A simple photochemical module implemented in RAMS for tropospheric ozone concentration forecast in the metropolitan area of São Paulo, Brazil: Coupling and validation

An in-line simplified photochemical module was coupled with RAMS, an atmopsheric mesoscale model, to produce an operational forecast of ozone and other constituent concentration for the Metropolitan Area of São Paulo (MASP), Brazil. Comparisons between surface pollutants concentrations data, provided by automatic network stations for air quality monitoring and modeled values, show good agreement, with correlation coefficients greater than 0.7 for all stations considered. Mean values over all analyzed stations have an index of agreement higher than 0.8. An important feature observed during the simulations was the ability of the model to simulate nocturnal concentrations of ozone over MASP which are usually observed as a result of transport of this pollutant from other regions and from higher levels of the atmosphere, representing the close coupling between the micro scale process and the chemical reactions, although these nocturnal maximums are overestimated by the model in some cases. The computational efficiency of the model shows that it can be considered for operational procedures with relatively small PC-based clusters and used as a tool for emission control strategies by environmental agencies concerned with the improvement of air quality.