HYSPLIT Forum: hysplitbbs.arl.noaa.gov

I'm using PC HYSPLIT and I'd like to enter the starting location altitude in MSL instead of AGL. Likewise, I'd like to get the HYSPLIT trajectory output in MSL as well.

I believe I can switch the altitude for the starting location to MSL by going into "Advanced - Trajectory - Define subgrid and MSL/AGL UNITS" and selecting "Relative to mean-sea-level". I think this corresponds to setting the "kmsl" variable in Setup.CFG to a value of 1. The "Starting Location Setup" dialog still says the height is (m-AGL) but it seems to accept it as MSL. Is all that correct?

Is there any way to get HYSPLIT to produce the calculated trajectory in MSL instead of AGL?

Thanks.

I believe I figured out how to get the calculated trajectory to be in MSL. In PC HYSPLIT, you have to go to Advanced - Trajectory - "Add METEROLOGY output along trajectory" and check "Terrain Height". This essentially adds to the output file another column which is the ground elevation for each point that you can then add to the AGL calculated value. This corresponds to the "tm_terr=1" value in TRAJ.CFG.

I wish to look at back trajectories arriving at a specific location at a specific pressure level. Could you tell me what formula you use to convert hPa to meters above sea level pressure ? The values I'm finding are different to those I end up entering in the Hysplit model to obtain the appropriate pressure..

Thanks for your help