جستجوی مقالات مرتبط با کلیدواژه « V wind » در نشریات گروه « جغرافیا »

Shamal wind is one of the local winds with high continuity and diversity in the Middle East and the Persian Gulf region, which often causes dust storms during the summer. In this research, the hourly data of sea level pressure, geopotential height, U and V winds were collected for a period of 44 years from the Copernicus database. First, these data were arranged as a long-term mean, secondly. In order to process the data, principal component analysis and cluster analysis were used. Applying the PCA showed that more than 97% of the variation of the data is explained by three components. The score map of the first component revealed the spatial mechanism of the Shamal summer wind and the eigenvector diagram of the first component of the time period of the Shamal summer wind activity. In addition, the hierarchical cluster analysis on the time-space matrix of SLP showed three-time clusters that represent the time period of the north wind in summer and winter. The analysis of the maps of the monthly pressure distribution pattern showed that the most important active and influential system in the region is the low pressure of the Persian Gulf in the summer season, and the low pressure of the Red Sea in the winter season. The results suggest that the changes in the patterns of the earth's surface at the levels of 500 and 700 hPa are not much significant while it shows a better existence in the 850 and 1000 hPa maps.

The Manjil wind is one of the Iran atmospheric phenomena that is blowing in the southwestern of the Caspian Sea and northern region of the Iran plateau. Daily regime with the specified direction and high intensity of Manjil wind cause to the first windy farm is foremed in this region. In this study the reanalysis data of NCEP/NCAR were used to identify synoptic weather systems during the period 2010 -1980. At first, the pressure gradient between northern and southern Alborz were obtained and were compared with observation data of Manjil wind intensity then synoptic patterns of wind were obtained during different months. In synoptic scale, long -term mean of sea level pressure indicate Siberian high pressure system in the cold months and the AZORZ high pressure system from the West Europe to the southern coastal of the Caspian Sea in the warm months lead to the formation of the North flows along Sefid Rood valley. In the warm season, meriditional extension of Pakistan monsoon low -pressure and Saudi Arabian thermal low - pressure toward the Iran plateau cause to increasing the pressure gradient and wind speed. long -term pressure variation for hours of maximum wind speed (12UTC) and minimum wind speed (00UTC), indicate radiation and thermal conditions are very important factors on both sides of the Alborz mountains, especially during the hours of the on the wind formation mechanism. The narrowing of the Sefidroud valley as a secondary force is the main cause of channelization and increasing of the Manjil wind velocity

In order to investigate the atmospheric mechanisms governing the occurrence of the Von phenomenon at the time of forest fires in northern Iran, four types of data were used in the research. First, by taking the statistics of fires, the forests of the north of the period were identified. The monitored data of temperature, pressure, and wind in the front and back slopes of the Alborz mountain range were examined, as well as the networked data related to the National Environmental Forecasting / Atmospheric Science Centers (NCEP / NCAR). The European Center for Atmospheric Prediction (ECMWF) was used to explain the structure of the atmosphere. Modis sensor images were used to investigate the surface temperature and a suspended particle regression model was used to track the air mass. Studies have shown that with the formation of hypertension in the south of the country and low pressure in the north of the Caspian Sea, a strong pressure gradient is created and causes the southern currents in the northern regions of Iran to be affected. So that with the rising of the air mass on the Alborz mountain range and evacuation of its moisture and then passing the air package over the mountain and the heatless heat resulting from that hot and dry air mass has entered the region, these conditions are accompanied by strong winds and areas Susceptible to fire. Studies show that there is a sharp temperature difference between the windward and backward areas of the mountains, which is due to the unreasonable decrease and increase of air closure in the region. Airborne tracking also indicates that the main source of current entering the region is in the northern Persian Gulf and Northeast Africa.

Identifying the patterns of the teleconnection and analyzing their effects on the dynamic components and circulation patterns of the atmosphere can be useful for better understanding and knowledge of climate systems and consequently their prediction (Mueller and Ambrizi, 2007). The Arctic Oscillation (AO) and the East Atlantic–West Russia teleconnection (EA–WR)are among the most important teleconnection in the Northern Hemisphere. The Arctic Oscillation is actually the anomaly of atmospheric pressure at the sea level in the north polar latitudes (55°N) and middle latitudes (45°N latitude), which was first discovered by two scientists named Thomson and Wallace in 1998 It was proposed as the main reason for the variability of the Subtropical regions of the Northern Hemisphere. In the positive phase of this index, the polar convection is stronger than normal and the jet at the top of the atmosphere is strengthened and moves in the form of a ring of strong westerly winds from around the North Pole, and this causes colder air to be limited in the polar regions. As a result, in this phase, the western winds are strengthened in the North Atlantic area and create warmer and more humid conditions than usual in Northern Europe. In the negative phase, the polar vortex ring and the upper level jet of the atmosphere take a meridional pattern and the western winds move towards lower latitudes (middle latitudes). Also, in this phase, the western winds are weakened in the northern part of the Atlantic and can penetrate to the areas located at low latitudes including southern Europe, the Mediterranean and the Middle East.East Atlantic-West Russia teleconnection EA-WR is obtained from the standardized pressure difference or geopotential height of East Atlantic Ocean from West Russia.This teleconnection was presented for the first time by Branston and Livesey (1987) using the method of principal components analysis in the form of a pattern of monthly changes in geopotential height of 700 hectopascals. This pattern includes four main centers of negative geopotential height anomaly along the orbits from the Atlantic Ocean to China. In the negative phase, this is reversed. In the negative (positive) phase, climate conditions are often drier (more humid) than the average situation over a large part of the Mediterranean region (Krichak et al., 2002).

To investigate the mechanism of the Arctic Oscillation (AO) and the East Atlantic/West Russia Oscillation (EA-WR) in relation to the atmospheric circulation of the Middle East and Iran in two seasons: autumn (September, October, November) and winter (December, January, February), National Center for Environmental Prediction/Atmospheric Sciences (NCEP/NCAR) gridded data were used. The reason for using data with a spatial resolution of 2.5*2.5 degrees is that they are suitable for studying low-frequency phenomena on a planetary scale (Mohab al-Hajjah et al., 2015). Based on the purpose of the research, the data of geopotential height, sea level pressure, orbital component of wind and amount of precipitation for two seasons of winter (December, January, February) and autumn (September, October, November) were obtained between 1948-2020. Due to the importance of the level conditions of 200 and 500 hectopascals on the dynamic components of lower levels (Standel et al., 2021), these atmospheric levels were selected for investigation and analysis. After receiving the mentioned data and extracting the time series of these data, the map of the desired dynamic components was drawn and analyzed.Then the correlation maps between the mentioned teleconnection with parameters of geopotential height of 500 hectopascals, orbital wind component of 200 hectopascals, sea level pressure and precipitation amount In order to determine the long-term relationship of these links with the dynamic components - synoptic and precipitation of the region in the cold period of the year, it was drawn.

The pattern of correlation values between the meridinal wind speed level of 200 hPa and the AO teleconnection in the autumn season showed that a Rayleigh-shaped positive correlation line was drawn in the direction of the meridinals from the United States of America, the Atlantic Ocean, North Africa to the east of Iran.Both teleconnection have a strong positive correlation with the meridinal wind speed of 200 hectopascals in autumn and winter, Which means that, with the increase in the value of each of them in the autumn season, along with the increase in the meridinal wind speed, the tropical jet stream first has an meridinal - wave pattern in the direction of the Atlantic Ocean, north and East Africa, the Red Sea, and then it is formed by changing the shape with a meridian pattern from Iran to the west of Russia. Almost along the same path, there is a negative correlation between the mentioned teleconnections and the geopotential height of the middle level of the atmosphere in the two seasons of autumn and winter. By increasing the value of each of the mentioned links, the value of the geopotential height of the middle level decreases from the northwest side of Iran to the north of the Red Sea and the east of the Mediterranean, which indicates the penetration of cold polar air through the west of Russia to the areas located throughout the western half. and the northwest of Iran.

The results showed that the fluctuations of both teleconnections have a significant effect on the climate of the Middle East, especially Iran. In autumn and winter season, there is a positive correlation between the above-mentioned teleconnections with the meridinal wind speed of 200 hectopascals and a negative correlation with the geopotential height of the middle atmosphere in Iran and the Middle East. Therefore, the increase in the value of each of these teleconnections is associated with an increase in the meridinal wind speed at the upper level of the atmosphere and a decrease in the geopotential height of the middle level of the atmosphere in autumn and winter seasons. The East Atlas-West Russia teleconnections affects a wider area of Iran in autumn and winter.

Among the many human and biophysical factors in fire, climate and weather are also the main drivers of fire initiation and spread. But the separation of atmospheric processes affecting fire complicates the possibility of fire modeling and makes its management difficult. Considering the importance of fire and its close relationship with weather conditions, it seems that a comprehensive analysis of the spatial distribution of fire points along with the wind in Rasht city has a suitable position for further study. Therefore, in this research, we will try to provide a correct analysis of the spatial pattern of fires in Rasht city. Also, by examining how the fire points are distributed in this city, it is possible to determine the high-risk areas in terms of the occurrence of fire events in order to perform a better management to deal with possible incidents and fire extinguishing during Foehn wind in this city.

In order to identify Foehn wind days in Rasht, the data of maximum temperature, relative humidity, wind speed and direction were used for 8 years (1392 to 1400). In this way, the Foehn wind days were divided into three groups of moderate, severe and very severe days based on the criteria of 1sd, 2sd and 3sd of the maximum daily temperature of the period compared to the maximum temperature of the Foehn day. Then, using the average nearest neighbor method (ANN) and Ripley's K function, the spatial pattern of fire points was determined for moderate, severe and very severe winds.

The results showed that out of 160 Foehn winds that occurred in this area, 72 were moderate, 59 were severe, and 29 were very severe. The results showed that 72, 59, and 29 of the 160 Foehn winds that occurred in this area were moderate, severe, and very severe, respectively. In total, 23.6, 6.9, 0, 0, 0, 0, 2.8, 1.4, 9.7, 13.9, 16.7, and 25% of 100% of Medium Foehn winds happened from April until March, respectively. Also, 11.9, 5.1, 0, 0, 0, 0, 1.7, 1.7, 13.6, 22, 16.9 and 27.1 percent of the total Severe Foehn winds, , 10.3, 0, 0, 0, 0, 0, 6.9, 0, 13.8, 34.5, 13.8 and 20.7 percent of the total very severe Foehn winds occurred from April to March, Respectively. In this regard, the relationship between the maximum daily temperature and the average maximum temperature of the period (40 years) is 0.608 and is a direct relationship and is significant at both α=0.05 and α=0.01 levels. This relationship between the daily maximum temperature and the minimum relative humidity that occurs at noon is negative, inverse and is -0.504, which indicates that the relative humidity of the air decreases during the occurrence of a Foehn wind days in this area. The results of the multivariate regression model to determine the effect of each of the climatic variables on the maximum daily temperature showed that the Adj.R2 value of this relationship is equal to 0.566. Considering the large value of F and the value of Sig=0.000<0.05, we conclude that the regression model is suitable and most of the changes in the dependent variable have been seen in the regression model. Also, the two variables of average maximum temperature of the period and minimum relative humidity have a relationship with the variable of maximum daily temperature, and the effect of the first is direct and the second is inverse. As a result, with the increase in temperature caused by the Foehn wind, the relative humidity decreases greatly. The two variables of wind direction and average wind speed do not have significant effects on the daily maximum temperature caused by the Foehn wind. The results of calculating the average index of the nearest neighbor indicate that all three types of random, cluster and scattered patterns can be seen in the fire points of medium, severe and very severe Foehn winds. But the pattern governing the distribution of all the fire points of the period is also cluster type. Also, the results of Ripley's K function showed that the K value observed in the 10 investigated steps is greater than the expected K value, and this confirms the clustering of fire points in Rasht city.

In this research, it was found that the pattern governing the spatial distribution of fire spots in Rasht city and its surroundings in the months of January, February, March, April, October, November and December is of all three types of random, cluster and scattered patterns. However, the frequency pattern of the entire distribution of fire points for medium, severe and very severe Foehn wind was obtained as a cluster type. In other words, the clustering of the total frequency distribution indicates that there are different fire hotspots in the city of Rasht and its surroundings, which can be identified as different clusters. This feature of fire points has a great impact on the construction of new fire stations and it can be used in locating new fire stations to speed up the arrival of firefighters to fire situations. Finally, it should be said that the spatio-temporal information about the Foehn winds can help to understand its various effects at the local, regional and global scale.

Severe coastal winds, either directly or by flooding the coastal waters, can damage installations or cause disorder in various human activities such as shipping, commerce, recreation, etc. This study investigated the temporal-spatial variability of maximum coastal winds using the maximum wind data from stations in Iran's northern and southern coasts. Statistical analysis of the average maximum wind speed showed that the Persian Gulf coast had the highest speed. The monthly changes of the maximum wind indicated that the maximum monthly average is related to November in Anzali port and the minimum rate is for Chābahār station in all months. Generally, the variability of summer and autumn months is less than spring and winter. The maximum wind direction on the shores of the Persian Gulf and the Caspian Sea has a clockwise shift from east to west. Linear regression analysis was used to study the trend of maximum wind speed, which indicated the heterogeneity of the line slope of the stations on the southern coasts and the homogeneity of the northern coast stations with a positive slope.Highlight The maximum average monthly is related to November in Bandar-e-Anzali and the minimum speed is related to Chabahar station in all months and the variability of summer and autumn is less than spring and winter seasons.The topography altitude in the coastal areas and their distance to the coast, play a decisive role in the direction of maximum winds.Linear regression analysis shows the maximum wind time series have a negative slope on the south coasts (except Chabahar and Abadan stations) and a positive slope on the north coasts.Extended Abstract Introduction Coastal areas are the confluence of hydrosphere, atmosphere and litosphere, and this triple link provides special biological conditions for humans and other living organisms. Due to the special characteristics of coastal areas, human life and activity in these areas are affected by the intense functions of natural factors. One of the most important natural factors in these areas is wind, and as the intensity of these winds increases, the effects increase. Severe coastal winds, either directly or by flooding the coastal waters, can damage installations and disorder in various human activities such as shipping, commerce, recreation, etc.In this study, the monthly data of speed and direction of maximum wind of the Meteorological Organization for coastal stations on the coasts of Oman, Persian Gulf and Caspian Sea were used in the thirty-year period of October 1992 to October 2021.MethodologyFirst, descriptive statistics related to each station were calculated. The maximum wind vane of each station was plotted. The frequency of wind vector events for each station was calculated and plotted. Linear regression related to each station was calculated to determine the temporal variations of maximum wind in each station.Results and discussion The study of the average maximum wind speed shows that the Caspian Sea coasts with an average of 12.75 meters per second have the highest and the Oman Sea coasts with 10.97 meters per second have the lowest average maximum winds; this amount in the Persian Gulf coasts is about 12.3 meters per second. Investigation of monthly changes of maximum wind shows that the maximum average monthly is related to November in Bandar-e-Anzali and the minimum speed is related to Chabahar station in all months and the variability of summer and autumn is less than spring and winter seasons. The severe winds direction in Chabahar station are from the west-southeast and in Jask station are from the west-eastern. The direction of the maximum wind on the shores of the Persian Gulf changes clockwise from east to west stations, so that from the south in Bandar Abbas, finally it turns north in Abadan; in the shores of the Caspian Sea, from east to west (Gorgan to Astara), the prevailing wind, like the shores of the Persian Gulf, moves clockwise and changes from west to north. On the shores of the Caspian Sea from east to west (Gorgan to Astara) the prevailing wind, like the shores of the Persian Gulf, has a clockwise movement and changes west to north (except Astara). In general, due to the maximum winds are the result of pressure daily changes and considering the clockwise changes in wind direction from east to west on both the north and south coasts of Iran, it can be concluded that the topography altitude in the coastal areas and their distance to the coast, play a decisive role in the direction of maximum winds. As a result, in areas where the altitudes are low or far from the coast, high pressures are formed in the water zones and therefore the direction of maximum winds are from the sea to the land. Linear regression analysis shows the maximum wind time series have a negative slope on the south coasts (except Chabahar and Abadan stations) and a positive slope on the north coasts. The highest line slope is related to Gorgan station in the easternmost part of the Caspian Sea coast.ConclusionOverall it can be said that with more concentration of human activities on the coast and an increase extreme climate events, including severe winds, the probability of human and financial losses on the coast has increased and the need for identification and planning to prepare with such hazards is inevitable. According to the results of this study, which shows the increasing trend of severe winds in the northern regions, and also due to the intense concentration of population on the northern coasts, this hazard must be taken seriously. The use of coastal meteorological stations to predict and warn of severe winds, the correct location of piers, strengthening of coastal structures and construction of coastal walls to deal with strong waves caused by severe winds and Educate local residents to deal with severe winds can reduce the risk of severe damage during these events.FundingThere is no funding support.Authors’ Contribution Authors contributed equally to the conceptualization and writing of the article. All of the authors approved the content of the manuscript and agreed on all aspects of the workConflict of Interest Authors declared no conflict of interest.AcknowledgmentsWe are grateful to Iran meteorological organization for providing data in this paper.

This study was conducted to investigate the foehn mechanism in the Alborz Mountains.For this purpose, daily temperature, mean and maximum daily temperature, minimum, mean and maximum daily relative humidity, hourly wind direction and velocity data were collected and prepared at 8 selected stations over a 10-year statistical period (2006-2010). To derive the sum of frequency of occurrence of foehn, hot days are extracted using Baldy index and taking into account wind direction relative to station position and temperature rise compared to previous days were identified as days associated with foehn. Then, using NCEP / NCAR database data, different atmospheric alignment maps were obtained for the selected samples and plotted in Grads software environment. Then the position of high pressure cores and adjacent low pressures on the maps were determined. Results showed that Masouleh station with 41 days frequency and Astara and Bandar Anzali station with 18 days had the highest and lowest occurrence of foehn. Investigations on the synoptic maps of 35 foehn events showed that a total of three groups of Anti-cyclone or high-pressure centers were affected by the synoptic pattern of the region in the days involved. The first group is the Siberian High Pressure Tabs, whose cores are located in the confines of Lake Baikal, Balchash and northern Pakistan, depending on the season and synoptic conditions. The low pressure cores are located on the Caspian Sea and the pressure difference between the high pressure tab of the Alborz Outer Slopes and the Caspian Sea causes a compressive stress. In this model, Cyclone currents with increasing moisture of the Caspian Sea on the western slopes of Alborz Heights cause precipitation and warm flow due to warming under windward slopes. The second group is the anticyclone of Saudi Arabia, in which specimens with spin cores are deployed on southwestern Iran. As the north side of the Arabian High Pressure extends northwest of Iran and the presence of low polar pressure in the Caspian region with intensified compressive flow causes currents southwest along the perpendicular heights. Western anticyclone currents in the Arabian Sea circulate the moisture of the southern warm seas to northwestern Iran. The third group is a combination of African anticyclones, immigrants, Siberian highs and its tabs that create a thermal and compressive style over the study area and west of the Alborz Mountains. And provide the basis for the formation of the foehn phenomenon.

To identify the physicochemical and atmospheric conditions of a dust storm at the Dezful station (As Dezful Regional Representative), at first the frequency of the dust storm phenomena was investigated at the Dezful station in Twenty years (1994 -2013). During three events on June 24, July 21, and July 28, 2018, dust samples were collected with sediment traps and physical condition was performed with X-ray diffraction device and chemical analysis of the elements and heavy metals detected by flame atomic absorption and dust particles were evaluated with the Igeo index. Also, the atmospheric circulation in the middle level of the atmosphere and sea level surface that led to a dust storm was identified by using ECMWF ERA-Interim meteorological data. The distribution of dust particles was detected with aerosol optic depth (AOD), and the pathway of dust particles was examined by the HYSPLIT model. The results represented that frequency of dust storm is an increasing trend which has led to a decrease in horizontal visibility in Dezful. The maximum of dust storm phenomena is in summer time and July; The minimum in the autumn time and January. The mean distribution of dust particles in Dezful showed that PM10 was dominant in the size of the silicate tissue. The elements of dominant were Mn, Zn, Pb, and Cd was 491, 311, 32.9, and 1.41 mg/kg respectively, which indicates moderate to severe contamination compared to the standard level. Among the soluble elements, Ca, K, Na, and Mg had the highest concentrations; the presence of these elements is evidence of their desert dust particles. Tracing and calculation of their backward pathway showed that the alluvial deposits of the Tigris and Euphrates in Iraq were its main focus.

Results show that the Persian Gulf's coastline structures and features (e.g. mountains) play key roles in determining wind characteristics in northern side of the Persian Gulf. By advancing from west to east part of the Persian Gulf, general wind pattern is controlled by various wind components (systematic or land-sea breeze components). While, systematic wind are govern in western head's wind structure, land-sea breeze play a key role for determining wind features in the eastern sections, where systematic component is impact inconsiderable. Decreasing of mountains distance from beach in eastern rather (Daier station to Bandar Abbas) than western coasts (Abadan station to Daier) is main reasons to decrease the systematic wind energy by its friction with mountains. The land-sea breeze effects on local wind structures increase due to positive impact of mountains that intensified it in eastern parts. In the other hand, land and sea breezes influence intensify when systematic wind is calm. Land and sea breezes speed decrease slightly about 2ms-1 to 3ms-1 from west to the east. Through the seasonal analysis, it is deduced that summer's sea breeze is more intense and the possibility of its occurrence is much more frequently than other seasons. Also it is more sharply rather than land breeze during all seasons. Since nighttime is longer than daytime, land breeze occurred more than sea breeze with less speed values during winter.

In this research, effect of environmental forcing like topography, direction and sharpness of slope, shape and trend of topography on wind regime formation have been studied in mountainous stations of gilan. The regime of mountainous winds has major effects on the air conditions in mountain regions. This research had been done using hourly data of wind speed and wind direction and also analysis and fitness of topography conditions with theoretical fundamental of research. So it was observed that Masouleh station is one of the best mountains stations in the subject of mountains climatology. Suitable location of this station in the middle slope caused to affected region by upslope wind and down slope wind (katabatic and anabatic winds). Location of Deylaman station on southern slopes of Alborz Mountains had important effect on wind speed decreasing. Wind occurrence mechanism is Mountain wind type along vallay in Deylaman station. Secondary dominant wind was north-northwest thus daily and seasonal behaviors of wind and location of Caspian Sea and Alborz Mountain represent affecting the region by sea-land breeze system. Jirandeh station’s behavior is as an exclusive mountainous station that indicated deep combination but imperceptible influence of the mountain on atmospheric phenomena in Mountains range. Position of station on southern slope provided appropriate conditions to form slope wind occurrence in this region. However stretching of Totkabon- siahrood valley as a wide valley that is branching of sefidrood valley provided appropriate conditions to influx sea-breeze wind. This condition caused destruction of local mountain wind effects during day and night.

Transferring the water vapor in the atmosphere directly depend on the conditions of atmospheric circulation, amount and path of humidity changes related to the atmospheric circulation variation. one of the main factors of atmospheric circulation affecting on transferring the moisture is high pressure centers that if placed on the water surface and humidity resources causes the moisture advection in a widely area. However, the role of low pressure systems and cyclones in advection and moisture flux, although not as much as high-pressure systems, but also played a significant role in transmitting and condition of moisture advection. the aim of this study is survey the moisture advection of Iran's precipitations. in this regard, pressure data, specific humidity, u wind and v wind parameters in 500, 700, 850 and 1000 hpa from NCEP/NCAR database were extracted and analyzed. the results showed that the moisture advection of iran's precipitations is related to the moisture advection pattern of low pressure of dual-core of Sudan and east Mediterranean - Europe high pressure, moisture advection pattern of multicore low pressure of central Iran, east Mediterranean and south east of Saudi Arabian, moisture advection pattern of highpressure of north west of Europe- low pressure of Persian gulf, moisture advection pattern of high pressure of Siberia and Kazakhstan- low pressure of south east of Iran and low pressure of Mediterranean. Overly, the results showed that Arabian Sea in low level and Mediterranean Sea in high level had an important role in moisture advection of Iran's precipitations.

The purpose of this study is to investigate the changes of temporal and spatial moisture advection in Irans atmosphere. To achieve this purpose, data -orientation and meridional components of the database during the 1390-1340 NCEP / NCAR related to the Oceanography Organization United States was extracted, examined and analyzed .For the calculation of features and software programming environment Mat lab, software Grads and Surfer software was used to perform graphics operations’. The largest decline occurred in summer. However, in all months, western and southern parts of zagros had the most intensive decreasing slope during the period. In all months, especially summer, south east have increasing consistency.

Shamal winds recognized as a climate regime with a common occurrence in the Persian Gulf that makes the event of adverse weather conditions in this region periodically. Among the phenomenas that occurring under effect of Shamal wind, can be noted to dust storms, Low-level winds and inappropriate sea conditions. Shamal winds are categorized into two types, winter Shamal and summer Shamal. Sea-land breezes also are classified as a frequent mesoscale and heat driven flow associated with coastal areas. Temperature gradient between sea and land is the main reason for the formation of a sea breeze circulation that blows from sea to land in low level coastal atmospheric boundary layer. The suitable conditions for Sea-land breezes establishment when the synoptic winds are weak (low synoptic forcing) and temperature level is high in the coastal city of Bushehr. The purpose of this research is to investigate seasonal Shamal wind event and its associated synoptic conditions by observations analyzing and numerical expriments on Persian Gulf. The impact of these conditions on wind pattern in the northwestern Persian Gulf coastal area and in optional case in the coastal area of Bushehr are studied and it is intruded interaction between meteorological mesoscale (sea-land breeze) and large-scale (synoptic pattern Shamal wind) forcing effects in this area. North of middle east are areas that dominated by the seasonal Shamal wind regime, that begin from the central deserts of Iraq and the mountains of northern Iraq, Turkey and Syriat to Persian Gulf. In this study, the coastal city of Bushehr that located in the northwest of Persian Gulf and southwest Iran have been selected to investigate about interaction of Shamal wind pattern on local breeze on the coastal areas . Based on the location of the Bushehr and sea-land breeze definition, sea breeze will occurr in the sector of 180-270 degree.
In this study, in order to analyze the time series of coastal wind, it is used hourly wind speed and direction data from meteorological tower and meteorological station of Bushehr power plant and also wind data from Bushehr airport weather station. In the next step, the NCEP FNL data used to generat the initial and boundary conditions for regional simulations by WRF model. This data has 1° × 1° resolution and are available for every 6 hours. This data produce by Global Data Assimilation System (GDAS) that continuously receive monitoring global data for analyze from Global Telemetry System (GTS) and other resources.
The results of the observational time series analyzes from the meteorological tower of Bushehr power plant are shown for winter (January) and summer (May) selective periods. These results show the mean detail information of typical wind regimes such as summer and winter Shamal and sea-breeze regimes during January and May 2010. In this work is represented formation quality, duration, mean speed, mean direction of sea-breeze wind in the beginning and ending of sea-breeze regimes during these months. It also is represented frequency of daily occurrence of typical wind regimes with themselves mean speed in Bushehr coastal area. It was observed that the northern of Saudi Arabia is influenced by a high pressure system and Persian Gulf and west of Iran by a low pressure trough and a heat low pressure system is seen over east of Iran (region of Afghanistan, Pakistan and etc.) during summer Shamal. Turkey, Iraq and west of Zagross mountain rang regions are affected with interaction of these thermal and dynamical systems that lead to the creation of Shamal wind in north west of Persian gulf. This area is affected by winter Shamal wind regime with significant cold advection after passage of synoptical cold front of a dynamical mid-latitude cyclone.
In general, Shamal wind affects Turcy, Iraq, Iran, Arabian Peninsula and adjacent areas. The maximum activity during 2010 observe in the winter in late of January and in the summer in June by maximum number of Shamal days. This result is obtained by analyzing data from the meteorological tower at height of 100 meters in Bushehr weather station that the summer Shamal causing disruption of coastal wind pattern in 14 days of May, 14 days in June and about 10 days in July of 2010 and in other months, usually less than three to five days. Winter Shamal occurs at intervals of 3 to 9 days from December to March. During the period that the sea-breeze is removed by synoptical Shamal winds forcing, the average daily wind speed more than period of sea-breeze activity.

In general, Garmesh wind in Rasht province increases the temperature by 9°C and reduces relative humidity by 47%. The direction of prevailing wind during the Garmesh wind is Southern and its average speed increases by 2 m/s to 5 m/s. The highest frequency of Garmesh wind occurs at 09 and 12 UTC in December and January. The occurrence of this phenomenon substantially increases the horizontal visibility, so the sky would be clear in more than 40% of the cases.
1.

Wind is one of the atmospheric elements which has a great impact on the region and local climate. Wind transfers air from one area to another. Thus, wind is very important in the regional climate study. Garmesh is a hot and dry wind that often blows from the north of Alborz Mountains in the cold season. The main reason for the creation of Garmesh wind is the simultaneous presence of high pressure system or its ridge on Iranian plateau and its association with low pressure system on the south of Caspian SeaGarmesh wind that is warm and dry is a well-known wind for the people in Gilan provience. This wind blows from the northern slope of Alborz Mountains and flows from Iranian plateau to the northern slopes of Alborz Mountains. The wind can last from several hours to several days. Relative humidity suddenly reduces and air temperature increases during the Garmesh wind. In many cases, the wind mostly covers the southern part of the Caspian Sea. According to Gilan Governor Documents, financial losses due to the Garmesh wind and fire forest was about 8.71478 million Rials in the period of 1381 to 1388.
2. Material and

Synoptic weather station of Rasht is located in the south of the Caspian Sea and north of Alborz Mountains in Gilan province. Its height is about 8 meters above the sea level. Atmospheric data including wind, pressure, cloudiness, air temperature and relative humidity were extracted in the period of 1982-2010. Then Visual Basic program was used to decode the data. Finally, these data were analyzed using statistical software such as Excel.
3.

The frequency of days with Garmesh wind during the statistical period (1982-2010) was 479 days. Mean kjnhgftr6yikmn bvds3 annual days with Garmesh wind is 16.5 days per year. In some cases, Garmesh wind blows for just one hour but in other cases it last for several days. This phenomenon is more frequent in the evenings times. The highest frequency of the Garmesh wind occurs in January, February and December. In more than 75% of cases the direction of this wind is southern. Under normal conditions 60% of times in the year, wind is calm in the Rasht station and more than 91% of cases, the wind speed is less than 3.6 m/s, but in more than 69% of the cases, the Garmesh wind speed is between 2.1 and 8.8 m/s.
Normally, the relative humidity in Rasht station is 82% but during Garmesh wind it decreases to 34%. With the onset of Garmesh wind, temperature increases and this increment continues until the end of Garmesh wind period. In some cases in the other regions in the world, during Garmesh wind, temperature increases or decreases by 20°C in less than three hours. But in Rasht station it increases more than 9°C. In most cases of Garmesh wind occurrences, temperature varies between 15 to 25°C, and in 92% of Garmesh wind occurrences, it varies between 10 and 30°C. The most important cause of Garmesh wind in Rasht is the presence of high pressure system or high pressure system tongue in Iranian plateau and low pressure system on the south of Caspian Sea. In more than 94% of cases mean monthly pressure (QFF) increases and varies between 1000 to 1020 hPa during Garmesh winds.
Usually, there are low values for horizontal visibility along with low pressure system, but at the beginning of Garmesh wind, horizontal visibility increases and then at the end of this phenomenon horizontal visibility decreases. In 23% of cases during the Garmesh wind, the sky is clear and in 43% of cases the sky is slightly cloudy (2.8 or less). In 13% of cases, Altocumulus cloud type 4 has been seen with Garmesh wind phenomenon.
4.

The results showed a jump in the number of hydro-climatic variables such as temperature, relative humidity, horizontal visibility, wind direction and wind velocity when Garmesh wind occurs in Rasht. The mean No. of days with Garmesh wind is 16.5 days during the year. In more than 91% of cases the wind speed is less than 3.6 m/s, but during Garmesh wind, the wind speed in 69% of cases is between 2.1 and 8.8 m/s. Normally the average relative humidity is 82% in Rasht, but during Garmesh wind, it decreases to 34%. In some cases, in less than 3 hours during Garmesh wind, temperature increases by 20 degrees Celsius or decreases on the contrary. Normally low horizontal visibility is along with low pressure system. At the start of Garmesh wind, horizontal visibility decreases and at the end of it, horizontal visibility increases.

Mountain systems have an important role on meteorological variations. Different components of the mountain affect the atmospheric parameters and have essential role in atmosphereic circulation. Garmesh wind is one of the most well-known phenomena that are related to mountain systems. In this research, mechanism of garmesh wind are identified using database of garmesh wind in the last 29 years and using remote sensing technology from 2005 to 2010.
To survey the Synoptic and dynamic conditions of atmospheric patterns in the Garmesh wind’s events in the region, SCDATA of several synoptic stations in Gilan province, including Rasht, Bandar Anzali, Astara and Jirandeh are used which had continuous long-term data in 1982-2010period After Identification of days with Garmesh wind, daily images of Modis sensor of terra and aqua satellites in visible band and 7-2-1 band are monitored for checking the cloudiness on the both sides (southern and northern slops) of Alborz mountains and data of Jirande station in southern slop of Alborz mountains are used for detecting atmospheric phenomena like precipitation and snowfall. Also for studying the synoptic and dynamic pattern of this phenomena, reanalysis data from NCEP/NCAR were used.
In this research, Based on the presence or absence of the atmospheric phenomenon (like rainfall and snowfall), three categories were identified. In the first category, Garmesh winds were happened in clear sky conditions and without any atmospheric phenomena on both side of mountain’s slope. In the second category, only cloudiness was seen at the time of the Garmesh wind. In the third category, precipitations (in this research, snowfall) were seen in southern slope of Alborz Mountains.
Statistical analysis of Garmesh wind in central plains of Gilan
Totally, Occurrence of Garmesh wind was 479 days in Rasht, during 1982-2010. The frequency of occurrence of this phenomena was in January, February, November and December and rarely, in September and June. Clouds that observed in the time of Garmesh wind were: Altocumulus (type 4), Cirrus, CirroCumulus.
Patterns of Garmesh wind mechanisms on western half of Alborz Mountain:B1. Garmesh wind without any phenomena
This category includes11 cases of total 47 studied cases. 29 January 2008 is an example of clear sky condition in the time of Garmesh wind. In this pattern, in the surface zonal extension of Mediterranean dynamical low pressure’s contours from west of Caspian to Gilan plain and at the same time formation of cold high pressure cell on Zagros mountains caused strong pressure gradient on southern coastal zone of Caspian Sea, As it led to the the increase of wind velocity in Rasht airport synoptic station from 11 kilometer per hour in 00 UTC to 36 kilometer per hour in 12 UTC. Dominance of warm core on southern Caspian versus dominance of cold surface air on Iran Plateau indicates adiabatic warming in northern slope of Alborz Mountains.
B2. Garmesh wind with cloudiness
This category includes 34 cases of total 47 studied cases. Free of air mass’s patterns in the surface and conditions of atmospheric flows in low-troposphere that are similar to previous category, transition of height trough in mid-troposphere and high-troposphere can be name variant component verses previous category.
B3. Garmesh wind and precipitation (snowfall)
This category includes 2 cases of total 47 studied cases. At the same time, surface high pressure was on Iran Plateau and low pressure system was on Caspian Sea and also Gilan providence that caused the formation of Northerly stream and west-east stream to southern coastal zone of Caspian Sea and backward of Alborz Mountains like other patterns, snowfall occurred on southern slope of Alborz Mountains. Strong southern and south-western stream and strong positive vorticity on southern slope of Alborz Mountains by deep height trough in low-troposphere has an important role on intensification of vertical motions on lee ward of Alborz Mountains.
Garmesh wind is an atmospheric phenomenon that occurs as a result of interaction between atmospheric systems in synoptic scale and topography on back ward of mountain. In the other words, existence of Alborz Mountain’s as a great wall has an important role in the interaction between synoptic systems and formation of Garmesh wind.
Formation of Garmesh wind phenomena in Gilan province, is affected by extension of Siberian high pressure’s counters and sub-tropical high pressure on central of Iran Plateau and also existence of advection of pressure’s counter like sub-polar low pressure and or the Mediterranean Sea on north of Alborz mountains are required. Without any notification to origin of air masses, three categories has been observed based on existence or absence of Phenomena (in this research, sowfall).
In 700 and 500 hPa, Geopotential height patterns and relative vorticity field indicate that in the first category, wide parts of Iran is affected by high height and negative vortisity like low troposphere, during peak hours the wind. But in the second and third category (specially in third category ) existence of upper trough and easterly extension of trough caused to reduction of height and formation of strong positive vorticity in upper level and all over of air column in both south and north slopes of Alborz mountains.

Wind is one of the important meteorological parameters which have an extensive application in environmental studies. The winds have various spatial and temporal scales regarding to their characteristics and structures. Sistan wind as an outstanding low level flow in eastern Iran is playing an important role to creation of local and regional climatic features. The Sistan wind initiates and ends with an abrupt change in wind speed and wind direction which mostly related to a regional scale atmospheric circulation pattern. Study Area: The Sistan area is located at the tail end of a large closed inland basin (Fig. 1)، in one of the driest regions of the world (Smith، 1974). The area has very varied climatic conditions. The annual precipitation in the lower Sistan basin is about 50 mm. The Helmand river plays a major role in the Sistan region by draining the snowmelt waters from the mountains of the southern Hindu Kush. The basin has no outlet and receives drainage from an area of about 335،000 sq km. Its floor occupies about a third of this area and lies at elevations that range from 500 to 900 m.، the west end of the Hindu Kush، with peaks more than 4000 m a. s. l.، borders the basin on the north. Mountains as much as 2000 m high border the basin on the west، south and east. The climate of this area is arid. Mean monthly low temperatures are near 5°C، and mean high monthly temperatures are near (35°C).

This research aims to clarify the onset and the withdrawal dates of Sistan wind by using a change point approach. The meteorological dataset، i. e. surface wind at 10 m above ground level (agl)، was obtained from the Zabol meteorological station، located well within Sistan basin and in close proximity (~10 km) from the Hamoun lakes. The dataset corresponds to 3-hrs and/or daily-averaged observations covering the whole period 1972-2012 with specific emphasis on wind velocity and wind direction. Three most popular change point techniques including Pettitt، SNHT and Buishand were applied to estimate the onset and withdrawal dates of Sistan wind during the whole period of the time. All three techniques are used wind velocity time series to clarify the specific time for each year. Also، the wind direction time series were used to confirm the results which obtained by change point techniques.

The result indicates that the wind over the Sistan basin experiences two types of abrupt changes during the warm period of the year. The first type of abrupt change is related to the eastward movement of synoptic systems originated from extra-tropics which can affect the region for a short term (i. e. for a couple of days). In contrast، the second type of the abrupt change can recognized as a sign of the onset and withdrawal of Sistan wind over eastern Iran. In the beginning of summer، when the wind over Sistan basin suddenly changes from an irregular and low intensity wind to a stable and strong northwesterly wind، one can suppose that the onset of Sistan wind is occurred. On the other hand، the withdrawal of Sistan wind is related to an abrupt change in direction and the intensity of wind where the stable and strong northwesterly wind replaces by an irregular and low intensity wind over the Sistan basin only during a few days at the end of warm period of the year.

The results indicate that the Pettitt is the most reliable method among three change point techniques، regarding to estimation of onset and withdrawal dates of the Sistan wind. The Sistan wind is initiated on 122nd Julian day (May 2)، and is ended on 287th Julian day (October 14)، on the base of Pettitt method. Therefore، the average duration of Sistan wind blowing is about 165 days in the year which is apparently longer than the duration which former researchers has been estimated. The results also indicate that the inter-annual variations of Sistan wind intensity are significantly high. Also، it should note that، there is no any significant trend in the behavior of Sistan wind، (i. e. onset، withdrawal and wind blowing duration)، when the wind velocity and direction of Sistan wind is analyzed. It should also conclude that the inter-annual variations of wind velocity and its onset and withdrawal times over Sistan basin are mostly related to the variation of regional to large scale atmospheric circulation over southwest Asia.

The lack of sediment gauging stations in the process of wind erosion، caused of estimate of sediment be process of necessary and important. Artificial neural networks can be used as an efficient and effective of tool to estimate and simulate sediments. In this paper two model multi-layer perceptron neural networks and radial neural network was used to estimate the amount of sediment in Korsya of Darab city. The simulations were performed with two methods common artificial neural network Initially، the sediment was sampled with sediment traps afterward by climatic factors such as average wind speed، evaporation، precipitation، relative humidity، minimum temperature، maximum temperature، average temperature and Percentage of vegetation، respectively، as the dependent variable and independent input to the model was chosen to simulate the sediment. The Results of the performance model show that MLP neural network (feedforward Back propagation algorithm) with learning technique of Calibrated dual gradient Compared to radial Neural Network Respectively with coefficient of determination. 95، Roots mean square error. 02 and coefficient of determination. 90، Roots mean square error. 40 for estimate of wind deposits were the higher efficiency and accurate. Course، it should be noted that an important advantage of the artificial neural network Multilayer Perceptron to Neural Network Radial is more flexibility.

Climate is a multidimensional, interacted- dynamic system. This characteristic tends to be variety effects-consequences in time and space scale. One of climatic characteristic that can exhibits climate effects-consequences is dry and wet winds. The continuity of dry and wet winds has a great importance from the view point of severity and frequency of precipitation occurrences. Since these features show the rainy climatic characteristics and affect on the other climatic parameters, has attracted the attention of some climatologists to itself.In the present research, based on the observations of daily precipitation in Zanjan city during 1961-2006 and based on non-parametric technique, the trends of maximum mean and continuation of dry-wet winds were estimated for each year. The results of this research showed that the study indices at each of yearly and monthly time scales had no meaningful trend.Low precipitations had a meaningful decreasing trend and with respect to the lack of trend in occurrence times, the number of these precipitations and consequently dry and wet winds were constant. Based on the study results, it was cleared that four seasons means (June, July, August and September) has no precipitation. Possible precipitation in these four months, are the results of local-accidental and irregular events. So these four said months are considered as the dry seasons of Zanjan city. The most frequent of precipitations are related to April and May, therefore spring has the most precipitation.

The study of bioclimatic comfort can help the process of planning and development in different geographic regions. There is a direct relation between human health and comfort in physical environment with the climatic conditions of the regions. Nowadays, human bioclimatic studies are considered as the base for most urban, civil, settlement, architect, and tourism planning. The present study has evaluated climatic comfort of Illam city based on Terjung, Beaker, Neurotic Pressure, Olgay and Chellwind bioclimatic indices using synoptic whether statistics of Illam station during 1986-2008. Findings show that there is a wide range of warm to cold bioclimatic conditions throughout the year. Among the applied methods, Terjung method operated better than others to show the bioclimatic conditions. Assessing the human comfort of bioclimatic conditions of Illam during different months of year can be considered as a base for different development plans of the city.