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ARL Current & Forecast Meteorology

Posted: August 13th, 2020, 10:35 am
by gmcurcio

Does anyone know how the Pasquill Stability Product in the suite of ARL Current & Forecast Meteorology addresses the timing of 1 hour before and after sunset. Pasquill Stability is calculated differently for day and night times. I was wondering how the stability calculation specifically accomplishes this task in its code. Some meteorologists use the Solar Radiation Delta T method to address this. I would like to know how this ARL product accomplishes this need. Thanks.

Re: ARL Current & Forecast Meteorology

Posted: August 25th, 2020, 4:11 pm
by Fantine
The utility program in HYSPLIT to compute the Pasquill-Gifford categories is "vmixing.f". It uses diffusivity (m2/s) to obtain the stability classes. The reference paper is Draxler (1979) Atmospheric Environ., Vol 13., pp.1559-1564.
Note that HYSPLIT has different options to estimate diffusivity. The default setting is to use the Kantha-Clayson method (KBLT=2 in SETUP.CFG). More detail about the diffusivity computation can be found here: