Amirhossein Halabian; Ali Ghasemi Siani
Abstract
In this research, for analysis the spatial- temporal trend of precipitation in Caspian basin, the monthly data of GPCC data base in the spatial resolution of 0.5°×0.5° during 63 years period(1951- 2013) have been used. In order to analyze of the spatial- temporal trend of precipitation, ...
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In this research, for analysis the spatial- temporal trend of precipitation in Caspian basin, the monthly data of GPCC data base in the spatial resolution of 0.5°×0.5° during 63 years period(1951- 2013) have been used. In order to analyze of the spatial- temporal trend of precipitation, the mean of annual, seasonal and monthly amounts of precipitation were prepared and then by applying Mann-Kendall nonparametric test at 0.95 level of significance, 17 maps precipitation spatial trend were produced in GIS. To examine the temporal trend of precipitation, first 17 graphs were prepared using the weighted amount of precipitation and then the trend was evaluated using Mann-Kendall nonparametric test at 0.95 level of significance. The evaluation of monthly precipitation spatial trend maps indicated a significant downward trend at 0.95 level of significance in March and April on the western, eastern and southwest regions of Caspian basin. Only in spring and autumn there have been a significant downward trend and in none of the other seasons no meaningful trend was detected. Also, the analysis of yearly precipitation spatial trend illustrated a significant downward trend on western region. The analysis of precipitation revealed significant downward trend on monthly time series at the 0.95 level of significance in March on Caspian basin.
Amirhossein Halabian; Nasrin Nikandish; Motahare Akbari
Abstract
In the present study is to identify patterns causing floods in the Mazandaran province to predict these patterns through before the flood could necessary precautionary measures to prevent the damage and take advantage of precipitation. In this reserch, two databases composed of two variables is necessary. ...
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In the present study is to identify patterns causing floods in the Mazandaran province to predict these patterns through before the flood could necessary precautionary measures to prevent the damage and take advantage of precipitation. In this reserch, two databases composed of two variables is necessary. a group of variables and atmospheric data including geopotential height at 500 hPa, zonal wind(uwnd), meridional wind(vwnd) and specific humidity(shum) in Synoptic four hours in the range 0 to 80 degrees north and 0 to 120 degrees east at a spatial resolution 2.5 × 2.5 degree from the database (NCEP / NCAR) have been harvested and other group of precipitation and discharge data in area, during the is 28 Aban to 2 Azar 1388. Then, taking advantage of environmental- circulation approach to mapping 500hpa circulation patterns, atmosphere thickness patterns of the levels1000-500 hPa, moisture flux convergence function and frontogenesis function in 500,925 and 1000 hPa levels on the occurrence of floods. The results of this research have shown that flood generating precipitation in the Mazandaran area are mainly caused by the eastern Mediterranean frontal lows. At the same time, thickness patterns have illustrated intense depressure zone that caused by meeting of cold air mass of the high latitude with humid and hot air mass of the southern Mediterranean. Analysis of the moisture flux convergence(MFC) patterns also have shown that flood generating precipitation are caused by moisture flux of water masses of the Caspian Sea and Black Sea to the Mazandaran area. Analysis of the frontogenesis function maps indicate that occurrence of flood generating precipitation in the study area is caused by the formation and occurrence of front in the Caspian sea and the Black sea in middle levels and east these two of water masses at lower levels of atmosphere (925 and 1000 hPa).
