Climatology
Yaghoob Rezazadeh; Bohloul Alijani
Abstract
Cold and freezinginthe North West ofthe country(Iran), has arrived allyearirreparabledamages to thetransportsectors, roadaccidents, gardens andagriculturalproductsandcrippled thenormal lifeof people incityand villagesAt first, theverycolddays of 18 stationsin the statistical periodwere extracted then ...
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Cold and freezinginthe North West ofthe country(Iran), has arrived allyearirreparabledamages to thetransportsectors, roadaccidents, gardens andagriculturalproductsandcrippled thenormal lifeof people incityand villagesAt first, theverycolddays of 18 stationsin the statistical periodwere extracted then of thestatistics, the number of 43 Severe and pervasive wave was selected..Finally, for Synopticanalysis ofcoldwaves, tworepresentativewaves on February1991 and January 2007were determined. The maps of Earth and the500Hpa pressuressurfaceof thefreezing from theNCEPwebsitehas been prepared andanalyzed. The results showed that in most cases of severe frost in the top level, a deep descends in the Iran west established and polar regionsCold Weatherwill leadtoIran. The establishment of above thebarrier in the East of this descends was due relativestagnation of descends and the continuity of cold inthe region intensifies. At the surface of Earth, west migrant high-pressures and the spread of Siberian high-pressure tab add to intensityat 500Hpa levels. Accordingly, we can at least 5 days prior to the deployment of these systems in the vicinity of the study area, predicted cold conditions, the managers and farmers are prepared to deal with cold.
Saeed Jahanbakhsh Asl; Roghayeh Roshani
Volume 18, Issue 48 , June 2014, , Pages 81-96
Abstract
In this research we have studied Tabriz temperature inversion using radio-sound information, Skew-t maps and synoptic maps during the 2004-2008 period in daily and monthly scales. After reviewing the information and data at first days with weak, medium, and intense and very intense temperature inversion ...
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In this research we have studied Tabriz temperature inversion using radio-sound information, Skew-t maps and synoptic maps during the 2004-2008 period in daily and monthly scales. After reviewing the information and data at first days with weak, medium, and intense and very intense temperature inversion conditions were specified. Thereafter, the synoptic pattern of very intense and weak samples relating to three earlier days and two days after the peak of temperature inversion were analyzed using ground surface synoptic maps of 850 and 700 hp. The results indicate that there is a strong correlation between the occurrence of high pressure systems and the intense and very intense temperature inversion. In such a way that the intensity of temperature inversion has a straight relationship with synoptic pattern conditions especially the entrance of high pressure systems in the area. When the high pressure system in a stable condition is coming to the area in few-days scale, the intensity of temperature inversion is maximized. After the entrance of the low pressure cells, the temperature inversion is eliminated. Findings of this research have shown that with analyzing the synoptic systems that lead to the occurrence of temperature inversion and through the recognition of the patterns dominating over it, one can predict extreme temperature inversion. In addition, we can distinguish the patterns leading to the air pollution
Faramarz Khoshakhlagh; Seaed omid Nabavi; Esmail Abbasi
Volume 16, Issue 40 , September 2012, , Pages 97-118
Abstract
The presented study aims to investigate synoptic atmospheric conditions along with heavy precipitation in Khorasan Razavi and Khorasan Shomali provinces. The identification of temporal and spatial distribution of heavy precipitation associated with these extreme conditions is another goal of this study. ...
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The presented study aims to investigate synoptic atmospheric conditions along with heavy precipitation in Khorasan Razavi and Khorasan Shomali provinces. The identification of temporal and spatial distribution of heavy precipitation associated with these extreme conditions is another goal of this study. The amount of precipitation greater than 20 mm was chose to distinguish heavy rainfall from others. The parameters such as sea level pressure, temperature, relative humidity, specific humidity at the level of 700 hPa and wind direction were analyzed to identify sources of heavy precipitation moisture. Geopotential height at the level of 500 hPa was considered to determine heavy precipitation synoptic patterns. Wind speed and direction at the level of 300 HPA were evaluated to track the high-speed wind (jet stream). Then, these parameters were averaged monthly to investigate the general behavior of the atmosphere status associated with heavy precipitation in the studied area. The results show that in cold period of year the foci of heavy precipitation are located in KhorasanRazaviCounty. Mediterranean deep trough and Red Sea were identified as synoptic pattern and the main moisture source of heavy precipitation, respectively. Subtropical jet stream also recognized along with almost all heavy precipitation cases at level of 300 hPa.
