A comparative assessment of meteorological drought characteristics in agro-climatic zones of Rajasthan (arid) and Tamil Nadu (humid), India

Understanding the long-term rainfall trends and characteristics of meteorological drought resulting from scanty rainfall, under the influence of changing climate, is vital in addressing the challenges associated with the management of water resources. An attempt has been made to analyze the changes in long-term rainfall trends and meteorological drought characteristics in agro-climatic zones of two different regions, i.e., Tamil Nadu and Rajasthan, India. A 52-year daily gridded precipitation dataset (0.25 degrees x 0.25 degrees) for the period of 1969 to 2020 has been obtained from the India Meteorological Department (IMD) to analyze region-wise agro-climatic rainfall variability and drought characteristics. In addition, IMD grids of both regions are divided into three zones based on the classification of agro-climatic zones (ACZs) of India. The ACZs-wise precipitation irregularity has been evaluated using the Rainfall Anomaly Index (RAI). The Standardized Precipitation Index (SPI) was also performed at different time scales (three, six, twelve, and twenty-four months) to identify the meteorological droughts. Further, the run theory was applied to characterize drought assessment for both regions. SPI results showed that in Tamil Nadu, the East coast plains and hills region (zone 3 ECH) experienced more frequent but less severe and short-lived droughts, while the West coast plains and hills region (zone 1 WCG) experienced less frequent but more severe and long-lasting droughts, whereas in Rajasthan, the Western Dry Region (zone 3 WDR) experienced more frequent but less severe droughts, while the Trans Gangetic Plains (zone 1 TGP) experienced less but more severe and long-lasting droughts. Findings revealed that the regional topography and moisture availability perform a major role in regional precipitation variability. A comparative evaluation of drought characteristics in different climatic regions using agro-climatic zones provides valuable information to planners for adopting management strategies to easily tackle drought conditions.