Climatology
Hossein Asakereh; Ali shahbaee kotenaee
Volume 22, Issue 64 , September 2018, , Pages 211-228
Abstract
Pervasive cold days are one of the abnormal continental events that have a lot of effects on environment and human activity. These events are created as a result of formation of complex atmospheric patterns. In these patterns, knowledge of how these atmospheric systems interact can be very useful in ...
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Pervasive cold days are one of the abnormal continental events that have a lot of effects on environment and human activity. These events are created as a result of formation of complex atmospheric patterns. In these patterns, knowledge of how these atmospheric systems interact can be very useful in prediction of the similar conditions and reduction the contingency damages. On this basis in this present research, it has been tried to analyze the earth's temperature conditions and dynamic and synoptic conditions of different levels of atmosphere on 21 January 1964 as pervasive cold day in Iran by using data from minimum temperature gained in different parts of the country and also the atmospheric data from 1960 to 2010. In this day 98.4 % of the area has been affected by the cold. The results of synoptic and dynamic analysis of atmospheric systems that creating the cold of this day showed that created a blocking system in west and center of Europe and establishment a low height system in north of Russia and the opposite movements of these two systems to each other has caused that cold polar air from northern Scandinavia have moved to Iran. It has also been recognized that height factor has performed an important role in cold extremity in this day across the country.
Climatology
Yousef Ghavidel Rahimi; Mohammad Rezaei
Volume 19, Issue 54 , February 2016, , Pages 253-277
Abstract
Heat waves are considered as one of the important climatic hazards in the world and especially in Iran and it seems that, due to intensification of global warming, their occurrence has increased in recent years than in the past. This study has paid attention to quality and quantity evaluation and synoptic ...
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Heat waves are considered as one of the important climatic hazards in the world and especially in Iran and it seems that, due to intensification of global warming, their occurrence has increased in recent years than in the past. This study has paid attention to quality and quantity evaluation and synoptic analysis of heat waves in the KermanProvince. For this purpose, At first, the daily maximum temperature data, in month of July (as the warmest month in the year) was put in a statistical period of 24-years (1986-2009) from meteorological organization, for 4 synoptic stations of Kerman, Bam, Anar and Sirjan. In order to classify heat waves, standardized temperature data and on its basis, anomalies of 0 to 0.75 as a heat wave, 0.75 to 1.5 as severe heat waves, and greater than 1.5 were determined as super heat wave. The threshold values of 43.1, 42.1 and 41.2° C were calculated for all stations, respectively as threshold of heat wave, severe heat wave, and super heat wave and its continuity were considered at least for two days. Accordingly, During Statistical period of study, it was found 7 heat waves, which were, identified within 3 severe heat waves, and 1 super heat wave. Super heat wave in July 1998, was selected For the Synoptic analysis. This three-day wave, with an average temperature of 43/11° C, has been the most severe heat wave in KermanProvince. Results of synoptic analysis of super heat wave indicated that the establishment of Ganges low pressure on the ground and the domination of subtropical high-pressure of azores in high levels and also, high thickness atmosphere on the study area caused the subsidence of warm air and excessive heating of earth's surface, and created them mentioned super heat wave.
Climatology
Mahmood Khosravi; Nematollah Safarzaie; Mohsen Armesh
Volume 19, Issue 52 , June 2015, , Pages 113-140
Abstract
Frost is one of the natural disasters that is usually are associated with financial losses and even mortality. The atmospheric circulation systems have a main role in the occurrence, severity and spatial distribution of frost especially in temperate regions. The purpose of this research is the detection ...
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Frost is one of the natural disasters that is usually are associated with financial losses and even mortality. The atmospheric circulation systems have a main role in the occurrence, severity and spatial distribution of frost especially in temperate regions. The purpose of this research is the detection and investigation of synoptic conditions simultaneous with occurrence of winter frosts in Sistan region. The method used in this analysis approach is peripheral circulation. For these purposes, two databases (surface and atmospheric) were required. For surface data, climate data from synoptic weather stations of Zabol and Zahak were used as a representative of the regional climate. The longest and most severe frost was selected during the last decade (2010-2000). Second database of sea level data and maps of 850 and 500 Hp levels was prepared from the National Center for Environmental Prediction (NCEP) and National Center for Atmospheric Research (NCAR). Spatial coverage of weather data is between 30 until 90 degrees east longitudes and 10 until 50 degrees north latitude. For representing the weather stream lines maps, Grads software was used. The results showed that cyclonic activity on the Balkhash Lake prepared the situation for downfall of cold air of high latitude and western flow of trough to region and caused frost in the Sistan region. Transferred axis of trough at the eastern regions and the above conditions caused more frost persistence. The most severe frost in Sistan region tll, place in the western part of trough and the flux of northern cold air. The factor that has created these conditions is the pressure gradient between the southern and northern regions of Sistan, especially South East of Sistan low-pressure system which led to the establishment of west part of trough to the region.
Kamal Omidvar; Mehdi Mahmodabadi; Farshad Safarpour
Volume 19, Issue 51 , April 2015, , Pages 21-39
Abstract
Abstract In this research we investigated synoptic pattern of heavy rain 1 and 2 February 2011 in southern and central regions of Iran specially Kerman province. At the first we calculated heavy rain for all of synoptic stations with use Extreme value type1 then thermodynamic characteristics of heavy ...
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Abstract In this research we investigated synoptic pattern of heavy rain 1 and 2 February 2011 in southern and central regions of Iran specially Kerman province. At the first we calculated heavy rain for all of synoptic stations with use Extreme value type1 then thermodynamic characteristics of heavy rain analyzed with use radio sounding and Skew-t data. For analyzing of this phenomenon we used daily rainfall data 32 synoptic stations of southern and central regions and SLP and 850, 500 and 300 hgt maps. In the 5 day periods, we investigated synoptic pattern formation and its trend in weather maps. The results show that main factor of precipitation in region is formation of cut off low on Mediterranean sea. This system act so blocking and with move onto east, it causes that trough of east Mediterranean reinforcement thus west systems penetrate to lower latitude and they get high level of humidity from south seas and they makes sever precipitations in the study area.
Yosaf Ghavidel Rahimi
Volume 19, Issue 51 , April 2015, , Pages 289-309
Abstract
Abstract
In this research in a survey and analysis of daily maximum temperature data in 13 stations of Khuzestan Province on 21 May to 31 September 2010, the stations were classified into four clusters using the Ward clustering method. Clustering results demonstrated that Abadan and Bostan stations ...
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Abstract
In this research in a survey and analysis of daily maximum temperature data in 13 stations of Khuzestan Province on 21 May to 31 September 2010, the stations were classified into four clusters using the Ward clustering method. Clustering results demonstrated that Abadan and Bostan stations were the warmest stations in Khuzestan province and maximum temperature in Izeh is lower than other stations. Also, based on the average maximum temperature data a separate criterion for determining the super-hot temperatures was presented, i.e., the threshold of 47.17 degrees Celsius. Temporal sequence of warm temperatures occurrence in more than one day temperatures have created super heat waves. During studied time interval, five heat waves were identified in the Khuzestan Province. The warmest super heat wave between five super heat waves was a 4-daily super heat wave which occurred from 5 to 8 July and selected for synoptic analysis. Results of synoptic analysis for mentioned super heat wave proved that institution of a low pressure at ground level and high pressure dominance in middle levels to 500 hp and also the sever increasing in the thickness of the atmosphere that caused on warm air subsidence and abnormal warm air heating and reflow of the earth surface were regarded as dynamic-synoptic agents of super heat wave day occurrence. Analyzing of atmospheric temperature advection maps proved that interneal source of heat air to Iran and Khuzestan Province was hot and dry air advection from the Africa, Arabian Peninsula and Iraq. This process is the effective and creative agent of super heat wave that occurred in 5 to 8 July 2010 in widespread sections of Iran particularly in Khuzestan Province.
Manochehr Farajzadeh; Saeed Rajaee Najafabadi
Volume 17, Issue 45 , November 2013, , Pages 142-162
Abstract
In this paper we study the heavy precipitation and probability of occurring flood as a result of it for Koohrang station. The synoptic and discharge maps were chosen and drawn in purpose of showing the discharge peak for 29 February by175 mm rainfall. In this day a low pressure center was located in ...
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In this paper we study the heavy precipitation and probability of occurring flood as a result of it for Koohrang station. The synoptic and discharge maps were chosen and drawn in purpose of showing the discharge peak for 29 February by175 mm rainfall. In this day a low pressure center was located in Greek. As this center expanded to the north, the thermal low pressure above the Sudan and Saudi Arabia became dynamic and stretched toward the west of Iran. According to the sea surface, 500 mb and moisture flow, this heavy rainfall was the result of the instability from surface to 500 geopotential levels and generated 5.7 m2/s discharges in the regain.
Hasan Lashkari; Noshin Aghasi
Volume 17, Issue 45 , November 2013, , Pages 203-234
Abstract
The thunderstorms are climate destroyer phenomena every year entering irreversible losses on the establishments, farms, houses and so on such as the hail, the flooding rains and the thunder strike. The recognition of the role of these storms is very important that can decrease the possible losses. In ...
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The thunderstorms are climate destroyer phenomena every year entering irreversible losses on the establishments, farms, houses and so on such as the hail, the flooding rains and the thunder strike. The recognition of the role of these storms is very important that can decrease the possible losses. In the present research after the analyzing the thermodynamic and synoptic characteristics about the Tabriz thunderstorms in a statistical ten-year period (1996-2005) and ensuring the results of the instability indicators, the researches show strong anticyclone dominance on Russia which extends to the westernorth of Iran and causes increasing thermal gradiant at this area. Also in the higher levels, the presence of strong cyclones on the eastern south of the black sea due to the constant raining of the northern latitudes on this area has caused high depth of the entering path of the black sea on the north western of Iran. With the insertion of two low pressure cells of Sudan and Mediterranean on Kuwait and south of Iraq and with the extention of it's dominance toward the western north of Iran and also the presence of a low pressure cell on Hormoz strait and north of Arabia and finally the transfering of heat and the moisture of Oman sea and the Persian Gulf on the areas have provided the necessary conditions for the higher instability and the thunderstrikes.
