A Robust Drought Index Accounting Changing Precipitation Characteristics

Abstract

AbstractA realistic evaluation of drought onset is inevitable for the effective implementation of mitigation strategies. Meteorological droughts indicating the onset of drought propagation are usually quantified through unbiased indices that consider the month‐wise magnitude variations in historical climatic variables, while completely ignoring their intramonthly distributions. However, the applicability of such indices under the present scenario of changing climate, where intense short wet spells are reportedly increasing, is questionable. Such changes in the wet spells could eventually lead to prolonged intramonthly dry spells, which in turn will pose many agricultural and socioeconomic risks. To monitor the changed scenario realistically, we propose a new drought index—the Standardized Net‐Precipitation Distribution Index (SNEPI), which incorporates the distribution characteristics of the daily net‐precipitation variable. The applicability of SNEPI is critically evaluated using synthetically generated and observed precipitation series over six diverse climatic locations of India, at 1‐, 3‐, 6‐, and 12‐month time scales. The utility of SNEPI is more profound for longer time scales, understandably due to the enhanced emphasis imparted on the distribution of rainfall spells by the longer periods. Standardized Net‐Precipitation Distribution Index proves to be efficient in capturing the present scenario of increasing dryness (wetness) in wet (dry) regions when compared with the traditional Standardized Precipitation Evapotranspiration Index. Hence, the proposed index, which incorporates the changing precipitation characteristics, may aid in better quantification and monitoring of meteorological drought under the scenario of changing climate.