Case Studies of Extratropical Cyclones with Satellite-Viewed Cloud Patterns

摘要

TIROS pictures of the cloud patterns of occluding extratropical cyclones were compared in detail with conventional meteorological data plotted and analyzed in charts and cross sections to obtain more meaningful interpretations of satellite cloud pictures. Ten case studies were performed for data-rich areas: three in North America and seven in Europe. The results showed that the vortex cloud structure in each picture gave a good representation of the cyclonic circulations in the upper troposphere east of the center and the lower troposphere west of the center. Patterns of large cloud units with clear-cut sharp edges indicated a young deepening baroclinic system with considerable tilt of the axis of low pressure; whereas small diffuse cloud units with irregular edges indicated an old, filling, and nearly barotropic system with a more nearly vertical axis. The jet stream curved cyclonically around young cyclones, but remained south of old cyclones and did not participate in their rotation. Sprial-shaped cloud bands and dry tongues behind them curved counterclockwise inward and tapered toward the center. The major cloud band was usually a good locator of the cold front or the cold-front type of occluded front. A pre-major band southeast of the center indicated a squall line; one northwest, a slow moving cold front north of the center. Post-major bands indicated developing troughs with secondary cold fronts. The cloud band associated with a warm front or a warm-front type of occluded front was generally wide and centered a considerable distance north of the surface front. (Author)