Consistency of Vertical Reflectivity Profiles and Echo-Top Heights between Spaceborne Radars Onboard TRMM and GPM

Globally consistent long-term radar measurements are imperative for understanding the global climatology and potential trends of convection. This study investigates the consistency of vertical profiles of reflectivity (VPR) and 20-dBZ echo-top height (Topht20) between the two precipitation radars onboard the Tropical Rainfall Measuring Mission (TRMM) and Global Precipitation Measurement (GPM) satellites. Results show that VPR coincidently observed by the TRMM's and GPM's Ku-band radar agree well for both convective and stratiform precipitation, although certain discrepancies exist in the VPR of weak convection. Topht20s of the TRMM and GPM are consistent either for coincident events, or latitudinal mean during the 7-month common period, all with biases within the radar range resolution (0.1-0.2 km). The largest difference in the Topht20 between the TRMM's and GPM's Ku-band radar occurs in shallow precipitation. Possible reasons for this discrepancy are discussed, including sidelobe clutter, beam-mismatch, non-uniform beam filling, and insufficient sampling. Finally, a 23-year (1998-2020) climatology of Topht20 has been constructed from the two spaceborne radars, and the global mean Topht20 time series shows no significant trend in convective depth during the last two decades.

Automated summary

This study compares the consistency of radar measurements between two precipitation radars onboard different satellites and investigates the possible reasons for discrepancies. The results show good agreement in vertical profiles of reflectivity and echo-top height for most precipitation types, with some differences observed in weak convection and shallow precipitation. Possible factors contributing to these differences include clutter, beam-mismatch, non-uniform beam filling, and insufficient sampling. Additionally, a 23-year climatology analysis reveals no significant trend in convective depth over the past two decades.