Tracer Transport by the Diabatic Circulation Deduced from Satellite Observations

Mean meridional circulations for the months of November through May 1979 are deduced from the net radiative heating rates obtained from detailed calculations based on satellite observations of temperature and radiatively important trace species. The satellite data are also used to calculate the rates of photochemical processes that destroy the atmospheric tracers, methane and nitrous oxide. The deduced circulations along with photochemical loss rates provide the basis for prediction of the temporal and spatial evolution of these species for the period from November through May. Comparison of the predicted behavior of the tracers to the Stratospheric and Mesospheric Sounder observations reveals good agreement, particularly in the tropics and in the summer hemisphere, suggesting that transport by the mean meridional circulation plays a critical role in determining the morphology of these constituents. However, at high latitudes in winter, comparison of the observed and modeled tracer fields suggests that transport through locally enhanced quasi-horizontal mixing and dispersion may be important. Possible causes for departures from radiative equilibrium and their associated transport effects through advection and dispersion are explored.