Objective and Dynamic Analysis of Tropical Weather.
Semiannual rept. no. 3, 18 Mar-18 Sep 69,
STANFORD RESEARCH INST MENLO PARK CA
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Three different aspects of a study to apply objective techniques to tropical weather analysis and forecasting are discussed. In the first section computer analysis techniques are used to analyze radiosonde observations taken by the U. S. Army in South Vietnam. These observations provide an unusually large number of upper-air soundings within a relatively small tropical region. The analyses are made at six-hour time intervals for a number of vertical layers between the surface and 10 km. Wind analyses that have been made for the month of September 1967 show a pronounced diurnal cycle with marked convergence in the low layers during the afternoon over a mountainous part of Vietnam. The mean September wind patterns for different altitude layers and diurnal times are presented. In the second section a comparison is made between a subjective analysis of cloud-motion vectors in the tropical Pacific made by Fujita, Watanabe, and Izawa and a computer analysis of the same data. The computer analysis is quite similar to the subjective one and can be brought into even closer agreement when the divergence and vorticity fields are objectively altered to agree with the cloud patterns. In the third section the effect of a vertically balanced three-dimensional divergence field derived from wind data in a multilayer forecasting model is investigated. Author