Efficiency of Some Meteorological Drought Indices in Different Time Scales (Case Study: Tajan Basin, Iran)

Abstract

 Drought  is  a  climatic  phenomenon  that  causes  much  detrimental  influence  on ecological  environments.  This  research  investigates  the  performance  of  meteorological  drought indices in different time scales in the Tajan basin in Iran. Indices undergone in this study include: Percent  Normal  Precipitation  Index  (PNPI),  Z-Score  Index  (ZSI),  Standard  Precipitation  Index (SPI), China Z Index (CZI), Modified CZI (MZCI), and Decile Precipitation Index (DPI). In this study, we used data of annual and monthly precipitation from meteorological stations in the basin. Drought  indices  were  determined  at  time  scales  of  1,  3,  6,  9,  12,  18,  24  year  of  minimum precipitation with very intense drought and the method of correlation coefficients between drought indices values and monthly precipitation. The results showed that DPI was the best index at annual time scale, while at the time scale of 1,6,12 and 24-months, PNPI was the best index. MCZI was the best index for time scales of 9 and 48-months, and the ZCI had the maximum efficiency for a three-month scale.