GDO Standardized Precipitation Index MERRA, 9-month accumulation period (SPI-9) (version 1.0.0)

The 9-month Standardized Precipitation Index (SPI-9) is an indicator used to monitor meteorological drought based on precipitation anomalies over 9-month accumulation periods. SPI-9 serves as a proxy indicator for medium-term impacts, such as reduced stream flow and reservoir storage. The input data for calculating the SPI-9 is MERRA (Modern-Era Retrospective analysis for Research and Applications) global precipitation, provided by the USA NASA (National Aeronautics and Space Administration) GMAO (Global Modeling and Assimilation Office).