CS(AR)-13/98-99 : Drought characterisation in sub-humid climate region

Abstract

The climatic regions are defined in terms of two readily available climatic parameters: (1) ratio of mean annual precipitation to global terrestrial mean annual precipitation, and (2) ratio of mean annual potential evapotranspiration to mean annual precipitation (Ep/Pa). As a first part of the study of drought characteristics across the climatic regions, this study has been limited to sub-humid climatic regions falling over different parts of the country. The study revealed that the drought frequency, and intensity have significant relationship with the above regional climatic parameters. Average drought frequency (yr) is seen to increase gradually from dry to wet regions, from 4 years in the regions with Ep/Pa >2 to >8 years in the regions with Ep/Pa <1.

For a given meteorological drought year, the areas with Ep/Pa ratio between 1.5-to-2.0 faced relatively more intense drought (i.e., severe drought) than the areas with Ep/Pa ratio between 1.0-to-1.5. The occurrence of severe or extreme droughts are much rare in the regions having Ep/Pa ratio less than 1.0. This revealed that the sub-humid region with greater mean annual deficit are susceptible to face relatively more intense drought.

The drought duration is seen to vary between 1 and 5 years in the sub humid climatic regions. The median value of drought of longest drought persistence among the different locations in sub-humid regions is 2 years. However no relationship could be established between drought duration and Ep/Pa ratio.

These results of drought characterization can be used as a framework for the systematic analysis of droughts and planning of drought management strategies in sub humid climatic regions in India.