Microwave Soundings in the Presence of Precipitation in the CPEX Experiment

A new retrieval system has been developed at the Jet Propulsion Laboratory (JPL) that is able to produce accurate vertical profiles of temperature and water vapor in the presence of precipitation. It is a “physical” method based on a widely used Optimal Estimation technique. The embedded forward model is a variant of the Community Radiative Transfer Model (CRTM), which accounts for scattering from hydrometeors, primarily frozen particles such as ice, snow and graupel. This results in valid retrievals even in the presence of heavy rain. Although there are large uncertainties related to the specification of the microphysical properties of the scatterers, the results are broadly valid. We have applied this new retrieval system to observations obtained with the High Altitude MMIC Sounding Radiometer (HAMSR) in the Convective Processes Experiment (CPEX), a field campaign conducted by NASA in May and June of 2017 over three ocean domains near Florida (Gulf of Mexico, Caribbean, western North Atlantic). HAMSR is a 25-channel microwave sounder developed at JPL that has many similarities to current satellite sounders such as the Advanced Microwave Sounding Unit (AMSU) and the Advanced Technology Microwave Sounder (ATMS) flying on NASA and NOAA satellites. In CPEX, HAMSR was deployed on the NASA DC-8 research aircraft along with other instruments, including a dropsonde system (Yankee Environmental System – YES) and a doppler radar (Airborne Second Generation Precipitation Radar – APR-2). The flights covered both clear-sky and convective-precipitative conditions. We will describe the retrieval system and show comparisons between HAMSR and dropsonde profiles in clear air as well as in the presence of precipitation.

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