Characteristics of Cloud Drop Spectra at Different Levels and with Respect to Cloud Thickness

Measurements on drop size spectra were made in cumulus clouds over Pune (inland) region on many days during the summer monsoon seasons. In this paper, the measurements in non-raining cumulus clouds made in the years 1984, 1985 and 1986 at different levels and for different cloud thickness have been studied. In general, the drop size spectra broadened with height and the concentration of drops with diameter \50 mm (NL), mean volume diameter (MVD), liquid water content (LWC) and dispersion increased with height while the concentration of drops with diameter B20 mm (NS) and the total concentration of drops (NT) decreased with height. The average drop size distributions were unimodal at the lower levels while they were bimodal at the higher levels. High water contents were confined to drops in the size range 5–25 mm at both higher and lower levels. The average drop size spectra were broader and NL, LWC, MVD and dispersion greater while NT and NS smaller for thicker clouds (range of vertical extent 1.1–2.1 km) as compared to those for thinner clouds (range of vertical extent 0.3–1.1 km). Water contents for the drops \28 mm were higher while those for the drops B28 mm lower in thicker clouds than in thinner clouds. The average drop size distributions were bimodal in the former case, while they were unimodal in the other case.