Automated estimation and analyses of meteorological drought characteristics from monthly rainfall data

The paper describes a new software package for automated estimation, display and analyses of various drought indices – continuous functions of precipitation that allow quantitative assessment of meteorological drought events to be made. The software at present allows up to five different drought indices to be estimated. They include the Decile Index (DI), the Effective Drought Index (EDI), the Standardized Precipitation Index (SPI) and deviations from the long-term mean and median value. Each index can be estimated from point and spatially averaged rainfall data and a number of options are provided for months' selection and the type of the analysis, including a running mean, single value or multiple annual values. The software also allows spell/run analysis to be performed and maps of a specific index to be constructed. The software forms part of the comprehensive computer package, developed earlier and designed to perform the multitude of water resources analyses and hydro-meteorological data processing. The 7-step procedure of setting up and running a typical drought assessment application is described in detail. The examples of applications are given primarily in the specific context of South Asia where the software has been used. Software availability Package: The SPATSIM software package; Availability: From the Institute for Water Research (IWR) at Rhodes University; Cost: No development cost involved, the Institute is obliged to pass on the application development license costs charged by ESRI. This amounts to approximately 200 USD; Description: Available on IWR website http://www.ru.ac.za/institutes/iwr/. Updates to the software are regularly posted on the IWR website and readily downloaded at no cost by registered users