Climatology
Atefeh Hoseini Sadr; Gholam Hasan Mohammadi; Firooz Abdoul Alizade; Vaheid Khjaste Golamei
Volume 23, Issue 70 , March 2020, , Pages 79-100
Abstract
Heavy rainfall occurrence on April 14th, 2017 which followed by flood in Azarshahr and Ajabshir regions caused 48 deaths at East Azerbaijan province. Detecting synoptic mechanisms for such event was our main motivation for this study. In this regard, observational, upper atmospheric and SkewT data were ...
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Heavy rainfall occurrence on April 14th, 2017 which followed by flood in Azarshahr and Ajabshir regions caused 48 deaths at East Azerbaijan province. Detecting synoptic mechanisms for such event was our main motivation for this study. In this regard, observational, upper atmospheric and SkewT data were used. First, spatial distribution of precipitation in the study area was plotted. Then, Geo-potential height, vorticity and omega, specific humidity, moisture transition, jet stream for upper level and Huff-Muller chart were analyzed for different atmosphere layers. Finally, some atmospheric stability indexes were surveyed by using SkewT charts. Results showed that, highest rainfall was occurred as a rain corridor between southwest of West Azerbaijan province and middle regions of Urmia Lake to the central regions of East Azerbaijan Province with 30 to 57 mm range. Synoptic maps showed that in this day simultaneous expansion of the ascending area of Mediterranean trough in mid atmospheric layers and the core of polar Jet stream in upper levels provided favorable conditions for unstable atmosphere on the northwest of Iran, so that the amount of omega was less than -0.3 Pascal per second. Specific humidity maps indicate that, at the same time a significant moisture flux has flown from the Red Sea to the northwest of Iran. Therefore, the rapid conversion of atmospheric moisture into the rain in the ascending area of Mediterranean trough was the main cause of the heavy rainfall occurring on this day. This issue was proved by convergence moisture flux map and the Hoff-Müller graph. SkewT charts and instability indexes of Tabriz station also confirmed high amount of moisture and favourable ascending conditions in the atmosphere on April 14th
Climatology
Aliakbar Shamsipoor Shamsipoor; Seyfolah Kaki; Ayob Jafari; Seyd Maysam Jasemi
Volume 22, Issue 64 , September 2018, , Pages 149-167
Abstract
The aim of the research is recognizing mechanisms of the heavy rainfalls in the west and southwest of Iran using synoptic and thermodynamic method. For analysis of case study at April 2016, At first was obtained and calculated hourly rainfall data from 70 weather stations in the research area and 10 ...
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The aim of the research is recognizing mechanisms of the heavy rainfalls in the west and southwest of Iran using synoptic and thermodynamic method. For analysis of case study at April 2016, At first was obtained and calculated hourly rainfall data from 70 weather stations in the research area and 10 weather stations bordering the research area. Then rainfall amounts in stations were calculated and zoned using Arc/Map10. After that Ki, Li, TTi, Cape and SWEAT instability indexes was calculated for Kermanshah and Ahwaz weather stations. Finally, the synoptic maps were analyzed. According to instability indexes, mostly atmospheric instability has been moderate and favorable conditions could be observed for convection and thunder storm, lightening and snow fall. The analysis of the sea level synoptic maps have shown that a few days before the rainfall, the study area has been under the influence of the Siberian high, and simultaneously cyclones centers were formed above the Mediterranean Sea. Their eastern-ward movements created the condition for instability and rainfall in the area. Cold air downfall from high-pressure centers toward the backside of the Mediterranean trough and lower latitudes beside the dislocation of warm humid air to the fore side of the trough created the front and resulted in intensifying the rainy system that finally resulted in heavy rainfall in the area. The atmospheric physical and dynamic indexes show that during the rainfall, voracity positive values, jet stream wind and negative omega figures were in their maximum.
Majid Rezaee Banafshe; Hoseyn Hossein Alipour Ghazi; Fatemeh Jaffari Shendi; Majid Alimohammadi
Volume 19, Issue 53 , September 2015, , Pages 117-135
Abstract
In this study, the heavy rainfall of Northwest of Iranhas been analyzed using environmental circulation approach. Isohyte maps were depicted using Kriging method on 14*14 km pixels from 21/3/1961 up to 31/12/2004 (a17508× 533 matrix). Based on these interpolated data we selected super heavy rainfalls ...
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In this study, the heavy rainfall of Northwest of Iranhas been analyzed using environmental circulation approach. Isohyte maps were depicted using Kriging method on 14*14 km pixels from 21/3/1961 up to 31/12/2004 (a17508× 533 matrix). Based on these interpolated data we selected super heavy rainfalls for all in Northwest of Iran as a whole. Heavy rainfall and their locations have been detected from 00 to 1200 E and 00 to 800 N in the five this levels (1000, 925, 850, 700, 600 and 500 hPa level) at 00:00, 06:00, 12:00 and 18:00 UTC. The results of this study showed that four thickness circulation patterns play role in producing these super heavy rainfalls. In analysis of these precipitations one representative day was introduced for every circulation pattern. The analysis showed that the circulation patterns 2 justify the most of precipitations. These findings can play an important role in forecasting the precipitation and preventing from flooding in the region.
Seayed Abolfazl Masoudian; Fatemeh Jafari Shendi
Volume 18, Issue 50 , February 2015, , Pages 305-331
Abstract
In this study, heavy rainfall of northern low rainfall region has been analyzed using environmental to circulation approach. In order to analyze these types of rains, Asfezari rain data base is used. A base with daily ranfall includes 15992 days, from 1340.1.1 to 1383. 1437 daily precipitation maps of ...
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In this study, heavy rainfall of northern low rainfall region has been analyzed using environmental to circulation approach. In order to analyze these types of rains, Asfezari rain data base is used. A base with daily ranfall includes 15992 days, from 1340.1.1 to 1383. 1437 daily precipitation maps of northern low rainfall region were created using Kriging method. Mean daily precipitation data for this station has been used. Spatial resolution of these maps were 18 Km*18 Km. So 1406 pixels cover the northern low rainfall region and temporal and spatial behavior of precipitation could be represented by a 1406*362 matrix. We selected 100 days of the heavy rainfall from IRIMO data base. A cluster analysis was applied on this matrix and four different circulation patterns were actived. As a result, 100 occurrences of broad and heavy rainfall have been assimilated according to the sea level pressure, humidiy flux convergensy, stream function and front function exorbitance. Spatial configuration of these patterns showed that the main reason of these rainfalls had been the siberian and Black Sea unticyclones, troughs of Red Sea and Persian Gulf.
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.
