Raindrop-Size Distributions in Humid Continental Climates, and Associated Rainfall Rate-Radar Reflectivity Relationships

Abstract

Raindrop-size spectra obtained with the raindrop camera have been analyzed from two locations, Island Beach, N. J., and Franklin, N. C. The spectra were analyzed with respect to total number of drops per average rain rate per cubic meter of sample, geometric mean diameter, mode diameter, and the diameter of drops at which half the liquid water content lies above that diameter and half below. The results indicate that the distributions from both locations are quite similar for corresponding rainfall rates. Rainfall rate-radar reflectivity relationships indicate that cold frontal rains in these areas generally have smaller drops than warm frontal rains. In addition, it was found that upslope rains are composed of smaller drops than rains of similar synoptic conditions without upslope effects. Finally, a small sampling of a tropical storm rain revealed that small drops may be characteristic of this type of rain.