Meteorological Drought Quantification with Standardized Precipitation Anomaly Index for the Regions with Strongly Seasonal and Periodic Precipitation

Abstract

In this study, an index, named as standardized precipitation anomaly index (SPAI), is proposed for the meteorological drought quantification in the context of the monsoon-dominated climatology, where the precipitation is strongly seasonal and periodic. In the computation of SPAI, the anomalies of the precipitation are normalized rather than normalizing the raw precipitation series. The SPAI is compared with the standardized precipitation index (SPI), with respect to certain shortcomings of the latter. It is shown that the SPAI, owing to its design, is able to successfully differentiate between the consequences of shortages/surplus in rainfall in the monsoon and nonmonsoon months which is not possible through SPI. The unique suitability of SPAI for monsoon dominated regions is also illustrated by comparing its premise of development with that of the standardized nonstationary precipitation index (SnsPI). Further, drought quantification through the SPAI is shown to be applicable for both periodic and nonperiodic precipitation series. This is demonstrated using a typical strongly periodic precipitation series (from India) and a typical nonperiodic precipitation series (from Arkansas, United States of America). As compared with SPI, the SPAI is found to have a better coherence with the consequences of droughts and wet spells faced by the country (India, as the study area) in the past.