Air density calculation 2007

Calculates moist air density according to the paper "Revised formula for the density of moist air (CIPM-2007)".

This function calculates the air density for moist air, as a function of temperature, pressure, humidity level, and carbon dioxide level. Calculations are, by default, based on the equations given in Ref. 2, dated from 2008. Ref. 2 is an update to a previous version of that study (Ref. 1), dated from 1992.

By default, predictions are based on Ref. 2 values. However, by changing the string Source in the code, results can be given using Ref. 1 values. Results can also be given under an ideal gas assumption, or when using the updated SI molar gas constant from 2019.

Any or all inputs may be vectors of equal length.

This function is very similar to the submittal "Air density calculation" that is based on Ref. 1 values, but includes a term for the current CO2 concentration. The submittal "Calculation of air properties" is based on Ref. 2 (and other) resutlts, and also includes the ability to calculate many more properties of air.