Numerical modelling of sea breezes and pollutant dispersion

Abstract

A suitably modified RAMS (Regional Atmospheric Modelling System) model was used to investigate the effect of sea breeze convergence circulations on the dispersion of near-surface non-localised pollutant emissions. High pollutant concentration events were shown to be primarily caused by the presence of the sea breeze convergence zone. The location of the sea breeze convergence zone was shown to depend primarily on the local land sea geography (i.e. the shape of the coastline). The only other important factor which affects where the convergence zone forms is the geostrophic wind. Low-level orography (<800m) was shown to play a minor role in determining where the convergence zone forms, but surface temperature variations (both land and sea) did not affect the positioning of the convergence zone at all. Cloud locations derived from AVHRR (Advanced Very High Resolution Radiometer) satellite data were located near the predicted convergence zones in the central Auckland region, but agreement was not as good near the model boundaries. The possible modification of cloud microphysical properties by anthropogenic pollutant sources was predicted to be confined to a handful of sources in industrial areas around the region.