Monash Publications No.55/GES
Monash Publications in Geography & Environmental Science: Number 55
Air Parcel Transport over the Maritime Continent as determined from Trajectory Climatologies, 1994-1999
by Alan Wain
The episodes of haze periodically experienced by the ASEAN countries, in particular Singapore and Malaysia, are good examples of transboundary air pollution. In these events, pollutants from outside source(s) impact upon air quality, health and economy over a wide area. One widely used method for studying the movement of air borne pollutants is the air parcel trajectory model. This monograph utilises the HYSPLIT-4 air parcel trajectory model in the production of climatologies of 168 hour backward trajectories from nine cities throughout the maritime continent. The trajectory model is validated using observations made during the ASEAN haze episodes of 1994 and 1997-98. In order to discern possible sources of pollutants which may be carried to the regional cities, daily backward trajectories were calculated from each of the nine cities over the period from June 1994 to May 1999. These are presented in both raw form and as average cluster trajectories, produced after the application of a clustering routine to the raw data. The patterns and variations in trajectories from each city are identified and discussed for each month. Forward trajectories from 30 source points, spread on a grid over the maritime continent were calculated to provide information about latitudinal and longitudinal variation in transport patterns. Results obtained show the HYSPLIT trajectories represent expected flow patterns quite well. The existence of significant transport to regional cities from a number of potential pollution sources was identified, as were distinct patterns in regional airflow. The potential capacity for Australia and Indonesia to exchange aerosols was found to be significant but the transport in reality is restricted by processes of removal and dispersion.