nsrdb.data_model.merra.RelativeHumidity

class RelativeHumidity

Bases: BaseDerivedVar

Class to derive the relative humidity from other MERRA2 vars. This is derived as the ratio of mixing ratio to saturation mixing ratio, times 100. Intermediate calculations are done to get saturation vapor pressure, mixing ratio, and saturation mixing ratio. Saturation vapor pressure is calculated using the Tetens formula. Mixing ratio is calculated from specific humidity. Saturation mixing ratio is calculated from saturation vapor pressure.

References

[atomclc2]

https://www.conservationphysics.org/atmcalc/atmoclc2.pdf

[esci241]

http://snowball.millersville.edu/~adecaria/ESCI241/esci241_lesson06_humidity.pdf

[wxcalc]

https://www.weather.gov/media/epz/wxcalc/mixingRatio.pdf

Methods

derive(air_temperature, specific_humidity, ...)

Derive the relative humidity from ancillary vars.

Attributes

DEPENDENCIES

static derive(air_temperature, specific_humidity, surface_pressure)

Derive the relative humidity from ancillary vars.

Parameters:

• air_temperature (np.ndarray) – Temperature in Celsius

• specific_humidity (np.ndarray) – Specific humidity in kg/kg

• surface_pressure (np.ndarray) – Pressure in Pa

Returns:

rh (np.ndarray) – Relative humidity in %.