Moist static energy: definition, reference constants, a conservation law and effects on buoyancy

Yano, Jun-Ichi ; Ambaum, Maarten H. P.

Année de publication
2017
Résumé
Atmospheric thermodynamic variables are commonly computed under approximations. Although exact formulae are available, they are rarely used. This article addresses some potential issues arising when using approximate formulae, by taking the moist static energy as an example. An important conclusion is that the temperature dependence of latent heat must be taken into account. We also demonstrate that the zero-point energies of various species do not affect the moist static energy budget. The use of an exact formula for moist static energy increases its surface value by 15 K for a typical tropical sounding. However, the change of the parcel buoyancy on using the exact formula is less dramatic, although not negligible. Calculating, for example, the convective available potential energy (CAPE) for convection parametrization, the use of an exact formula is likely not critical for practical purposes, but quantitative discrepancies can be as large as 50-200 J kg−1.
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