I downloaded the latest version of HYSPLIT for the PC. How do I run the dispersion simulation backwards? I tried a negative number of hours run time, as for backward trajectories, but I got the same result as with positive number of hours.


Setting up the backward run can be a little tricky. Your run appeared to produce the same result because it didn’t create a new output file and hence the display program used the concentration output file from the previous successful forward calculation.

In addition to the run time being negative, the emission start-stop and sampling start-stop times must be reversed. A sample configuration is available below.

95 10 18 00
1
40.0 -90.0 10.0
-12
0
10000.0
1
./
oct1618.BIN
1
TEST
1.0
3.0
95 10 18 00
1
0.0 0.0
0.05 0.05
30.0 30.0
./
cdump
1
100
95 10 18 00
95 10 06 00
00 12 00
1
0.0 0.0 0.0
0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0
0.0
0.0