Comments on "MSE minus CAPE is the True Conserved Variable for an Adiabatically Lifted Parcel"
Marquet, Pascal
<span style="font-family:comic sans ms,cursive;"><span style="color: rgb(128, 0, 128);"><span style="font-size: 8px;"><font style="font-size: 12pt">In a recent paper, Romps (2015, hereafter R15) argues that the quantity MSE minus CAPE (MSE 2 CAPE) must be used as a true conserved variable for an adiabatically lifted parcel, where MSE is the moist-air static energy and CAPE is expected to be the so-called convective available potential energy.<br>It is shown in this comment that the quantity denoted by CAPE in R15 is the opposite of the convective available potential energy. It is explained that the vertical adiabatic ascent considered in R15 is not realistic, since it generates condensed water on the order of 10-20 g kg21 at height above 6 km. Moreover, the thermodynamic equations are written in R15 by making several assumptions, not all of which are explicitly mentioned.<br>This comment aims to clarify the hypotheses made in R15. It will show that these assumptions call into question the validity of the moist-air internal energy, enthalpy, and entropy functions in R15. It also demonstrates that it is possible to obtain more precise and general formulations for moist-air energy, enthalpy, and entropy functions, in particular by using the third law of thermodynamics. The large differences between the thermodynamics formulas derived in R15 and those depending on the third law are illustrated by studying a realistic pseudo adiabatic vertical profile.<br>The same notations as in R15 will be used as far as possible in this comment.</font></span></span></span></p>
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