Density

Functions related to density and specific volume.

These are a subset of the TEOS-10 table category “specific volume, density, and enthalpy”.

We are grouping the functions related to enthalpy and internal energy in their own “energy” module.

gsw.density.alpha(SA, CT, p)[source]

Calculates the thermal expansion coefficient of seawater with respect to Conservative Temperature using the computationally-efficient expression for specific volume in terms of SA, CT and p (Roquet et al., 2015).

Parameters
SAarray-like

Absolute Salinity, g/kg

CTarray-like

Conservative Temperature (ITS-90), degrees C

parray-like

Sea pressure (absolute pressure minus 10.1325 dbar), dbar

Returns
alphaarray-like, 1/K

thermal expansion coefficient with respect to Conservative Temperature

gsw.density.alpha_on_beta(SA, CT, p)[source]

Calculates alpha divided by beta, where alpha is the thermal expansion coefficient and beta is the saline contraction coefficient of seawater from Absolute Salinity and Conservative Temperature. This function uses the computationally-efficient expression for specific volume in terms of SA, CT and p (Roquet et al., 2015).

Parameters
SAarray-like

Absolute Salinity, g/kg

CTarray-like

Conservative Temperature (ITS-90), degrees C

parray-like

Sea pressure (absolute pressure minus 10.1325 dbar), dbar

Returns
alpha_on_betaarray-like, kg g^-1 K^-1

thermal expansion coefficient with respect to Conservative Temperature divided by the saline contraction coefficient at constant Conservative Temperature

gsw.density.beta(SA, CT, p)[source]

Calculates the saline (i.e. haline) contraction coefficient of seawater at constant Conservative Temperature using the computationally-efficient 75-term expression for specific volume in terms of SA, CT and p (Roquet et al., 2015).

Parameters
SAarray-like

Absolute Salinity, g/kg

CTarray-like

Conservative Temperature (ITS-90), degrees C

parray-like

Sea pressure (absolute pressure minus 10.1325 dbar), dbar

Returns
betaarray-like, kg/g

saline contraction coefficient at constant Conservative Temperature

gsw.density.kappa(SA, CT, p)[source]

Calculates the isentropic compressibility of seawater. This function has inputs of Absolute Salinity and Conservative Temperature. This function uses the computationally-efficient expression for specific volume in terms of SA, CT and p (Roquet et al., 2015).

Parameters
SAarray-like

Absolute Salinity, g/kg

CTarray-like

Conservative Temperature (ITS-90), degrees C

parray-like

Sea pressure (absolute pressure minus 10.1325 dbar), dbar

Returns
kappaarray-like, 1/Pa

isentropic compressibility of seawater

gsw.density.rho(SA, CT, p)[source]

Calculates in-situ density from Absolute Salinity and Conservative Temperature, using the computationally-efficient expression for specific volume in terms of SA, CT and p (Roquet et al., 2015).

Parameters
SAarray-like

Absolute Salinity, g/kg

CTarray-like

Conservative Temperature (ITS-90), degrees C

parray-like

Sea pressure (absolute pressure minus 10.1325 dbar), dbar

Returns
rhoarray-like, kg/m

in-situ density

gsw.density.rho_alpha_beta(SA, CT, p)[source]

Calculates in-situ density, the appropriate thermal expansion coefficient and the appropriate saline contraction coefficient of seawater from Absolute Salinity and Conservative Temperature. This function uses the computationally-efficient expression for specific volume in terms of SA, CT and p (Roquet et al., 2015).

Parameters
SAarray-like

Absolute Salinity, g/kg

CTarray-like

Conservative Temperature (ITS-90), degrees C

parray-like

Sea pressure (absolute pressure minus 10.1325 dbar), dbar

Returns
rhoarray-like, kg/m

in-situ density

alphaarray-like, 1/K

thermal expansion coefficient with respect to Conservative Temperature

betaarray-like, kg/g

saline (i.e. haline) contraction coefficient at constant Conservative Temperature

gsw.density.rho_t_exact(SA, t, p)[source]

Calculates in-situ density of seawater from Absolute Salinity and in-situ temperature. Note that the output, rho, is density, not density anomaly; that is, 1000 kg/m^3 is not subtracted from it.

Parameters
SAarray-like

Absolute Salinity, g/kg

tarray-like

In-situ temperature (ITS-90), degrees C

parray-like

Sea pressure (absolute pressure minus 10.1325 dbar), dbar

Returns
rho_t_exactarray-like, kg/m^3

in-situ density (not density anomaly)

gsw.density.sigma0(SA, CT)[source]

Calculates potential density anomaly with reference pressure of 0 dbar, this being this particular potential density minus 1000 kg/m^3. This function has inputs of Absolute Salinity and Conservative Temperature. This function uses the computationally-efficient expression for specific volume in terms of SA, CT and p (Roquet et al., 2015).

Parameters
SAarray-like

Absolute Salinity, g/kg

CTarray-like

Conservative Temperature (ITS-90), degrees C

Returns
sigma0array-like, kg/m^3

potential density anomaly with respect to a reference pressure of 0 dbar, that is, this potential density - 1000 kg/m^3.

gsw.density.sigma1(SA, CT)[source]

Calculates potential density anomaly with reference pressure of 1000 dbar, this being this particular potential density minus 1000 kg/m^3. This function has inputs of Absolute Salinity and Conservative Temperature. This function uses the computationally-efficient expression for specific volume in terms of SA, CT and p (Roquet et al., 2015).

Parameters
SAarray-like

Absolute Salinity, g/kg

CTarray-like

Conservative Temperature (ITS-90), degrees C

Returns
sigma1array-like, kg/m^3

potential density anomaly with respect to a reference pressure of 1000 dbar, that is, this potential density - 1000 kg/m^3.

gsw.density.sigma2(SA, CT)[source]

Calculates potential density anomaly with reference pressure of 2000 dbar, this being this particular potential density minus 1000 kg/m^3. Temperature. This function uses the computationally-efficient expression for specific volume in terms of SA, CT and p (Roquet et al., 2015).

Parameters
SAarray-like

Absolute Salinity, g/kg

CTarray-like

Conservative Temperature (ITS-90), degrees C

Returns
sigma2array-like, kg/m^3

potential density anomaly with respect to a reference pressure of 2000 dbar, that is, this potential density - 1000 kg/m^3.

gsw.density.sigma3(SA, CT)[source]

Calculates potential density anomaly with reference pressure of 3000 dbar, this being this particular potential density minus 1000 kg/m^3. Temperature. This function uses the computationally-efficient expression for specific volume in terms of SA, CT and p (Roquet et al., 2015).

Parameters
SAarray-like

Absolute Salinity, g/kg

CTarray-like

Conservative Temperature (ITS-90), degrees C

Returns
sigma3array-like, kg/m^3

potential density anomaly with respect to a reference pressure of 3000 dbar, that is, this potential density - 1000 kg/m^3.

gsw.density.sigma4(SA, CT)[source]

Calculates potential density anomaly with reference pressure of 4000 dbar, this being this particular potential density minus 1000 kg/m^3. Temperature. This function uses the computationally-efficient expression for specific volume in terms of SA, CT and p (Roquet et al., 2015).

Parameters
SAarray-like

Absolute Salinity, g/kg

CTarray-like

Conservative Temperature (ITS-90), degrees C

Returns
sigma4array-like, kg/m^3

potential density anomaly with respect to a reference pressure of 4000 dbar, that is, this potential density - 1000 kg/m^3.

gsw.density.sound_speed(SA, CT, p)[source]

Calculates the speed of sound in seawater. This function has inputs of Absolute Salinity and Conservative Temperature. This function uses the computationally-efficient expression for specific volume in terms of SA, CT and p (Roquet et al., 2015).

Parameters
SAarray-like

Absolute Salinity, g/kg

CTarray-like

Conservative Temperature (ITS-90), degrees C

parray-like

Sea pressure (absolute pressure minus 10.1325 dbar), dbar

Returns
sound_speedarray-like, m/s

speed of sound in seawater

gsw.density.specvol(SA, CT, p)[source]

Calculates specific volume from Absolute Salinity, Conservative Temperature and pressure, using the computationally-efficient 75-term polynomial expression for specific volume (Roquet et al., 2015).

Parameters
SAarray-like

Absolute Salinity, g/kg

CTarray-like

Conservative Temperature (ITS-90), degrees C

parray-like

Sea pressure (absolute pressure minus 10.1325 dbar), dbar

Returns
specvolarray-like, m^3/kg

specific volume

gsw.density.specvol_alpha_beta(SA, CT, p)[source]

Calculates specific volume, the appropriate thermal expansion coefficient and the appropriate saline contraction coefficient of seawater from Absolute Salinity and Conservative Temperature. This function uses the computationally-efficient expression for specific volume in terms of SA, CT and p (Roquet et al., 2015).

Parameters
SAarray-like

Absolute Salinity, g/kg

CTarray-like

Conservative Temperature (ITS-90), degrees C

parray-like

Sea pressure (absolute pressure minus 10.1325 dbar), dbar

Returns
specvolarray-like, m/kg

specific volume

alphaarray-like, 1/K

thermal expansion coefficient with respect to Conservative Temperature

betaarray-like, kg/g

saline (i.e. haline) contraction coefficient at constant Conservative Temperature

gsw.density.specvol_anom_standard(SA, CT, p)[source]

Calculates specific volume anomaly from Absolute Salinity, Conservative Temperature and pressure. It uses the computationally-efficient expression for specific volume as a function of SA, CT and p (Roquet et al., 2015). The reference value to which the anomaly is calculated has an Absolute Salinity of SSO and Conservative Temperature equal to 0 degrees C.

Parameters
SAarray-like

Absolute Salinity, g/kg

CTarray-like

Conservative Temperature (ITS-90), degrees C

parray-like

Sea pressure (absolute pressure minus 10.1325 dbar), dbar

Returns
specvol_anomarray-like, m^3/kg

specific volume anomaly