Transport diagnostics of GCMs and implications for 2D chemistry-transport model of troposphere and stratosphere

The middle atmosphere version of NCAR Community Climate Model (MACCM2) and the GEOS-STRATAN data assimilation system (DAS) of NASA/GSFC have been used to generate a zonally averaged set of transport parameters (meridional circulation and resolved eddy mixing) for use in two-dimensional (2D) chemistry transport models (CTMs). This was done by performing 3D transport numerical experiments with two orthogonal tracers. Some transport diagnostics from the MACCM2 and DAS are compared with each other, and with other approaches and estimates of horizontal mixing (K_yy) obtained from satellite data and GCMs. Some differences in the derived K_yy values for these passive tracer experiments and using the potential vorticity (PV) methods are discussed, as well as the annual and interannual variations, and the interhemispherical asymmetries in K_yy structures. The set of 2D parameters obtained from the MACCM2 transport diagnostics has been used in a 2D CTM to simulate the distribution of CH₄, N₂O, O₃, and the age of air (AOA). These 2D simulations compare well with the zonally averaged results obtained from 3D simulations of these constituents and for AOA in previous studies. The derived 2D transport parameters from the MACCM2 gave an annual cycle of constituent structure and values of mean age that compares well with those of the parent 3D model.