Atmospheric forcing of the three-dimensional distribution of dust particles over Australia: A case study

Abstract

Knowledge of atmospheric processes responsible for horizontal and vertical distribution of dust particles is important for identifying their transport pathways. The Weather Research and Forecasting with Chemistry (WRF/Chem) model, complemented by observations, was used to simulate and observe the three-dimensional distribution of Australian dust for a severe dust event during 22-23 September 2009. The passage of a cold front modified the boundary layer structure during this event, allowing dust to be lifted and subsequently transported for a significant distance. The model simulated the maximum dust concentrations to be located behind the cold front as a result of strong post-frontal wind speeds. The boundary layer depths were also shown to be significantly deeper behind the cold front where dust particles could be lifted to the top of the boundary layer by turbulent fluxes associated with strong mixing. However, dust was predicted to reach its maximum height ahead of the cold front as a result of lifting in the warm conveyor belt. Both Moderate Resolution Imaging Spectroradiometer (MODIS) data and the WRF/Chem model results for this event highlight two transport pathways of dust: southeastward to the Tasman Sea and northward toward tropical regions of Australia. The vertical distribution of dust from Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) satellite data and cross-sectional analysis of the model results indicate that significant amounts of dust aerosols were transported over the Tasman Sea toward New Zealand within the lower atmosphere. Copyright 2012 by the American Geophysical Union.