In this research, we are trying to determine the “beginning time” as well as the “end” of the climatic seasons; and we will focus on identifying the displacement of these dates, which is influenced by the “climate changes” and “descriptionAbstract
The purpose of this study is to investigate possible changes and displacements in Iran's climatic seasons due to climate change. To do this, temperature, relative humidity, water vapor, wind and cloud data for 36 stations were received from the Meteorological Agency over 40 years. The data were divided into two 20-year series to allow comparison. Daily temperature data for each clustering time series were determined, then by considering 7-day sequences, the beginning and end of the seasons. The designated times were tested using the Rayman model. The results of comparing the seasons in the two time series indicated that in all stations, changes in climatic seasons occurred from Insignificant to significant. Climatic seasons in Iran do not correspond to calendar seasons, and climate change, especially temperature changes in recent decades, has caused the seasons to shift and shorten and lengthen. Although the beginning and end of the seasons do not generally correspond to their calendar dates, most of the days of these seasons occur in its calendar periods. The changes that have taken place have not only affected the length of the seasons, and these shifts have also changed the quality of the natural seasons.
Keywords: Climate change, natural seasons, cluster analysis, Rayman model of the qualitative conditions” created in them, compared to the past climatic periods. “Meteorological Organization” data has been used in this research. Forty years of received data, was divided into two groups of 20. Applying SPSS, each group was divided into four stages representing each seasons. From these stages, the beginning time and the end of seasons were determined and the accuracy of the obtained dates was controlled with the comfort indicators of the Rayman model. The results of the comparison of seasons in two time series indicated that, the changes occurred in natural seasons from an almost non-existent one in all stations. Climatic seasons in Iran are not compatible with the summer season and climate change, especially the change in temperature in recent decades, has caused changes and shortening of seasons. Most of the days in these seasons occur during its monthly periods, although the beginning and end of the seasons generally do not match their calendar dates. Changes have not only affected the duration of the season, and these changes have also led to a change in the natural quality of the season.

Change in precipitation features is one of climate change outcome. Change in precipitation amount, especially in warm season, may influences climato-environmental phenomenon as well as human activity. In current research the decadal changes of monthly precipitation over the Caspian coast of Iran territory was evaluated. Accordingly, a large number of rain gauge stations (385 stations), where rainfall is measured painstakingly, have been used. these stations are under the supervision of Meteorological Organization of the country and Ministry of Energy. Since the original dataset pertaining to the precipitation prior to 1966 had noticeable missing values, and the data after 2016 were not accessible, a continuous time period from January 1966 to December 2016 was selected. From the daily precipitation of aforementioned stations contour maps were created using an ordinary Kriging method. The spatial resolution of these precipitation maps was 3 km * 3 km. Our finding showed that during the under investigation period the maximum gradient of precipitation moved from coastal parts toward mountainous area. Decrease in the area with high precipitation and increase in the low precipitation area is an other prominent decadal characteristics. According to the previous study, these changes might attributed to changes in systems which effect precipitation in the Caspian coast of Iran (northward movement in polar vortex, sub-tropical high pressure and cyclone truck). In addition, increasing temperature trends in the summer tend to decrease temperature spatial differences. Therefore, the convectional precipitation during summer has been decreased.

The aim of this study is to synoptic analyze of the number of frost days in a year of Khuzestan province. For this purpose, using the minimum daily temperature data of 12 stations during the statistical period of 1992 to 2017, the Meteorological Organization of the country, 54 days of frost was identified. Sea level pressure, Geopotential Height, Zonal and meridian wind and temperature of 500 hPa data with size of 2/5 * 2/5 degree arc from the National Oceanic and Atmospheric United States of America were extracted. On the matrix of the variance of sea level pressure data in 54 days, the analysis of the basic components was performed and 10 components which identified 83% variance of the sea level pressure. Then, by applying the hierarchical cluster analysis method, the integration method was applied to the scores of the 10 components and 5 patterns of sea level pressure were identified. The results showed that frost phenomenon in Khuzestan province occurs from November to march and its trend is decreasing during the statistical period. Also northern and western parts of the province have allocated the most frequency of frost. Also the synoptic condition analysis of troposphere showed that 5 sea level pressure pattern with different make ups lead to pervasive frosts of Khuzestan province. Weak and moderate frosts formed by the influence of Siberian and European cold high pressure systems. But severe frosts occur with spread of Iceland low pressure to Iran, along with strong cold pressures. Meanwhile, the powerful Siberian high pressure is present in most of the patterns, which its interaction with sub polar and Icelandic low pressure, plays the most role in the most severe frost in the province of Khuzestan. Also in the middle level of troposphere penetration of deep troughs from northern latitudes and east European huge blockings has the most role, which has advection of cold air from the side west of troughs on the country and during the intensity of the frost added to its continuity.
 

Recognition and determination of ecological susceptible regions for proper bedding is importance and vital affair for regional planning and specially agriculture part. Climate and topography are main environmental components which altitude and cultivation product generation capability are depend their in every region.  So , studying of effective climate factors and elements on agriculture have special importance. In current study , in order to agriculture ecological homogeneous geographical regions determination ; satellite images of Geographical Information Bases (GIS) were used which they are provider of new horizon and dimensions for effective discovering and fields resources management and we try to show Rapeseed cultivation ecological zoning usage development by combining modern tools , instruments and methods at Ardebil plain region. In order to recognition of mentioned susceptible regions in studied case climate data statistics were used that they include ; temperature degree , precipitation, relative humidity and environmental capability data such as ; inclination, height and multi-criteria decision making based on Analysis of Networks Process(ANP). Then layers were prepared by weighting and according to criteria and they were combined and also layers overlapping were done on GIS environment and ultimate layer of fields proportion was prepared for Rapeseed cultivation. Based on results analysis , studied region fields for Rapeseed cultivation include 33/38% without limitation ; 02/10% of fields with low limitation; 96/33% with medium limitation ; 71/17% of fields with high limitation

Atmospheric circulation is important to determine the surface climate and environment, and affect regional climate and surface features. In this study, to quantify its effect, the classification system, developed by Lamb is applied to obtain circulation information for Ardabil, North West Province in Iran, on a daily basis, and is a method to classify synoptic weather for study area. For that purpose, daily mean sea-level pressure (MSLP) for extreme precipitation days from 1971 to 2007 is used to derive six circulation indices and to provide a circulation catalogue with 27 circulation types. The frequency of circulation types over different periods is computed and described. Five circulation types are most recognised in this study: E, SE, A, C and CSE. The catalogue and the associated indices provide a tool to interpret the regional climate and precipitation, and deal with the linkage between the mean extreme regional precipitations in north western of Iran and the large-scale circulation. Five circulation types E, A, SE, C and CSE are associated with high precipitation and rainy seasons (spring and September) but the most precipitation rate is resulted of cyclone family. Low pressure of north latitudes and central area of Iran with low pressure of gang from Pakistan and India.  SE is almost dominant circulation type over the years. The cold season started from august to march is characterized by frequent directional flows, especially E, SE, A, C and CSE whereas in  warm period (Apr–Aug) SE, NE, AE have  smaller role, especially in July, August and September more frequent flows dominated by SE and E. 

 The study of meteorological characteristics and its variability is important in assessing the climate change impacts for water resources management. Trend analysis of hydrological and meteorological time series is a method for determining the change in climate variables that is performed with different parametric and non-parametric methods. In this research, the annual, seasonal and monthly trends were analyzed regarding rainfall and temperature time series for 1986-2017 in 28 stations of Kashafroud basin in the Northeast of Iran. For this purpose, the annual, seasonal and monthly trends were evaluated using non-parametric Mann Kendall and Pettitt test at 95% level significance. The results showed the trend for the monthly maximum temperature in spring and winter and also the annual trend for all stations was increasing, whereas the summer and autumn pattern differed. The trend of minimum temperature in all seasons and stations do not have a uniform pattern. The results of precipitation trend indicated that the annual precipitation of the basin had not changed and did not have a significant trend in 5% level of significance. Precipitation of the basin in the winter decreased. There was an increasing trend in the Southern half of the basin in autumn. The noticeable decrease of precipitation in winter season especially during January and February with an increase in November can be a serious challenge for water resource management of basin during the dry season.

The main purpose of this research is to test the agglium of Hormozgan province for the development and development of aloe vera plant cultivars in the base period and the period of change. In this regard, the influential data in the various stages of the aloe vera plant, including the minimum and maximum temperature and precipitation, as climatic agents and height variables, gradients, direction of gradient, soil, as stable elements in the evaluation of aloe vera cultivation areas were used. The multidimensional decision-making technique in the GIS environment was used using fuzzy gamma function for interruption and eventually identifying appropriate arenas for aloe vera plant. The role of climatic changes in two levels of alteration of B1 and A2 was investigated to evaluate changes in Aloe Vera cultivation agriculum in Hormozan province. The results of the implementation of the Fuzzy Gama integration function in Hormozgan province showed that in the base period, 0.35 of the area of ​​the province has good and excellent culture for this plant. These areas are generally consistent with the lowlands of the southern sections of the southern province and are consistent with the soils with tissue and depth and drainage, namely, the arid soils of Sevil and anti-Seville, while in the northern parts of the province, the supply factor, supply The need for an aloe vera plant, tolerance in the year and nightly, the product performance is very weak and the development of aloe vera farms in these areas is not recommended. In the simulated climatic conditions for 2070 under the 2ndretic scenarios, aloe vera arenas will have relatively significant changes compared to the climate of the base period, so that the most variations related to the A2 scenario, in which poorly functional floors are lacking. And moderate culture capabilities have been exposed to an area of ​​30 to 40 percent, while the two floors of the agricultiva capability and good culture capabilities, under the same system, will show an increase of 20 to 40 percent.

Today climate change cause increase in concentration of greenhouse gases has been cause increase extreme events and atmospheric hazards. goal of this research, analyze and review climate future is for atmospheric hazards in sistan region. In this study, to simulate minimum and maximum temperature data used from model data CanESM2 under three scenarios (RCP2.6, RCP4.5, RCP8.5) with SDSM statistical scrolling and to simulate rainfall data from the Hadcm3 model under scenarios (A1B, A2, B1) with statistical scrolling LARS-WG. For this purpose, after calibration, validation and data modeling at the selected station, the performance of the model from the viewpoint of the compliance of the base temperature data (1984-2005) and rainfall (1986-2015) with simulation values (2020-2039) evaluated at a significant level of confidence. To adapt base data to simulated data Used of the three criteria root mean square error (RMSE), coefficient of determination (R2) and mean squared error (MSE). According to simulated data were examined four important atmospheric hazard frost, heat waves, extreme precipitation and drought. The results showed that heat waves and drought in the future are serious threats in the region So that in 2021, under release scenario RCP 2.6, Predicted 32 heat waves and the study area will experience more than five heat waves in the year. In addition, most frequent drought forecast in 2020, under release scenario A1B. Extreme precipitation in some years under scenario B1 can be significant threat in the region. Intensity and abundance annual frost under release scenario RCP2.6 more than other scenarios and lower relative to investigated atmospheric threats.

General circulation of Persian Gulf has a cyclonic pattern that affected by tide, wind stress and thermohaline force. Although tidal force is very effective in values of current speed, but thermohaline force is dominant in long time because tidal forcing has a short period and returning nature. Tide and density parameters are important in navigating and shipping, especially when ships approaching the shore and shallow water to determine the drainage of them. In this study using the Mike model based on the three-dimensional solution of the Navier Stokes equations, assumption of incompressibility, Boussinesq aproximation, and hydrostatic pressure, Persian Gulf circulation modelled. After model stability, the effects of tidal force on horizontal and vertical distribution of density were investigated. Results show that forcing of tide caused current direction be regular and without tidal force, wind stress dominates on isopycnal and turbulent pattern forms in sea surface layer especially in cool season. Also, with the elimination of the tide effect, the velocity of current is reduced to 75% and the water density is increased to 1-2 kg/m³. Density profile show that the Persian Gulf is a baroclinic environment and it is stronger in cool season relative to warm season. The impact of forces is not the same in different regions of the Persian Gulf, so that the effects on the change in density in the Strait of Hormuz are more perceptible and moving inward to the Gulf, the intensity of its effect is reduced.

The purpose of this study is to determine the long-term variations in rainfall data as well as to identify wet and dry periods of 35 synoptic stations in Iran. In order to know the variation of rainfall in studied stations, average maps, coefficient of variation and skewness were drawn. Then, using the Mann-Kendall test, the significance of the trend on each station was tested at 95% confidence level. Finally, wet and dry periods were identified by using 20% high and low extreme rainfall during the 50-year study period. The results show that the general model of the country's regime is that the rainfall levels from the north to the south-east and from the west to the east of the country are reduced. The lowest values of the coefficient of variation and skewness are related to the northern regions especially the Caspian seaside and the highest amounts are in the southern regions, especially in the south and south-east. In general, the results of the Mann-Kendall test show that rainfall data in the seasonal scale, with the exception of several synoptic stations, do not show a significant trend. Most wet periods occur in the spring and the lowest in summer and the highest dry periods occur in the autumn and the lowest in spring. The number of droughts in the cold periods is significant. Also, the frequency of occurrence of dry periods is more than wet periods.

In the meantime it can cause serious and irreparable damage to other social, economic and structural sectors of society. A look at the history of human life on Earth shows that human beings have always been exposed to all kinds of natural hazards. Natural hazards have many types, one of which is drought and water crisis. The recent droughts in Iran and the severity of the damage indicate the continued vulnerability of urban and rural areas. At present, drought management in our country is based on crisis management and thus less attention is paid to drought impacts and preparedness. Therefore, the purpose of this study is to evaluate the resilience of Zahedan city against water crisis and drought. The present study is applied in terms of purpose and in terms of research, descriptive and analytical. The statistical population of the study is all households in Zahedan city based on the census of 1395 168480 households (672589 people). From the household heads, a sample size of 383 people was selected randomly using Cochran formula. Descriptive statistics and inferential statistics were used to analyze the findings. The results of one-sample t-test show that the economic, social and institutional resiliency status in Zahedan city is lower than the average (2.815, 2.873 and 2.886, respectively); The results showed that Zahedan city is not in a good position in terms of resilience to drought and water crisis and this city has many water problems in rural areas and Zahedan city. Rural water shortages and droughts have caused extensive damage to farmers and ranchers. The effects of the water crisis on the economic, social and environmental structure of the villages have been very negative and these negative effects have ultimately led to the migration of villagers to Zahedan

So far, several models have been proposed for estimating different climate parameters, but due to the lack of valid and long-term data in some meteorological stations, some models have been difficult to use. The SIMETAV V.1.0 model has been developed in cooperation with the University of California Davis and the Water Resources Authority of California in 2005. The SIMETAW model is a new and innovative tool for the estimation of applied water evapotranspiration (ETAW). SIMETAW simulation model is presented to estimate potential evapotranspiration and also estimate the net amount of water required for irrigation (ETaw). In addition, using this model, you can simulate daily meteorological data from meteorological data. The simulation of daily weather information where there are only monthly averages is a great tool for filling out lost data. In this research, Simetaw simulation model predicts different climate parameters such as solar radiation, minimum and maximum temperature, wind speed, dew point, precipitation and evapotranspiration potential in four different semi-arid climate zones (Mashhad). Dry (Bandar Abbas), moderate and humid (Ramsar) and Mediterranean (Sanandaj) during the years (1967-2017). The results of these studies showed that SIMETAW model has high ability to simulate climate variables and has the highest model accuracy in precipitation simulation (R2 = 0.998) and maximum temperature (R2 = 0.997) for semi-arid climate (Mashhad) , Dew point (R2 = 0.998) for temperate and humid climate (Ramsar), for radiation (R2 = 0.998) and wind speed (R2 = 0.9) for Mediterranean climate (Sanandaj) and minimum temperature (R2 = 0.998) for warm and dry climates (Bandar Abbas).