Book Description

The visual and microphysical properties of a large scale cloud system are described as that system developed from an open wave in Oklahoma to a deep occlusion covering most of the east coast of the United States. Microphysical properties examined include particle size, liquid water content, particle density, crystal type, and Form Factor (a measure of uniformity of particle sizes within a sample). Visual and microphysical observations were made at four levels, approximately at the 400, 400, 700, and 850-mb surfaces, on four consecutive days. On each day the MC-130E aircraft instrumented for cloud physics research by AFGL flew at each level for approximately 30 minutes. In addition to examination of the continuous data provided by the aircraft, a detailed examination of 32 samples of 2 min each was undertaken. Sampling was conducted in the northeast quadrant of the storm. During the first day, the storm was mainly convective in nature, and as a result, had high liquid water content and particle distributions which were uniform along the vertical axis. As the storm moved eastward, it became more stratified. As it did, the observed particle size and types showed greater variations. The upper levels were affected less than the lower levels, thus reducing the uniformity along the vertical axis. As the system occluded, it lost moisture, producing smaller hydrometeors, lower liquid water content, and lighter precipitation at the surface. Later, an influx of water air increased the liquid water content and the intensity of the precipitation.