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 6 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 6 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.
During most months of the year wind speeds at the surface are low, conducive to maintaining high concentrations of radioactive tracer in the region near the potential release point in Turkey. The low wind speeds also complicate the prediction of where the impacts associated with a particular radioactive release event will occur, making it difficult to respond in an emergency. During the winter months (Figure 1) Westerlies prevail taking air masses from Southern Turkey to Syria, Israel, Lebanon, Iran, Iraq, Saudia Arabia and the gulf states, Uzbekistan and Kazakhstan. During the summer months (Figure 2) the NE trade winds dominate taking air masses from Southern Turkey to such countries as Syria, Israel, Lebanon, Jordan, Egypt, Saudi Arabia and Libya.
Figure 1 - The wind direction and average wind speed at 1000 hPa for January.
Figure 2 - The wind direction and average wind speed at 1000 hPa in July.
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