Joan Amini, Mehri Akbari, Zahra Hejazizadeh, Ali Akbar Shamsipur,
Volume 0, Issue 0 (3-1921)
Abstract
Green spaces have a key role in moderating urban micro-climatic conditions, beautifying urban landscapes, citizens' leisure time, and also reducing noise and air pollution and absorption of Aerosols. In addition to the significant advantages of green space, water consumption and irrigation needs is one of the main limitations of green space development in Tehran that nowadays faced to critical water shortage. Calculating water footprint in green spaces, as the total amount of fresh water required to maintain green space throughout the year, is one of the indicators by which the compatibility of tree and plant species with climatic conditions can be assessed. The main object of this study is to estimate the water footprint of Laleh Park in Tehran province of Iran. The Green space soil water balance (SWB) model was used to calculate water footprint in this park. The required data that including: average daily temperature, total precipitation and moisture depth of zero to 30 cm of soil, were obtained from the Geophysical meteorological station of Tehran for 2018. Data related to soil water drainage were also estimated based on standard laboratory samples of green space soils. The results indicated that in the warm months (June to September) of the year, the total water footprint of Laleh Park in Tehran was 4 to 5 thousand cubic meters per month (m3/m), while the winter months (December to March) total estimated water footprint were less than 1400 cubic meters per month. The generalization of 30 Centimeters depth soil moisture data of the geophysical meteorological station to Laleh Park, released that, in the warm month of the year, Green Water (groundwater or surface water) had the largest portion (more than 90%) in the water footprint of Laleh Park, While in the winter months (December and to march), the green water (water from snow and rain) is main participant in providing soil moisture, more than 90% of the total water footprint of Laleh Park has related to this source.
Farzad Shirzad, Mr Bohlol Alijani, Mehry Akbary, Mohammad Saligheh,
Volume 0, Issue 0 (3-1921)
Abstract
Climate change and global warming are very important issues of the present century. Climate change process, especially temperature and precipitation changes, the most important issue is environmental science. Climate change means a change in the long-term average. Iran is located in the subtropical high pressure zone in arid and semi-arid regions and the Hyrcanian forest is a green area between the Caspian Sea and the Alborz mountain range. At the 43rd UNESCO Summit, the Hyrcanian forests were registered as the second natural heritage of Iran. Beech is one of the most important tree species and the most industrial species of Hyrcanian forests It accounts for about 18 percent of the northern forest volume (from Astara to Gorgan with a life span of about 250 years). The study area is located in the Shanderman basin in western Guilan province. In this research using tree dendroclimatology, Use of vegetative width of beech tree rings, Weather station statistics located in the study area, And Mann-Kendall nonparametric statistical method, To Investigate Climate Change Trend on Growth Time Series and Pearson Statistical Method, in order to evaluate the correlation of diameter growth of beech tree rings with climate variables in the region, an attempt was made. Results of time series of beech tree growth rings over 202 years. Using the nonparametric method Mann- Kendall showed, Changes in growth rings of beech trees have a downward and negative trend, at level 5 %, it was significant. Temperature Minimum, Average, Maximum, and Evaporation during the growing season, there was an upward trend and Annual precipitation there was a downward trend. Using the Pearson method Fit correlation of growth ring diameter with temperature, For the average monthly in February and the average minimum temperature in July, August and September and Negative correlation, for average maximum temperature in February, July, August and September at 95% level, it was significant and precipitation in June, the correlation was 95% positive and significant.
Hamzeh Alizadeh, Mehry Akbary, Zahra Hejazizadeh, Mohamad Ahmadi,
Volume 0, Issue 0 (3-1921)
Abstract
Kermanshah province, especially Ravansar city is one of the important regions of the country in the agricultural and horticultural sector, most of the time the hail phenomenon causes significant damage to these sectors. One way to reduce this damage is to install an anti-hail system. To achieve this goal, 37 station hail data were clustered and three main clusters were obtained representing hail days; Each of the clusters has been plotted and analyzed in terms of geopotential height of 500 hPa, moisture level of 700, and map of 1000 to 500 hPa of temperature and omega. The results of the study of hail patterns show; A low-altitude system is essential in the Middle East; To direct hot and humid air from the southern offerings to the region; At the same time, it is necessary to have high instability and weak static stability in the atmosphere on the surface of the earth, as well as the presence of sufficient moisture that can provide showers. Hierarchical analysis (AHP) method was used for location in GIS environment and parameters such as (slope, slope direction, temperature, humidity ...) were evaluated. These criteria were classified as operating maps, each separately and were scored according to the degree of priority in establishing the device. The final map shows the location of the system: Parts of the northwest of the region (Mansour Aghaei and Ghori Qaleh) and northeast of the central part of Ravansar and parts of the southwest of the area due to the appropriate geographical conditions and appropriate to them, sufficient temperature and humidity and the direction of the southwest slope, and having Favorable conditions for severe instability followed by hail; Anti-hail system is very important for construction in these areas. In general, about 32.6 square kilometers have relatively favorable conditions and about 3 square kilometers have very favorable conditions for the construction of the system.
Rastegar Mohammadi, Mohammad Saligheh, Mohammad Hossein Naserzadeh, Mehri Akbari,
Volume 0, Issue 0 (3-1921)
Abstract
Extratropical cyclones according to the frequency, duration, and intensity, the major cause of mid-and high-latitude precipitation across the Mediterranean during winter and autumn. For this research using network data of ECMWF climatic variables with 6-hour time resolution and 0.25 × 0.25 spatial resolution from1979-2016 and were used of 4 Basin stations precipitation data from the Asfezari database from 1979-2016. The results showed that the first pattern is the Mediterranean trough pattern which has the highest frequency of 42%. In this pattern, the low-level due to the presence of a high-level that acts as a barrier have caused the deepening of the Mediterranean low-level and its axis extends to the Red Sea, and due to the collision of low-level and high-level on the region, instability is intensified and has caused the most rainfall among the patterns. In contrast to the first pattern, The fourth pattern has the lowest frequency of 10% Which is the trough pattern of western winds which is located on the Caspian Sea but due to high-level in the south of the region has prevented the entry of low-level and is located in the northern part of the study area due to this, the isobar in the north of the region have become orbital as a result, fewer cyclones enter the area, resulting in less rainfall between patterns. The results also showed that the frequency of cold-core cyclones was 60% in winter and 40% in autumn, but the frequency of hot core cyclones was 62% in winter and 38% in autumn, which in winter, the frequency of hot core cyclones has increased compared to cold-core cyclones, while in the fall the frequency of hot-core cyclones has decreased compared to cold-core. In the last decade, both the frequency of occurrence of cyclones and their intensity has decreased compared to the last two decades. In terms of cyclogenesis places, the western part of the study area has always been active, And with the onset of the cold season from autumn to winter, cyclogeneses places are gradually becoming more active.
Ms Asieh Asgari Dastnaei, Dr Amir Gandomkar, Dr Morteza Khodagholi,
Volume 0, Issue 0 (3-1921)
Abstract
Teleconnection patterns represent large changes that occur in the pattern of atmospheric waves and tornadoes and affect temperature patterns in large areas and are also used to predict average weather conditions over time periods, usually several months or annually. In this study, the effects of 26 Teleconnection patterns with the average monthly maximum temperature on a quarterly and annual basis were investigated. In this study, 4 synoptic stations of Borujen, Shahrekord, Lordegan and Koohrang in Chaharmahal and Bakhtiari province were analyzed. Data were analyzed using descriptive statistics, correlation and Mann-Kendall test. The results showed that the patterns of PNA, WP, NAO, SOI, TNA, TSA, WHWP, Niño 4, NP, Trend, AO, AAO, AMO, AMM, NTA, CAR and GMLO have a positive relationship with all stations studied and The patterns of EA WR, Niño 3, ONI, MEI V2, Niño 1 + 2, Niño 3.4 and TNI had a negative relationship with all studied stations.
Dr Hassan Kharajpour, Dr Zahra Hejazizadeh, Dr Bohloul Alijani, Dr Mohammad Hossein Nasserzadeh,
Volume 0, Issue 0 (3-1921)
Abstract
Considering the undeniable impact of agricultural plants on climatic and regional changes, it seems necessary to conduct regional research to understand the reaction of each agricultural plant in different stages of growth in relation to weather elements. If the temperature of the air along with the warm cloud is lower or higher than a certain threshold, its development will stop. Between the two limits, there is an optimal temperature where the plant grows the fastest. Temperature and clouds are both the most important climatic elements in agriculture. Both climatic parameters together cause stress in wheat and lower the productivity of the product. Considering the strategic nature of wheat, in order to increase the level of production, in the present research, while taking advantage of the experiences and methods and models used in foreign and domestic researches, it was practical in Kermanshah province due to the extent of the land under wheat cultivation and The significant amount of production, which has a special place in this field at the level of the country, the determination of the statistical threshold and the synoptic analysis of warem cloud temperatures on the performance of the wheat crop are investigated. According to the investigations and consultations with agricultural engineers, the maximum temperature along with cloudy days causes the phenomenon of greenhouse and excessive heat, which causes the fall of flowers, rot, sterility of pollen grains, fruit reduction, Premature aging and poverty become seeds, and this phenomenon occurs mostly in the months of May and June.
Toba Alizadeheh, Majid Rezaie Banafsh, Gholamreza Goodarzi, Hashem Rostamzadeh,
Volume 0, Issue 0 (3-1921)
Abstract
Dust is a phenomenon that has many environmental effects in various parts of human life, including: agriculture, economy, health and so on. The purpose of this study is to investigate and predict the dust phenomenon in Kermanshah. Meteorological data with a resolution of 3 hours in the statistical period (2020-2000) of Kermanshah station was obtained from the Meteorological Organization. First, the dust data were normalized and then using ANN neural network models to predict dust concentration and ANFIS adaptive neural network to debug and predict the time series of dust occurrence in MATLAB software were debugged and predicted. Findings showed that the maximum predicted dust concentration related to the minimum fenugreek point with the highest Pearson correlation with dust was estimated to be 3451.23 μg / m3. Also, the results of time series prediction using ANFIS model showed that the linear bell membership function with grade 3, in the training and testing stages, has the most desirable input function among other membership functions. According to the forecasting models, the highest probability of maximum dust occurrence in the next 20 years in Kermanshah was 94%.
Mahnaz Sadeghi, Zahra Haejazi Zade, Mohhamad Saligeh,
Volume 0, Issue 0 (3-1921)
Abstract
The purpose of this study is to increase awareness and flexibility towards climate change and its effects on the environment through education. In the first step, to achieve the reproduction of climatic data and compare the scenarios of the general circulation model of the atmosphere, three important climatic parameters including precipitation, minimum temperature and maximum temperature were used and also SDSM software was used to predict the data. In this study, two stations of Zabol and Chabahar were used during the statistical period of 1961-2005. Three scenarios of RCP2.6, RCP4.5 and RCP8.5 in the period 2020-2050 were used to compare the results of the CanESM2 general circulation model, which is mentioned in the fifth IPCC report. The results of CanESM2 model showed that the minimum and maximum temperature and precipitation in the studied stations will have an increasing and decreasing trend in the future, respectively, in other words, the effects of climate change will be more obvious. In the second step, a questionnaire was distributed to teachers and students in Zabol and Chabahar in the education department; The results of validation of Cronbach's alpha test indicate that this questionnaire had good validity and reliability. The selection of the statistical population was purposeful; That is, from all the related schools, schools were purposefully selected at the discretion of the professors and were also evaluated and questioned. Analysis of the results of questionnaires related to teachers and students showed that the research hypothesis was confirmed according to T-Test.
Shahram Emamgholi, Gholamrezaa Janbaz Ghobadi, Parviz Rezaei, Sadroddin Motevali,
Volume 0, Issue 0 (3-1921)
Abstract
Temperature is one of the basic elements of climate, so its sudden or short-term and long-term changes can change the climate structure of any place. Intense heat waves are one of the most important climatic disasters that have far-reaching effects on various human activities and when they are of high intensity and frequency, they can produce major problems. In this study, to investigate the trend of 49-year frequency series (1970-1970) of hot wave events in Tehran, from two indices of hot days and hot waves (hot days lasting 2 days or more), non-parametric statistics of Sens trend analysis were used. All stations indicate an increasing trend both in the number of hot days in Tehran and in the frequency of hot wave events in 5 stations in Tehran. In this study, two hot waves were identified in Tehran, the first wave in 2010 covered a large part of the central and western parts of the country and the second wave in 2013, which was in all stations of Tehran and even many provinces. Are registered in the country. The results of spatial analysis of hot wave temperature in the statistical blocks of Tehran showed that generally the central areas of Tehran, including areas 6, 7, 8, 10, 11, 12, 14, 15, 4, 7, and 19 significantly It has been affected by the critical temperatures caused by the warm wave rule, while the northern parts of Tehran have been affected by the lower intensities of the hot wave.
Mr Ebrahim Bairanvand, Dr Amir Gandomkar, Dr Alireza Abbasi, Dr Morteza Khodaghoi,
Volume 0, Issue 0 (3-1921)
Abstract
The occurrence of torrential rains in April 2017 in Lorestan province was a clear example of heavy rains that left very heavy damage to agricultural, urban, transportation and communications infrastructure. The purpose of this study is to investigate and reveal the relationship between the physical structure of clouds producing two waves of heavy rainfall in April 2017 in the Doroud catchment area of Boroujerd. In this regard, the statistical characteristics of two precipitation waves on March 25 and April 1, 2019 were analyzed. The supernatural properties of the clouds producing these two heavy rainfall waves were investigated using the Madis superconductor product, MOD06. 4 Microphysical factors of generating clouds These two waves of heavy rainfall in the Doroud-Borujerd basin, including cloud peak temperature (CTT), cloud peak pressure (CTO), optical cloud thickness (COT) and cloud cover ratio (CF) were analyzed. Statistics of these two waves of heavy rainfall showed that in the first wave of heavy rainfall, ie the wave of March 25, 2019, (5 April 1398) 15% of the total annual rainfall and in the second wave, the wave of April 1, 2019 (April 12, 1398) 20% of the total The total average annual rainfall of the region was recorded in these two days. The results of analyzing the microphysical structure of the generating clouds of these two precipitation waves using the MODSI cloud sensor product data showed that the four microphysical factors of the cloud showed a significant spatial correlation with the recorded precipitation values of these two heavy precipitation waves. The two factors of temperature and pressure of cloud peak, which show a vertical expansion of clouds in the area, showed a significant inverse relationship with the amount of precipitation in the basin, while the two factors of cloud ratio and cloud optical thickness have a direct and significant spatial correlation with values. Recorded rainfall showed. The results of this study showed that in these two events of heavy rainfall, a significant and strong relationship was established between the microphysical structure of the cloud and the amount of rainfall recorded in the region.
Mostafa Karampour, Yeganeh Khamoshian Sahneh, Zohreh Ebrahimi, Hamed Heidari,
Volume 0, Issue 0 (3-1921)
Abstract
In recent years, much attention has been allocated to the study of atmospheric rivers because atmospheric rivers are massive carriers of moisture from remote areas. In this study, atmospheric rivers were studied for Iran and the neighboring countries in terms of their source of formation and their relationship and correlation with the NAO index. To study them the 1994 to 2019 data of various climatic elements such as Vwind, Function wind, NAO,, wind Shum, Meridonal wind were used. The results showed that during the study period, the ARs direction became more southerly, and jet streams played a major role in producing and determining the direction of river flow. Jetstream performance can also be used to determine the potential of an area in identifying atmospheric rivers. The highest correlation of the Transatlantic Transplant Index is with the tidal currents at the levels of 500 and 400. If the pressure centers are located in the southern part of the atmospheric rivers and the jet streams reach the eastern regions about 60 degrees, the length of the atmospheric rivers will reach more than 12,000 kilometers and affect the eastern regions of Iran to Pakistan, Bangladesh and Afghanistan.
Miss Sorayya Derikvand, Dr Behrooz Nasiri, Dr Hooshang Ghaemi, Dr Mostafa Karampoor, Dr Mohammad Moradi,
Volume 0, Issue 0 (3-1921)
Abstract
sudden stratospheric warming has an obvious effect on the Earth's surface climate. In this research, the changes in precipitation during the occurrence of this phenomenon have been investigated. For this purpose, after revealing the warmings that occurred during the studied period (1986-2020), 18 warmings were identified. The 5th decile and 9th decile of precipitation were calculated for the precipitation data of 117 stations. And the size of the difference from the normal rainfall was checked in two ways. First, the precipitation at the time of warming was compared with the long-term average, and then the trend of changes in precipitation at three times before thewarming, at the same time as the warming, and after the warming was finished. Finally, these results were obtained. Warmings according to the month in which they occur; They have a different effect on the amount of precipitation. In the sudden stratospheric warming that occurred in December, January and February, the northwest experiences the most rainfall changes and is above normal, and the probability of rainfall above the 9th decile increases up to 65%. Western and southwestern regions also have higher than average rainfall and the probability of heavy rainfall is high. Precipitation on the shores of the Caspian Sea shows an inverse relationship with sudden stratospheric warming, so in all the investigations of this research, the lack of precipitation at the time of warming in these areas is significant. Southern regions have less than normal rainfall in all sudden stratospheric warming events. The center of Iran has higher than average rainfall in the sudden stratospheric warming months of March. Eastern Iran also has heavy rains compared to normal during the sudden stratospheric warming months of March.
Mr Danesh Nasiri, Dr Reza Borna, Dr Manigheh Zohorian Pordel,
Volume 0, Issue 0 (3-1921)
Abstract
Widespread and frequent droughts in recent decades in Khuzestan province have become one of the most important challenges of this province. The use of remote sensing products in temporal and spatial monitoring of drought can play a key role in managing this risk and reducing and adjusting its destructive effects. The main goal of this research is to provide a remote sensing index for temporal and spatial monitoring of drought in Khuzestan province and its validation using station meteorological drought indices. In this research, by using the products of vegetation (MOD13C2) and land surface temperature (MOD11C3) of MODIS sensor, a drought index based on vegetation called VHI plant health index was produced. SPI Meteorological Drought Index, which was based on station rainfall data during the statistical period of 2000-2012, was used to evaluate and quantify this index. The comparison of VHI drought index with three-month SPI meteorological drought index values showed a significant correlation between 0.68 and 0.75. By identifying 4 years with widespread and relatively severe drought in Khuzestan province (based on both VHI and SPI indices), which included the years 2000, 2005, 2012, 2015, the spatial distribution pattern of meteorological drought and VHI plant drought to In general, it indicated that the northern parts of the province were generally involved in mild to moderate droughts and the southern parts were generally involved in moderate to severe droughts. The spatial correlation matrix based on the number of 2500 pixels with dimensions of 5x5 km, which included VHI and SPI values of selected drought years, indicated the existence of a significant spatial correlation between the two mentioned indicators. In the widespread drought of 2000, at the level of Khuzestan province, two drought indices VHI and SPI, the correlation was equal to 0.47, and in 2005, equal to 0.35, and
Monireh Rodsarabi, Mohammad Baaghideh, Dr Alireza Entezari, Fatemeh Mayvaneh,
Volume 0, Issue 0 (3-1921)
Abstract
In order to evaluate the thermal comfort conditions in the classroom, a field study was conducted in Sabzevar. Students' thermal sensations of class conditions were recorded at different hours of the day during the 2009-2010 academic year for different classes. At the same time, the temperature and humidity values of the classes were collected by a Data logger. To examine the differences, ANOVA, and Kruskal-Wallis methods were used. The results showed that the location of the classrooms in terms of geographical direction and building floor did not make a significant difference in the temperature and humidity, while the hourly differences of these parameters were significant.
In general, the responses related to the sensation of cooling had higher percentages than the state of heating (24% vs. 12%).
The thermal sensation in different months showed significant differences and the month of October had the lowest frequency in the feeling related to thermal comfort. In all months, except for October, the students' preferred was "heating". Although the performance of the heating system has been assessed as adequate, the operation time of this system should be done at a shorter distance from the start of morning classes to avoid wasting a significant portion of energy.
Although the temperature and humidity inside the classrooms did not show a significant monthly difference, but in terms of students' thermal sensation between different months, there was a statistically significant difference, therefore, the thermal sensation is something beyond physical characteristics (temperature and humidity) and In addition to being affected by climatic parameters, it is also strongly influenced by individual characteristics (sex, age, weight, height, clothing and activity level).
Mohsen Azizi, Hossein Mohammadi, Dariush Taleghani,
Volume 0, Issue 0 (3-1921)
Abstract
The aim of the current research is to show the potential areas for autumn sugar beet cultivation in Golestan province according to temperature and precipitation parameters. For this purpose, temperature (daily) and precipitation (annual) statistics were used for a statistical period of 15 years (2006-2020). In order to analyze the data, the methods of thermal potential diagrams, deviation from optimal conditions, phenology and zoning of Golestan province in terms of the amount of irrigation during growth were used from the annual rainfall data. The results of temperature evaluation using the thermal potential method based on the thermal threshold showed zero, 4 and 10 degrees Celsius at the level of stations in Golestan province; Inche Brun station has the highest cumulative thermal unit and Aliabad Katul station has the lowest cumulative thermal unit. Examining the date of the probability of late spring frost at the level of 95% showed that due to its occurrence at the end of April in the center, east, north, northeast and west of Golestan province, it coincides with the phenological stage of root bulking and sugar accumulation. Also, based on the deviation from the optimal conditions in Golestan province, Inche Brun station was calculated to have the lowest deviation (-20.64). Also, in terms of phenology, in the stage of budding, six leaves, root bulking and sugar accumulation and full ripening of the autumn sugar beet plant in Golestan province, the favorable areas for autumn sugar beet cultivation in Golestan province were determined, including Gonbadkavus, Bandar Turkman, Kalaleh, Inche Brun and Bandar Gaz. Also, the evaluations in terms of rainfall according to the annual rainfall zoning map of Golestan province, it can be concluded that in terms of rainfall and water supply required for autumn sugar beet, there is not much limitation towards Golestan province, however, considering the recent multi-year droughts, the cultivation of this plant in the province needs additional irrigation for growth.
Dr Mohammad Hossein Nasserzadeh, Dr Alireza Karbalai Derai, Mr Mohammad Siah Kamari,
Volume 0, Issue 0 (3-1921)
Abstract
Drought is one of the natural disasters whose long-term effects affect the economy and society. This phenomenon is considered a challenge in arid and semi-arid regions, including Iran. Nowadays, the use of remote sensing methods can help us in understanding the drought behavior of vegetation. In order to monitor and analyze the behavior of drought in Kermanshah province, the data of Sanjande Weathers products (VIIRS) and AVHRR data indexed by NOAA STAR were used. In this study, the Vegetation Health Index was used in the period of 1982-2021 in a seven-day format with a spatial resolution of 4 x 4 km. After extracting the data in the Kermanshah area, the vegetation drought trend was investigated on 65,387 cells using the Mann-Kendall test. The results showed that in the winter season, the trend of vegetation cover in the western areas of the province was decreasing and significant at the level of 0.05. While in the northern, central and eastern regions of the province, the trend is increasing and significant. In the spring and summer seasons, especially the months of June, July, August and September, which correspond to the dry months of the year, the size of the areas with a significant decreasing trend of vegetation cover has increased, while in the autumn season, with the beginning of the water year, the size of the areas with a decreasing trend has decreased.
Sharifeh Zarei, Dr. Bohloul Alijani, Dr. Zahra Hejazizadeh, Dr. Bakhtiar Mohammadi,
Volume 0, Issue 0 (3-1921)
Abstract
In this research, the most important synoptic patterns of widespread snowfall in the eastern half of Iran have been investigated. For this purpose, the current weather code data and snow depth of synoptic stations in the eastern half of the country during the statistical period of 1371-1400, for the months of October to March, were received from the country's meteorological organization. In order to investigate widespread snowfall, the days when more than 70% of the studied area saw snowfall at the same time were extracted as a widespread day. In order to perform synoptic-dynamic analysis of widespread snowfall in the eastern half of Iran, the classification method using cluster analysis was used and the maps of the representative days including atmospheric temperature, moisture flux, geopotential height, vorticity, front formation, jet stream, omega index and orbital and meridian wind data were drawn. Trend analysis was also performed using the Mann-Kendall test. The results showed that 3 patterns justify the snow cover in the studied area. These patterns are: high pressure in Siberia and central Europe-low pressure in eastern Iran, high pressure in western Iran-low pressure in Sudan, high pressure in central Europe-low pressure in eastern Iran and Afghanistan. In all the patterns in the middle of the atmosphere, the intensification of the meridian currents of the western winds along with the formation of high pressure and low-pressure centers has caused blocking in the path of the western currents and has provided the conditions for the ascent of the air. The concentration of the negative omega field and the relative positive advection, along with the location of the northeastern region of Iran in the left half of the outlet of the Subtropical Jet, have caused severe instabilities and widespread snowfall in the region. Also, the results showed that despite the absence of a trend in the number of snow days in the northeast of Iran, the number of snow days has decreased over time.
Hossein Asakereh, Mansureh Taheri,
Volume 0, Issue 0 (3-1921)
Abstract
One of the climatic characteristics of temperature is the occurrence of extreme temperature. In the present study, the trend of hot days with extreme temperature associated with the coastal plains of the Persian Gulf was investigated. Two environmental and atmospheric databases were used. Environmental data include the average of daily maximum temperature reported from 12 synoptic stations in Persian Gulf coastline (Khuzestan, Bushehr, and Bandar Abbas Provinces) from 1961 to the end of 2018. The extreme temperature for each day temperature was defined to be higher than the average of 75th percentile of the observations at each station and on the same day. Also, the ‘day with extreme temperature’ was applied to a day when the extreme temperature occurred in at least 50% of the stations. The number of hot days with extreme temperature in the study is 554 days, of which 291 days occurred in the warm season and 263 days in the cold season. These days were classified into six groups by performing cluster analysis on sea-level pressure in hot days. Then, for each group, the trend of hot days was examined. In general, it can be concluded that the slope of the line in all groups except the fourth and sixth groups were positive and, as a result, hot days with extreme temperature were increasing.
Sayyed Mohammad Hosseini,
Volume 0, Issue 0 (3-1921)
Abstract
for the spatial analysis of precipitation in the Middle East, have been used gridded precipitation data from the World Precipitation Climatology Center (GPCC) with a monthly temporal resolution and a spatial resolution of 0.5×0.5 arc degrees. Therefore, a matrix of 80 x 160 dimensions was obtained for the Middle East region (160 longitudinal cells and 80 transverse cells). The reason for choosing network data is their proper spatial and temporal separation and their up-to-date compared to station data. The period under investigation is from 1970 to 2020 AD. Finally, the long-term maps of the Middle East precipitation were drawn on an annual and monthly basis. The results indicate that precipitation in the Middle East tends to concentrate and cluster in the spatial and temporal dimension. In other words, due to the special geographical location of the Middle East region, such as uneven topography, distance and proximity to moisture-feeding sources (Caspian Sea, Black Sea, Mediterranean Sea, Atlantic Ocean, and Indian Ocean) and the direction of unevenness, Precipitation in high altitude areas, It is concentrated in the neighborhood of seas and oceans and also in the windy slopes of the mountain range of the region. The uneven distribution of geographical conditions has caused uneven distribution of Precipitation in the Middle East. So that; The center and gravity of the Middle Eastern Precipitation is concentrated in the eastern end of the Black Sea, southern Turkey in the neighborhood of Syria and Iraq, the Ararat-Zagors belt in the west of Iran, the southern shore of the Caspian Sea, the Pamir highlands and the Bay of Bengal in India, and the Hindu Kush highlands in Pakistan. Is. However, the many parts of the Middle East, due to their proximity to large deserts (African Sahara, Lut Desert, Dasht-Kavir, Arabia's Rab-al-Khali and Afghan deserts), have less than 100 mm of Precipitation. The results showed that the maximum Precipitation of this region has been transferred to the winter season, and the summer season is still the driest period in the Middle East, and only the coasts of the Indian Ocean and the Bay of Bengal have monsoon rains
Ms. Aida Faroghi, Professor Manuchehr Farajzadeh, ,
Volume 0, Issue 0 (3-1921)
Abstract
In this research, the frequency of merging of the polar-front and subtropical jet streams and its effect on the amount of precipitation received from the atmospheric pattern in western Iran during the 10-year statistical period of 2010-2019 was investigated. Then, by coding in Grads, the maps of jet stream level 300 hPa were drawn with a time interval of 6 hours. During the statistical period, these two jet streams merged along their axis. By examining the frequency of the merging of two jet streams, it was found that until 2015, the frequency of the merging of two jet streams in December was an increasing trend and in 2016 and 2017, there was a decreasing trend. It has increased again in 2018 and 2019. In all cases, the merging of two jet streams has not resulted in heavy precipitation events (December 2011, 2014 and 2017). So, considering the heavy rainfall of 110 mm from Dehloran station, the date of 12th to 15th of December was chosen to analyze and understand the system that led to the occurrence of rainfall. From December 12 to 15, 2010, the decrease in air temperature over Europe and Southwest Asia led to a large meridional movement of the polar-front jet stream, which resulted in merging with the subtropical monsoon. On the 12th of December 2010, along with the medicalization of the polar-front jet stream and its penetration into the tropical regions, its velocity core merged with the core of the subtropical jet stream over the northern Arabian Peninsula, the Red Sea and northeastern Africa. The merging of these two jet streams has led to the vertical expansion of the jet to lower levels, and in the middle level of the atmosphere, very low meridional movement is observed. As a result, the Sudan low moves to higher latitudes and merges with the Mediterranean low pressure.
