How to calculate moist Brunt-Vaisala frequency?

WRF model-related NCL questions/topics
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sekluzia
Posts: 180
Joined: Mon Oct 15, 2018 12:42 pm

How to calculate moist Brunt-Vaisala frequency?

Post by sekluzia » Sun Aug 23, 2020 5:09 am

Dear Colleges,

The ncl script from https://www.ncl.ucar.edu/Document/Funct ... sala.shtml is applicable for estimation of dry Brunt-Vaisala frequency.
How to calculate the moist Brunt-Vaisala frequency?

Kind regards,
Artur

skew_t_pie
Posts: 12
Joined: Tue May 12, 2020 9:03 pm

Re: How to calculate moist Brunt-Vaisala frequency?

Post by skew_t_pie » Mon Oct 05, 2020 2:03 pm

You need to calculate equivalent potential temperature. It appears NCL does this and can be acquired via calling for "eth" in the get_var function. This requires knowing the temperature of the lifted condensation level for which there are several empirical methods to do so. A better approach would be to make a correction for the moist adiabatic lapse rate so that

N2 = g/t(dt/dz + gamma)

where gamma is the lapse rate, approximated as in the AMS glossary: https://glossary.ametsoc.org/wiki/Moist ... lapse_rate

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