Analysis of the New Long-Term IMERG V07 Precipitation Record and Comparison with V06

As the Global Precipitation Measurement (GPM) mission’s Core Observatory satellite nears its ten-year anniversary in space, the developers of the Integrated Multi-satellite Retrievals for GPM (IMERG) algorithm have completed a nearly five-year development cycle to upgrade IMERG from V06 to V07. Some of the major changes introduced in V07 include: (1) improvements in the underlying passive microwave (PMW), infrared, and combined radar-radiometer precipitation algorithms; (2) improved intercalibration between PMW sensors; (3) incorporation of instantaneous PMW precipitation in the Kalman filter; (4) inclusion of PMW precipitation estimates over frozen surface, allowing for full global coverage; and (5) use of the SHARPEN technique to reduce the tendency towards unrealistically large areas of light precipitation that result from averaging satellite overpasses.

The predecessor V06 IMERG Final Run product has been well characterized in numerous studies since its introduction in 2019, and its precipitation estimates have been used for a wide variety of applications. The recent V07 reprocessing of the entire 23-year record, encompassing both the Tropical Rainfall Measuring Mission (TRMM) era (June 2000-May 2014) and the GPM era (June 2014-present), provides the opportunity to examine the characteristics of this new long-term climatology and to compare them against V06. Global maps and zonal profiles of ocean, land, and total precipitation averages will be presented.

One key feature that will be examined is whether there is improved consistency bridging the TRMM and GPM eras. Although intercalibration methods have been instituted in V07 to address this issue, additional work is likely needed. This analysis will help to assess and characterize V07 in preparation for the development of V08.