Forecasting and Analyzing of Rainfall Changes in the Southern Coasts of Caspian Sea in Order to Environmental Planning Using SDSM Model..

The southern coast of Caspian Sea is considered the wettest part of Iran. It is a major center of agriculture and tourism and is regarded as a great geomorphological entity in the area. In the southern coasts of Caspian Sea, rainfall, as the most important climatic element, has a complicated temporal and spatial distribution. One of the major factors that influence rainfall in this region is climate changes. The current study attempts to investigate the impact of climate changes on rainfall in the southern coasts of Caspian Sea. For this purpose, rainfall data related to 32 Rain gauges were collected from the Ministry of Energy and data related to the global climatic model (AOGCM)were collected from the American climate change website. In addition, data related to HADCM3 model were obtained from the Canadian website CCCSN. The data underwent quality control and their validity was investigated. Then, stations having records for more than 30 years were selected. After the preparation of the data, SDSM model and A2 and B2 Emission scenarios were used for the purpose of downscaling rainfall data. Findings of the study on rainfall data showed that NCEP model has a higher conformity to the observed rainfall data in estimating the amount of rainfall. The estimations made by A2 and B2 scenarios are close to the observed rainfall, except for the months with very higher or very lower rainfall than the average amount documented in the stations under investigation. The model showed a higher degree of error in months with higher rainfall (such as in the fall) compared to months with lower rates of rainfall. The highest variance of NCEP and HADCM3 models occurred in the fall (when maximum amounts of rainfall occurs) or in months in which sudden rainfalls have been documented in the areas investigated. Based on the analysis performed in the study , autumn total received rainfall in the region will increase. So for detailed planning and proper use from received precipitation it is necessary that use results of such researches .