Dual-frequency radar retrievals of rain evaporation at the Barbados Cloud Observatory during the ORCESTRA-SCORE campaign

Rain evaporation drives mesoscale organization through downdrafts and cold pools, influencing cloud cover and the radiative budget, yet its magnitude and variability remain poorly constrained by observations and models. To address this gap, we develop a rain evaporation dataset at the Barbados Cloud Observatory (BCO) using observations from the SCORE (Sub-Cloud Observations of Rain Evaporation) sub-campaign of ORCESTRA. Because rain evaporation cannot be measured directly, it must be inferred from changes in the drop size distribution (DSD) as rain falls. DSDs can be derived from cloud radar Doppler spectra, but these are affected by vertical air motion, turbulence broadening, and attenuation.

By using Doppler spectra from BCO cloud radars at two frequencies (Ka- and W-band), we can overcome the limitations of single-frequency approaches and retrieve the full shape and concentration of the DSDs. The application of an optimal estimation method to this data also allows us to retrieve total differential attenuation, vertical velocities, and turbulence. We derive rain evaporation rates from DSDs during stationary periods. These retrievals can be used to evaluate evaporation estimates from one-dimensional rain shaft models, including the super-droplet model CLEO. If robust, the retrieved cloud-base DSDs provide a basis for fast and reliable long-term rain evaporation estimates at the BCO. Here we present first results from the SCORE evaporation and environmental conditions dataset, including analyses of individual rain events and statistics from the full sub-campaign.