Document Type : Research Paper
Author
Abstract
Of the many Climatic events that influence earth’s environmental fabric‚ drought is perhaps the one that is most linked with desertification(WMO‚1997).This Investigation is an effort for assessment of acceptability about many of Climatic current Drought Indices in reagent and sample stations of Salt Lake Basin of Iran. These drought indices which are used in world active systems, are Percent of normal precipitation Index PNI, Deciles of precipitation Index DPI, Standardized precipitation Index SPI, and Z Score Index ZSI.The above mentioned indices were calculated first by average of monthly precipitation data for a 44 years period from 1957 to 2000 relate to 34 synoptic and climatological stations in their common time scales. Based on obtained results from one hypotheses, DPI and SPI indices in the contemporary with minimum occurrence, showed, extremely drought in the studied stations. These acceptability of indices in more than of other indices and according of this investigation,DPI index sit on the first place, SPI sit on the second place, ZSI index sit on the third place, and finally PNI Index, sit on the forth place. In next stage the Standardized Precipitation Index SPI, based on precipitation values from 34 monitoring stations around the Salt Lake Basin of Iran, is computed monthly and was performanced for climatic interpret and characteristic include assess drought relative frequency, intensity, expand and duration and calculated return period of the most intense drought and according to the point stations data, drew intense map. This investigation indicate the most intense drought in Salt Lake Basin of Iran belong to Hamadan(Nozheh) and the longest drought duration in Avaj ‚Dooshantappeh‚ and Kashan Stations with the highest relative frequency digit of drought (38/6%) and the lowest relative frequency digit of drought (18/1%) belong to Golpayegan. The most of severe year has occurred in 1973 and 1967 in 44 years period.
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