Drop Size Distributions and the Lack of Small Drops in RICO Rain Shafts

Data from the new two-dimensional stereo (2D-S) probe are used to evaluate drop size distributions in rain shafts observed during the Rain in Shallow Cumulus over the Ocean (RICO) experiment. The 2D-S takes images of both precipitation drops and cloud droplets with 10-mm resolution. These are the first reported measurements of rain to include sizes smaller than 100 mm. The primary result is that there are almost no hydrometeors smaller than about 100 mm in these rain shafts. The measured low concentration of small hydrometeors implies that their rate of production is slow relative to their removal rate. Algorithms for removing the spurious effects of splashing precipitation and noisy photodiodes on 2D probes are also described.