First-Year Evaluation of GPM Day-1 IMERG and TMPA Version-7 Legacy Products over Mainland China at Multiple Spatiotemporal Scales

Abstract:

The post-real time product of Day-1 Integrated Multi-satellite Retrievals for Global Precipitation Measurement (IMERG) is evaluated over Mainland China from Apr to Dec 2014 at the hourly timescale, against data from more than 2,200 ground-based gauge stations. In addition, the IMERG product is compared with its predecessor, the Version-7 post-real-time 3B42 (3B42V7) product of Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA) at original 3-hourly and then daily timescales for the same period. All the products are cross-evaluated at gridded, regional, and national scales. Results show that: (1) the Day-1 IMERG shows appreciably better performance than 3B42V7 at both sub-daily and daily timescales among the gridded, regional, and national scales. However, the gaps between the two products are narrow in terms of all metrics; (2) Out of the six sub-regions, IMERG especially performs better than 3B42V7 at the mid- and low-latitudes, as well as relatively mild and wet climate regions; (3) IMERG can better reproduce structures of probability density functions (PDFs) as function of precipitation intensities, particularly during no rain or drizzle events; and (4) although IMERG better captures the rainfall diurnal variability, both IMERG and 3B42V7 have room to further improve the capability of reproducing the diurnal cycle, particularly over the dry climate and high-latitude regions. This study is among the early satellite precipitation estimation studies focusing on evaluation and comparison of IEMRG and 3B42V7 products, which could be valuable in providing reference for the improvement of IMERG algorithms and associated products.