thermodynamics {metR} | R Documentation |
Thermodynamics
Description
Functions related to common atmospheric thermodynamic relationships.
Usage
IdealGas(p, t, rho, R = 287.058)
Adiabat(p, t, theta, p0 = 1e+05, kappa = 2/7)
VirtualTemperature(p, t, e, tv, epsilon = 0.622)
MixingRatio(p, e, w, epsilon = 0.622)
ClausiusClapeyron(t, es)
DewPoint(p, ws, td, epsilon = 0.622)
Arguments
p |
pressure |
t |
temperature |
rho |
density |
R |
gas constant for air |
theta |
potential temperature |
p0 |
reference pressure |
kappa |
ratio of dry air constant and specific heat capacity at constant pressure |
e |
vapour partial pressure |
tv |
virtual temperature |
epsilon |
ratio of dry air constant and vapour constant |
w |
mixing ratio |
es |
saturation vapour partial pressure |
ws |
saturation mixing ratio |
td |
dewpoint |
Details
IdealGas
computes pressure, temperature or density of air according to the
ideal gas law P=\rho R T
.
Adiabat
computes pressure, temperature or potential temperature according to
the adiabatic relationship \theta = T (P0/P)^\kappa
.
VirtualTemperature
computes pressure, temperature, vapour partial pressure or
virtual temperature according to the virtual temperature definition
T(1 - e/P(1 - \epsilon))^{-1}
.
MixingRatio
computes pressure, vapour partial temperature, or mixing ratio
according to w = \epsilon e/(P - e)
.
ClausiusClapeyron
computes saturation pressure or temperature according
to the August-Roche-Magnus formula es = a exp{bT/(T + c)}
with temperature
in Kelvin and saturation pressure in Pa.
DewPoint
computes pressure, saturation mixing ration or dew point
from the relationship ws = \epsilon es(Td)/(p - es(Td))
. Note that the
computation of dew point is approximated.
Is important to take note of the units in which each variable is provided.
With the default values, pressure should be passed in Pascals, temperature and
potential temperature in Kelvins, and density in kg/m^3
.
ClausiusClayperon
and DewPoint
require and return values in those units.
The defaults value of the R
and kappa
parameters are correct for dry air,
for the case of moist air, use the virtual temperature instead of the actual
temperature.
Value
Each function returns the value of the missing state variable.
References
http://www.atmo.arizona.edu/students/courselinks/fall11/atmo551a/ATMO_451a_551a_files/WaterVapor.pdf
See Also
Other meteorology functions:
Derivate()
,
EOF()
,
GeostrophicWind()
,
WaveFlux()
,
waves
Examples
IdealGas(1013*100, 20 + 273.15)
IdealGas(1013*100, rho = 1.15) - 273.15
(theta <- Adiabat(70000, 20 + 273.15))
Adiabat(70000, theta = theta) - 273.15
# Relative humidity from T and Td
t <- 25 + 273.15
td <- 20 + 273.15
p <- 1000000
(rh <- ClausiusClapeyron(td)/ClausiusClapeyron(t))
# Mixing ratio
ws <- MixingRatio(p, ClausiusClapeyron(t))
w <- ws*rh
DewPoint(p, w) - 273.15 # Recover Td