كليدواژه :
خشكسالي , شاخص SPI اگ نيو , شهرستان زاهدان , توزيع گاما , فصل رشد
چكيده لاتين :
Regarding the geographical condition and location of Zahedan township and its location at low geographical ,as well as, being far away from the influence area of Mediterranean winds, has lower humidity in comparing with the other areas of Iran. Consequently it is always confronted with the hazards and side effects of drought, particularly the frequent droughts in recent has caused a lot of damages to agricultural products and gardens of the area.According to SPI index introduced by McKee, 50 percent of region is faced with drought. This definition is takes questioned the drought event as an exceptional and rare occurrence. So for more compatible this index with the existing reality, Agnew was corrected the McKee SPI index.
Therefore in order to study the drought of Zahedan township , the modified 3 months SPI index (improved by Agnew) has been applied for a period of 16 cultivating years from 1990-1991 to 2005-2006 in monthly periods for 5 meteorological stations including Zahedan, Nosratabad, Ghetar khanjack, Nickmohammad abad, and Ladiz.
The results obtained from this research would be as following: Short - term SPI (Three months) will react immediately to the monthly precipitation changes, therefore they can show clearly the decrease of monthly precipitation. So that, its results can be used in different one - year agriculture and planting systems. With respect to Agnew classification, we can realize the non - uniformity of drought severity in different stations of Zahedan township, so that, the great amount of drought severity is related to the medium drought. The zoning maps of the droughts intensities indicate that the east and central parts of Zahedan are being more affected by the drought in comparing with west parts.
