A one-dimensional photochemical model of the troposphere with a trade-wind boundary-layer parameterization

Refinement of the vertical transport parameterization in a one-dimensional photochemicalmodel of the troposphere by incorporating results from a model of boundary layer dynamicsrepresentative of a remote tropical environment is presented. The photochemical model isthen used to compute tropospheric profiles of selected trace constituents to advance ourunderstanding of how vertical transport processes affect the distributions and budgets of tracegases in the troposphere.The boundary layer model used in this study simulated the multi-layer structure thatcharacterizes the divergent trade-wind regions of the earth. The vertical transportparameterization includes the stuctural and mass-flow characteristics of a layer of shallow,dispersed cumulus. Vertical mass fluxes of trace constituents were calculated with reference tothe better-known flux of water vapor. Model-derived vertical profiles of key trace constituentsare compared with profiles from the photochemical model with conventional fluxparameterizations and to the available measured data for the remote marine troposphere. Theexperiment simulates the observed vertical structure of tropospheric ozone in marine tradewindenvironments reasonably well. In addition, this study indicates that the abundance ofreactive nitrogen species found in remote tropical regions of the world cannot be supported bythe estimated magnitude of local sources, implying that long-range transport from higherlatitudes may account for a sizeable input of reactive nitrogen to remote tropical regimes.