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Atmospheric enthalpy flux

Posted: Tue Sep 12, 2023 12:27 am America/New_York
by fivedolphins
In MERRA-2, the vertically integrated diagnostics dataset (M2T1NXINT) has variables "eastward and northward flux of atmospheric enthalpy", or CPT U and CPT V.

How are these values calculated? Are they dry enthalpy or the 'virtual' enthalpy CpTv discussed in the documentation? Thank you.

Re: Atmospheric enthalpy flux

Posted: Tue Sep 12, 2023 7:18 am America/New_York
by GES DISC - mgreene
Hello,

Our MERRA-2 data and subject matter experts will examine your question and formulate a reply shortly.

Re: Atmospheric enthalpy flux

Posted: Tue Sep 12, 2023 11:11 am America/New_York
by mikeb610.1
These are H=CpTv, virtual enthalpy. Please see the MERRA-2 File Specification Document page 67 for more information.
https://gmao.gsfc.nasa.gov/reanalysis/MERRA-2/docs/

One issue exists with DHDT_DYN, while it includes the divergence of H, it also includes other terms from the dynamical routines, and so, does not globally integrate to ~0 as divergence should. Just be aware that we do not have the divergence H written as its own term.

Re: Atmospheric enthalpy flux

Posted: Sun Oct 08, 2023 7:10 pm America/New_York
by fivedolphins
Thank you for the reply. Given this information, what is the most appropriate way to calculate vertically integrated moist static energy (MSE) from MERRA-2 outputs, as there is no dry enthalpy variable? Is it appropriate to use CpTv instead, given that the correction for virtual temperature is relatively small?

Thank you!

Re: Atmospheric enthalpy flux

Posted: Fri Oct 27, 2023 1:33 pm America/New_York
by mbosilov
Take a look at this paper, it has a complete total energy budget discussion, with equations and also variable names in the appendix. The paper is MERRA, but most of that still holds for what is included in MERRA-2.