Abstract

This study analyses seasonal drought characteristic for the period spanning from 1960 to 2008 for North Eastern region. The component of drought investigated in this study includes severity, duration, Frequency, persistence and probability of occurrence. The Standardized Precipitation Index (SPI) of run 3 for March-April-May (MAM) season and October-November-December (OND) season have been calculated and used to quantify the precipitation deficit. Frequencies of various drought categories were calculated and used to determine the probability of occurrence and persistence of various drought episodes. Time series analysis for the parameters was done to determine the trend and periodicity of drought characteristic while frequency analysis was done to determine the number of occurrence of extreme events. In order to determine whether some of the observed drought patterns were periodic, spectral analysis of observed drought pattern was investigated using Single Fourier spectral analysis. Due to analysis of the two rainy season, SPI analysis done returned only two types of drought namely the mild drought with values ranging between -0.01 to – 0.99 and moderately dry condition with SPI values ranging from -1.0 to -1.49. There is high probability of mild drought in both seasons in all stations that were studied with Wajir recording the highest probability. Droughts of varying intensity were observed to last for several seasons and individual drought category had low probability for higher runs. The result from spectral analysis indicates existence of quasi-periodic oscillation with the following cycles dominant 2-3 yrs, 4.5-6.5 yrs and 8-12 yrs.

Keywords: Drought; Standard Precipitation Index (SPI); March-April-May (MAM); October-November-December (OND)