Investigation of meteorological drought Indixes in Mazandaran synoptic Stations

Drought is caused decrease by of rainfall، runoff and soil moisture and also increase of air temperature and water table compared to long time average condition. Drought can be divided into four major groups of Meteorological، Hydrological، Agricultural and Social- economical which meteorological drought will be evaluated by rainfall values comparing with its average. In this study، by use of monthly rainfall data of Babolsar، Noushahr and Ramsar synoptic Stations which are related to Mazandaran Meteorological Organization، Drought events was quantified by Standardized Precipitation Index (SPI)، Percentage of Normal Index (PNI)، Deciles Index (DI)، Chinese Z Index (CZI)، Modified Chinese Z Index (MCZI) and Z- Score Index and Mohan & Rangacharia method. Results shows that PNI and DI in all stations have similar trends and the Curves of SPI، ZSI and CZI in all stations are well coincide with each other and have a very good fitness but MCZI. In Mohan & Rangacharia method، drought events characteristics consists of commencement، termination، duration and intensity were determined for all stations. Applying this method for preparing iso-duration and iso- intensity maps of drought (Drought zoning) for determination of the drought susceptible area and also forecasting the future condition are recommended.