The Contribution of EarthCARE's Doppler Radar to Synergy Retrievals of Clouds and Precipitation

Doppler radar measurements of the fallspeeds of hydrometeors can provide insights into the size of raindrops and the morphology of ice particles, improving remote-sensed estimates of precipitation and resolving microphysical processes in clouds. The upcoming ESA/JAXA Earth Cloud Aerosol and Radiation Explorer (EarthCARE) satellite will facilitate advanced remote-sensing of clouds and precipitation with the first Doppler cloud profiling radar in space, in synergy with a high spectral resolution atmospheric lidar and multispectral radiometer. We have developed an optimal estimation algorithm for radar--lidar--radiometer synergy retrievals, called CAPTIVATE, which will provide official EarthCARE L2 retrievals of cloud, aerosols and precipitation.

In this study we illustrate the improved retrievals of rain and snow facilitated by Doppler radar using case studies from aircraft and ground-based Doppler radar observations. Airborne measurements from the TC4 field campaign are used to show improved estimates of drop size and number concentration in tropical stratiform rain, demonstrating clear differentiation between the microphysics of warm rain and rain from melting ice. Ground-based observations from an ARM mobile facility deployment are used to demonstrate the use of Doppler velocity to estimate the density and morphology of snow particles from their terminal velocities, with insights into aggregation and riming processes in mixed-phase cloud. Finally, we demonstrate synergy retrievals from A-Train data, and consider where the improvements in snow and rain estimates from EarthCARE’s Doppler radar are likely to have the most impact on global retrievals of cloud and precipitation.