Cloud droplet size distribution from 2-D polarization measurements of specMACS during EUREC4A

The data of the two polarization resolving cameras (lower left camera: polLL and lower right camera: polLR) of the spectrometer of the Munich Aerosol Cloud Scanner (specMACS) of the LMU are used to provide a dataset of the cloud droplet size distribution of liquid water clouds. During EUREC4A, specMACS was mounted onboard the research aircraft HALO in a downward-looking perspective. From the polarization measurements of the cloudbow, the effective radius and the effective variance of the cloud droplet size distribution (CDSD) are determined (Pörtge et al., 2023). This dataset provides the CDSDs for individual cloud targets with a target size of approximately 100 m x 100 m for all flight segments flown by HALO during the EUREC4A campaign. As a specific solar and viewing geometry is required to observe the cloudbow, not all flight segments can be evaluated. The effective radii and variances are determined individually for the measurements of all three color channels of the camera. The method derives the CDSD by fitting pre-calculated simulations of the cloudbow to the measurements. Various quality measures (RMSE, quality Index, scaling factor) of the fit are included in the dataset. The polarization signal of the cloudbow is a single scattering signal. Therefore, the derived CDSD should be representative of the CDSD at the cloud top. Furthermore, the mean coordinates of the target are given in both WGS-84 coordinates and in a cartesian reference frame which has its origin at 13.1°N and -57.4°E.