Airborne Passive Microwave Retrievals of Cloud Liquid Water, Total Precipitable Water, and Near‐Surface Wind Speed in the Maritime Tropics

Abstract This paper describes improvements to geophysical retrievals from NASA's Advanced Microwave Precipitation Radiometer (AMPR) during the Cloud, Aerosol and Monsoon Processes Philippines Experiment (CAMP 2 Ex). The retrieved products are validated using independent data sets, and example applications in addressing science questions about the maritime tropics are provided. Multi‐linear regression equations previously developed to retrieve cloud liquid water path (CLW), total precipitable water vapor (WV), and 10‐m wind speed (WS) from AMPR brightness temperatures in the midlatitudes were examined. Initial testing revealed that the CLW methods required modification for the maritime tropics, likely due to the stark environmental differences. Minor WS adjustments were also needed to account for the presence of a new AMPR radome. Compared with numerical simulations, the updated CLW equation performed nearly an order of magnitude better than its predecessor. Validating AMPR CLW with airborne polarimeter‐derived CLW throughout CAMP 2 Ex yielded a median absolute deviation that is less than the predecessor CLW equation's uncertainty and comparable to CLW precisions observed in past studies. In situ WV and WS validation using dropsondes was promising, with mean deviations that are less than their target uncertainties. Correlating AMPR CLW with polarimeter‐derived cloud‐top height (CTH) indicated an expected CLW ∝ CTH 2 relation for CTH < 4 km, but reduced CLW for CTH > 4 km may have been associated with cloud droplet removal via accretion and/or mixed‐phase onset. These results demonstrate the power of airborne radiometer geophysical retrievals as standalone metrics and the insight they provide when used alongside other data sets.