pressure.from.elevation {bigleaf}

Atmospheric Pressure from Hypsometric Equation

Description

An estimate of mean pressure at a given elevation as predicted by the hypsometric equation.

Usage

pressure.from.elevation(
  elev,
  Tair,
  VPD = NULL,
  constants = bigleaf.constants()
)

Arguments

elev

Elevation a.s.l. (m)

Tair

Air temperature (deg C)

VPD

Vapor pressure deficit (kPa); optional

constants

Kelvin- conversion degC to Kelvin
pressure0 - reference atmospheric pressure at sea level (Pa)
Rd - gas constant of dry air (J kg-1 K-1)
g - gravitational acceleration (m s-2)
Pa2kPa - conversion pascal (Pa) to kilopascal (kPa)

Details

Atmospheric pressure is approximated by the hypsometric equation:

pressure = pressure_0 / (exp(g * elevation / (Rd Temp)))

Value

pressure -

Atmospheric pressure (kPa)

Note

The hypsometric equation gives an estimate of the standard pressure at a given altitude. If VPD is provided, humidity correction is applied and the virtual temperature instead of air temperature is used. VPD is internally converted to specific humidity.

References

Stull B., 1988: An Introduction to Boundary Layer Meteorology. Kluwer Academic Publishers, Dordrecht, Netherlands.

Examples

# mean pressure at 500m altitude at 25 deg C and VPD of 1 kPa
pressure.from.elevation(500,Tair=25,VPD=1)