Application of MM5 and CAMx4 to local scale dispersion of particulate matter for the city of Christchurch, New Zealand

Abstract

A numerical model, Mesoscale Model version 5 (MM5), is used in conjunction with a three-dimensional Eulerian/Lagrangian dispersion model (CAMx4) to model PM 10 dispersion for a period of 48 h for the city of Christchurch, New Zealand. In a typical winter, Christchurch usually experiences severe degradation in air quality. The formation of a nocturnal temperature inversion layer during stagnant synoptic conditions, and the emissions of particulate matter (PM 10) mainly from solid fuel home heating appliances (the ‘Domestic’ factor) leads to severe smog episodes on about 30 nights each winter. The modelling results from the highest resolution computational grid are compared with observed meteorology and air pollution dispersion for winter 2000, when the Christchurch Air Pollution Study (CAPS2000) was underway. The numerical modelling system is able to simulate surface-layer meteorology and PM 10 spatial distribution with a good level of skill, with the Index of Agreement and Pearson's correlation coefficient greater than 0.8 for PM 10.