bigleaf.constants {bigleaf}

Constants Used in the bigleaf Package

Description

This function defines the following constants:

Usage

bigleaf.constants(
  cp = 1004.834,
  Rgas = 8.31451,
  Rv = 461.5,
  Rd = 287.0586,
  Md = 0.0289645,
  Mw = 0.0180153,
  eps = 0.622,
  g = 9.81,
  solar_constant = 1366.1,
  pressure0 = 101325,
  Tair0 = 273.15,
  k = 0.41,
  Cmol = 0.012011,
  Omol = 0.0159994,
  H2Omol = 0.01801528,
  sigma = 5.670367e-08,
  Pr = 0.71,
  Sc_CO2 = 1.07,
  Le067 = 0.93,
  Kelvin = 273.15,
  DwDc = 1.6,
  days2seconds = 86400,
  kPa2Pa = 1000,
  Pa2kPa = 0.001,
  umol2mol = 1e-06,
  mol2umol = 1e+06,
  kg2g = 1000,
  g2kg = 0.001,
  kJ2J = 1000,
  J2kJ = 0.001,
  se_median = 1.253,
  frac2percent = 100
)

Arguments

cp

Specific heat of air for constant pressure (J K-1 kg-1)

Rgas

Universal gas constant (J mol-1 K-1)

Rv

Gas constant of water vapor (J kg-1 K-1) (Stull 1988 p.641)

Rd

Gas constant of dry air (J kg-1 K-1) (Foken p. 245)

Md

Molar mass of dry air (kg mol-1)

Mw

Molar mass of water vapor (kg mol-1)

eps

Ratio of the molecular weight of water vapor to dry air (=Mw/Md)

g

Gravitational acceleration (m s-2)

solar_constant

Solar constant (W m-2)

pressure0

Reference atmospheric pressure at sea level (Pa)

Tair0

Reference air temperature (K)

k

von Karman constant

Cmol

Molar mass of carbon (kg mol-1)

Omol

Molar mass of oxygen (kg mol-1)

H2Omol

Molar mass of water (kg mol-1)

sigma

Stefan-Boltzmann constant (W m-2 K-4)

Pr

Prandtl number

Sc_CO2

Schmidt number for CO2

Le067

Lewis number for water vapor to the power of 0.67

Kelvin

Conversion degree Celsius to Kelvin

DwDc

Ratio of the molecular diffusivities for water vapor and CO2

days2seconds

Seconds per day

kPa2Pa

Conversion kilopascal (kPa) to pascal (Pa)

Pa2kPa

Conversion pascal (Pa) to kilopascal (kPa)

umol2mol

Conversion micromole (umol) to mole (mol)

mol2umol

Conversion mole (mol) to micromole (umol)

kg2g

Conversion kilogram (kg) to gram (g)

g2kg

Conversion gram (g) to kilogram (kg)

kJ2J

Conversion kilojoule (kJ) to joule (J)

J2kJ

Conversion joule (J) to kilojoule (kJ)

se_median

Conversion standard error (SE) of the mean to SE of the median

frac2percent

Conversion between fraction and percent

Details

This function is passed as an argument to every function that uses one or more constants. Individual constants passed to a function can be easily altered. E.g. the following command will change the value of the von Karman constant from 0.41 to 0.4:

bigleaf.constants(k=0.4)

the value of a constant can be returned by calling:

bigleaf.constants()$*name_of_constant*

To permanently change the constants contained within this function (which makes sense for some of them, e.g. for the von Karman constant), the command fixInNamespace can be used. E.g.

fixInNamespace(bigleaf.constants,ns="bigleaf")

Note that this has to be repeated every time the package is newly installed/loaded.