Latent Heat Induced Divergence and the Ultra-Long Waves of the Subtropics and Midlatitudes

摘要

Winter and summer Goddard Institute of Space Studies (GISS) Data System Test (DST) (prototype Global Atmospheric Research Project (GARP) data) time average fields are compared with several average data sets. An analysis of the GISS DST data involving kinematically and noneliptically computed divergent flow fields suggests that the positioning of the subtropical jets and ultra-long waves (wavenumbers 1-3) may be partially in response to strong longitudinal variations in tropical convective heating. Experiments with divergent barotropic and two-level primitive equation models are used to test the short (1-3 days) and long (15-30 days) range effects of large scale tropical heating patterns upon the subtropical and midlatitude long and ultra-long waves and flow patterns. The barotropic model experiments suggest that forcing in the tropics of one hemisphere can significantly accelerate (by means of gravity wave energy propagation) the opposite hemisphere subtropical jet in a matter of one of three day's time, regardless of easterly or westerly tropical flow. The maximum subtropical jets due to forcing in one hemisphere are shown to exist in the opposite hemisphere. Two-level primitive equation model experiments are conducted for the spherical earth with uniform mid and high latitude net diabatic forcing.