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Bohloul Alijani, Bahram Molazadeh, Mohammad Saligheh, Mohammad Hossein Nassrzadeh,
Volume 1, Issue 4 (1-2015)

Climate is one of the important natural factors that affect all stages of life, particularly human exploitation. Selection of the type of clothing, housing, cultures, architecture, civil engineering, and settlements are influenced by climatic factors. It can be said that the climatic circumstances of the surface of the earth and atmospheric circulation patterns have an important role in shaping and organizing the environment (Alijani, 2009). In some cases, the normal weather conditions become abnormal and cause many damages, which are mostly catastrophes rooted in climatic changes, such as hail, frost, heat and cold waves, floods, storms and so on. Blizzard is one of the atmospheric phenomena, which happens as the result of snow combined with wind (15 meters per second), and low temperatures (below zero°C), and it causes severe losses.

Due to its special geographical location, Iran is placed in the transition region of the large-scale patterns of common tropospheric circulation, and is the intersectional place of the of extra-tropical and tropical circulation system. This feature along with its complex topography caused the land to have a considerable climatic diversity. The climatic diversity makes the various climatic phenomena to be observed with intensity, energy, and different frequencies, therefore, the climatic phenomena with high intensity always causes damage to natural resources and the human civilization. This undesirable phenomenon is called climatic risks. Since the West Azerbaijan Province is located in mountainous areas and high latitudes, the feature is triggered many climatic risks such as flood, hail, snow, snow storm, and so on. Therefore, snowstorm is one of such phenomena that have occurred every year or every few years due to the specific characteristics of the region and have caused damages in the fields of transportation, energy, livestock, closeness of schools and offices.

The purpose of this study is the statistical and synoptic analysis of snowstorm in west Azerbaijan province. Therefore, the data related to the present weather codes were collected during the period 1986 to 2009 from the National Meteorological Agency. The data related to the weather codes entered in Excel, and data related to the snowstorm were selected through Filter tool and isolation of codes related to the strong snowstorms (codes 37and39) and weak snowstorms (codes 36 and 38). Then the data related to the snowstorm was entered in SPSS, and the statistical analysis was performed. In the next step, three cases of the strong and common snowstorm (code 37 and 39) were selected for synoptic analysis. Then, the synoptic maps of the different layers of the atmosphere were selected as the samples for strong snowstorm for the days before the event of the phenomenon, the day of event, and the day after the event of the phenomenon by the using of the accuracy of 2.5 degrees from website. The study area has been selected in 10 to 80 degrees north latitude, and 15 to 90 degrees east longitude for identifying the patterns that affect West Azerbaijan Province. The data was received on wind speed and direction in digits from the National Center for Environmental Prediction. Then, the maps of the wind direction and speed were provided in Grads. Finally, the daily analysis and interpretation of pressure (500hPa at sea level), instability (700hPa level and the ground level), Earth's surface temperature, wind speed and direction maps for 700hPa level, and identification of patterns that have caused snowstorm in West Azerbaijan province were carried out. Statistical and synoptic analysis of snowstorm phenomenon in West Azerbaijan province during was performed in the period 1986 to 2009. To do this, using codes 36 to 39, which represent a variety of snowstorm (weak and strong), the frequency of snowstorm days on monthly and annual average, distribution of the snowstorm in the extracted stations, the frequency of strong snowstorms (codes 37and39), weak snowstorms (codes 36 and 38), all types of snowstorms (codes 36 to 39), and the frequency of storms in the station level were compared. Out of 322 snowstorms occurred during the period 1986 to 2009 in seven synoptic stations 108 have been determined as strong snowstorm and 214 as weak snowstorm. In order to analyze the synoptic snowstorm in West Azerbaijan province, in the first place, the strong snowstorms were identified, and then five of the strong and comprehensive storms were selected for the synoptic analysis. The snowstorms of choice are as follows: On 18 January 1986, on January 19, 2000, on February 7, 1992, on February 5, 1997, and on December 25, 1990.

For applying the study, pressure maps, Omega (700hp level at ground level), Earth's surface temperature, and wind speed and direction at 700hPa were analyzed, and patterns and conditions that are causing this phenomenon in the West Azerbaijan province were identified.

      In this study, to perform statistical and synoptic analysis of snowstorm in Western Azerbaijan province, the statistical data were examined during the period 1986 to 2009 from 7 stations, and the results of the statistical analysis showed that:

• Out of a total 322 snowstorm event days of 7 synoptic stations during the period 1986 to 2009, 108 and 214 days were strong and weak snowstorms, respectively.

• Review the annual and monthly snowstorm during the study period showed that the 1992, 1997, and 1989 with a total of 69, 29, and 25 days, as well as the 1999, 2006 and 2007 with 0, 1, and 1 day have the most and the fewest days of snowstorm, respectively. The statistical analysis showed that the snowstorm phenomena happened in January, February, March, April, November, and December. January had the most and April had the fewest snowstorms with 119 and 3 days, respectively. February with 39 days, and April and November, with the number 0 and 1 had the most and the fewest days of strong and constant snowstorms.

• Distribution of the snowstorms in the stations indicated that out of the studied seven synoptic stations, which had a great impact on the synoptic situation of the region, topography, and height, Sardasht-Maku station had the most, and stations of Khoy, Mahabad, and Orumiyeh by having no snowstorms had the fewest days of snowstorm.

• The results of the maps of the different levels of the atmosphere and Earth’s surface in the days before the storm, event day and the day after the snowstorm were selected for the snowstorm pattern, which indicated that the snowstorm in the winter due to low compliance pressure formed in the earth's surface with synoptic patterns of middle levels of the atmosphere have provided the conditions for the event, in a way that among the sample cases of the strong snowstorms occurred in the West Azerbaijan Province two circulation patterns were involved in the formation of natural hazards: The Caspian Sea low pressure pattern- Eastern Europe high pressure pattern and the north of the Black Sea low pressure pattern.

Mohamad Saligheh,
Volume 2, Issue 3 (10-2015)

Tehran, in the south of Alborz Mountains, is faced with three types of weather risk, weather risk caused by geography, climatic risks caused by air resistance and weather risk due to global warming. The aim of this study is to examine the three types of risk in Tehran. The method of this study was to evaluate the changes of synoptic factors that affect global warming and urban development. In order to detect the height changes of 500 hPa two 5-year periods including 1948 to 1952 and 2010 to 2014, were studied.

     The results showed that changes in heights of 500 geopotential, there was an increased risk in the city of Tehran. The effect of climate change in recent decades,  increased the stability of  air in Tehran. Human factors in the formation of heat islands, increase LCL height and density of the air balance is transferred to a higher altitude. Changing urban wind field, atmospheric turbulence intensified, exacerbated thermodynamic gradient, fat and refugee cyclones, heat island effect of the city.

Thermal stability in the warm period will appear. The thermal stability of all levels of lower, middle and upper troposphere was intensified. Thermal stability couraged the  development of subtropical high pressure in the area. With the arrival of the atmospheric pressure during calm and humid days the stability and pollution were increased. Negative vorticity from early June  developed the intensive high pressure over the region. Compare the conditions of the two study periods  showed that  : the height of the high pressure was 100 meters higher than the second period. The number of days of intensified subtropical high increased during the second period.  The high pressure has moved to the northern areas during the second period. This change in the subtropical high pressure increased the dry periods motivating the loss of vegetation. Heat island effect was increased as well. More than 90% of the  temperature inversions occurred  at an altitude of less than 500 meters in both warm and cold periods of year. Wind direction at both stations has shown that the establishment of any pollutant source in the West of Tehran will increase the pollution.

Hasan Mostafaii, Bohloul Alijani , Mohammad Saligheh,
Volume 2, Issue 4 (1-2016)

Heavy and torrential rains are one of the hazardous phenomena of atmosphere which always cause several severe damages over Iran. For this reason in every developmental program their intensity and frequency should be understood and predicted. The main factor to their development and intensification are the atmospheric pressure patterns and motions. Therefore, in order to predict their occurrence, in this study we extracted the   highest daily precipitation of days with 90th percentile and above of the year for the 40 selected stations during the 1980- 2009 period. Of these days we selected the days in which at least 25 percent of the stations had the highest daily precipitation. For the selected days we extracted the 500 hPa and sea level pressure maps. Then we clustered the sea level

maps through the use of factor analysis and cluster analysis. We extracted five pressure patterns for the whole country explaining 77.63 percent of the total variation. In each pressure pattern we divided the daily rainfall intensity of its days by the daily intensity of all selected rainy days. In this way we developed an index which measures the share of each pressure pattern in the hazardous capacity of the country,s torrential rain days. 

   The results showed that during all of the torrential rain days there was a deep trough in the region between the Mediterranean Sea and Iran at the 500 hPa level which is accompanied with a low pressure center over Iran. The upper level trough brought the atmospheric instability and the low level pressure system brought the moisture from the western and southern water bodies and intensified the upper level instability. But the variations of their location and intensity caused different pressure patterns and rainfall intensities. Thus predicting the position and intensity of these pressure patterns are very important to monitor the torrential rainfall episodes of the country.

   The CP3 pattern with 30 percent of the days showed the highest during this pattern the western trough was bifurcated to the west of Iran but merged to the east. Thus tow maxima of intensive rain days were developed over the south and northwest of the country. The surface low center was deepened up to the northeast of the country bringing moister from the southern water bodies to the country. This pattern was dominant through the fall and winter seasons. The CP4 pattern with 12 percent frequency was the least occurring pattern. This pattern caused the heavy rains of the western parts of the country. The very deep trough to the west of Iran cause very heavy rains in the region. The CP1 pattern was strong in the north and northeast of the country where as the CP2 and CP5 patterns were dominated the southern parts of the country.

Mostafa Karampour, Mohammad Saligheh, Meysam Toulabi Nejad, Zahra Zarei Choghabaki,
Volume 3, Issue 1 (4-2016)

In issues related to air pollution, the thickness of the boundary layer is known as the depth of the mixed layer because the pollution on the ground surface is mixed in this entire layer through turbulence processes. In most cases, the boundary of the area is clearly visible on big industrial cities. The depth of the mixed layer has an important effect in the concentration of air pollution which is dependent on the intensity and duration of solar radiation and wind speed. Usually after 2 to 3 hours from the time of maximum solar radiation, air temperature near the earth's surface reaches its maximum value. At this time convection of heat is formed in the air near the earth surface and transfers the heat from the surface to higher altitudes. These vertical movements will cause atmospheric turbulence and increase in instability. This is when the growth of the mixed layer reaches to its highest level. After sunset, night temperature inversion occurs near the surface. This temperature inversion is due to the rapid cooling of the Earth's surface. In such condition, the cold air layer is near the earth's surface and the warm air layer sits on top of it and air is in a stable condition.  As a result, the accumulation of contamination, if there are sources of pollutants, will increase in the earth's near-surface layer. If the conditions remain steady during the day, the mixed layer will not have much growth and as a result, contamination in the shallow layer near the surface of the Earth reduces solar radiation.

Each year, thousands of gaseous pollutants and particulate matter are emitted in the metropolitan area of Tehran and due to the geographical and climatic conditions of Tehran, temperature inversion phenomenon is not something unexpected. By formation of the inversion layer, these pollutants will remain near the earth's surface for a long time which in turn will be the cause of a lot of heart and respiratory problems. Therefore, identifying the characteristics of this layer on polluted days is of particular importance to the health of the residents of this city.

In this research, the study area is Tehran which is in the foothills of the southern Alborz and between longitudes 51 ° 2 'to 51 degrees 36' east and latitude 35 degrees 34 minutes and 35 degrees 50 minutes northern. The height of the northernmost point of this city is 1800 and up to 1200 meters in the center and 1050 meters in the south.

To conduct this research, inversion data including temperature, wind, atmospheric pressure and humidity and vertical navigation radiosonde data at the Mehrabad weather station from January to 29 December 2013, were taken from the Meteorological Organization of country. Then the statistics of daily vertical scroll of atmosphere above the Mehrabad synoptic station was received from the University of Wyoming. Also, the hourly data of air pollutants including gaseous pollutants CO, N2O, O3, SO2 and particulate matter (PM10) were prepared from the air quality control center (AQCC) for the stations Aghdasiyeh, Geophysics, Poonak, Rey and District 11.

After receiving information about the vertical scroll of the atmosphere in Mehrabad station, in order to have a closer examination of the vertical profiles of potential temperature changes in the lower atmosphere, using daily data from the radiosonde to obtain potential temperature changes in height were measured. Then, in order to identify the days with high pollution levels (the unhealthy condition for sensitive groups) and days with good conditions, so that all stations under study were the same, based on a standard index of air pollution Table 1 was developed. In the end, 4 days with critical inversion of potential temperature, including two polluted days (February 6th and August 16th) and two clean days (9 February and 5 June) were detected. Then according to the proposed method of Hefter, the approximate height of the boundary layer was calculated for these 4 days.

In this study, it was observed that the boundary layer height in contaminated cold season of the year reached 1,200 meters in the morning hours while in the afternoon in the cold samples, it grew to 1900 meters. In the warmer months based on the height of critical inversion layer in the selected days it reached more than 6,000 meters. In pure samples of warm and cold seasons, the boundary layer height had significant growth to the extent that in the cold sample of the year it reached to 2,100 meters in the morning and 2,600 meters in the afternoon. On June 5, which is intended to represent the clean and pure heating season, boundary layer height was of 5300 meters in the morning hours which shows a 4,000-meters increase in comparison to its polluted counterpart. The point to be noted is that since the active track of potential temperature can be considered as a measure of air stability, in the critical inversion, for the case of polluted samples of morning hours that were irradiated with inversion, active track of the potential temperature was very high in them. Thus on days with radiated inversion (polluted days) we can say that border of boundary layer was based on the inverted layer. Also the methods used in these types of inversions are more efficient for the determining height of the boundary layer.

Saeed Balyani , Mohammad Saligheh,
Volume 3, Issue 2 (5-2016)

The results of this study indicated that the synoptic patterns that lead to heavy rainfall in 22 March 1996, 24 mar 1995 and 17 November 1994 in the northern portion of FARS province includes: the low pressure that located in eastern part of Mediterranean and Black sea and southern part of Caspian Sea that created by trough that located at the middle level of atmosphere. In addition to this low pressure, the bipolar pattern in of Saudi Arabia  having negative vorticity that lead to transporting moisture from (India ocean, Red sea, Arab sea, Persian gulf and Oman Sea )   and also to be alignment with east Mediterranean sea and black sea low pressure as ascending agent lead to precipitate of rainfall in mentioned days . and also we found that in 29feb 1996 as second patterns rainy day, a strong deep trough transporting moisture from Soudan region and east Mediterranean  low pressure, cause alignment of this atmospheric systems. In fifth patterns (21 mar 2001), existing an low pressure and positive vorticity center in east of Pakistan simultaneously with existing negative vorticity center in central part of Iran, lead to high pressure gradient which cause rainfall events in study area. The main founding of this study were that reveals the role of low pressure of east, north and south of Caspean sea in heavy rainfall events in study area.

Pre-warning of natural hazards events such as heavy rainfall has a significant effect in damage reducing. The analysis of synoptic-dynamic condition of atmospheric circulation patterns, has great importance in recognize affective agents in heavy rainfall events. Especially this heavy rainfall could lead to flash floods suddenly. This study's aim is to analysis and extraction of daily heavy Rainfall lead atmospheric patterns in northern portion of Persian gulf (Helle and Mond Subbasin).

The study area, Helle and Mond basins, with about 21,274, 47653 km2 area,respectively are located in the south of Iran. The Helle basin approximately is between 28° 20'N and 30° 10'N latitudes and between 50° E and 52° 20'E longitudes and Mond basin is between 27° 20' and 29° 55' latitudes and between 51° 15' and 30° 27'E longitudes.These basins are located in sides of a massive sources of moisture, Persian Gulf.

In this study we investigate the data of daily rainfall of 37 synoptic and meteorological station of study area during 1991 to 2011(20 years) to extraction the atmospheric patterns lead top heavy rainfall. In this study in order to archiving heavy rainfall days based on 95 percentile in study area, the data of sea level pressure, geopotantial high of 300 and 500 hp and also data of verticit and stream line and omega in the spatial framework of -10 to 100 longitude and 10 to 70 Latitude has been selected. Then we create the sea level pressure matrix as rainfall associated days, based on Lond method of Correlation to classify days.

Our founding indicated that the main synoptic systems that lead to heavy rainfall is related to low pressure in eastern Mediterranean  and southern part of Caspian sea. So that in detected rainfalls patterns shown that the transporting moisture from nearby sea by high pressure of Saudi Arabia by associating eastern Mediterranean low pressure and deep strong trough in east and southern part of Caspian sea  cause heavy rainfall events in study area. So that the low pressure located in eastern and southern portion of Caspian sea could affect the study area.

Ali Bayat, Mohammad Saligheh, Mehri Akbari,
Volume 4, Issue 2 (7-2017)

Cyclones as the most important factor in the turbulence of mid-latitude regions are low pressure centers that have one or more closed Isobaric curves. Mid-latitude cyclones are responsible for transfer of the heat and moisture between the tropics and the polar regions. Mediterranean cyclones have the most important role in Iran's rainfalls and get from different tracks to the country and affect Northwest, West and South West of Iran in the cold period of the year. Cyclones are the prevailing weather phenomenon in Mid-latitude region and studying the characteristics and effects of these phenomena has always been of interest to climatologists and meteorologists. Iran which is located in mid-latitude region, actually is located in the path of one of the world's largest cyclone formation and the Mediterranean Sea has a main impact on the rainfall occurrence in Iran. Regarding the importance of cyclones in rainfall occurrence in Iran, especially in cold season, studying this atmospheric event seems very necessary.
The aim of this study, is to identify, tracking and analysis of the winter season (December, January and February or DJF) rain producing cyclones using special database and algorithm during three recently decades (1979-2009). 
In this study, in order to specify, tracking and statistical analysis of the DJF rain producing cyclones, relative Vorticity of 700 hPa were received from ECMWF data center  with AWT IMAGE spatial resolution  and temporal resolutions of 6-hourly for a 30 years period (1979-2009). The study domain includes Mediterranean and Middle East, from AWT IMAGE E to AWT IMAGE E and AWT IMAGE N to AWT IMAGE N.
Cyclone identification will follow the approach presented in Blender et al. (1997) and Flaounas et al. (2014), including two important points and conditions: 1- A cyclone is considered to be a relative Vorticity extrema, thus the aim will be to look for the maximum value of relative Vorticity at the 700 hPa level in a box of AWT IMAGE grid points. 2. For the intensity of the cyclone, the threshold of relative Vorticity, is considered equal or greater than AWT IMAGE. Then by 6-hour tracking the maximum amount  points of Vorticity  and connecting them to each other, identification and routing of cyclone is implemented. The track AWT IMAGE can be written as AWT IMAGE, where AWT IMAGE describes the cyclone position in sequential time steps t = 0, … , T, which are given at 00, 06, 12 and 18 GMT. The initial position is considered the first detected maximum of relative Vorticity. During the cyclone detection and tracking method, different threshold values are commonly applied to eliminate, for instance, the weakest centers and short living systems. For this reason, the threshold of equal or greater than 8 time steps (3 days and more) is considered based on Alijani (1366) to eliminate short living cyclones.
In this study, climatology of cyclones such as genesis and lysis centers, tracks and frequencies in the Mediterranean Basin and Middle East were analyzed. The results showed that, center and eastern part of the Mediterranean region include Aegean Sea, Cyprus, and northern borders of Mediterranean Sea, Adriatic Sea and also Red Sea, Sudan and Iraq, are most important cyclogenesis centers in winter season.
These cyclones which form in these cyclogenesis centers, move to the east with two eastward and northeastward distinguished directions. In northwest of Iran, the cyclones by passing over West and East Azerbaijan and Ardebil provinces in eastward and northeastward directions, move into western and southern shores of Caspian Sea. In southwest of the country, the cyclones are entered into Iran over Khozestan, Chaharmahal and Kohkilouyeh provinces. Part the cyclones are moved into center and northeast of the country with northeastward direction and other part by crossing over southern shores of the country move to the southeast of the country. In mid-west of the country, the cyclones are arrived into Iran in three different tracks. The most important path is Kordestan's path which the cyclones in the origin of Mediterranean are entered eastward into Iran by crossing over Zanjan and Hamadan provinces, under the Alborz ranges are moved into east and northeast of the country. Two other paths are observed in Ilam and Kermanshah Provinces which in these tracks also the cyclones are approximately moved eastward into center and northeast of the country. The results also showed that eastern part of the Mediterranean region specially Cyprus, Aegean sea, Adriatic sea, Red sea and Sudan and also Iraq are most important wintertime cyclogenesis centers of Iran. The main entrance paths of the cyclones includes northwest, mid- west and southwest. The averages cyclones lifetime are 4.5 days, movement speed is about 20 km/h and also travelling length is about 1700 km. Of the other notable results we can refer to decreasing of the rain producing cyclones during 3 last decades. 

Kaveh Mohammadpour, Mohammad Saligheh, Ali Darvishi Bloorani, Tayeb Raziei,
Volume 7, Issue 1 (5-2020)

Analysis and Comparing Satellite Products and Simulated
 Of AOD in West Iran (2000-2018)
Kaveh Mohammadpour, Ph.D. Student in Climatology, Kharazmi University of Tehran
Mohammad Saligheh, Associate Professor in Climatology, Kharazmi University of Tehran
Ali Darvishi Bloorani, Assistant Professor in RS & GIS, Tehran University
Tayeb Raziei, Assistant Professor in Climatology, SCWMRI, Iran
Dust are the main type of aerosols that affects directly and indirectly radiation budget. In addition, those affect the temperature change, cloud formation, convection, and precipitation. In recent years, the increase of different sensors and models has made possible to research the dust. The most important studies about dust analysis has been considered of Aerosol Optical Depth (AOD) as the most key parameter, which are based on the use of remote sensing technique and global models for analyzing the behavior and dynamics of dust in recent two decades. To achieve this, it has used of MODIS and MACC to study and identify the behavior of dust in the last two decades over west Iran.
Materials and methods
Areas in this study are Ilam, Kermanshah, Kurdistan, Lorestan and Hamedan provinces. The area has studied of two data series such as: first is MACC data with a spatial precision of 14 km2 and a 3-hour time scale; and other one is MODIS sensor production on the Terra satellite with a 10-square-kilometers resolution. In order to analyze the dust in the area in the period 2000 to 2018, statistical methods and simulation has used of the AOD parameter in MACC and MODIS. Before any processing, the data regraded to 0.2 × 0.2 degrees in order to compare the data. Then, the average daily AOD formed in a 22 × 23 matrix with 560 pixels that presented with 3653 × 560 for MACC during 2003 to 2012 and 6489 × 560 for MODIS during 2000-2018. Average of daily AOD obtained of MACC and MODIS calculated using of statistical equations. Then, the spatial distribution of AOD during the dusty months for synoptic stations and total province surface extracted using of R packages during the daily time series of the periods. Finally, the spatial distribution of the obtained AOD interpolated using the kriging function.
Results and Discussion
The average annual AOD obtained from Deep Blue algorithm from MODIS was less than MACC in all of the interested stations, except for Hamedan and Khorramabad stations, and provinces surfaces.
Correlation of AOD between MODIS and MACC shown that the correlations is high between model and sensor data (R2 = 59). In addition, the spatial correlation map shows 0.38 to 0.76 in which indicates a significant relationship between the MACC and MODIS pixels and the relationship is more in the western provinces of the area than the northeast of the region (Hamedan). The monthly comparison of the mean of AOD of the sensor and the model in the whole the area shows a highest correlation between the AOD in February and October.
The interpolation of the spatial distribution in the decade of the study (2003-2012) in MACC showed that the spatial variations of AOD is decreasing from the south of Ilam to the north of Kurdistan and reached the lowest level in the north of Kurdistan province. In general, the findings of annual and seasonal spatial distribution (dry period) of dust showed that MACC overestimated AOD compared to MODIS in the area. Nonetheless, the dust pattern in both of the sensor and the model increased from south to north. Although, the dust pattern is more regular in the sensor than the model. The spatial distribution of dust in Ilam, Kermanshah, and Kurdistan provinces in MODIS and MACC shows that dust in the southern point of the Ilam province has the highest concentration and the lowest is observed in the northeast of Kurdistan province. This spatial distribution of dust showed that dust in western provinces of the area follow latitudinal trend , in which is influenced by the high topography of Kermanshah and Kurdistan provinces and the proximity of Ilam province to dust sources in the distribution of dust intensity.
The results showed that there was a significant correlation between the sensor and the model and the coefficient was more than 0.4 in all months on the area. The findings of the annual amount of dust in MODIS showed that the amount of dust in the years 2000 to 2009 has increased in whole areas and from 2009 onwards, this annual trend has been reduced by 2018. MACC findings also showed that the AOD has been growing up in the period, although AOD amount have had a steep slope by 2010, but since 2010, dust has a steady slope. Therefore, West Iran has experienced two active (before 2010) and inactive (after 2010) periods in dust during an 18-years period on the area. The findings of MODIS and MACC in the study area indicate that the monthly distribution of dust from April to August has the highest concentration. In general, the annual and seasonal spatial distribution (months with the highest AOD) of dust indicates that the intensity of AOD in MACC was higher than MODIS in the area. Although the sensor and model has a roughly similar pattern and increases from south to north, but the trend in MODIS is more regular than MACC.
Keywords: Aerosol Optical Depth (AOD), MACC, MODIS, West Iran
Mrs Fatemeh Falahati, Dr Bohlol Alijani, Dr Mohammad Saligheh,
Volume 8, Issue 4 (1-2021)

In many areas, snow cover in the mountains is a major source of surface and underground water supply. Due to climate change and its effect on the time of melting ,it  is very important for environmental planning to predict the arrival time of water from snow melt to water consumption cycle. The purpose of this study is to investigate the volumetric changes and time distribution of snow flood flows in future by integrating remote sensing , GIS and climatic models.The studied area is the Upper Basin of Amir Kabir Dam, which is located on the southern slopes of Alborz Mountains. In this study, digital elevation maps (DEM) and GIS software were used to estimate parameters such as area, environment, main length, highest and lowest elevation points. In order to complete the snow cover data, MODIS products (MOD10A100) were extracted and the snow cover was extracted in the Upper Basin of Amir Kabir Dam. Next, runoff and snow melting models were simulated using SRM software. Calibration and validation of the model's acceptable performance were estimated. Then, in order to investigate the effects of climate change on the future of snowmelt runoff production in the basin of Amir Kabir Dam, the latest CMIP5 climatic models were used under four scenarios RCP2.6, RCP4.5, RCP6.0 and RCP8.5. A survey on the relationship between snow cover area , temperature and precipitation was used to predict snow cover in the future. The increase in temperature in the autumn and winter season has led to a reduction in the shape of precipitation in the form of snow, and as a result, the amount of snow storm is reduced. The results show that the amount of runoff in the autumn and winter increases due to increased rainfall in the form of rain, and it will be  increased late winter and spring due to the increase in the amount of water resulting from snow melting. The results of this study are based on the increase of snow melt as a result of increased runoff volume, reduction of snow reserves and maximum flow transmission to earlier than normal conditions due to early snow melting due to temperature rise. Generally, in the future, the average annual runoff will be decreased about 1.1 cubic meters per second, and the average annual melting share will be about 13.9%
- Mahmoud Roshani, - Mohammad Saligheh, - Bohlol Alijani, - Zahra Begum Hejazizadeh,
Volume 8, Issue 4 (1-2021)

In this study, the synoptic patterns of the warm period of the year that lead to the cessation of rainfall and the creation of short to long dry spells were identified and analyzed. For this purpose, the rainfall data of 8 synoptic stations were used to identify the dry spells of the warm season for 30 years (1986 to 2015). The average daily rainfall of each station was used as the threshold value to distinguish between wet and dry spells. Then, according to the effects of dry spells, they were defined subjectively and objectively with different durations. Thus, 5 numerical periods of 12 to 15, 15 to 30, 30 to 45, 45 to 60 and more than 60 days were identified. By factor analysis of Geopotential height data at 500 hPa, 4 components were identified for each period and a total of 20 components for 5 dry spells. Therefore, 5 common patterns control the stable weather conditions of dry spells. Most dry days are caused by subtropical high-pressure nuclei, which have a wide, even, dual-core, triple-core arrangement. The effect of subtropical high pressure on the dryness of the southern coast of the Caspian Sea is quite evident. Other dry days were caused by southerly currents, weakening of northern currents, and the trough Anticyclones’ area. Also, the anomaly map of the components days at the 500 hPa level showed that the anticyclones and cyclones correspond to the positive and negative phases of the anomalies, respectively.

Ms Mahsa Sepasian, Dr. Bohloul Alijani, Dr. Mohammad Salighe, Dr. Mehry Akbary,
Volume 8, Issue 4 (1-2021)

Tehran metropolitan with its large population, daily migrant workforce and many students, needs to planning and designing watch/warning system to reduce the climatic problems for human health.for this purpose, we need to study the climate accurately and Since the factors affecting the climate of warm and cold periods in Iran are different, in this study , the meteorological variables of Tehran warm period (May to September 2002) turned into 4 components in Temporal Synoptic Index (TSI) using PCA Method and using P-Array and Varimax rotation.By the scores of components for each day, the clustering method (in ward method) were used and, the warm days of the year was divided into two cluster named favorable and oppressive airmasses. The average maximum air temperature that is more effective in mortality, was 36.13 ° C. Days with temperatures above  34 ° C, less pressure, mild winds , dryness and more sunshine resulted in more adverse weather conditions, which resulted in a 34% increasing in mortality compare with favorable weather. The total number of deaths from cardiovascular disease during the study period was 154046 that about  67%of deaths have been simultaneous with oppressive airmass.The epidemiological study of mortality also confirms the results of previous research in this area and shows that the incidence of mortality is higher in older people as well as in men. It is clear that not all mortality can be attributed to the effects of climate, but results show that change in climatic conditions will affect on mortality and also for study the effect of climatic hazards on human health, it is better that we study the effect of all variables together on humans.

Halimeh Kargar, , Mohammad Saligheh, Mehry Akbary,
Volume 8, Issue 4 (1-2021)

The results showed that the length of the precipitation period in the study area is 8 months (out of 213 systems, 60 systems were recorded in January and 50 systems were recorded in December). June, July, August and December did not have a comprehensive rainfall system. The difference in height between the Mediterranean Cyclone  and the Arabian Anticyclone, i.e. the MAI index, was identified in 5 categories. The results showed that the higher the value of MAI index, the less rainfall systems and the higher the rainfall intensity. Most rainfall systems occur when the MAI index reaches 100 to 150 geopotential meters. In addition, the concentration of precipitation occurred in February when the MAI index reached 200 geopotential meters and above. In the continuation of the research, the difference between the Sudan Cyclone and Arabian Anticyclone, i.e. the SAI index, was also identified in 5 categories. The results showed that most of the systems occurred in the third category with a value of SAI index between 100 and 150 geopotential meters. Moreover, the results showed that the higher the value of the SAI index (, the lower the number of rainfall systems and the higher the average of rainfall systems.

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