نشریه پژوهش های اقلیم شناسی
پیاپی 41 (بهار 1399)

The potential of each country's water resources is more and more pressed by population growth and the need for food and drink every day, while agriculture with the highest water use (83%) and its relation to soil, water, plant and climate, and climate impact Reducing the capacity of renewable water resources and increasing agricultural consumption will impose more pressure on each day and threaten the country's water potential. In this study, to study the persistence of surface water and groundwater in the Najafabad area, three indicators of water intake ratio Renewable (C / RW), Available Water (WAI) and Water Tension (WSI) have been used to check the quantitative balance of water resources in the Najafabad area. According to the results, the proportion of water consumed to renewable water in Najafabad region was 0.87, which according to the standard table of indicators showed a sign of balance imbalance and exposure in critical area. Also, the available water index in this area is in the range of 1- 1, which is within the range of Najafabad about -0.3, indicating an imbalance in supply and demand. Finally, the water stress index in this range was estimated at 1.27, indicating severe water stress in the range. The results of all indicators indicate that the current development in the Najafabad area caused an imbalance of water resources in this area, which would result in the aquifer's instability in the future. In this regard, the achievement of the conditions for the sustainable development of water resources will be based on restoring the balance and achieving optimal water use in all sectors of consumption, especially in the agricultural sectornot only has not been reduced the use of underground water resources, but the need for renewable water sources has increased as a consequence of which the withdrawal of these resources has increased. Although the amount of renewable water in each watershed is fixed and constant, the time and space distribution of the amount of renewable water is completely variable and is not proportional to the distribution of population and water needs of human societies. While harvesting and consuming of these limited and almost constant sources of water due to population growth is steadily increasing (2012). (Birkenesse called shortage of fresh water as demand for physical water shortage and found that water supply shortages were the result of poor supply, water demand, or could be of different origin, such as climate change and diversification, underground water extraction, construction and population growth The results of all of the world's water scarcity analyzes indicate that a large part of the world's population will be affected by dehydration in the next few decades (Rijsbermansberman et al., 2006). As the years and decades In the near future, water per capita has increased sharply, due to the increase in welfare and, consequently, the diversification of water needs (Somoni et al. 81). In Iran, due to population growth, the growth of the agricultural sector and the expansion of urbanization, the extraction of groundwater resources has exceeded the limit in most areas, and the final cost of providing additional water and pollution of water resources has accelerated. (Ministry of Energy, 2006). On the other hand, the agricultural sector has not had a satisfactory performance in comparison with other leading countries, not only in rain fed areas, but also in soils and modern networks, which receive adequate water. The survival of Iranian agriculture is heavily dependent on irrigation water, and if we consider the future and the shortage of water resources in the future and its impact on the country's agricultural development, Certainly, with the current trend of water resource management, agriculture will be faced with a large damages (the good and Khaled, 1382). In development of Isfahan province, water is the most important and at the same time the most limiting factor. On the one hand, the sharp decline in water resources caused by unauthorized exploitation and, on the other hand, the sharp increase in demand in different sectors of consumption has led to severe water stress and unbalanced consumers.Therefore, in order to preserve aquifers, assessment of their sustainability is necessary based on the indicators of water resources sustainability against future events and events. In this regard, world-class studies have been conducted to solve the challenges using water resource sustainability indicators. For example (Jingwei Li, 2017), the use of WSI water stress index to increase legal concerns regarding the impact of shortages Water has been explored on the sustainable development of dryland lands in northern China. In this research, this indicator was calculated for 2003 and 2014, and then the difference between these indicators for the years mentioned above has been evaluated with a dynamic view. Finally, the water stress dynamics in three levels of catchment area, urban areas and the entire study area, the results showed that areas with higher water stress should be the priority of effective measures. (Kong et.al., 20011) successfully applied the WSI index to assess the sustainability of water resources in the Geum Basin in South Korea.

The urban heat islands are hazardous to the health of urban residence, their activities, lifestyle and the quality of their life. This phenomenon occurs, in particular, as a result of the urbanization process, land use/cover changes and the rate of impervious surface coverage. Since early 1970s, the urban heat islands have been studied using remotely sensed data; because this approach is cheaper, more efficient and faster than traditional techniques to detect the heat islands as well as to examine the severity of them. However, less attention has been paid on the relationship between urban heat island (UHI) and impervious surface patterns. Therefore, this work aims to study UHI based on the analysis of land-surface temperature (LST) and impervious surface patterns (ISP) retrieved from remote sensing data covering a 29-year period.

In this research, the city of Rasht as the center of Gilan province, Iran, is taken as the study area. Rasht is the largest city in the South Cost of Caspian Sea. In order to study the relationship between UHI and both LST and ISP, the time series of Landsat-5 / Thematic Mapper (TM) sensor, Landsat-7 / Enhanced Thematic Mapper Plus (ETM+) sensor and Landsat-8 / Operational Land Imager (OLI) sensor as well as Thermal Infrared Sensors (TIRS) of Landsat-8 from 1989 to 2018 have been utilized. Then preprocessing of satellite images including geometric correction and image referencing, radiometric corrections, and atmospheric corrections were applied on the images prior to other image processing steps. Then, by using the Normalized Difference Impervious Surface Index (NDISI), the impervious urban surfaces classified. The Otsu thresholding method was employed to determine a threshold value for the separation between impenetrable surfaces (constructed) and permeable surfaces (not constructed) in each utilized image. The classification accuracy was evaluated considering 300 randomly selected points. After mapping land use change over the years from 1989 to 2018, the future land use changes in the impenetrable urban areas were simulated to the year 2036 using CA-Markov model. Finally, the relationship between urban impermeable coverage and thermal island intensity changes were studied.

The results of this study showed an overall accuracy of 84.5 percent to 90 percent for impervious surface classification using the NDISI method and the Otsu threshold. The results of the CA-Markov's model also indicate overall accuracy of 83.6 percent for impervious surface prediction. The difference in CA-Markov's prediction map with a reality map was less than 8 percent; hence, CA-Markov can be considered as reliable method in predicting land-use change in Rasht. Moreover, the obvious peaks and valleys values can be seen in the histogram of NDISI index; therefore, the determined threshold has well been able to classify the impervious surface. The spatio-temporal change of impervious surface showed an increasing trend, more than double over the city, from 1989 to 2018. Moreover, the prediction results of CA-Markov model indicates that the impervious area would double again within the next 18 years. The highest levels of urban impervious are located at an average distance of 5,000 meters from the city center, which has had an important impact on the thermal island's severity. The relationship between impervious surface and thermal islands showed a positive and strong correlation coefficient between 0.69 and 0.89 for various years. Furthermore, the pattern of urban impervious surface growth and thermal island intensity changes coincided with each other. The spatio-temporal change of UHI showed that the spatial extent of heat islands in Rasht was increasing with time and the temporal trend of UHI was also increased. Moreover, the trend of heat island changes illustrated that area of regions with very low and low temperature were decreased. On the other hand, the coverage of regions with medium, high and very high temperature were increased.

The time series of Landsat images along with spectral indices are the convenient dataset to classify the impervious surface of the city with proper accuracy. The produced land cover map can also be employed as a proper input data for prediction models. The spatio-temporal analysis of urban heat island in Rasht illustrated that the urban heat intensity was increased. This trend was because of increasing rate of impervious urban surface. Ultimately, in order to control the heat island, it is required to prevent the unplanned urban construction and developments.

Although precipitation is very important in various aspects of human life but sometimes occurring the heavy precipitations suddenly or in relatively short time have unpleasant effects on human and his life environment. So, more accurate identification of atmosphere circulation patterns mechanism which is effective in occurring this kind precipitations is very important, especially because in recent decades, the climate changes have been resulted in changing the atmosphere patterns and happening climatic anomalies in the most of world regions. At the same time, identification and synoptic and dynamic analysis the systems producing such precipitations can help to forewarning and preparing for encountering them. Therefore, the first step for better use of a region precipitation is sufficient identifying the synoptic and dynamic conditions occurring precipitation in the region. With this approach, this research try to identification circulation patterns producing heavy precipitations and synoptic and dynamic analysis them.

In this research, for identification and analysis the synoptic and dynamic patterns of heavy precipitations on Yasouj, by using environment- circulation approach, the daily precipitation data from 21.3.1987 to 20.3.2014 have been received. On the basis of 95th centile base index, 82 precipitations selected as heavy precipitations among rainfall days. Then, using cluster analysis by “Ward” method four atmosphere thickness patterns between 500-1000 hpa levels have identified. Then, for analysis the precipitations in every thickness pattern, the representative day defined on the basis of correlation coefficient with 95% threshold and in these days, the maps of sea level pressure, atmosphere thickness, frontogenesis for 500 and 1000 hpa levels and moisture flux convergence have been drawn and analyzed for 925 and 1000 hpa levels.

The identified circulation patterns indicated that occurring heavy precipitations on Yasouj resulting from forming and trough settlement on eastern Mediterranean and immigrant low pressures together with the front that flow to Iran. The atmosphere thickness maps explain that falling the cold air from high latitude and encountering with influential moist and warm air from low latitude especially from Persian Gulf and Red Sea have been created the strong baroclinicity region on Iran which play important role in occurring heavy precipitations. Analysis of the frontogenesis function of representative day for atmosphere thickness patterns indicate existing the frontogenesis cores on Yasouj region, too. Analysis the moisture flux convergence function maps in Yasouj indicate existing the maximum core of moisture aggregation in this region. For this reason, cyclonic movement from eastern Mediterranean, Arabian Peninsula and Persian Gulf import the humidity from eastern Mediterranean, Red Sea and Persian Gulf in to studied region.

The results of this research indicate the relatively deep trough settlement with nearly northern- southern axis in eastern Mediterranean between Mediterranean Sea and Aral Lake in the eastern Caspian Sea, which result in occurring heavy precipitations in studied region. Analysis the frontogenesis patterns on Yasouj and it’s around regions, such as Red Sea and Arabian Peninsula. Analysis the effective moisture resources in occurring heavy precipitations of Yasouj indicate the importance and role of eastern Mediterranean, Red Sea and Persian Gulf in supplying the moisture of these precipitations too.

Past climate and environmental change is of longstanding and fundamental interest to archaeologists. a number of recent syntheses have examined the role of climate change and environmental modiication in understanding the rise, spread, and in some instances collapse of early complex societies. One of the most pronounced and abrupt climatic events of the Holocene occurred around 8200 years ago (Alley et al., 1997). Numerous proxy data as well as climate models indicate colder and more arid conditions throughout the Northern Hemisphere (Alley and Agustsdottir, 2005). The effects of the 8.2 ka event on societies in Southwest Asia are under discussion, and interpretations vary from collapse and abandonment of sites, large-scale migration, to continuation of occupation (Flohr et al. 2016). in an Iranian context, various scholars have highlighted the role of human-environment interactions in the expansion of Neolithic communities (e.g. Hole 1994, 1998). Also the eastward expansion of the Neolithic, into Central and Eastern Iran, and especially in the Southern Zagros province of Fars, may be contemporaneous with the 8.2 ka event. In the Southern Zagros, cultural changes (the more mobile ‘Mushki’ during the event, and ‘Jari’ farming villages after) may also be associated with the 8.2 ka event (Nishiaki, 2010, Weeks, 2013) but dates from other sites are crucially needed to ascertain if the difference between these two sites is generally applicable to the region. Here we review proxy evidence of climatic and environmental conditions to provide an independent background to societal development in Iran during the seventh millennium BC.

The materials of this study are the result of excavations in the Hormangan site and also the use of publications by other researchers in this field. An attempt is made to analyze the role of environmental factors on the formation of human settlements in the second half of the seventh millennium BC based on cultural materials obtained from excavation. The site is located on the west of Jeshnian village, situated on the southern basin of Bavanat River, on eastern Fars province in Iran. which was identified in 2015 and then it was excavated  2016. Three trenches were dug for excavation, During excavations in these trenches, two phases of the settlement were identified; in the old phase, the lack of architecture, as well as the existence of multiple ovens and ash dispersion, indicate a lack of sedentary and possibly nomadism. On these deposits, a stratiform architectural structure, including several rooms and spaces, was identified that walls were coated. According to the survey, one coal sample from an older phase showed a date about 6373-6236 B.C and coal samples that were taken from a later phase show a date between 6000-6200 B.C. According to the excavation results and C14 dating, it can be concluded that the Hormangan region had been occupied seasonally in about 6450/6350 B.C and later after 6200 B.C, had been occupied permanently by inhabitants with the same culture.

The earliest evidence agricultural village comes from Pre-Pottery Neolithic (PPN) layers of Tepe Rahamat Abad, which is dated to late 8th or early 7th millennium BC (Azizi Kharanaghi et al. 2014). Cultivation and herding of goats/sheep had already begun in this period, however, Pottery Neolithic (PN) farmers came back to rely on hunting to large extent in following Mushki phase. Cultural findings indicate complex of social-economic changes from late half Seventh in Fars ragion. The stereography and architectural remains as well as geometrical stone tools, wild animals’ bones, Gazelle and equid bones, are all indicating the existence of a seasonal settlement based on hunting in Hormangan Site and Tol-e Mushki. These artifacts indicate tendency toward local stone mines whereas exploitation of obsidian is very limited. Regarding technology of stone tools, more extensive exploitation of geometrical stone tools may reflects significance of hunting at Hormangan Site and Mushki. The changes in subsistence are also visible on the stone tools, like the increase in geometric microlithes with the society’s transition into hunting style of livelihood. The emergence of geometrical arrows is not a local phenomenon, yet it is widespread all over the Middle East and it needs a trans-regional approach, considering global climatic factors (Nishiaki et al. 2015). bulk of equid bones from the site have been identified as onager, Equus hemionus, as well as Tal-e Mushki. The large number of gazelle bones (Gazella cf. subgutturosa; goitered gazelle) has been found at Hormangan, indicating that hunting activity on the dry- steppe environment must have played an important role for the habitants. Biometric data suggests that most of goat bones belong to domestic (Capra hircus). Considering that it had already been introduced to this region in early 7th millennium BC, the absence of sheep bone in Hormangan assemblage seems to be curious (Arai, unpublished). One explanation for the exclusive reliance on goat may attribute it to climatic reason: adaptation to drier condition during the 8.2 ka. Therefore, due to the changes in livelihoods and the absolute dates of the Hormangan and the Mushki(Nishiaki 2010), it issue could be resualt of climate change of 8.2 ka. Probably Neolithic communities of Fars, have adopted new strategies for livelihood such as hunting and gathering food instead of farming, That Hormangan site was provider a part of these livelihoods needs. This unclear economic phenomenon has been stopped at the beginning of the sixth millennium BC, when the economy based on agriculture was fully integrated. So, given the prevalence of Das blades for reaping as well as the reduction of wildlife and hunting in the 6th millennium, Jeri period can be considered as an economic reliant on agriculture.

Archaeological excavations in Fars, illustrate the consequences of climate change on the social and economic structures. It seems that due to climate change in the middle of the seventh millennium BCE and its improvement in 6200 BC, we are witnessing changes in subsistence patterns of this period. The cultural materials of the Mushki and Hormangan sites show that the Neolithic people of Fars in this period to adapt to the new conditions choose changes in subsistence and settlement patterns. During this period, due to the cold weather and agricultural constraints, the people to provide part of their subsistence needs, change their life based on agriculture and turn to the social structure based on hunting.

Study of the wind field of the meteorological Stations to detect the dust and salt prone storm and soil erosion was the concern of the meteorologists, natural researchers and agro meteorologists. To show the wind power in sand storm creation and sand displacement; the researchers used the wind rose, storm rose and sand rose which is a simple and efficient method to detect the wind's role on dust storm. Many Iranian researchers; used the Friberger,s  method  in which Ahmadi and et el(2001and 2002) are the frontiers who used the dust rose from 1994 to 2013 over many Iranian provinces. In this study the power of wind in dust and salt displacement is discussed in Orumiya Lake basin. The aim of this research is detection of the potential annual sand and salt transfer by wind around Ormia Lake due to its drying. To do that, the continuous three hourly wind data of the Oromia, Mahabad, Salmas and Piranshahr meteorological stations in west Azarbaijan and Bonab, Maragheh, and Tabriz stations from their stablishment till the end of 2014 in east Azarbaijan are statistically analyzed and then the diagrams of the wind rose, storm rose and sand rose are depicted by suitable soft wares. 

In this study the wind speed and direction data of the Met. stations around the Orumiya Lake are received  from Iranian Meteorological Organization(from starting activity up to 2014). Regarding the adequate historical length and quality of data, the Tabriz, Orumiye, Bonab, Maragheh, Piranshahr and Mahabad in Orumiye Lake basin are selected as the representative stations of the area. The monthly, seasonal and annual wind roses of these stations are depicted and then analyzed using the WRPLOT software. Since the frequencies of calm winds was high, they are deleted and then using the threshold wind speed of 6m/s, the storm roses are depicted and then analyzed. Applying the Friberger method, the sand rose software was designed and after depicting the monthly, seasonal and annual sand rose, the wind sand displacement ability in these stations are analyzed.   

Study the sand rose figures in meteorological stations around the Orumiya Lake shows that the sand displacement in Tabriz is strong from March to August, moderate in February, September, October and November and weak in March and April. In Orumiya it is moderate in March and April and feeble in other months. In Maragheh dust displacement power in July and August is very strong ,in March, June and September it is strong; in September it is feeble an in other months is moderate. In Bonab the sand displacement power is moderate from February to August and in other months it is feeble. In Mahabad the sand displacement power is very strong in January till April and in October till December it is strong, in June and September it is moderate and in other months it is feeble. In Piranshahr it is very strong from January till April, strong in September till December, moderate in June and feeble in other months. IN Salms the sand displacement power is very strong in March and April, strong in May till July, feeble in November and December and it is moderate in other months.    

The results of the study detected the potential of sand and salt displacement in the east and west Azarbaijan provinces.  Regarding the position of the different stations around the salt and dust basin of the Ormiya Lake and the net annual transfer of dust and sand, it can be concluded that Mahabad, Maragheh, Bonab, and Tabriz cities are more under danger of sand and salt transfer and their out coming air and soil pollutions. In other stations either due to topographical blocking or lack of sand and salt sources, the probability of air and soil pollution lowers.

Investigating the behavior of atmospheric circulation during different periods can broaden our knowledge of large-scale changes in the climate. Based on recent Intergovernmental Panel on Climate Change assessments, the increase in greenhouse gases and other human activities will lead to the warming of the troposphere, atmosphere temperature drop, thickening of tropopause, less atmospheric circulation activity in the tropics, migration of atmospheric disturbance from poles toward middle latitudes, increasing of precipitation in tropical areas, etc. Since the middle-level atmosphere has the greatest effect on the occurrence of atmospheric phenomena in the surface of the earth, many studies have investigated the temporal and spatial changes of this level across the world. Most of these studies confirm the changes in the geopotential height anomalies at 500 hPa in some areas and identify them useful in forecasting temperature and precipitation variables, as well as phenomena such as flood and frost.

This study explored changes at 500 hPa using daily data of the US National Center for Atmospheric Research for the period from 1972 to 2015. Using cluster analysis, the behavioral patterns at 500 hPa were analyzed for a 44-year period, and the Mann-Kendall graphical test was used to identify the trend of change and its significance.

The clustering results show two main long-term patterns in middle-level atmosphere. In the first group with more days, the domination of the Mediterranean high landing over a large part of the study area and the its penetration toward Iran is noteworthy, whereas in the second group with far less days, there is the dominance of the sub-tropical high with one of its bulges over a vast area of Iran, which leads to sustainability and hot air in the warm days of the year. The analysis of the trend of changes in the middle-level atmosphere height using the Mann-Kendall method indicates significant changes in the study area during the period; with the significant increase being recorded for the last decade (after 2000) during the annual period and in the summer months of July and August. These results also showed no significant trends in the autumn, especially in October and November, either individually or collectively.

One of the results of climate change is the change in atmospheric patterns such as sea level pressure and the height of different layers of the atmosphere. The results show that the middle-level atmosphere height, which is a key components in atmospheric disturbances and precipitation, or lack thereof, especially in regions such as Iran, has experienced increase in various periods and throughout the statistical period under study. This height increase can lead to a decrease in rainfall and an increase in the duration and severity of droughts in these areas. On the other hand, occurrence of extreme temperature and precipitation anomalies in these areas is another result of this height increase. A suitable solution for dealing with its adverse effects is the optimal management of water resources.

Wireless sensor networks are new generation of networks which consists of a large number of sensor nodes distributed in environment and each follows special porpuse independently with cooperation of other nodes. where as data transmission is one of the most important operation in wireless sensor networks, so reduction of data in these networks causes reduction in energy consumption and accordingly increase networks’ lifetime. The frequently used methods to reduce the amount of data transmissions in WSNs for power saving include the data aggregation , and the data prediction and filtering. On the other hand, usage of suitable routing protocols has important role in protection of nods, energy consumption. In this research it was tried to reduce energy consumption in whole of the network by some of classification techniques and hierarchical routing protocols. these experiences was done on sensor data of automatic weather station of kashan . The results show by appling support vector machine technique with polynomial kernel of 3 degree, and with adjustment coefficient of 10 in the proposed sensor network, accurately about %92 of data is detected in 2 second, and then by filtering outliers and redundant data as well as sending new and correct data, helped to save energy and increase of network lifetime.

Wireless sensor networks consist of a large number of sensor nodes distributed in environment randomly.so location of these nodes isn,t determined or clear that cause to leave them in dangerous or inaccessible places. on the other hand , every sensor nodes operate independently and also are able of cooperating with other sensor nodes to achieve the purpose. in wireless sensor networks , the energy issue and optimum usage is one of the most important challenges encounter with these networks , because wireless sensor nodes are usually feed with battery and network,s lifetime depends on battery lifetime. differend methods have been proposed for wireless sensor networks that the most importants are: decrease of data transmission,usage of routing protocols, clustering in wireless sensor networks .a suitable method and solution for encountering with energy depends on variety of network and usage. Data transmission in wireless sensor networks has been identified as one of the most energy consumption operations [1],as well battery lifetime decrease considerably by data transmission in sensor node, one way to reduce data transmission ,is outlier,s detection, in order to prevent their transmission in network. In wireless sensor networks,data that digressed from normal patterns,have been detected as outlier and they are important because they show significant abnormalcy. after detecting outliers depending on system decision, outliers can be removed or saved in sensor memory to evaluate more and totally prevent their transmission in network which decrease energy consumption in the whole network. on the other hand , if distance of sensor nodes is small when an event occurs in a region , it will be sense by several nodes and they send the same massage. also in many monitoring applications, wireless sensor network like aerology that sensors sense data from environment sequentially, since environmental data like temperature and other parameters change slowly it may be similar sequential senses of one node and cause sending redundant data , that in addition to aggregation in network, causes great decrease of energy. so by preventing creation of redundant data of filtering can decrease energy consumption in the whole network . Purpose of this research , is usage of common classification techniques and acquiring optimal values for its parameters to form a model to detect outlier with high speed and accuracy. in this research was tried to reduce energy consumption in the whole network by detecting sensed outliers and redundant data by sensors and preventing their transmission in wireless sensor network that use backboneformation for multi-hop transmission. In second part history of research will be reviewed. in third part program and necessary algorithms will be checked. in forth part proposed structure of wireless sensor network will be introduced. in fifth and sixth parts evaluation and results will be mentioned as well as next activities in order .

Recently , most of wireless sensor networks in real world were used to collecting valuable raw data. in analizing these data the main step is recognization and remove of abnormal data ( outlier , noise , …..) in [2] outline of ways of outliers, detection . SVM is one of the machine learning techniques. Separating normal data from abnormal data has been introduced in [3] by SVM technique . Outlier detection techniques based on one-class support vector machine use spatial and temporal correlations between sensor data for identifying outliers , but this technique for large scale training samples , take more spatial and temporal overhead to process and optimize . In [4] a technique was defined based on bayesian for detection of local outliers in data flow sensor. according to what was mentioned in [5] , we can use combination of some techniques for outlier,s detection. for example, combination of k-nearest neighbor and SVM methods proposed for outliers detection that use k-nearest method for reducing scale of training sample. this method can shorten training time and optimize time however for data in large scale, k-nearest neighbor has considerable temporal and spatial consumption. or in [6] combination of SVM and fisher discriminant ratio (FDR) proposed for redundant data detection that at first distributed clustering is applied on sensor data, then by FDR (fisher discriminant ratio) there is boundaries for discriminant between clustering data and scattered data in clusters. the clustered data are regarded as redundant data and will be removed. thus the number of data samples for training SVM is greatly reduced however classification accuracies in this method is a little lower than the traditional incremental SVM training methods. in [7] proposed combinational technique of k-nearest neighbor and clustering to calculate interesting events for outliers detection. in [8] three techinques for outlier detection including a machine learning technique,a principal component analysis - based methodology and an univariate statistics-based approach were studied in wireless sensor networks.

Global observation in recent years has shown remarkable changes in the behavior and characteristics of extreme atmospheric phenomena. Geographic location, topography and variety in the occurrence of atmospheric systems causes a number of these phenomena in the Mazandaran province every year. In recent years, the number and severity of extreme events in the province has increased. Therefore, it is necessary to identify temporal and spatial distributions of the mentioned hazards in order to adapt to these hazards and reduce the effects of extreme phenomena.  

Daily temperature and precipitation data were used in the 15 stations of the Mazandaran province in order to identify the temporal and spatial distribution of the extreme parameters. To ensure the quality of them, homogeneity, adequacy of data and recovering and estimation of lost data implemented. Data homogeneity was investigated by Run-Test method. In this method, each of the series values is compared with the mean of the data. The parameter z is computed (relation 1). If its magnitude is greater than 1.96, the data is considered at 95% heterogeneous confidence level here r, m and n are the total number of sequences, the number of values smaller than the mean and   the number of values greater than the mean, respectively. In the study of sufficient number of years for stations, the Makus relationship (relation 2) was determined. (2)   where y, t and R are the minimum number of required years, the Student’s t test value at the 90% confidence level and the ratio of y value based on 100 year return interval to y value based on a 2 year return interval. The minimum statistical years are 10 years old and a 15-year statistical period (2017-2003) selected in the present study. To study the trend of changes in extreme indices, Spearman nonparametric test was used in the Babolsar and Ramsar stations with long-term data (1971-2017). This method uses data’s rank instead of the actual values. Data are arranged in increments and ranks from 1 to n. If the Spearman correlation coefficient () (Equation 3) was greater than 1.96, the assumption of the trend in the data series was accepted, otherwise, the data series would be considered without trend. Here, for a sample of size n, i and  are the historical rankings in order of occurrence and the ordered historical rankings are in incremental order. The temporal and spatial frequency of  twenty extreme indices from the expert team ETCCDM[1]  for temperature and precipitation were determined using Rclimdex software.  

Long-term trend of extreme indices The number of cold nights and cold days as well as the number of frost days in recent years were dropped significantly. CSDI index was decreased only in Babolsar, while the WSDI was increased significantly at both stations. The number of summer days and tropical nights has increased. The max Tmax have been increasing in Ramsar. The min Tmin was increased at both stations. DTR index was dropped significantly. Rainfall indices at either of these two coastal stations do not show a meaningful change in recent years.   Daily temperature extreme indices The maximum number of FD was in Baladeh and the maximum number of ID was in Siyahbisheh. The maximum number of SU was in Amol, Sari and Ramsar and the maximum number of TR20 was in Babolsar. The monthly max of Tmax was happened in Sari, Galougah in May, and the monthly min of Tmin was happened in Baladeh in the month January. Most of the cool days and nights and cold spell duration were in Alasht and most of the warm days and nights and warm spell duration were in Ramsar.   Precipitation indices The highest and lowest total annual precipitations were observed in Ramsar (1915.4 mm) and Kojur (449 mm), respectively. The most RX1day and RX5day were in Ramsar. The highest number of days with heavy rainfall greater than 25 mm per year was in Ramsar (21 days) and the highest number of dry periods was happened at Amir Abad station (108 courses).   Seasonal indices The max Tmax was in Sari, Galougah and Dasht-e-naz (42.6 ˚C) during spring, in Galougah (42.2 ˚C) during summer, in Galougah (42 ˚C) during autumn and in Gharakheil (34.6 ˚C) during winter. The min Tmin was in Baladeh every Season, it was 4.6 ˚C in spring, 12 ˚C in summer, 6.2 ˚C in autumn and -9.4 ˚C in winter.

In the study of trend, it was found that the warm duration index, number of summer days and tropical nights were increased significantly and the temperature difference between the daily maximum and minimum values was decreased significantly. No significant change was observed in rainfall indices at any of two stations in recent years. Investigating phenomena associated with extreme temperature indices showed that the frequency of frost days is higher in highlands, and ice days in the coastal-plain areas occur rarely. The minimum daily temperature, cold days and nights indices show a direct correlation with elevation in the province. The average of maximum temperatures and the number of warm days and nights in the east coastal zone of province are the highest and it goes down to the high and western regions of the province. Diurnal temperature range has the highest amount in the mountainous areas of the province. Therefore, the indices of maximum air temperature in the eastern parts of the province have higher values. the minimum temperature distribution is in a good agreement with topography of the region in Mazandaran province. The rainfall indices determine that the amount and severity of rainfall reduce from the west to the highlands and east of the province. So far, the largest number of days with a very heavy rainfall of more than 25 mm in the period 2003- 2017 belongs to Ramsar (351 millimeter).

The polar vortex is dominated by the dynamic of winter circulation in the lower seam, and the middle and upper parts of the windsurf, the most important feature of the weather, the presence of extreme winds at the outer edge, and low temperatures in the vortex area. In Iran, the temperature and precipitation conditions are controlled by polar water and high pressure. Whenever the axis of polar vortex from 40 to 50 degrees eastward deepens and extends to southern latitudes, the country's rainfall will be widespread and more intensive. Stack deployment in the west of the Black Sea and Eastern Europe will increase with precipitation and decline. The temperature is in the country. Determining the effect of atmospheric circulation on precipitation and temperature is one of the most important dynamical and synoptic meteorological goals. The study of the displacement of polar velocities and the strengthening and weakening of the polar waters can provide long-term predictions. In this study, using the data of the mean sea level pressure and the height of different pressure levels from 500 hPa to 010 hPa within the northern hemisphere, it was tried to use a daily rainfall data in October 2015 to investigate a flood event in the southwest region of Iran. It was analyzed with polar velocity changes. With the spread of polar fissures to southern latitudes along the lengths of 40 to 50 degrees, the establishment of a strong heap on the Black Sea, the East and the Mediterranean Sea, the presence of strong winds at the outer edge of the Dao, which leads to the capture of cold air within the vortex, Winds that bring humidity and heat from lower latitudes to Iran and the presence of tangible temperature conflicts between the western strip of Iran with higher latitudes can be deduced. Polar fence strengthening in the period from October 26 to 29, 2015 has a significant impact on rainfall increase in the studied area had.

In this research, the required data are taken from the NCEP / NCAR archive. These data are available from the CDC REANALYSIS Internet site in the form of netcdf, at a time interval of 6 hours and a 2.5-degree step along the latitude and longitude, all points on the planet from 90 to 90+ degrees latitude and zero to 357.5 degrees longitude. The data include the mean sea level pressure, temperature, geopotential elevation, daily precipitation data of western stations of the country, and wind pattern vector. Available files, each containing one-year data, are converted to text files by the ncdump command, which is one of the pcgrads executable commands. In this research, the ncread command was used in the programming language for converting data into text files, then using the average mean sea level pressure patterns, the geopotential height of the middle and upper levels of the atmosphere (500 and 050 hPa), the wind pattern vector The 200hp level, the 500hp temperature pattern, and the daily rainfall data of the western stations of the country in October 2015, examined the dynamics and dynamics of the meteorological conditions governing the precipitation system October 27-30, which resulted in flood events in the western part of Iran. To reduce the volume of content in this article, only analysis of October 28 and 29 is presented.

The study of the mean surface-to-ground and geopotential heights of different barley levels revealed that on October 27, the axis of the vortex crevices extends along the longitude of 40 to 50 degrees, and witnesses the presence of backs on the Black Sea and the East and the Mediterranean Sea. On Oct. 28, the stack and the waves are the widest. On October 29th, the nave has moved slightly toward the higher latitudes with its intensity. Considering that previous research has shown that whenever the axis of polar gravity from the southern latitudes along the longitude of 40 to 50 degrees is drawn, the precipitation rate in Iran increases and the stack is located in the east and center of Europe, The Black Sea and the East, and the center of the Mediterranean Sea, are also rising in Iran. Therefore, the results also indicate that conditions are favorable for precipitation. A wind field survey at 200 hp in October 2015 showed that at this level, a polar jet flows along the meridian to the Black Sea and the Mediterranean Sea. There is also a tidal jet in the eastern Mediterranean and the western strip of Iran. The cold weather with these currents falls into the Mediterranean Sea, and warmer low latitudes also penetrate the southern winds of the area and make the situation more conducive to creating temperature conflicts in the region. The results of the study of the temperature field at a 500 hp peak in October 2015 showed that on October 27-30, the Arctic Cooling Center covered vast areas of the poles, and the caverns of this cold air reached the southern latitudes on the Black Sea, the Mediterranean, and Siberia It has extended and influenced the country of Iran. With the spread of polar fissures to southern latitudes along the lengths of 40 to 50 degrees, the establishment of a strong heap on the Black Sea, the East and the Mediterranean Sea, the presence of strong winds at the outer edge of the Dao, which leads to the capture of cold air within the vortex, Winds that bring humidity and heat from lower latitudes to Iran and the presence of tangible temperature conflicts between the western strip of Iran with higher latitudes can be deduced. Polar fence strengthening in the period from October 26 to 29, 2015 has a significant impact on rainfall increase in the studied area had.