Impacts of Light Precipitation Detection with Dual Frequency Radar on Global Precipitation Measurement Core Observatory (GPM/DPR)

Abstract:

The Dual-frequency Precipitation Radar (DPR) on board the GPM Core Observatory consists of Ku-band (13.6 GHz) and Ka-band (35.5 GHz) radars, with an improved minimum detection sensitivity of precipitation compared to the Tropical Rainfall Measuring Mission Precipitation Radar (TRMM PR).

We have studied impacts of improved detection sensitivity with the GPM DPR compared with the TRMM PR. One example of light precipitation is, a scattered rainfall around a trough over the subtropical South Pacific Ocean, which consists of weak but erect precipitation reaching over the melting level of ~2.5 km and trailing precipitation above, which reaches as high as 5km. Another example is a light anvil precipitation spreading from convective cores of a storm in the upper troposphere, overcasting shallow convective precipitation below. The ability of globally detecting such light precipitation will improve our knowledge of precipitation processes.

Utilizing an early version of the DPR product, a quick evaluation on statistical impacts of increasing the detection sensitivity from 17dBZ to 12dBZ has been performed. Here, 17dBZ is the value which is mostly accepted as the performed detection sensitivity of the TRMM PR, and 12dBZ is the guaranteed sensitivity for GPM Ka-band radar. For the near surface precipitation, impacts are significant in terms of numbers, but limited to several regions in terms of the rainfall volume. Volume impacts are much larger at the upper troposphere, which is indicated by the detection of the anvil precipitation, for example. The upper level improvements are mostly found where the deep precipitation systems exist.

Quantitative discussions utilizing the latest version of the DPR data, which is scheduled to be released to the public in September, will be presented at the session.