Correcting TRMM Data

The Problem

Despite the unique areal coverage and advanced algorithm of the Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA), numerous studies have shown that TRMM-TMPA precipitation product displays differences when compared to ground-based observations. In this project, we find that the inaccuracy in the satellite product has a high dependence on some environmental factors that cause bias in the satellite data relative to the ground-based observation.  

Our Approach

In this study, we investigate the differences between satellite-based and ground-based precipitation estimates as a function of various environmental factors. By using this relationship, we are able to remove the identified factors’ effect on the satellite product, thereby improving the accuracy of the satellite product.

^{Averaged seasonal precipitation map in mm (from 1998 through 2015) over the conterminous United States from three different data sources: 1) gridded precipitation based on the rain gauge measurements (GAUGE), 2) parameter-elevation regressions on independent slopes model product (PRISM), and 3) the TRMM-3B43 satellite product (TRMM).}

Results to Date

The bias between the satellite precipitation product (TRMM 3B43) and ground-based estimates were compared with surface elevation. The analysis of bias with respect to elevation indicated a strong bias-elevation relationship associated with two distinct elevation ranges, below and above 1500 m amsl, with significant negative bias at the high elevations. We developed a model to correct the TRMM 3B43 product under the assumption that the bias is related to retrievals from the TRMM multisatellite, as well as from merging the ground-based estimate with TRMM multisatellite estimates, and in particular, is dependent on elevation. The results showed major improvement in the satellite product (1998-2015) by reducing bias up to 95% in the high mountainous areas of the conterminous United States (CONUS).