Abstract :
: Drought occurrence of the main characteristics of climate can be considered in the realm of wet weather and dry visible. In this study, a history of Rasht and Anzali droughts and the time scales standardized precipitation index SPI criteria and annual precipitation was investigated SIAP. Scale statistical study period, daily for 30 years and monthly and annual scales, 50 were considered. SPI model of monthly time scales 1, 3 and 6 months to evaluate short-term drought and agricultural meteorology and time scales of one, two and four years to evaluate long-term hydrological drought was, The purpose of the preparation and application of each drought index, providing a simple and quantitative evaluation of the three characteristics, drought severity, and extent of spatial continuity is. Given that the drought year, a lot of damage directly and indirectly to the countryʹs infrastructure and agricultural imports, study, and ultimately identify the appropriate policy actions in confronting the ills of natural essential. Thus, a component of drought indices and to provide access to risk management is in drought. These indicators can help the severity and extent of the drought can be few and be evaluated periodically. Process for predicting droughts in coming months, ARIMA statistical models or integrated moving average models and their one-year return on the SPI results were fitted , The results show more or less continuous mild drought period is late 2009. SPI index, so in most months is less than zero. Daily effective rainfall in the model, or ERI hypothetical 15-day period to assess agricultural drought and the hypothetical 365-day period to evaluate the hydrological drought area was used In fact, the hypothetical 15-day period of rainfall during the past two weeks and the hypothetical 365-day precipitation drought last year involved in the calculation are provided below.
