ABSTRACT
This chapter provides the Palmer Drought Index serves as one means of quantitatively evaluating drought events. Most of the world's agricultural areas are subject to drought, but the duration and intensity vary greatly from one climatic zone to the next. Drought commonly remain unbroken for over a year, while on rare occasions droughts have continued with only negligible relief for nearly ten years. The beginning and ending times of a drought are often rather vague, particularly the onset of a drought which often cannot be dated within two months. Droughts develop over a period of time. Drought is a regional manifestation of a generally fluctuating climate associated with a persistent aberration of the atmospheric circulation. The areal extent of drought ranges from "small area" to so-called "continental droughts". The major purpose for developing a drought index is to provide a means for summarizing and periodically disseminating drought and crop moisture information on a regional basis.
