Assessment of Seasonal Rainfall Drought Indices, Nyala City Sudan

Drought is an unpredictable hydrological phenomenon, and climate change has made it difficult to predict analyze droughts. Nyala city airport metrological station rainfall records from 1943 2017 (75 years) were investigated. Four statistical drought indices used; the standardized precipitation index (SPI), anomaly (RAI), decile percent (RDI), normal (PNI). The study analyzes, assesses, compares, determines proper index. Results show that annual class (DC4) percentages for PNI, RDI, RAI are not significantly different at average of 42% 65.3% SPI a frequency 49 years. In comparing monthly yearly values considering historical dry wet droughts, results showed performance rank as: SPI, RAI, PNI. Result reveals was superior in all analyses, but had some defects detecting when dominated by rare or zero (start end rainy season). This concluded revealed conducting zone chart showing deviations standard deviation about mean. Thus, outperforms other three indices.