Meaning of the dramatically varying PBLH value

[sahil.bhandari]

We looked at the PBLH value. The PBLH value given at the top in each profile (corresponding to a given profile time) is changing dramatically (20m, 1222 m, 0m, back to 20 m). What is happening here? PBLH cannot possibly vary that dramatically.

[Fantine]

The profile generated in section 9.5 is in a 6-hr time interval. If you print out the profile hourly, you will see the diurnal variation of PBL height ( (pretty much depending on the surface temperature, and of course the surface characteristics). Its value can be low at night, a few hundred meters or even close to the surface, and go up to thousands of meters during the day, especially in the afternoon. The 1222 m PBLH was at 18 UTC, 2 pm local time. The other three small PBLH were at night, early in the morning, or after sunset.

[Fantine]

There is a parameter in SETUP.CFG to set a minimum mixing depth for HYSPLIT. You can use it to avoid the very low PBLH values from the met data file. The default is 150 m. You can set it to another value in the Advanced menu #7, in the "Mixed Layer Depth Computation", the box for "Default minimum (m)".