A STREAMLINED FAMILY PHOTOCHEMISTRY MODULE REPRODUCES MAJOR NONLINEARITIES IN THE GLOBAL TROPOSPHERIC OZONE SYSTEM

Tropospheric photochemistry is central to terrestrial climate change a nd pollution effects and so will be modelled on global 3-D grids. The chemistry is also complex, numerically stiff and kinetically nonlinear . A packaged family based integrator has been developed specifically t o combat the difficulties associated with computational modelling of a tmospheric chemistry on the global scale. The present work describes i ts ability to reproduce the major nonlinear features of tropospheric k inetics-those relating the nitrogen oxides (NOx) and oxidizing organic s to ozone. It is shown that the family modules can duplicate typical changes in ozone production as a function of NOx level while consuming a minimum number of mathematical operations. The tests are first perf ormed in the box model mode for a variety of pristine and pollutant sc enarios. Zero-dimensional runs are patterned largely after the nonline arity investigations of Liu and coworkers. The testing is then extende d to column representations for vertical mixing of ozone precursors in convective storms. Here the calculations follow the climatology of oz one production enhancements assembled by Pickering and colleagues. Ben chmarking is reported for a mechanism containing full inorganic kineti cs as well as decomposition sequences for six nonmethane hydrocarbons. Chemical species in the simulation number 92. The operations count is roughly 10,000 per cell step for time increments of 1 h or more. The coding should thus enable decadal scale runs on massively parallel pro cessors. Scaling experiments indicate full vectorization has been achi eved. The chemistry packages are optimized not only for speed but also for convenience. Modularity and routines automating setup of solution s to the kinetic continuity equations are outlined as incidentals.