Abstract:
Drought Indices (DIs) have been commonly used to define drought conditions. In general, DI is a function of several hydro-meteorological variables and can be integrated in a decision support system as a drought management tool to trigger drought relief programs. Globally, droughts have been studied using many different indicators, but, among them, the Standardized Precipitation Index (SPI) has significant advantages. SPI has been selected by the World Meteorological Organization (WMO) as a key indicator for monitoring drought (‘Lincoln declaration’) and is one from the two most used in Europe. The obtained from the authors’ four global gridded data-sets of the SPI are presented. They are computed from the UDEL/GEOG/CCR v3.02, GPCC v7.0, the NOAA-CIRES 20CR v2c and the ECMWF ERA20C monthly precipitation databases and each of them is with more than a century long time extent. The SPI is calculated for the most frequently used time scales of 1, 3, 6, and 12 months and, except ECMWF ERA20C, are in the highest available grid resolution, native for the precipitation database. The popularity of the SPI in the geophysical community and the strong conviction of the authors that the free exchange of data and software services are basis of effective scientific collaboration, are the main motivators to open the produced data-sets for free of charge download. The paper shows also in concise form some possible use of this information, revealing its suitability for various objective long-term drought studies at any geographical position.