جستجوی مقالات مرتبط با کلیدواژه « North West of Iran » در نشریات گروه « جغرافیا »

Rainfall is considered as one of the most important climatic elements and main and determining components in the water balance of any region. In addition to being semi-arid, the north-western region of Iran, due to its mountainous nature, witnesses many temporal and spatial changes in terms of precipitation. In this research, a time series was used to predict the annual rainfall of selected stations in the northwest of Iran including: Tabriz, Orumiyeh, Saqez, Zanjan, Sanandaj and Khoy during a statistical period of 61 years (1961-2021). In order to evaluate the stationarity of the model, the autocorrelation function was used, and the unstable data were converted to static data using the differentiation method. Then, the random models were evaluated to determine the best model to fit the rainfall of the stations. The distribution of time series and the trend analysis of the equation of the regression line of precipitation in the north-west synoptic stations in terms of millimeters show that the slope of the line in all stations has a decreasing trend and the decrease in precipitation in the stations is between 1 and 3 mm per year. It is estimated. Among the moving average (MA), autoregression (AR), autocorrelated moving average (ARMA) and autocorrelated cumulative moving average (ARIMA) models, according to the absolute value of the T statistic, it is greater than 2, P-value is less than 0.5 0 and the lowest value of Akaike information criterion (AIC), the (0, 0, 1) AR model for Saqez, Zanjan, Orumiyeh, Khoi and Tabriz stations and the (1, 0, 1) ARIMA model for Sanandaj station were determined as the best models. The forecast results show an increase in rainfall for 2023 and a decrease in rainfall for 2024 and 2025.

The polar vortex oscillation is one of the prominent manifestations of troposphere and stratosphere interaction, which plays an important role on the climate extremes. Therefore, in the present study, the concept of linking the daily extreme precipitation with the polar vortex and its control effect on synoptic systems was analyzed in the temporal-spatial analysis of the polar vortex at north-west stations of Iran. In this study, according to the statistic-synoptic approach, at first, the homogeneity of precipitation data and precipitation trend of all six stations were examined by linear regression test. 6 components explaining 90% of the data variance were identified in order to analyze the companionship and awareness of the trajectory and the effect of polar vortex on the studied stations, the location of the polar vortex investigated by T-type principal component analysis. Then, the position of vortex in each of these patterns was investigated by considering the polar vertex reagent contour in the geo-potential elevation maps of 500 hPa level. 6 general patterns were recognized by analyzing temporal and spatial position of the vertex during the given days in which spatial position, the extension and depth of the ridges were different. The highest positioning of the vertex was seen in the first pattern and the ridges obtained from vertex had the highest depth and expanse on the Black Sea. In all patterns, the daily extreme precipitation was caused by the placement of the receiving vessel from the polar vortex on the required area, which was due to the establishment of the massive Rex and Omega dams on Europe.

Rainfall is amongst the most important climatic elements with a lot of spatial and temporal changes; in contrast to the other climatic phenomena, rainfall features more notable movement complexity. The studies performed in this regard indicate that such a climatic element as rainfall features a non-stationary behavior with a vast part of this non-stationariness being the result of the rainfall’s being influenced by the spatial properties and the complex pattern of the spatial organization causes the emergence of complex behaviors in the precipitations. The importance of the rainfall as the country’s water resource and the daily increasing reduction of the country’s water reservoirs demands the study of the rainfall’s behaviors. In the present study and by the assistance of the methods of spatial statistics, the spatial pattern of the spring rainfalls in the northwest of Iran will be elaborated. 
Data and

The study area of the present study is the regions in the northwest of Iran (Azerbaijan-e-Gharbi, Azerbaijan-e-Sharghi, Ardabil, Kurdistan and Zanjan Provinces) and, to perform the study, use has been made of the monthly precipitation data acquired from 121 synoptic stations as well as climatological investigations and precipitation studies for a period between 1994 and 2014.In order to perform the spatial analysis of the precipitations, use has been made of the digital map of the elevation in the environment of ArcGIS software for extracting slope and dip. In the next part and in order to analyse the spatial structure of the rainfall and investigate the degree of similarity between the data acquired from 121 station points, use has been made of the half pseudo-variance spatial correlation index. The Semivariogram has been estimated based on the arithmetic mean of the intervals.In the present study, use was made of the longitude and latitude of every station point and the rainfall rates of every point for delineating the empirical Semivariogram for three months, namely April, May and June in the environment of Variowin Software, version 2.2; then, various theoretical models were estimated in terms of their goodness of fit and the exponential model was selected as the best model for every month.In order to analyse the spatial factors influencing the spring rainfalls in the northwest, the balanced geographical regression model was estimated in terms of its goodness of fit with its output being the indicator or indicators influencing the occurrence of spring rainfalls according to the explanatory variables of slope, dip, elevation and latitude.

Following the investigation of the data related to April, it was made clear that the effect of the elevations on the rainfall variations is significant in this month in the entire parts of the region. The highest significant effect of the elevation has been in the central parts of the region for such a reason as the large density of the mountainous masses in this part and the passing of precipitation systems from these regions. In parts of the region’s north (north of Azerbaijan-e-Gharbi, Azerbaijan-e-Sharghi and Ardabil), the significance rate of elevation is reduced because these regions are plains and plateaus and lower in elevation than the other areas. Latitude has been found having a significant effect in the southwestern sections of the region (south of Azerbaijan-e-Gharbi, Kurdistan and Zanjan) and, in a more scattered manner, in the north of Urmia Lake and it seems that the reason for such a significance is the passing of the precipitation systems from the southern sections of the region.As in April, the effect of the elevation on the rainfall has been also found significant in all the sections of the region in May. The highest rate of significance has been found centered in the western and central sections of the region (particularly in the central parts) and this is completely due to the existence of the mountainous air masses. Considering the gradual displacement of the western winds towards the northernmost parts of the region and the vertical irradiation of the sunlight onto the sun-facing foothills, the role of the elevations becomes more accentuated in the creation of convectional rainfalls and the regions with lower elevation would receive lower precipitations. In June, as well, except the south-eastern section of the region (eastern half of Zanjan Province), the other regions have been found with the significant effect of elevation on the creation of rain. In this month, the conditions fit the occurrence of foothill convection in the studied area. The highest effect of the rising and falling lands on the creation of the rain has been evidenced for the north-western sections and this is in match with the path through which the western winds pass on these days; that is because the rain-causing winds are present in this section in this month and, considering the region’s elevations, cause the occurrence of rainfall. The effects of latitude in June is like those in May and the presence of the western winds and setting of the ground for the foothill convention causes rainfalls in the northern and central section of the study region.

Elevation has been found influential in the entire studied region on the rainfall because the high density of high grounds causes the ascension and condensation of the humid air that causes rainfall. Besides elevation, the dip also influences the rainfall in Kurdistan and south of Azerbaijan-e-Gharbi because the orientation of the foothills in this section sets the ground for the dynamic ascension of the humid air. In Ardabil and north of Azerbaijan-e-Sharghi, slope is also an effective factor. The high slope of these regions causes the acceleration of the humid air masses’ ascension. The effects of the latitude on rainfall during spring are different and mostly related to the presence of the western winds; in April in Kurdistan and in May and June in Azerbaijan-e-Sharghi, latitude has been found with the highest effect on the rainfall.

Rivers are dynamic forms of natural landscapes with different changes at different times and places. The effects of river adjustment caused by the natural factors require much longer span to reveal. However, sometimes the natural factors such as river floods, landslide, or earthquake can lead to canal adjustments in a very short time (Chaiwongsaen et al, 2019:153(. In contrast, human activities can have a significant and rapid impact on natural processes and trends, resulting in a short time scale for river adjustments (Rinaldi & Simon, 1998:57).  River canal instability plays a major role in erosion, destruction of beaches and riverbanks. This role becomes more significant when the canal and bed of the river is alluvial (Rezaei Moghadam, 2012:33). One of the key issues in studying the erosion and stability of rivers is the initiation of sedimentary particle movement. The motion of sediments occurs if the bed shear stress (available shear stress) induced by the flow exceeds a certain critical value. An alluvial canal, either artificial or natural, persists to deform its boundary by itself while transporting water and sediments. Therefore, erosion and riverbank instability have created major concerns worldwide over the past few decades and significant amount of money have been spent to sustain the riverbanks. Givi-Chay River which is almost 54 kilometers long, is one of the permanent rivers of Ardabil province, Iran; problems of bed and bank erosion are evident in different areas of this river and they damage agricultural lands and adjacent river installations. In addition, a review of the research shows that sufficient studies have not been carried out so far to reveal the stability, erosion and sedimentation process in Givi Chay River.Therefore, this study aimed to analyze and evaluate the erosion stability of Givi Chay River channel.

In this research, the topography map with a scale of 1: 50000, geology map with a scale of 1: 100000, and google earth and Landsat Eight images, including OLI sensor (2019), bedrock maps and the Givi-Chay River area at a scale of 1:2000 hydrological data from two Abegharm stations (upstream of the dam) and Firoozabad (downstream of the dam) and field data are used. In addition, to control the results obtained by quantitative methods, field studies are applied for confirmation and verification. ENVI 5.3, Arc GIS 10.5, Excel, and HECRAS software were also used for image processing and data analysis. The geomorphological parameters of the river and their variations including bending coefficient and central angle were measured. The curvature coefficient is one of the few criteria used in river shape segmentation using s=1/(y.2), i.e., by dividing the valley length by wavelength for each arc, it is calculated. The central angle of the arcs on each of the intervals was calculated using the relation A=180L / Rπ, where A is the central angle, R, of the fitted circle radius.The increased shear stress in the riverbed increases the load of the floor and the scour of the bed, which can affect the riverbanks as erosion, destruction, and rupture of the walls. Direct measurement of shear stress is a difficult task and therefore researchers have developed methods for indirect calculation of shear stress. Existing shear stress (boundary), lateral shear stress, and critical shear stress were calculated by means of equation 1, 2, and 3, respectively:  (1)  (2)  (3) Relative Stability Index Calculation (RBS):Judet has introduced this index as the ratio of critical bed velocity to actual bed velocity. Olsen et al (1997) defined this index as the ratio between the critical shear stress and the shear stress of the sides. Relative stability index (RBS) was obtained using the following equations:(4) (5) (6)

Investigation of the morphology of the intervals shows that in the first, second and fourth intervals the conduit is sinusoidal and in the fourth interval, the pattern is meandering. In addition, according to the results of the study, the first, second and third intervals are developed in a very meandering manner and the fourth interval is just a meandering one. shear stresses in sections 4, 3 (second interval) are more than other sections, and given the direct relationship between shear stress and depth and width of sections, even under current conditions there will be phenomena such as scouring and damaging river bank and rivers. In addition, in terms of critical shear stress, the highest shear stress is in sections 3 and 7. Due to the relative stability values, sections 5 and 7 are stable and other sections are unstable. In the first period, the river flows into a valley bed, and in parts formed by erodible formations and at sections close to the dam, the river width is approximately increased. Therefore, sections 1 and 2, which pass through alluvial terrace sediments, are in unstable condition. In the second interval and immediately after the Givi Dam, the river passes through the valleys overlooking the Givi town, where the width of the bed due to the types of the banks decreases and the riverbed contains coarse sediments  covered by broken rocks. In other parts of the city of Givi, erosion conditions prevail and large volumes of flanking material (especially during floods) are eroded and loose flanks lead to the widening of canals and intra-canal ridges, and these sediments are clearly visible in bends, middle islands and marginal lands and steep banks. At sections where the river width is excessive and the slope decreases, the stability factor is almost high (sections 5 and 7). At the beginning of the third period, Firouzabad area is located on path of the flood of the previous interval and by joining Sanghor Chay, the river enters the mountainous part and the coastal areas have deep valleys with steep slopes. Along the river, due to collision with high mountains and rocky outcrops, the alternate route has a meander and river changes are subject to valley changes, and the meandering state is seen throughout the valley. In the fourth period, the river width is reduced and the riverbed is covered with coarse sediments, which extends to Ghezelozan.

According to the study results, in the plain interval, the main factor affecting the river meandering is the alluvial formation; here, the slope is low and the meanders are inscribed and plain, whereas in the mountainous part, the river changes are subject to valley changes and the meandering state is seen throughout the valley. According to the values of shear stress, the lowest boundary and bank shear stress is in sections 5, 6 and 7 and the highest is in sections 4, 3, 11 and 12. The highest critical shear stress is in sections 3 and 7 and the lowest is in sections 4, 2 and 12. The study of the relative stability of the river shows that the river is more unstable in sections crossing the old and new alluvial terraces, and in sections where the river width is high and the bed slope and flow rate have a decreasing trend, the coefficient of stability is relatively high. The third and fourth intervals are mountainous and semi-mountainous, respectively. In these intervals the river width is small and there is no agricultural land use .Lithologically, most of the third and whole of the fourth period consist of Eocene igneous and pyroclastic formations and they are resistant to erosion and the existing alluviums are the result of transport of water from sediments of other intervals.Therefore, the morphology of the river is affected by lithology and according to field evidence, the interval is stable .But the results of using mathematical and experimental methods have introduced the third and fourth intervals as unstable . Therefore, it can be acknowledged that the methods used in this study apply to the study of stability in rivers and alluvial intervals

Heavy precipitations and severe floods are one of the most important hazards affecting many parts of the country, including the northwest of the country, and it causes extensive damage to farms, gardens, houses, urban facilities, etc. In this research, the atmospheric conditions accompanying the occurrence of flood events in the northwest of the country on April 14, 2017 are studied. For this purpose, the data of sea level pressure, geopotential height, vertical velocity, zonal and meridional components at pressure levels of 850, 700, 500 and 300 hpa, as well as specific humidity in pressure levels of 1000 and 850 hpa(12 hours before the flood event) were obtained from European Centre for Medium-Range Weather Forecasts with a .075 -degree spatial resolution and the desired maps were drawn and the following results were obtained. The presence of severe gradient of pressure in the sea level in the northwestern region of the country and the high humidity in the lower atmosphere as well as the presence of western troughs at all levels of the troposphere exacerbate the meridian flows, and cause the subsequent formation of jets at a pressure of 700 to 300 hpa on the northwest region of Iran. On the other hand, extreme ascent, due to the severe vertical shear of the horizontal wind and the presence of a great deal of moisture, especially in the lower layers of the atmosphere, have created cumulonimbus clouds from a pressure level of 850 to 370 hpa, with lightning strikes at a pressure of 850 to 600 hpa. All of the above conditions have caused the instability and flooding and extreme precipitations in this region of the country.

Aims of This research is investigation and reconstruction of climate change during quaternary period according to Urmia Lake terraces and we use elevation changes of this lake as indicator of climate change. 14 lake terraces were found during field work. Elevation of this lake terraces are between 1298 to 1365 meter above mean sea level. Absolute age of 6 lake terraces determined using C14 analysis. Age of this lake terraces are between 35850 to 54150 years ago. According to dating results and elevation changes of Urmia Lake terraces, we calibrate this results with climate changes during late Pleistocene we reconstruct climate conditions in this area. Age of lake level rise and formation of the Urmia lake terraces belong to late Pleistocene and synchrony to Wurm Gelation Period in north of Europe. Age of four lake terraces synchro to Heinrich event 5 and 4 and correlate to transgression of glacial in north of Europe and this evidence is the first evidence of Heinrich Events in Iran. Decrease of temperature and glaciation periods in north of Europe in late Pleistocene and Heinrichs events synchronal to lake level rise in the Urmia lake and shows effects of this intensive climate change in this region. Results present rainy periods during late Pleistocene and decrease in evaporation and temperature and increase in precipitation in this region. Increasing in River discharge lead to lake level rise and formation of lake terraces in the Urmia lake during late Pleistocene

Importance of location factors substantially change the climatic phenomena and developments can be enjoyed. Influence of these factors can be strengthened, diluting and determine how the distribution of climatic processes be flashed as a result recognizing the role and relationships of these factors can lead to the understanding of the spatial patterns of climatic variables and the improvement of environmental planning. Accordingly, in the present study using monthly rainfall data of the synoptic station 121, climatology and rain Northwest of Iran in the period of assessment 1987 until 2014, and the use of the data, elevation, latitude, tilt and direction of tilt was trying features and relationships in spatial distribution and location factors of rainfall changes about the analysis. Therefore, the purpose of the center of the circle, half the average of the standard geographic change and even regression (GWR) was used. The results of the investigation showed that during the month of October due to the low amount of variance in the Western region, winds, rainfall, low spatial and spatial factors play an important role in the changes of precipitation. In November, while strengthening the system of precipitation in the region, the role of spatial factors in changes to rainfall reaches its peak in December, but due to the power systems of the proper moisture and nourishing rainfall, of the role of regional rainfall eased on location factors and changes in precipitation are more associated with atmospheric agents.

The heat waves today are one of the most important climatic hazards in the world. According to many scientists, the Severe and frequent occurrence of heat waves in recent years has been due to the emission of greenhouse gases and consequent increased global warming. The purpose of this study is to investigate changes in the frequency and intensity of heat waves As well as their relationship with Global land-ocean temperature anomalies and greenhouse gases in the north-west of Iran. At First, maximum temperature of two meters of the surface during the period from 1851 to 2014 for 164 years was obtained from NASA’s website, then the maps of heat waves was drawn and extracted. Then, we analyzed and evaluated the frequency and severity of the heat waves, as well as changes in the annual, decade, fifty years old fluctuations and their centenary were analyzed. To achieve the research objectives, Pearson and Spearman correlation methods, linear and polynomial regression and non-parametric Mann-Kendall test were used. The results showed that the frequency of occurrence of heat waves in the considered period interval is incremental and relevant, and the most frequency of occurrence was in decades. Also the intensity of the heat waves is associated with a relatively significant increase, and the most intense heat waves occurred in the decades of the late 20th and early 21st century until the present period. The results of the correlation coefficients indicated that the intensity and frequency of the heat wave incidence have a positive and significant correlation with the Global land-ocean temperature anomalies. The results of investigating the relationship between frequency and intensity of heat waves with 4 important greenhouse gases, including: (CO2, CH4, N2O, SF6), showed that, except for the positive and significant correlation of carbon dioxide gas with the most severe heat waves in June, There was no meaningful relationship between them. The results of the Mann-Kendall test indicate an incremental and significant increase in the frequency and intensity of heat wave events in the North-West region of Iran.

One of the most important issues that human societies are currently facing is the phenomenon of climate change that attracted the attention of many researchers around the world. One of the effects of climate change is the increase in the frequency and severity of occurrence of extreme weather events, such as frost temperatures and extreme rainfall. The effects of climate change on changes in cold-wave temperatures in recent years, as well as the effects of cold waves on various aspects of human societies, have always been the concern of various scholars in most parts of the world, including cold weather, and atmospheric hazards. Several definitions of cold waves are presented. In general, scientists used cold weather or cold weather for at least 2 days or more at temperatures below zero degrees Celsius. In general, the characteristics of the cold wave can be summarized in three characteristics: 1. the intensity and velocity of the temperature drop 2. the numerical value of the drop or deviation in the daily temperature value 3. the duration of the continuity (time continuity) of the cold wave. For the purpose of this research, data from the upper levels of the atmosphere were used to analyze the data of the 20th century. The data listed on the website was https://www.esrl.noaa.gov/psd/data/gridded/data.20thC_ReanV2.html and was used. NASA's Twentieth Century Data has a good place in comparison with the normal data from time separation, and has a better and more accurate accuracy than it is. The data used are 142 years old from 1871 to 2012. The data are 6 hours and 4 daily observations (0, 6, 12 and 18 Zulu) with spatial resolution of 2 degrees longitude at 2 degrees latitude and 24 pressure levels from 1000 to 10 hPa. For the purpose of this study, at first, the cold waves with a minimum temperature of -15 ° C and continuity of time for at least 2 days in 142 years of statistical period were extracted from a minimum of two-meter surface temperature data. Then the relevant data was categorized in terms of frequency, severity, duration and spatial extent. In order to validate the extracted data, they were controlled to the point where they met the ground stations and ensured the accuracy of the data. For synoptic analysis, the coldest waves occurred in each of the months. For this purpose, combinational maps of ground pressure, geopotential heights and wind current of 500 hPa, bar thickness map, temperature map, and a minimum temperature of two meters of ground level were used. The results of the synoptic analysis of the selected days indicate the dominance of the high-pressure system on the surface of the earth and the collapse of the block, followed by the cavern and stack at the upper levels of the atmosphere. In most of the study days, the high pressure (Siberian high-pressure migratory force) system in the Earth has been flowing on the Earth's surface, which has intensified its intensity. The meridian flow formed by the flood-blocking blocks has led to a very cold, northwest northern part of Iran's cold air and, on the other hand, has increased the duration of the deployment of these cold waves. According to the results, 44 cold currents at -15 ° C and colder in the north east of the country were identified during the studied time period. The waves are mostly due to January, February and December. Which is very good for the influence of Siberian cold pressures, shows such waves. A noticeable decrease has occurred in these waves from 1907 onwards. The frequency of these waves has decreased over the years, but has been added to the severity and duration of its deployment. According to the results of the studies, it can be said that changes in the process of cold weather are not related to global warming and climate change. This cold wave is formed in most cases when the Siberian high-pressure earth is merged with the Western Immigrant High.On the other hand, in the upper levels of the atmosphere, due to the high surface pressure of the western winds, they collide with blocking barriers and convert the orbital flow of the western wind to a meridian stream. The process mentioned above leads to the formation of a heap over Eastern Europe to the middle of the Red Sea and the formation of a ravine over the Mediterranean and Turkey. As explained above, it leads to the very cold weather flowing north to the northern part of Iran. Also, the thinness of barley thickness over the atmosphere of northeastern Iran formed as a result of a very cold, semi-arctic flow; the very cold weather has dominated the northern latitudes for several days. The study of temperature patterns indicates the domination of the northern and northwest winds, and also indicates an increase in the cold intensity of the waves occurring with the increase of the latitude of the source. Very cool temperatures occur when the source of cold air is from latitudes above 60 degrees.

In the present study, the main aim was the spatial evaluation summer rainfall of northwest of Iran based on30 stations in northwest of Iran during 30 years of statistical period (1985-2014). An attempt, using geo-statistical modeling by ordinary least squares (OLS) and geographically weighted regression (GWR) procedures, was also made. The results represented that the GWR model with higher S2, lower residuals and lower RMSE is an optimized geo-statistical model for rainfall modeling of this area. This model can explain spatio-temporal rainfall distribution in northwest of Iran in a diversified topographical and geographical background. This model revealed that two spatial factors including elevation and slope, have the most important role in the summer rainfall behavior.Therefore Elevations in the mountainous and eastern parts of Lake Urmia, Latitude in the northern regions and slopes in the east of the region, have the most role in the spatial variations of summer precipitation in northwestern Iran.

One of the natural disasters that each year around the world provides a great human and financial losses are caused by Thunderstorms and related its phenomena. To investigate the spatial distribution of thunderstorms 16 Stations North West meteorological data with common statistical 22-year period (2009-1988) was taken from the National Weather Service. Then the codes of thunderstorms (17, 29 and 91 to 99) was extracted. Since the identification of phenomena detected a significant role in its behavior over time and space. Therefore, to study the spatial pattern of thunderstorms and analysis of spatial autocorrelation, Anselin Local Moran's Index was used. The results showed that the maximum area of ​​thunderstorms is adapted to highland areas. While the peak time of thunderstorms in May and June has occurred. The results of partial correlation and linear regression showed that the geographic factors such as altitude, latitude and longitude the influence of height is more powerful than the two other factors.

Growing degree-day parameter is one of the most important indicators in the agricultural climatology in which the recognition of it can have an important role in water resources management. This study is predicting climate changes and investigating the effects of climate change on the growing degree-days in the northwest of Iran. For this purpose the climatic data of seven synoptic stations during a 25 years period (1985-2009) was collected including Oroomieh, Tabriz, Zanjan, Sanandaj, Ghazvin, Kermanshah, and Hamedan were used as the base period and And thus temperature variations periods (2030-2011 and 2065-2046) through HadCM3 model was simulated. For the little power of temporal and spatial distinction of this model, its outputs were downscaled using LARS-WG software and presented under Emission Scenarios including A1B (moderate scenario), A2 (maximum or pessimistic scenario), and B1 (minimum or optimistic scenario). Calibration, verification and Performance Model with the rate of the adaption of observed data and the simulated measures through statistics , RMSE and MAE were analyzed. Finally, using the simulated temperature growing degree-day was calculated and compared under 4 Base temperature including 0°,5°,10°, and 15° centigrade in the basic span (1985-2009) and future span (2011-2030 and 2046-2065). The results of simulation show that temperature change in north-west areas under all three A1B, A2, and B1 scenario are increasing in the future, but the differences among these three scenarios in each period is inconsiderable. In total the most temperature increasing was detected as 0/7 centigrade in A2 scenario for 2011-2030 period and 2/3 centigrade under A1B scenario for 2046-2065 period. Generally with the temperature increasing, the amounts of growing degree-day without exception increases in review periods and under the four Base temperature. Under studied scenarios, the Bases temperature of 0° centigrade had the most and 15° centigrade had the least impressibility from climate changes, so that the most increasing in calculated degree-day measures under 0° and 15° centigrade bases in the first period to the basic scenario (1985-2009) respectively was simulated as 207/4 and 120/6 degree-day under A2 scenario and for the second period to the 752/5 and 463/5 degree-day under A1B scenario.

As an indicator of the intensity of the heat temperature air is a basic element of understanding and view of the solar energy received by the Earth's irregular changes included extensive. Ice cold waves and one of the most important phenomena in Climatology is the study of daily temperature changes over time arises. The aim of this study was to analyze the spatial variability of core cooling in the North West of Iran during the various waves. For this purpose minimum temperature data and climatology station 42 were the highest during the period of the country's Meteorological Agency. The day was considered as a cold wave that has a standard score equal to or less than 2 / -1. In accordance with this definition programming using MATLAB software environment days with cold wave extraction and analysis of spatial autocorrelation Moran was studied and analyzed. The results of this study indicate that although core cooling waves of distributed heterogeneous spatial distribution has been but the major focus of this core cluster pattern in the eastern part of the study area is high. The results of the analysis showed that in the course of recent decades addition to the marked decline in the range of core cooling, The intensity of cooling cores for different durations, especially the continuation of five and six days has been reduced.

Drought is the most important natural disaster, due to its widespread and comprehensive short and long term consequences. Several meteorological drought indices have been offered to determine the features. These indices are generally calculated based on one or more climatic elements. Due to ease of calculation and use of available precipitation data, SPI index usually was calculated for any desired time scale and it’s known as one of the most appropriate indices for drought analysis, especially analysis of location. In connection time changes, most studies were largely based on an analysis of trends and changes in environment but today special attention is to the variability and spatial autocorrelation. In this study we tried to analyze drought zones in the North West of Iran, using the approach spatial analysis functions of spatial statistics and detecting spatial autocorrelation relationship, due to repeated droughts in North West of Iran and the involvement of this area in the natural disaster.
In this study, the study area is North West of Iran which includes the provinces of Ardebil, West Azerbaijan and East Azerbaijan. In this study, the 20-year average total monthly precipitation data (1995-2014) was used for 23 stations in the North West of Iran. In this study, to study SPI drought index, the annual precipitation data of considered stations were used. According to the statistical gaps in some studied meteorological stations, first considered statistics were completed. The correlation between the stations and linear regression model were used to reconstruct the statistical errors. Stations annual precipitation data for each month, were entered into Excel file for the under consideration separately and then these files were entered into Minitab software environment and the correlation between them was obtained to rebuild the statistical gaps. Using SPI values drought and wet period’s region were identified and zoning drought was done using ordinary kriging interpolation method with a variogram Gaussian model with the lowest RMS error. Using appropriate variogram, cells with dimensions of 5×5km were extended to perform spatial analysis on the study area. With the establishment of spatial data in ARC GIS10.3 environment, Geostatistic Analyze redundant was used to Interpolation analysis Space and Global Moran's autocorrelation in GIS software and GeoDa was used to reveal the spatial relationships of variables.
The results showed that most studied stations are relatively well wet and this shows the accuracy of the results of the SPI index. Validation results of the various models revealed that Ordinary Kriging interpolation method with a variogram Gaussian model best explains the spatial distribution of drought in North West of Iran. So, using the above method the stations data interpolation related to SPI index in North West of Iran was done. The results showed that Moran index values for the analysis of results of standardized precipitation index (SPI) in all studied years, is more than 0.95. Since Moran’s obtained values are positive close to 1, it can be concluded that drought, in the North West of Iran during the statistical period has high spatial autocorrelation cluster pattern of 90, 95 and 99 percent. Results also showed that in all the years of study, Moran's global index is more than 0.95 percent. This type of distributed data suggests that spatial distribution patterns of drought in North West of Iran changes in multiple scales and distances from one distance to another and from scale to another and this result shows special space differences in different distances and scales in this region of the country. Results also showed that drought in North West of Iran in 2008 is composed of two parts: Moderate drought in parts of West and North West region (stations of Maku, Khoy, Salmas, Urmia, naghadeh, Mahabad and Piranshahr) and severe drought in the southeastern part of the study area (stations: Sarab, Khalkhal, Takab, Tabriz and Mianeh). So the pattern of cluster drought in the North West of Iran in 2008 is on the first and fourth quarter. The results of this index showed that drought and rain periods are similar in the studied stations. The results of the application of Moran's index about identifying spatial distribution of drought patterns showed that The values of the different years during the period, have a positive a positive coefficient close to 1 (Moran's I> 0.959344) and this shows that the spatial distribution of drought is clustered. The results of the standard score Z values and the P-Value proved the clustering of spatial distribution of drought.
The results of the analysis of G public value, In order to ensure the existence of areas with clusters of high and low values showed that The stations of Maku, Khoy, Salmas, Urmia, naghadeh, Mahabad, Piranshahr and Parsabad follow the moderate drought pattern in the region and are significant at the 0.99 level. Jolfa station also has a mild drought of 0.95 percent confidence level and for Sardasht station is significant in 0.90 percent. High drought pattern in Sarab, Khalkhal, Takab, Tabriz and Mianeh stations was significant in 0.99 percent level and also for Ardabil, Sahand and Maragheh stations very high drought pattern was significant in 0.95 percent level and for Meshkinshahr and Ahar high drought pattern is significant in 0.90 percent. By detection of clusters of drought and rain in the North West of Iran using Moran’s spatial analysis technique and G general statistics a full recognition of the drought affected areas in this region can be obtained and take the necessary measures in its management.

In this study , for analyzing the spatiotemporal changes of the trend for continuity cooling waves of the North West of Iran, the minimum temperature data from year 1981 for 42 synoptic and Climatology stations, which have had maximum statistical length have been used. The extracted data, by using programming facilities in Surfer environment was interpolated and a matrix of size 5082 × 11323 ( cell* day) for a 31-years statistical period was obtained, which was used as a data base in the next stages. For the calculations, the programming facilities in Matlab software and for graphical operations, Surfer software have been used. The results obtained from the study showed that cooling waves, while having high spatial changes, has had sharp daily drops. While the under study areas at the east and north east regions has had the most spatial changes.
However, in the continuation of six and seven days, the spatial variation of coefficient variation is reduced. The results of the trend analysis indicate that the cold waves have experienced many changes during different periods, so that in the first period (1989-1980) and the third (2010-2000), the cooling waves in most studied area has experienced a decreasing trend( especially in the south and south east parts) , While in the second period (1999-1990) the cold waves of the north and north west has had a noticeable increase. So that , this increase is more sensible in the east and the south east part of the study area. In total, it can be said that while the cooling wave trend has been decreased, to ward the recent periods, has had a low covering, so that in two days continuation, this feature is more visible.

The main purpose of this research is synoptic analysis for the occurrence of springtime heavy rainfall in the Northwest of Iran. Therefore, daily precipitation data were obtained from 15 synoptic stations for a period of 34 years (1981-2014). Then by using percentile index of above 95th, it was identified 98 days with heavy precipitation. So, to determine the synoptic patterns by applied the NCEP/NCAR reanalysis dataset, the maps of geopotential height, sea level pressure, streamlines, vorticity, and specific humidity at different levels were prepared and the regional pattern flow and atmospheric conditions two days before the occurrence of precipitation analyzed. The results indicate that heavy precipitations in North West of Iran are categorized into four synoptic patterns. At the first pattern, the main cause of heavy precipitation in North West is passing cyclone or low-pressure migratory systems and the regional dynamic convergence and its association with cyclonic circulation. The main factor for the transferring of moisture to the inner side of these cyclones is the anti-cyclone stationed in Saudi Arabia. At the second pattern, the couple blocking system in the middle level of troposphere system is caused heavy precipitation with stop-motion circulation systems in the middle and lower levels of the atmosphere. At the third pattern, a deep cyclonic circulation center has not been formed on their area and seems deepening a trough of extratropical and stimulates the local convergence condition dynamically, and is regarded as the main mechanism of precipitations occurrence.

The occurrence of erosive winds in the North West of Iran always causes damage to urban facilities and agricultural fields. By identifying behavior and synoptic patterns of Strong winds, necessary strategies can be chosen to deal with this destructive phenomenon. In this study, the fastest erosive winds and its steadiness coefficient were analyzed in selected stations of North West of Iran. Suitable model was introduced to predict these winds by using descriptive statistics analysis and logarithmic and order 6 polynomial trend. To understand the synoptic reasons for the occurrence of erosive winds in study area, 500hPa geopotential height, wind vector and sea level pressure maps were interpreted for the days with occurrence of erosive winds. Statistical analysis showed that the distribution of wind speed data follows from two-parameter Weibull and normal distributions. The results of the logarithmic and order 6 polynomial trend of data also indicate increase trend in erosive winds in Ardabil and Zanjan stations and decrease trend in wind steadiness coefficient at all stations. Synoptic analysis also showed that the erosive winds in stations under study were related to pressure gradient at sea level, the establishment of a relatively deep through and the polar front jet stream in 500hPa level.

In this study, appropriate interpolation methods for precipitation changes are introduced, The performance of the methods was examined by Geostatistical techniques. Geostatistical method are of the most important methods to estimate the spatial distribution of precipitation. For this purpose, the monthly precipitation data from 16 meteorological stations and 31 synoptic stations from the East Azerbaijan Regional Water Authority in a joint 20-year period (2005-1986) was prepared. The method of simple Kriging (SK), ordinary Kriging (OK), and universal Kriging (UK) were used to estimate the annual average rainfall in the North West. calculated and plotted for each model, the rooted mean squared error and determination coefficient (r) between the observed and estimated errors of the maps, and a map was selected. The results based on the criteria of RMS and RMSE showed that the geostatistics method Kriging simple exponential model was selected due to its standard measurement error, and also a correlation coefficient (r) greater than other methods. As the most suitable method for the preparation of the map element it was determined by rainfall in the North West.

Drought is one of the natural hazards that humans are constantly exposed. Therefore, it is necessary to recognize and analyzed. Drought indices, in fact Indicate the normal limits of droughts occurred during Time period to do possible to evaluate different spatial and temporal scales. Daily precipitation data in a 57-year period (1951-2007) were received. Data in this database is in form of cell 0/25× 0/25 degree arc to the Middle East. To convert the database to a text file (TXT) format, it converted to useable formation MatLab software by programming in Grads software. The next step is the calculation of the indices described in MatLab software. To map the output data, the Surfer and ArcGIS software were used. In this study the data output is seasonal and annual, ultimately standard rainfall index shows the drought rate and has been compared with DI index. Comparison annual maps of deciles Index and the Standardized Precipitation Index shows that the eastern part in Northwest of Iran is Wetter than the western part according to a period of 58 years and The western and central regions of Azerbaijan have drought.