Backtrajectories are calculated with the NOAA HYSPLIT 3.2 code using 
the Australian Bureau of Meteorology (ABoM) GASP model.  This model has
approximately 5 degree horizontal resolution and 18 levels in the 
vertical.  These data are then interopolated onto omega fields for use
with HYSPLIT.  

For each series of trajectories we provide
an ASCII file which contains the time, lat, lon, pressure, U, V, vertical 
velocity in pressure, temperature, relative humidity and surface pressure. 
These fields come from the GASP data set.  

Trajectories will fail if the track hits the surface, rises above approx
500 HPa or flows off the restricted domain of the GASP data.  Also, the 
lowest interpolated GASP data is to the 0.991 omega level.  This corresponds
to roughly 110 meters height.  Trajectories below this level are not 
accurate.  Most likely they will be moving too quickly as they do not 
reflect the physics of the surface drag on the air flow.  They still provide 
a good estimate of the air motion for the first 12-24 hours.  
These back trajectories are designed to aid in the analysis of 
the Discoverer and Southern Surveyor observations.  

In these files, the 00Z and 12Z daily 5-day backtrajectories 
may be located for the period of 15 Nov through 12 Dec 1995. 

Each series of trajectories has source altitudes of 100m, 500m
and 2000m. 

Please contact steve siems (s.siems@sci.monash.edu.au) 
regarding questions.