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How to calculate moist Brunt-Vaisala frequency?

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sekluzia

Member
Dear Colleges,

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

Kind regards,
Artur
 
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-adiabatic_lapse_rate
 
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