Numerical simulation of sea breezes over the Auckland region,New Zealand — Air quality implications

The air pollution meteorology of a typical sea breeze day is investigated using the Colorado State University Mcsoscale Model. Results are qualitatively compared with observations and reveal a complex wind field characterised by migratory sea breeze convergence zones. Associated with these features, the model predicts enhanced upward vertical velocities and doming of the planetary boundary layer (PBL). The diurnal variation in PBL depth is shown to vary markedly at different locations and is dependent on position in relation to the migratory convergence zones. These complex spatial and temporal variations in the wind and PBL depth have important implications for air quality in Auckland and confirm that simple Gaussian or box trajectory approaches are inappropriate for air quality assessment in such environments. The inclusion in the model of variable surface properties, a dynamic synoptic state and improved PBL parameterisations, as well as coupling with a Lagrangian particle model, are recommended if the model is to be used as a tool for further air quality studies in the Auckland area.