THERMODYNAMIC BALANCE OF 3-DIMENSIONAL STRATOSPHERIC WINDS DERIVED FROM A DATA ASSIMILATION PROCEDURE

The NASA/Goddard three-dimensional chemistry and transport model is dr iven by winds from a stratospheric data assimilation system. Synoptic- and planetary-scale patterns, apparent in satellite observations of t race constituents, are successfully reproduced for seasonal integratio ns. As model integrations proceed, however, the quality of simulations decreases, and systematic differences between calculation and measure ment appear. The differences are explained by examining the zonal-mean residual circulation. The vertical residual velocity wBAR is calcula ted two ways: (i) from the diabatic heating rates and temperature tend ency and (ii) from the Eulerian vertical velocity and the horizontal e ddy beat flux convergence. The results from these calculations differ substantially. Periodic insertion of observational data during the ass imilation process continually shocks the general circulation model and produces these differences, which leads to an overestimate of the mea n vertical heat and constituent transport. Such differences are expect ed to be general to all data assimilation products. This interpretatio n is corroborated by two-dimensional (2D) model calculations. When wBA R is calculated from (ii), the 2D ozone evolution is unrealistic and qualitatively similar to the 3D model simulation. The 2D ozone evoluti on is reasonable when wBAR is calculated from (i).