PHOTOCHEMICAL MODELING IN SUPPORT OF THE PEM-TROPICS B CAMPAIGN

PHOTOCHEMICAL MODELING IN SUPPORT OF THE PEM-TROPICS B CAMPAIGN

Jose M. Rodriguez (jose@aer.com)

Anthropogenic perturbations to tropospheric concentrations of several trace gases could alter the oxidative capacity of the lower atmosphere. The Pacific has been identified as one of the cleanest regions in the globe. This presents an opportunity to study the relative role of natural vs. anthropogenic processes in controlling the oxidative capacity of the atmosphere by analyzing the concentrations of key trace gases measured simultaneously in conjunction with meteorological data. This task becomes particularly important in view of the potential significance of current biomass burning processes to the chemistry of this region, and the future impact of anthropogenic pollution arising from motorization of the West Pacific Rim. Analysis of these data with the aid of photochemical "process" models will help determine the role of the natural and anthropogenic mechanisms in maintaining tropical OH.

We propose to provide photochemical modeling support to the PEM-Tropics B mission by continuing to utilize the point-by point photostationary model, the steady-state diurnal model, and the trajectory photochemical process model used previously during PEM-West A and B, and PEM-Tropics A. The specific objectives of the proposed research are:

o to provide pre-mission, on-site, and post-mission support for PEM-tropics by utilizing a hierarchy of photochemical models which can calculate point-by-point local steady state concentrations and diurnal variability along aircraft flight paths, and photochemical evolution along specific air parcels;

o to utilize above models to understand the processes maintaining the oxidative capacity of the tropical Pacific, with particular emphasis on the HOx budget;

o to intercompare our model results with other similar models, both within the GTE mission and in the wider scientific community;

o to contribute to analysis of data quality on the field by examining correlations of long-lived tracers and ratios of short-lived species;

o to compare and incorporate the data analysis into ongoing global modeling efforts carried out by other NASA agencies, and to use the results from the global models to provide further context and implications for the PEM-Tropics measurements.