Comparison of Meteorological Drought Indices in Mazandaran Province

Drought caused by abnormal dry period which its continuation makes unbalance hydrologic system in a region, if some prevention countermeasures are taken against drought, its damages will be declined. In order to Drought monitoring and management by use of some indices, 33 meteorological stations which belongs to ministry of Energy in Mazandaran province were selected. Thus required data were collected and statistically analyzed. To reconstruct and statistical prolongation of incomplete station, differential and ratios method are applied. Run test was used for homogeneity assessment of data. Finally, based on available data analysis, 35 year data series from 1976 to 2000 as a research statistical period was used. Then, drought indices includes Standardized Precipitation Index (SPI), Normal Percentage(PN), Chinese Z(CZI), Modified Chinese Z(MCZI), Z- Score Index(ZSI), Deciles Index(DI) on 1 year time scale in all stations was calculated and related curves were drawn. Based on Correlation test, pair significance of these indices was satisfied at 5% level in all stations. PN, ZSI and SPI with maximum average correlations and least standard errors respect to others, had better results, but MCZI with minimum correlation had the worst results. Maximum correlation between annual precipitation and each one of indices belongs to PN, ZSI, SPI, CZI, DI, MCZI with determination coefficient of 0.998, 0.99, 0.986, 0.942, 0.908 and 0.057 respectively. Results show that for study and investigation of meteorological drought in Mazandaran province, PN, ZSI and SPI indices has the same status and prior to other indices.