The study defines the climatic regions in terms of readily available climatic parameters like ratio of mean annual precipitation to global terrestrial mean annual precipitation and ratio of mean annual potential evapotranspiration to mean annual precipitation (Ep/ Pa).
The study focuses on the drought characteristics of the sub-humid climatic regions across different parts of the country. It establishes that the drought frequency and intensity have a 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 above 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 faced relatively more intense drought (i.e., severe drought) than the areas with Ep/Pa ratio between 1 to 1.5. The occurrence of severe or extreme droughts is rarer in regions having Ep/Pa ratio less than 1. This revealed that the sub-humid region with greater mean annual deficit is susceptible to more intense drought.
The drought duration is found to vary between 1 and 5 years in the sub-humid climatic regions. The median value of drought of longest drought persistence in 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 for planning of drought management strategies in the sub-humid climatic regions of India.
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