Can we observe a correlation between vertical Doppler velocity and upwelling solar radiance for shallow marine boundary clouds?

Clouds play an important role in the climate system since they have a profound influence on Earth’s radiation budget and the water cycle. Uncertainties in current climate models arise from a limited understanding of the coupling between cloud dynamics, cloud microphysics and, in turn, cloud radiative properties. Over decades, radiative properties of cloud tops were extensively studied using passive observations from multiple satellite missions. In recent years, our understanding of the inner workings of clouds has been greatly advanced by the deployment of cloud profiling microwave radars from low-earth orbit like CloudSat or the upcoming EarthCARE satellite mission. In order to exploit the future synergy between the cloud radar and the passive imager on EarthCARE, the scientific community is in dire need of collocated and spatially highly resolved measurements in advance of future spaceborne missions.  

In this context, the German research aircraft HALO is equipped with the high-power (30kW) cloud radar HAMP MIRA operating at 35 GHz and the hyperspectral imager specMACS (400 nm – 2500 nm). During the EUREC4A campaign, a number of flights were conducted over shallow marine boundary clouds in the vicinity of Barbados to collect simultaneous measurements with both instruments. For the first time, the spatial resolution of the Doppler velocity measurements from HALO now better match (<100 meter) the spatial resolution of the radiance imager, allowing for a more detailed separation of small up- und down-drafts.

In this presentation, we will give first impressions of these collocated, highly resolved radar-imager measurements of shallow marine boundary clouds during EUREC4A. On the basis of this data set we will try to answer the question if a correlation between the vertical Doppler velocity and the upwelling solar radiance for this kind of clouds can be observed. Such a relationship could prove valuable to assist synergistic retrievals (e.g. radar-lidar) in narrowing down the microphysical assumptions on which these retrievals rely upon. Furthermore, this data set could serve as a benchmark for cloud resolving modeling by constraining the relationship between cloud dynamics and radiation.