Virtual temperature

In atmospheric thermodynamics, the virtual temperature ${\displaystyle T_{v}}$ of a moist air parcel is the temperature at which a theoretical dry air parcel would have a total pressure and density equal to the moist parcel of air.

In atmospheric thermodynamic processes, it is often useful to assume air parcels behave approximately adiabatically, and approximately ideally. The specific gas constant for the standardized mass of one kilogram of a particular gas is variable, and described mathematically as

where ${\displaystyle R^{*}}$ is the molar gas constant, and ${\displaystyle M_{x}}$ is the apparent molar mass of gas ${\displaystyle x}$ in kilograms per mole. The apparent molar mass of a theoretical moist parcel in Earth's atmosphere can be defined in components of water vapor and dry air as

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