Cloud mask derived from airborne HAMP Microwave Radiometer measurements during the EUREC4A field campaign

The HAMP Microwave Radiometer (MWR) cloud mask is based on thresholding liquid water path (LWP) retrievals. The MWR is part of the near-nadir-pointing HALO Microwave Package (HAMP) which is described in detail by Mech et al. (2014). The LWP retrieval is based on the warm microwave emission signal by the clouds over the radiatively cold ocean surface as described by Jacob et al. (2019). The LWP observations have a 1 s temporal resolution and are representative for a footprint of about 1 km. A scene is considered "probably" and "most likely" cloudy if the LWP exceeds 20 g/m², respectively, 30 g/m². These thresholds correspond to (about) two to three times the clear-sky retrieval uncertainty, respectively.