Climatology
masoud jalali; Vahab Kamariyan
Abstract
Strong winds have been named as the storms that blow in different shapes and too fast for a short time and are usually associated with unstable weather. If the unstable air have had humidity thunderstorms was happen other case was caused the dust storms. The purpose of this study was the analysis of ...
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Strong winds have been named as the storms that blow in different shapes and too fast for a short time and are usually associated with unstable weather. If the unstable air have had humidity thunderstorms was happen other case was caused the dust storms. The purpose of this study was the analysis of temporal oscillations of Thunderstorms in the North West of Iran (Ardebil, East Azerbaijan and West Azerbaijan) using spectral analysis. For this purpose, a daily 16-synoptic data (in the form of current weather data) of the Meteorological organization during the period 1988-2009 were used. In the following codes of 17, 29, 91 until 99 related to thunderstorms were identified. In order to analyze the Thunderstorms cycles in North West of Iran were used possibilities of programming in the Matlab software and Surfer software was used for graphical operations. The results showed that the frequency of the 2-year cycles is more than any other state; Therefore, the frequency of significant cycles, 2 cycles of 5 stations with the highest proportion allocated. Maku and Khoy and central stations, including stations of Tabriz, Maragheh, Mahabad and being involved, 6. 2-year cycles, respectively, and in terms of risk is most likely to occur in these areas.
Climatology
Masoud Jalali; Ali SHahbai; Vahab Kamrian
Abstract
In this paper, we attempted to identify the synoptic patterns of Summer heavy rainfall in the southern coast of the Caspian Sea by using environment- to- circulation method. To attain this aim , by using statistics of daily Precipitation of 40 synoptic and climatology stations located in the region for ...
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In this paper, we attempted to identify the synoptic patterns of Summer heavy rainfall in the southern coast of the Caspian Sea by using environment- to- circulation method. To attain this aim , by using statistics of daily Precipitation of 40 synoptic and climatology stations located in the region for periods of 20 years of 1991 to 2010 and by percentile method , 29 days have rain more than 15 mm which have occurred in at least 30 percents of region stations , were determined as days with heavy rain. By using factorial analysis and cluster analysis methods , 3 synoptic patterns were determined as agent of creating rain in 29 days that the first pattern 48.3 percent , second pattern , 30 percent and the third pattern have allocated 21.7 percent of days of heavy rain in the studied region. In order to synoptic analysis of these patterns , maps of sea level pressure , 500 hectopascal level , omega (atmosphere vertical motions) , vorticity and moisture flows of level of 850 hectopascal related to two days before rain was used until rain day and finally it is determined that the main cause of occurring heavy summer rainfall in southern coast of the Caspian Sea is the penetration high-pressure system and after that formation of cool and moist northern flows as well as incidence of vast convection in the region. Each three patterns emphasize on occurrence of this condition and their difference is the place of deployment of high-pressure system and consequently the number of rainy days and severity of rain in these days.
