The Evolution of Raindrop Spectra in Warm-Based Convective Storms as Observed and Numerically Modeled

• Published in: Journal of the atmospheric sciences 1978-12, Vol.35 (12), p.2302-2314
• Main Authors: Carbone, R. E., Nelson, Loren D.
• Format: Article
• Language: English
• ISSN: 0022-4928; 1520-0469
• DOI: 10.1175/1520-0469(1978)035<2302:TEORSI>2.0.CO;2

Airborne optical spectrometer measurements of raindrop spectra were performed in Texas with 10- and 3-cm radar observations. The observations reveal large drop spectra emanating from cloud base with low concentrations of small drops compared to the Marshall and Palmer (1948) distributions. Systematic patterns of exponential spectrum parameters (N sub(0) and lambda ) are revealed to constitute a parametric cycle in time and space. Drop spectrum form is attributed principally to updraft sorting of smaller drops. Subsequent to updraft sorting, the importance of the collision breakup process with regard to spontaneous breakup appears to be greatly diminished. Recent theoretical studies by Srivastava (1971, 1978) partially support conclusions drawn with regard to the relative importance of spontaneous vs. collisional breakup. A one-dimensional, time-dependent numerical model was used for initial conditions simulating the observations. The resultant spectra emanating from the model were quantitatively similar to the measurements and exhibited temporal evolution consistent with the observed parametric cycle. Implications for estimation of spectral moments, such as liquid water content, radar reflectivity factor, and rainfall rate, are discussed.