magnus: Thermodynamic helper functions

In achtmalklug/Retp:

Description

Various useful calculations and conversion functions.

Usage

magnus(temp)

rh2dewpoint2(temp, rh)

rh2vp(temp, rh)

vp2rh(temp, vp)

dewpoint2rh(temp, dp)

dewpoint2rh(temp, dp)

psychro(p)

satpressslope(temp)

alt_pressure(altitude)

rsurf_(LAIact = 1.44, rstom = 100)

ra_(zom, zoh, d = 2 * h/3, uz = 2.8, h = 0.12, zm = 2, zh = 2)

wind2m(windz, z)

Arguments

temp	air temperature in °C
rh	relative air humidity in %.
vp	water vapour partial pressure in kPa
dp	dewpoint temperature in °C
p	air pressure in kPa
LAIact	active LAI in m²/m².
rstom	stomatal resistance in s/m.
zom:	roughness length for momentum transfer (m)
zoh:	roughness length for heat transfer (m)
d:	zero plane displacement height (m)
uz:	wind measured at zm (m/s)
h:	crop height (m)
zm:	height of wind measurement (m)
zh:	height of humidity measurements (m)

Value

rh2dewpoint: returns dewpoint temperature in °C

rh2vp: water vapour pressure in kPa.

vp2rh: relative humidity in %.

rh2dewpoint relative air humidity in %.

dewpoint2vp water vapur pressure in kPa.

psychrometric constant in kPa/°C

satpressslope: slope of the curve in kPa/°C

alt_pressure: air pressure in kPa.

rsurf: canopy surface resistance in s/m (=stomatal resistance/active LAI). Default values for FAO grass reference surface.

ra: aerodynamic resistance in s/m. Default arguments for canopy represent the FAO grass reference surface.

wind2m:

Details

magnus calculates the saturation water vapour pressure (over liquid water surfaces) in kPa for a given temperature using the magnus formula.

rh2dewpoint calculates the dewpoint temperature for a given relative air humidity and temperature.

rh2vp calculates the water vapour pressure from relative air humidity and temperature.

vp2rh calculates the relative air humidity from water vapour pressure and temperature.

rh2dewpoint calculates the relative air humidity for a given dewpoint and air and temperature.

dewpoint2vp calculates the relative air humidity for a given dewpoint and air and temperature.

psychro calculates the psychrometre constant (water in air) for a given air pressure.

satpressslope calculates the slope of the water vapour saturation pressure curve in kPa/°C for a given temperature in °C.

alt_pressure calculates the atmospheric air pressure at normal conditions for a given altitude above the sea level.

rsurf

rsurf

wind2m

Examples

rh2dewpoint(50,20)
rh2vp(50,20)
rh2vp(50,20)
rh2dewpoint(50,20)
psychro(101.3)
satpressslope(20)
alt_pressure(1000)
rsurf()
ra()

achtmalklug/Retp documentation built on June 7, 2019, 12:47 a.m.