Meteorological data

This study employs meteorological data derived from data compiled by the European Centre for Medium Range Weather Forecasting in Reading, England and is based on observations collected around the world every 12 hours. This wind field data set is considered one of the best available for studying the transport of tracers and atmospheric chemistry and is employed by research groups worldwide for this purpose.

Wind fields used in ANU-CTM are based on the monthly means and variances of 12 hourly ECMWF data and were calculated at the United States National Center for Atmospheric Research by Kevin Trenberth. The method of calculation is as described in Trenberth (1992). The data are available on a T42 grid approximately 2.8 degrees in longitude and latitude. Dr Jay Larson processed the data into a format suitable for application with ANU-CTM and transferred this data to ANU.

Wind field data sets are available for the period 1980-1995. More recent data sets include data at 15 pressure levels in the atmosphere whereas data from the early 1980's include data at only 7 levels. Accordingly data from a more recent year was selected, in this case 1993.

The meteorological data clearly indicate the importance of the Asian monsoon in determining the transport of a tracer released from Java. During the Australian summer prevailing wind conditions are to the south, from Java towards Australia.

Figure 1 - The average wind speed at 1000 hPa for January in South-East Asia.

Figure 2 - The wind direction at 1000 hPa is to the north and countries such as Singapore, Thailand and Malaysia are at risk.

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