Standardized Precipitation Index (SPI) Analyses of Multiple Global Precipitation Datasets at LDEO/IRI Climate Data Library

The index is based entirely on monthly precipitation accumulations and its values can be compared across different climatic and geographic regions. These characteristics of the SPI have contributed to its popularity for application towards drought and water resource monitoring.

SPI analyses were performed on the following climatological data sets: NASA GPCP V2 NOAA NCEP CPC CAMS_OPI NOAA NCEP CPC Merged_Analyis (CMAP) UEA CRU New CRU05 Studies have suggested that a minimum of 50 years of precipitation data be used to calculate SPI values. It should therefore be noted that the UEA New data set is the only precipitation data set in the current set of analyses that meets that recommendation. Extreme SPI values in the other three datasets (CAMS OPI, CMAP, GPCP) may be suspect as they are based on roughly half of the recommended amount of data.