Cloud macrophysical properties from airborne observations during EUREC4A

Trade wind cumulus clouds are the predominant cloud type over the tropical Atlantic east of the island of Barbados. Parameters describing their macroscopic shape can help characterizing and comparing general features of clouds. This characterizing will indirectly help to constrain estimates of climate sensitivity, because models with different structures of trade wind cumuli feature different response to increased CO2 contents.

Two aircraft campaigns with the HALO (High Altitude LOng range) aircraft took place in the recent past in this region: NARVAL-South (Next-generation Aircraft Remote-Sensing for VALidation studies) in December 2013, during the dry season, and NARVAL2 in August 2016, during the wet season. During these two campaigns, a wide range of cloud regimes from shallow to deep convection were sampled. This past observations are now extended with observations from this year’s measurement campaign EUREC⁴A, again during the dry season. EUREC⁴A is endorsed as WCRP capstone experiment and the synergy of four research aircraft, four research vessels and numerous additional observations will provide comprehensive characterizations of trade wind clouds and their environment.

Part of the NARVAL payload on HALO is a 35 GHz cloud radar, which has been deployed on HALO on several missions since 2013. These cloud radar measurements are used to segment individual clouds entities by applying connected component analysis to the radar cloud mask. From these segmented individual clouds, macrophysical parameters are derived to characterize each individual cloud.

This presentation will give an overview of the cloud macrophysics observed from HALO during EUREC⁴A. Typical macrophysical parameters, i.e. cloud depth, cloud length, cloud fraction, are analyzed. We will relate these to observations from past campaigns and assess the representativeness of EUREC⁴A. As special focus of the EUREC⁴A campaign, measurements will be performed during different times of the day to detect diurnal cycles. Macrophysical parameters can be used to characterize changes over the day and cloud scenes of similar clouds types can be identified.