Correcting Biased Evaporation in CloudSat Warm Rain: Fid-Bau Portal

Correcting Biased Evaporation in CloudSat Warm Rain

Kalmus, Peter

The CloudSat mission's Cloud Profiling Radar has provided the first global-scale estimates of light rainfall from warm marine clouds. Because surface radar reflection prevents hydrometeor detection below ~720 m, the CloudSat 2C-RAIN-PROFILE retrieval uses an evaporation-sedimentation model to extend its profile estimates to the surface. We use in situ radar measurements from the ship-based Marine ARM GPCI Investigation of Clouds (MAGIC) campaign in the Northeastern subtropical Pacific, which sampled a diverse set of shallow marine cloud regimes, to evaluate the evaporation-sedimentation model near the surface. We suggest an empirical bias correction, which can be applied to the 2C-RAIN-PROFILE retrieval. Before this correction, the evaporation-sedimentation model produced a mean surface rain rate bias along the MAGIC transect of 57%; after correction, this bias was effectively eliminated. We also present the evidence of the validity of this bias correction across regimes in the MAGIC region, and also in the southeast subtropical Pacific, where the magnitude of the mean bias for surface rain due to the evaporation-sedimentation model is reduced by a factor of 4.