HYSPLIT Forum: hysplitbbs.arl.noaa.gov

Hi there,
I am running ensemble back trajectories for sites around 30*W,70*S using GDAS meteorological data. Unfortunately, the terrain in this region seems to be poorly constrained, so my models often run into the ground and become a little useless. I would like to take my ensemble trajectories and pull out/remove those trajectories that run to the ground. I think I can do this by altering text files of data, but that becomes a little tedious. Is there an easier way to go about this?

(For example, in this image (http://imgur.com/vTTmjpy) I want to remove those trajectories that fall below 1000m-agl...)

You could write a computer program to read the trajectory output file and delete the trajectories that go along the ground. In the endpoints file, on the lines with the trajectory latitude-longitude, the first value identifies the trajectory by a 'trajectory number'. The "Record #3 as described at http://www.ready.noaa.gov/hypub/trajinfo.html#FORMAT would need to be edited to delete the trajectories removed and give the revised number of trajectories.

If you want to change the vertical offset in the ensemble, through the HYSPLIT GUI, it is Advanced - Configuration Setup - Trajectory - (7) Meteorological grid offset ENSEMBLE.

The GDAS1 terrain is on a one degree latitude-longitude grid.