Cloudy Bands Research Articles

Formation and Structure of Equatorial Anticyclones Caused by Large-Scale Cross-Equatorial Flows Determined by ATS-I Photographs

Because of poor coverage by synoptic stations, the tropical circulation over the eastern Pacific has not been known too well. As a result of photographic experiments, using the geosynchronous ATS-I satellite, fields of cloud motion over the eastern equatorial Pacific were mapped in detail on a number of days in September 1967. It was found that a large-scale flow from the Southern Hemisphere recurves after crossing the equator to form an anticyclone centered around 10N. Dynamical characteristics of this type of anticyclone were investigated by estimating the vorticity dissipating force from computed values of divergence and vorticity of low-cloud velocities determined from successive ATS-I pictures. The vorticity dissipating force seems to be related closely to the sea-surface temperature which would reduce the frictional coupling between the low-level atmosphere and the underlying sea surface. It was found that the anticyclone in its development stage results in a discontinuity of the intertropical band of cloudiness, before it travels westward with an active cloud band along its leading edge. Based upon evidence found through case studies, a model of an equatorial anticyclone is proposed in this paper. Numerical computations of cross-equatorial trajectories were performed by using the divergence-vorticity relationships and the vorticity dissipating force, which were obtained through numerical analyses. This paper thus presents an initial step toward the further development of tropical synoptic meteorology, which is expected during the next few years as a result of photographic experiments using the ATS-I and III.

Cloud Structure of an Occluded Cyclone Over the Gulf of Alaska as Viewed by TIROS I1

The cloud structure of an occluded cyclone and its environs over the Gulf of Alaska is revealed in detail by a series of TIROS pictures. The pictures clearly portray:(1) the nature and extent of dense cloudiness around the inner core of the cyclone;(2) a broad band of cloudiness associated with the main polar front;(3) the pattern of overrunning cloudiness marking a newly developing wave south of the main storm;(4) a previously undetected, old cyclonic vortex in mid-troposphere; and(5) the striking cellular arrangement of cumuliform clouds in the cyclonic flow to the rear of the storm. These features are related to the conventional meteorological data and analyses over this area and are found in many places to corroborate them rather well. On the other hand, there are several places, particularly in view of the sparsity of conventional data, where the cloud pictures suggest that improvements could be made in the map analyses and numerically computed vertical motions on the basis of the TIROS cloud information.