Drought Termination and Amelioration: Its Climatological Probability

Abstract

The preliminary PDSI is calculated and disseminated operationally by the NOAA/USDA joint agricultural weather facility. This index is more aptly described as the PHDI in order to differentiate it from its hincast value, the PDSI. Using the PHDI the approximate precipitaiton required to ameliorate or terminate any ongoing drought was calcualted across the US for various prescribed periods (months). The probability calcualtions indicate that in many portions of the country, it is quite unlikely that serious drought can be terminated in a single season or even two seasons. Furthermore, due to the varying climatologies across the country, the probability of ending a drought varies both spatially and temporally in a systematic manner. The annual pcp cycle and the probability of receiving substantial excess pcp above normal are two important characteristics of drought termination.