A158-08
Cloud Droplet Size Distributions from Observations of Glory and Cloudbow during the EUREC4A Campaign

Monday, 14 December 2020: 07:24
Virtual
Veronika Pörtge1, Tobias Kölling2, Tobias Zinner1, Linda Forster3,4, Claudia Emde1 and Bernhard C Mayer1, (1)Ludwig Maximilian University of Munich, Munich, Germany, (2)Max Planck Institute for Meteorology, Hamburg, Germany, (3)NASA Jet Propulsion Laboratory, Pasadena, United States, (4)Ludwig-Maximilians-Universität Munich, Meteorological Institute, Munich, Germany
Recorded Presentation
Abstract:
The evolution of clouds and their impact on weather and climate is closely related to the cloud droplet size distribution. The droplet size, for instance, determines the cloud radiative effect while the formation of precipitation depends both on the droplet size and the shape of the distribution. Therefore, measurements of the size distribution are important to further our understanding of clouds and their role in the earth system. We present an airborne remote sensing technique to determine droplet size and width of the size distribution based on multi-angle polarized observations of the glory and the cloudbow.

Glory and cloudbow are mainly caused by single scattering of sunlight by liquid water cloud droplets. This backscattering results in colorful concentric rings surrounding the observer’s shadow. The angular radius of the rings is the most accurate and direct measure of the droplet size at cloud edge. In addition, the sharpness of the rings conveys information about the width of the droplet size distribution. The visibility of glory and cloudbow is significantly enhanced by the use of polarized observations which reduce the contribution of multiple scattering.

The specMACS sensor of LMU Munich has been upgraded recently by a polarization-sensitive wide-angle imager which is ideally suited for the glory-cloudbow technique. The sensor was operated for the first time on the HALO aircraft during the EUREC4A campaign (January to February 2020, based in Barbados). It offers a high spatial and temporal resolution, allowing the study of small-scale variability of cloud microphysics at cloud top with a horizontal resolution of about 20 m. Vertical profiles of the droplet size distribution are derived by combining the polarimetric technique with an existing stereographic retrieval of cloud geometry. specMACS measurements made during EUREC4A and first retrieval results of vertical profiles using the glory-cloudbow technique are presented.

<< Previous Abstract | Next Abstract