Given virtual temperature and relative humidty, tvrh2q returns specific humidity, q, in g/g. Specifically:

tvexpr     A GrADS expression that represents virtual temperature, in Kelvin.
rhexpr     A GrADS expression that represents relative humidty, in percent (values from 0 to 100).

This function works only on gridded data.

Usage Notes

  1. The conversion formula requires a pressure in mb. tvrh2q assumes that the Z coordinate system is pressure in mb. If Z is a varying dimension, the pressure valid at each grid point is used. When Z is a fixed dimension, the Z value from the current dimension environment is used.

    Note that it is possible to provide values from an incorrect pressure level by overriding the current dimension environment:

    set lev 500
    d tvrh2q(tv(lev=850),rh(lev=850))

    In this case, the tvrh2q function assumes a pressure of 500mb, which is the current setting for the Z dimension environment. However, tvexpr and rhexpr are providing data from the 850mb level, so the function will produce incorrect results.