Subsynoptic Scale Dynamics as Revealed by Use of Filtered Surface Data.

摘要

A band-pass filtering technique,based on an exponential weight function interpolation method,is presented. Both spatial and temporal filtering are simultaneously accomplished and the center of the band can be positioned within the spectral domain to satisfy user needs. The filter is applied to conventional surface meteorological observations for eight severe thunderstorm days in Oklahoma. Surface subsynoptic systems are shown to be well correlated with severe weather events. Combining results of the filtering with available numerical studies permits a scale analysis for subsynoptic systems. Three fundamental findings about these systems are developed:first,the data support the hypothesis that the circulations derive their energy from baroclinic sources;second, anisentropic processes of eddy mixing and latent heat release are apparently vital to the subsynoptic flow;and third,evidence supports the existence of a balance between pressure forces and momentum transport via vertical circulations.