thermo

A collection of function definitions to handle common thermodynamic calculations for the atmosphere.

climlab.utils.thermo.EIS(T0, T700)

Convenience method, identical to thermo.estimated_inversion_strength(T0,T700)

climlab.utils.thermo.Planck_frequency(nu, T)

The Planck function B(nu,T): the flux density for blackbody radiation in frequency space nu is frequency in 1/s T is temperature in Kelvin

Formula (3.1) from Raymond Pierrehumbert, “Principles of Planetary Climate”

climlab.utils.thermo.Planck_wavelength(l, T)

The Planck function (flux density for blackbody radiation) in wavelength space l is wavelength in meters T is temperature in Kelvin

Formula (3.3) from Raymond Pierrehumbert, “Principles of Planetary Climate”

climlab.utils.thermo.Planck_wavenumber(n, T)

The Planck function (flux density for blackbody radition) in wavenumber space n is wavenumber in 1/cm T is temperature in Kelvin

Formula from Raymond Pierrehumbert, “Principles of Planetary Climate”, page 140.

climlab.utils.thermo.T(theta, p)

Convenience method, identical to thermo.temperature_from_potential(theta,p).

climlab.utils.thermo.blackbody_emission(T)

Blackbody radiation following the Stefan-Boltzmann law.

climlab.utils.thermo.clausius_clapeyron(T)

Compute saturation vapor pressure as function of temperature T.

Input: T is temperature in Kelvin Output: saturation vapor pressure in mb or hPa

Formula from Rogers and Yau “A Short Course in Cloud Physics” (Pergammon Press), p. 16 claimed to be accurate to within 0.1% between -30degC and 35 degC Based on the paper by Bolton (1980, Monthly Weather Review).

climlab.utils.thermo.estimated_inversion_strength(T0, T700)

Compute the Estimated Inversion Strength or EIS, following Wood and Bretherton (2006, J. Climate)

Inputs: T0 is surface temp in Kelvin

T700 is air temperature at 700 hPa in Kelvin

Output: EIS in Kelvin

EIS is a normalized measure of lower tropospheric stability acccounting for temperature-dependence of the moist adiabat.

climlab.utils.thermo.lifting_condensation_level(T, RH)

Compute the Lifiting Condensation Level (LCL) for a given temperature and relative humidity

Inputs: T is temperature in Kelvin

RH is relative humidity (dimensionless)

Output: LCL in meters

This is height (relative to parcel height) at which the parcel would become saturated during adiabatic ascent.

Based on approximate formula from Bolton (1980 MWR) as given by Romps (2017 JAS)

For an exact formula see Romps (2017 JAS), doi:10.1175/JAS-D-17-0102.1

climlab.utils.thermo.mixing_ratio_from_vapor_pressure(p, e)

Water vapor mixing ratio p is air pressure e is vapor pressure p and e must be in same units (e.g. hPa)

climlab.utils.thermo.mmr_to_vmr(mmr, gas)

Convert mass mixing ratio to volume mixing ratio for named gas. ( molecular weights are specific in climlab.utils.constants.py )

climlab.utils.thermo.potential_temperature(T, p)

Compute potential temperature for an air parcel.

Input: T is temperature in Kelvin

p is pressure in mb or hPa

Output: potential temperature in Kelvin.

climlab.utils.thermo.pseudoadiabat(T, p)

Compute the local slope of the pseudoadiabat at given temperature and pressure

Inputs: p is pressure in hPa or mb

T is local temperature in Kelvin

Output: dT/dp, the rate of temperature change for pseudoadiabatic ascent

in units of K / hPa

The pseudoadiabat describes changes in temperature and pressure for an air parcel at saturation assuming instantaneous rain-out of the super-saturated water

Formula consistent with eq. (2.33) from Raymond Pierrehumbert, “Principles of Planetary Climate” which nominally accounts for non-dilute effects, but computes the derivative dT/dpa, where pa is the partial pressure of the non-condensible gas.

Integrating the result dT/dp treating p as total pressure effectively makes the dilute assumption.

climlab.utils.thermo.qsat(T, p)

Compute saturation specific humidity as function of temperature and pressure.

Input: T is temperature in Kelvin

p is pressure in hPa or mb

Output: saturation specific humidity (dimensionless).

climlab.utils.thermo.rho_moist(T, p, q)

Density of moist air. T is air temperature (K) p is air pressure (hPa) q is specific humidity (hPa)

returns density in kg/m3

climlab.utils.thermo.temperature_from_potential(theta, p)

Convert potential temperature to in-situ temperature.

Input: theta is potential temperature in Kelvin

p is pressure in mb or hPa

Output: absolute temperature in Kelvin.

climlab.utils.thermo.theta(T, p)

Convenience method, identical to thermo.potential_temperature(T,p).

climlab.utils.thermo.vapor_pressure_from_specific_humidity(p, q)

Vapor pressure (same units as input p) p is total air pressure q is specific humidity (dimensionless) – mass of vapor per unit mass moist air

climlab.utils.thermo.virtual_temperature_from_mixing_ratio(T, w)

Virtual temperature Tv T is air temperature (K) w is water vapor mixing ratio (dimensionless)

climlab.utils.thermo.vmr_to_mmr(vmr, gas)

Convert volume mixing ratio to mass mixing ratio for named gas. ( molecular weights are specific in climlab.utils.constants.py )