Liquid water cloud properties during the Polarimeter Definition Experiment (PODEX)

- Water cloud retrievals from Research Scanning Polarimeter (RSP) data are presented.
- The measurements were made during the Polarimeter Definition Experiment (PODEX).
- The retrievals include cloud optical thicknesses and droplet size distributions.
- Examples of marine Sc clouds and fog over California Valley are discussed in detail.
- Multi-modal droplet size distributions were detected and analyzed.

We present retrievals of water cloud properties from the measurements made by the Research Scanning Polarimeter (RSP) during the Polarimeter Definition Experiment (PODEX) held between January 14 and February 6, 2013. The RSP was onboard the high-altitude NASA ER-2 aircraft based at NASA Dryden Aircraft Operation Facility in Palmdale, California. The retrieved cloud characteristics include cloud optical thickness, effective radius and variance of cloud droplet size distribution derived using a parameter-fitting technique, as well as the complete droplet size distribution function obtained by means of Rainbow Fourier Transform. Multi-modal size distributions are decomposed into several modes and the respective effective radii and variances are computed. The methodology used to produce the retrieval dataset is illustrated on the examples of a marine stratocumulus deck off California coast and stratus/fog over California's Central Valley. In the latter case the observed bimodal droplet size distributions were attributed to two-layer cloud structure. All retrieval data are available online from NASA GISS website.