Open AccessTropical Wave Driving of the Annual Cycle in Tropical Tropopause Temperatures. Part II: Model Results
Author(s) -
W. A. Norton
Publication year - 2006
Publication title -
journal of the atmospheric sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.853
H-Index - 173
eISSN - 1520-0469
pISSN - 0022-4928
DOI - 10.1175/jas3698.1
Subject(s) - tropopause , stratosphere , rossby wave , troposphere , atmospheric sciences , equator , quasi biennial oscillation , climatology , tropical wave , zonal flow (plasma) , african easterly jet , equatorial waves , advection , potential vorticity , environmental science , kelvin wave , latitude , middle latitudes , vorticity , geology , physics , tropical cyclone , meteorology , vortex , plasma , quantum mechanics , tokamak , thermodynamics , geodesy
The atmospheric response to a localized distribution of tropical heating is examined in terms of the stationary waves excited and how these impact the mean flow near the tropical tropopause. This is done by examining nonlinear simulations of the Gill model with a primitive equation model that extends from the surface up into the stratosphere. The model produces strong cooling of zonal mean temperatures near the tropical tropopause when the heating is on the equator but weaker cooling with the heating at 15°N. The model shows that equatorial Rossby waves that penetrate the lower stratosphere and changes in EP flux divergence that correspond to the observed changes between December and August. It is suggested that ascent in the upper tropical troposphere is driven by vorticity advection or equivalently potential vorticity fluxes due to these equatorial Rossby waves, particularly when the heating is close to the equator. The model results provide support to the hypothesis that the annual cycle in tropical tropopause temperatures is a result of the annual variation in latitude of tropical heating and that equatorial Rossby waves are key in producing the response in the upper troposphere and lower stratosphere.