Microphysical Properties of a Large Scale Cloud System, 1-3 March 1978.
Environmental research papers,
AIR FORCE GEOPHYSICS LAB HANSCOM AFB MA
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This report describes the microphysical properties observed by a specially-instrumented C-130 while flying in portions of a large cloud system on 3 successive days in March 1978. Each of the flights was made slightly east of an upper level trough as it moved across the U.S. Horizontal sampling passes of 50 to 100 nm 93 to 186 km in length were made at various levels from approximately 2 to 9 km above ground in portions of the cloud system that were relatively homogeneous horizontally and vertically. Particle spectra data from PMS 1-D spectrometers were averaged for consecutive 20-sec periods. On each of the 3 days the particles having the smallest mean size were observed at the highest levels flown and had median diameters near 100 micrometers. The calculated equivalent liquid water content from 7 to 9 km was near 0.0 1 g cu m. The total particle count was between 8,000 and 18,000 cu m over Arkansas and coastal Delaware, but was near 25,000 cu m over the mountains of New Mexico. Values of mass and particle size increased with particle distance fallen, by indicating growth by collective means. The largest equivalent liquid water content values were near 1 g cu m and were recorded in the large snow just above the freezing level. The form factor, a mathematical parameter, was found useful in studying particle spectra. Certain maxima and minima observed in several plotted spectra, especially those from 7-km altitude data, are suggested as being due to an aggregation mechanism. Author