GDO Standardized Precipitation Index MERRA, 1-month accumulation period (SPI-1) (version 1.0.0)

The 1-month Standardized Precipitation Index (SPI-1) is an indicator used to monitor meteorological drought based on precipitation anomalies over 1-month accumulation periods. SPI-1 serves as a proxy indicator for immediate impacts of droughts such as reduced soil moisture, snowpack, and flow in smaller creeks. The input data for calculating the SPI-1 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).