According to the first data processing and high frequency of days with CO and PM10 pollutants in the cold half of the year; the analyses were limited to fall and winter. The data includes 29 polluted days in autumn and 23 polluted days in winter for carbon monoxide during a period of four years. The data for polluted days by aerosols includes 74 polluted days in autumn and 63 polluted days in winter. To identify the atmospheric patterns of the days with air pollution in the cold half of the year, 500 hPa height and surface pressure data were collected from Environmental Prediction National Center and Atmospheric Research National Center website. Then, to identify atmospheric patterns, principle component analysis method and clustering statistics method were employed. First, data was prepared in the S mode of principal component analysis, the array in which the nodes were the columns and rows represented observations (days). In this method, points of high correlation and spatial homogenous limits were determined using a linear relationship for the nodes during the study procedure. In the next phase, primary factors were determined considering the correlations in the data for each array. In this array, the value for each node in the new factors is specified and if they change to a map, they show the spatial centers of pressures in the study scope. Then the value for each of those days in the new factors which are known as factor scores (pc score)was determined by the principal component analysis method. This array also shows temporal-series of factors, which represent the relation of each day with the new factor. During this phase, those factors whose eigenvalues were higher than 1 and justified more than 4 percent of diffraction in data were selected. These factors were used to determine the pressure patterns. The ultimate result of principal component analysis method was the factor scores which are the primary data input for clustering method. Clustering method with Ward array was used for the classification of pressure patterns, and polluted days for two pollutants of carbon monoxide (CO) and aerosols (PM10) were determined for autumn and winter. Ultimately, in order to identify pressure patterns, compound maps of days for each group were prepared. These maps, which are prepared for the ground level and 500 hPa level, indicate that synoptic patterns are the resonators of the discussed pollutants in autumn and winter in Mashhad. 4- Discussion Atmospheric pollution synoptic results in autumn and winter for both carbon monoxide (CO) and aerosols (PM10) pollutants in Mashhad indicate that the high level atmospheric patterns and earth surface play significant roles in air pollution in Mashhad. As a result, autumn and winter patterns for main atmospheric pollutants of carbon monoxide, trough of westerly winds of North and East of Caspian Sea in high atmospheric levels, East of Aral Lake Siberian high pressure and immigrant anticyclones from Eastern Europe and North West of Iran on high pressure patterns of earth surface, are the main synoptic factors. With the arrival of cold waves, these patterns which are linked together lead to a decrease in temperature, a decrease of the atmospheric mixed layer (atmospheric boundary layer), and an increase and high concentration of carbon monoxide over the earth's surface. Consequently, much of the flows from the North, North East and North West in these two seasons have air pollution concentration for the city. In addition, central Mediterranean trough, low pressures of Turkmenistan and Kazakhstan, the cut-off in Caspian Sea and the entry of dust from the deserts of Touran plateau, including Qara Qum, Serakhs and central deserts of Iran, bring contaminants of aerosols for Autumn and Winter in Mashhad. Furthermore, in some patterns, Mediterranean cyclones become weak and carry aerosols approaching Mashhad. Furthermore, the other synoptic studies in Iran indicate that the Siberian high-pressure and input air masses from north are associated with severe reduction in temperature in the cold half of the year, which in most high levels are observed as major centers in East of Lake Aral and the North of Caspian Sea. 5- Conclusion and Suggestions Atmospheric pollution synoptic results in autumn and winter for both carbon monoxide (CO) and aerosols (PM10) pollutants in Mashhad indicate As a result, autumn and winter patterns for main atmospheric pollutants of carbon monoxide, trough of westerly winds of North and East of Caspian Sea in high atmospheric levels, East of Aral Lake Siberian high pressure and immigrant anticyclones from Eastern Europe and North West of Iran on high pressure patterns of earth surface, are the main synoptic factors. Furthermore, in some patterns, Mediterranean cyclones become weak and carry aerosols approaching Mashhad. It is recommended that the relevant agencies gather accurate statistics which are essential for a healthy society. Polluted days can be identified and appropriate measures be conducted based on these statistics and the study of synoptic maps

Climate in the south of the Caspian Sea is very different from other parts of Iran. The existence of the Caspian Sea، complex terrain، and the fact that large-scale circulation patterns، as well as local، regional، and extra-regional circulations affect this region، has caused the climatic characteristics of the region to become very unique. The south part of the Caspian Sea receives a significant rainfall in autumn and winter، but in contrast، the least amounts in spring. The incidence of extreme rainfall and flooding in this season could impose damages to the region. Therefore، it is reasonable to identify mechanisms of development، strength، and laws of movement and extension of the synoptic and dynamic patterns to amid positive effects and avoid the harmful results or decrease them. Dynamical studies have a very special place in the study of climate of a region، so that by using the dynamic indices، we can analyze more accurate atmospheric phenomena. This paper attempts to apply a dynamical and synoptic approach to investigate extreme spring precipitation، zoning amounts of total rainfall of every pattern، and provide a model for dynamic and synoptic patterns in the study area. Study Area: The study area is includes the northern provinces of Iran، Gilan، Mazandaran and Golestan in the southern coast of the Caspian Sea and north of the Alborz mountain. This area is between latitudes 36 degree and 34 minutes to 38 degree and 28 minutes of north and longitude 48 degree and 50 minute to 54 degree and 2 minute of east (figure1). Also the rainiest stations and consequently perennial rivers and dense forest cover has been in this region of Iran

In this study، a statistical - synoptic method is used to investigate the dynamical patterns of the extreme spring precipitation in the southern coast of the Caspian Sea. In this regard، the daily rainfall data from 11 weather stations located on the southern shores of the Caspian Sea over a period of 50 years (1961-2010) were obtained from Iran Meteorological Organization. The selection criterion for extreme precipitation is the 24-hour rainfall in which 70% of stations would be equal or more than 20% of the long-term average of the seasonal rainfall. Using data from National Centers for Environmental Prediction / National Center for Atmospheric Research with a horizontal resolution of 2. 5°×2. 5°، the prevailing daily average atmospheric conditions were analyzed. The data include geopotential height، the zonal (u) and meridional (v) wind components، specific humidity and vertical velocity for 1000 hPa and 500 hPa levels. By using abovementioned data، the dynamical parameters of relative vorticity، vertical velocity، divergence and convergence of wind fields and vertical profiles of relative vorticity، divergence and convergence of wind fields separately for each model studied and produced by GrADS software. The maps were analyzed and finally dynamical patterns were identified.

The main objective of this study is to determine the extreme spring precipitation patterns associated with the dynamical quantities in the north coastal strip of Iran، so the weather map of severe-pervasive rainfall are extracted and dynamical analysis is done. The 500 hPa level maps show that the extreme spring rainfall in the southern coast of the Caspian Sea mainly follows four patterns. The main feature of the first pattern is the blocking system (Omega)، which is primarily located in the east of Europe. The system is created from the northward extension of high pressure of North Africa and southward development from the low level polar front in high latitude and also strengthening of a blocking system by the Mediterranean cyclone. In this pattern، Mediterranean cyclones are a major factor of spring rainfall in the southern coast of the Caspian Sea. Also، the European cyclones with amplification by low heights of the high latitude will cause a large amount of rainfall in this season in the north of the country. In addition، the extension of the Saudi high pressure to the East، and expansion of the subtropical high pressure outbreaks to above 80 degrees north latitude، makes a good condition to merge the European cyclones and Mediterranean cyclones in the study area، which eventually lead to create the heavy rainfall in the northern region of Iran. The third spring rainfall pattern is influenced by blocking systems in the Central Asia and Siberian regions. However، the expansion of the subtropical high pressure in the north-east and existence of the Saudi Arabian high pressure in the south of country، have a negative effect on the trough of low heights so that it prevents the system to create heavy and flash flood rainfall and it decreases the rainfall. In the fourth pattern، the blocking system is the dominant form of the spring precipitation in the southern coast of the Caspian Sea. This pattern is somewhat similar to the first pattern، which the different subtropical high pressure systems abnormally extend to the north in the spring. It is observed that even outbreaks reach to the 50°-60° N. In addition، low heights of the high latitude and Mediterranean cyclones also play a major role in the precipitation pattern. To provide a comprehensive view of the nature of atmospheric circulation in the southern coast of the Caspian Sea in spring، vertical profiles of divergence and convergence in patterns of along the 37 N were prepared. The results showed that the southern coast of the Caspian Sea and East Mediterranean during the active patterns of precipitation in the spring have a prevailing western streams (Eastward) at levels of 500 hPa to 150 hPa. Eastward flows through the orbital inclination have the maximum intensity in 300 hPa to 100 hPa levels and areas of divergence maxima and minima convergence and also the fields of horizontal divergence and convergence match at 1000 hPa.

The results showed that extreme spring precipitation in the southern coast of the Caspian Sea follows four major patterns. The main feature of the first pattern is the blocking- omega system that is located in Eastern Europe and Ural Mountains that lead precipitation induced systems to the southern shores of the Caspian Sea. In the second pattern، the Mediterranean cyclones are considered as a main factor of the spring rainfall in the study area. The third pattern of spring rainfall is formed when a blocking system exist over Siberia and Central Asia. Finally، in the fourth pattern، the blocking system is also the main cause of spring precipitation in the southern shores of the Caspian Sea. This pattern is somewhat similar to the first pattern، which is different from the subtropical high pressure systems abnormally extend to the north in spring. It is observed that even outbreaks of it reaches to the 50°-60° N. Investigation of the dynamical parameters showed that during the activities of the system، in all cases، the vertical velocity of the atmosphere is negative and the positive vorticity is high and the convergence zone is located on the shores of the Caspian Sea. All these factors imply that the dynamical weather condition in the region is appropriate for dynamically fast rising of particles to the middle and upper atmosphere، which eventually create heavier spring rainfall.

Mountain geosystems are not unusually fragile but they show a greater range of vulnerability to disturbances that human induced than many landscapes. The combination of extreme geomorphic events with exceptional population growth and land use modifications underlies the urgency of better understanding of these interactions for investigating of the effects of drivers of change on landforms and landscapes. The combination of natural and human factors provides conditions for these unstable events within the geomorphic transport processes. The present study focuses on the identification of the Kan watershed topple initiation factors and the susceptibility ratio zonation of this event using fuzzy logical model. The distance to road، distance to lineament، distance to fault، slope، aspect، slope formation، elevation، land cover، cryocl

The upper level pressure patterns control the climate of the surface. The identification of these patterns in the regional scale is useful for the study of the surface climate elements and their forecasting. In order to understand the pressure centers controlling the climate of Iran during the cold period of the year, the daily 500 hPa. geopotential height of the grid points of 2.5 degrees distance within the windows of 10 to 70 North and 10 to 80 E. were obtained from the NCEP data center for the 1948-2010 period. The action centers or the controlling points of the climate of Iran were determined using the PCA. Each action centre controlled the climate of Iran through a specific pressure pattern. The results showed that about eight controlling points affect the climate of Iran during the cold period of the year. The northern Siberia is the most important center in controlling the climate of Iran. Most of the controlling centers are located north of Iran. Only the Monsoon of Pakistan is located to the south of Iran. Most of the pressure patterns indicated a meridional orientation with low index cycle accompanied with cut-offs and blocking patterns. Deep troughs and strong ridges are the frequent phenomena of the westerly winds over Iran.