Conversion functions

Conversions involving temperature, salinity, entropy, pressure, and height.

Those most commonly used probably include:

gsw.CT_from_t()
gsw.SA_from_SP()
gsw.SP_from_C()
gsw.p_from_z()
gsw.z_from_p()

gsw.conversions.CT_from_enthalpy(SA, h, p)[source]

Calculates the Conservative Temperature of seawater, given the Absolute Salinity, specific enthalpy, h, and pressure p. The specific enthalpy input is the one calculated from 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
harray-like: Specific enthalpy, J/kg
parray-like: Sea pressure (absolute pressure minus 10.1325 dbar), dbar

Returns:

CTarray-like, deg C: Conservative Temperature ( ITS-90)

Notes

Note that the 75-term equation has been fitted in a restricted range of parameter space, and is most accurate inside the “oceanographic funnel” described in McDougall et al. (2003). The GSW library function “gsw_infunnel(SA,CT,p)” is available to be used if one wants to test if some of one’s data lies outside this “funnel”.

References

IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. Available from https://www.teos-10.org/

McDougall, T.J., 2003: Potential enthalpy: A conservative oceanic variable for evaluating heat content and heat fluxes. Journal of Physical Oceanography, 33, 945-963.

McDougall, T.J., D.R. Jackett, D.G. Wright and R. Feistel, 2003: Accurate and computationally efficient algorithms for potential temperature and density of seawater. J. Atmosph. Ocean. Tech., 20, pp. 730-741.

McDougall, T.J., and S.J. Wotherspoon, 2014: A simple modification of Newton’s method to achieve convergence of order 1 + sqrt(2). Applied Mathematics Letters, 29, 20-25.

Roquet, F., G. Madec, T.J. McDougall, P.M. Barker, 2015: Accurate polynomial expressions for the density and specific volume of seawater using the TEOS-10 standard. Ocean Modelling., 90, pp. 29-43.

gsw.conversions.CT_from_entropy(SA, entropy)[source]

Calculates Conservative Temperature with entropy as an input variable.

Parameters:

SAarray-like: Absolute Salinity, g/kg
entropyarray-like: Specific entropy, J/(kg*K)

Returns:

CTarray-like, deg C: Conservative Temperature (ITS-90)

References

IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. Available from https://www.teos-10.org/ See appendix A.10 of this TEOS-10 Manual.

gsw.conversions.CT_from_pt(SA, pt)[source]

Calculates Conservative Temperature of seawater from potential temperature (whose reference sea pressure is zero dbar).

Parameters:

SAarray-like: Absolute Salinity, g/kg
ptarray-like: Potential temperature referenced to a sea pressure, degrees C

Returns:

CTarray-like, deg C: Conservative Temperature (ITS-90)

References

IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. Available from https://www.teos-10.org/ See section 3.3 of this TEOS-10 Manual.

gsw.conversions.CT_from_rho(rho, SA, p)[source]

Calculates the Conservative Temperature of a seawater sample, for given values of its density, Absolute Salinity and sea pressure (in dbar), using the computationally-efficient expression for specific volume in terms of SA, CT and p (Roquet et al., 2015).

Parameters:

rhoarray-like: Seawater density (not anomaly) in-situ, e.g., 1026 kg/m^3.
SAarray-like: Absolute Salinity, g/kg
parray-like: Sea pressure (absolute pressure minus 10.1325 dbar), dbar

Returns:

CTarray-like, deg C: Conservative Temperature (ITS-90)
CT_multiplearray-like, deg C: Conservative Temperature (ITS-90)

Notes

Note that the 75-term equation has been fitted in a restricted range of parameter space, and is most accurate inside the “oceanographic funnel” described in McDougall et al. (2003). The GSW library function “gsw_infunnel(SA,CT,p)” is available to be used if one wants to test if some of one’s data lies outside this “funnel”.

References

IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. Available from https://www.teos-10.org/

McDougall, T.J., D.R. Jackett, D.G. Wright and R. Feistel, 2003: Accurate and computationally efficient algorithms for potential temperature and density of seawater. J. Atmosph. Ocean. Tech., 20, pp. 730-741.

Roquet, F., G. Madec, T.J. McDougall, P.M. Barker, 2015: Accurate polynomial expressions for the density and specific volume of seawater using the TEOS-10 standard. Ocean Modelling, 90, pp. 29-43.

gsw.conversions.CT_from_t(SA, t, p)[source]

Calculates Conservative Temperature of seawater from in-situ temperature.

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:

CTarray-like, deg C: Conservative Temperature (ITS-90)

References

IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. Available from https://www.teos-10.org/ See section 3.3 of this TEOS-10 Manual.

gsw.conversions.C_from_SP(SP, t, p)[source]

Calculates conductivity, C, from (SP,t,p) using PSS-78 in the range 2 < SP < 42. If the input Practical Salinity is less than 2 then a modified form of the Hill et al. (1986) formula is used for Practical Salinity. The modification of the Hill et al. (1986) expression is to ensure that it is exactly consistent with PSS-78 at SP = 2.

Parameters:

SParray-like: Practical Salinity (PSS-78), unitless
tarray-like: In-situ temperature (ITS-90), degrees C
parray-like: Sea pressure (absolute pressure minus 10.1325 dbar), dbar

Returns:

Carray-like, mS/cm: conductivity

Notes

The conductivity ratio returned by this function is consistent with the input value of Practical Salinity, SP, to 2x10^-14 psu over the full range of input parameters (from pure fresh water up to SP = 42 psu). This error of 2x10^-14 psu is machine precision at typical seawater salinities. This accuracy is achieved by having four different polynomials for the starting value of Rtx (the square root of Rt) in four different ranges of SP, and by using one and a half iterations of a computationally efficient modified Newton-Raphson technique (McDougall and Wotherspoon, 2013) to find the root of the equation.

Note that strictly speaking PSS-78 (Unesco, 1983) defines Practical Salinity in terms of the conductivity ratio, R, without actually specifying the value of C(35,15,0) (which we currently take to be 42.9140 mS/cm).

References

Hill, K.D., T.M. Dauphinee and D.J. Woods, 1986: The extension of the Practical Salinity Scale 1978 to low salinities. IEEE J. Oceanic Eng., OE-11, 1, 109 - 112.

IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. Available from https://www.teos-10.org/ See appendix E of this TEOS-10 Manual.

McDougall T. J. and S. J. Wotherspoon, 2013: A simple modification of Newton’s method to achieve convergence of order 1 + sqrt(2). Applied Mathematics Letters, 29, 20-25.

Unesco, 1983: Algorithms for computation of fundamental properties of seawater. Unesco Technical Papers in Marine Science, 44, 53 pp.

gsw.conversions.SA_from_SP(SP, p, lon, lat)[source]

Calculates Absolute Salinity from Practical Salinity. Since SP is non-negative by definition, this function changes any negative input values of SP to be zero.

Parameters:

SParray-like: Practical Salinity (PSS-78), unitless
parray-like: Sea pressure (absolute pressure minus 10.1325 dbar), dbar
lonarray-like: Longitude, -360 to 360 degrees
latarray-like: Latitude, -90 to 90 degrees

Returns:

SAarray-like, g/kg: Absolute Salinity

References

IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. Available from https://www.teos-10.org/ See section 2.5 and appendices A.4 and A.5 of this TEOS-10 Manual.

McDougall, T.J., D.R. Jackett, F.J. Millero, R. Pawlowicz and P.M. Barker, 2012: A global algorithm for estimating Absolute Salinity. Ocean Science, 8, 1123-1134. https://os.copernicus.org/articles/8/1123/2012/os-8-1123-2012.pdf

gsw.conversions.SA_from_Sstar(Sstar, p, lon, lat)[source]

Calculates Absolute Salinity from Preformed Salinity.

Parameters:

Sstararray-like: Preformed Salinity, g/kg
parray-like: Sea pressure (absolute pressure minus 10.1325 dbar), dbar
lonarray-like: Longitude, -360 to 360 degrees
latarray-like: Latitude, -90 to 90 degrees

Returns:

SAarray-like, g/kg: Absolute Salinity

References

IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. Available from https://www.teos-10.org/

McDougall, T.J., D.R. Jackett, F.J. Millero, R. Pawlowicz and P.M. Barker, 2012: A global algorithm for estimating Absolute Salinity. Ocean Science, 8, 1123-1134. https://os.copernicus.org/articles/8/1123/2012/os-8-1123-2012.pdf

gsw.conversions.SA_from_rho(rho, CT, p)[source]

Calculates the Absolute Salinity of a seawater sample, for given values of its density, Conservative Temperature and sea pressure (in dbar). This function uses the computationally-efficient 75-term expression for specific volume in terms of SA, CT and p (Roquet et al., 2015).

Parameters:

rhoarray-like: Seawater density (not anomaly) in-situ, e.g., 1026 kg/m^3.
CTarray-like: Conservative Temperature (ITS-90), degrees C
parray-like: Sea pressure (absolute pressure minus 10.1325 dbar), dbar

Returns:

SAarray-like, g/kg: Absolute Salinity.

Notes

Note that this 75-term equation has been fitted in a restricted range of parameter space, and is most accurate inside the “oceanographic funnel” described in McDougall et al. (2003). The GSW library function “gsw_infunnel(SA,CT,p)” is available to be used if one wants to test if some of one’s data lies outside this “funnel”.

References

IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. Available from https://www.teos-10.org/ See section 2.5 of this TEOS-10 Manual.

McDougall, T.J., D.R. Jackett, D.G. Wright and R. Feistel, 2003: Accurate and computationally efficient algorithms for potential temperature and density of seawater. J. Atmosph. Ocean. Tech., 20, pp. 730-741.

Millero, F.J., R. Feistel, D.G. Wright, and T.J. McDougall, 2008: The composition of Standard Seawater and the definition of the Reference-Composition Salinity Scale. Deep-Sea Res. I, 55, 50-72.

Roquet, F., G. Madec, T.J. McDougall, P.M. Barker, 2015: Accurate polynomial expressions for the density and specific volume of seawater using the TEOS-10 standard. Ocean Modelling., 90, pp. 29-43.

gsw.conversions.SP_from_C(C, t, p)[source]

Calculates Practical Salinity, SP, from conductivity, C, primarily using the PSS-78 algorithm. Note that the PSS-78 algorithm for Practical Salinity is only valid in the range 2 < SP < 42. If the PSS-78 algorithm produces a Practical Salinity that is less than 2 then the Practical Salinity is recalculated with a modified form of the Hill et al. (1986) formula. The modification of the Hill et al. (1986) expression is to ensure that it is exactly consistent with PSS-78 at SP = 2. Note that the input values of conductivity need to be in units of mS/cm (not S/m).

Parameters:

Carray-like: Conductivity, mS/cm
tarray-like: In-situ temperature (ITS-90), degrees C
parray-like: Sea pressure (absolute pressure minus 10.1325 dbar), dbar

Returns:

SParray-like, unitless: Practical Salinity on the PSS-78 scale

References

Culkin and Smith, 1980: Determination of the Concentration of Potassium Chloride Solution Having the Same Electrical Conductivity, at 15C and Infinite Frequency, as Standard Seawater of Salinity 35.0000 (Chlorinity 19.37394), IEEE J. Oceanic Eng, 5, 22-23.

Hill, K.D., T.M. Dauphinee & D.J. Woods, 1986: The extension of the Practical Salinity Scale 1978 to low salinities. IEEE J. Oceanic Eng., 11, 109 - 112.

IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. Available from https://www.teos-10.org/ See appendix E of this TEOS-10 Manual.

Unesco, 1983: Algorithms for computation of fundamental properties of seawater. Unesco Technical Papers in Marine Science, 44, 53 pp.

gsw.conversions.SP_from_SA(SA, p, lon, lat)[source]

Calculates Practical Salinity from Absolute Salinity.

Parameters:

SAarray-like: Absolute Salinity, g/kg
parray-like: Sea pressure (absolute pressure minus 10.1325 dbar), dbar
lonarray-like: Longitude, -360 to 360 degrees
latarray-like: Latitude, -90 to 90 degrees

Returns:

SParray-like, unitless: Practical Salinity (PSS-78)

References

IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. Available from https://www.teos-10.org/

McDougall, T.J., D.R. Jackett, F.J. Millero, R. Pawlowicz and P.M. Barker, 2012: A global algorithm for estimating Absolute Salinity. Ocean Science, 8, 1123-1134. https://os.copernicus.org/articles/8/1123/2012/os-8-1123-2012.pdf

gsw.conversions.SP_from_SK(SK)[source]

Calculates Practical Salinity from Knudsen Salinity.

Parameters:

SKarray-like: Knudsen Salinity, ppt

Returns:

SParray-like, unitless: Practical Salinity (PSS-78)

References

IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. Available from https://www.teos-10.org/ See Appendix A.3 of this TEOS-10 Manual.

gsw.conversions.SP_from_SR(SR)[source]

Calculates Practical Salinity from Reference Salinity.

Parameters:

SRarray-like: Reference Salinity, g/kg

Returns:

SParray-like, unitless: Practical Salinity (PSS-78)

References

IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. Available from https://www.teos-10.org/

gsw.conversions.SP_from_Sstar(Sstar, p, lon, lat)[source]

Calculates Practical Salinity from Preformed Salinity.

Parameters:

Sstararray-like: Preformed Salinity, g/kg
parray-like: Sea pressure (absolute pressure minus 10.1325 dbar), dbar
lonarray-like: Longitude, -360 to 360 degrees
latarray-like: Latitude, -90 to 90 degrees

Returns:

SParray-like, unitless: Practical Salinity (PSS-78)

References

IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. Available from https://www.teos-10.org/

McDougall, T.J., D.R. Jackett, F.J. Millero, R. Pawlowicz and P.M. Barker, 2012: A global algorithm for estimating Absolute Salinity. Ocean Science, 8, 1123-1134. https://os.copernicus.org/articles/8/1123/2012/os-8-1123-2012.pdf

gsw.conversions.SR_from_SP(SP)[source]

Calculates Reference Salinity from Practical Salinity.

Parameters:

SParray-like: Practical Salinity (PSS-78), unitless

Returns:

SRarray-like, g/kg: Reference Salinity

References

IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. Available from https://www.teos-10.org/

gsw.conversions.Sstar_from_SA(SA, p, lon, lat)[source]

Converts Preformed Salinity from Absolute Salinity.

Parameters:

SAarray-like: Absolute Salinity, g/kg
parray-like: Sea pressure (absolute pressure minus 10.1325 dbar), dbar
lonarray-like: Longitude, -360 to 360 degrees
latarray-like: Latitude, -90 to 90 degrees

Returns:

Sstararray-like, g/kg: Preformed Salinity

References

IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. Available from https://www.teos-10.org/

McDougall, T.J., D.R. Jackett, F.J. Millero, R. Pawlowicz and P.M. Barker, 2012: A global algorithm for estimating Absolute Salinity. Ocean Science, 8, 1123-1134. https://os.copernicus.org/articles/8/1123/2012/os-8-1123-2012.pdf

gsw.conversions.Sstar_from_SP(SP, p, lon, lat)[source]

Calculates Preformed Salinity from Absolute Salinity. Since SP is non-negative by definition, this function changes any negative input values of SP to be zero.

Parameters:

SParray-like: Practical Salinity (PSS-78), unitless
parray-like: Sea pressure (absolute pressure minus 10.1325 dbar), dbar
lonarray-like: Longitude, -360 to 360 degrees
latarray-like: Latitude, -90 to 90 degrees

Returns:

Sstararray-like, g/kg: Preformed Salinity

References

IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. Available from https://www.teos-10.org/ See section 2.5 and appendices A.4 and A.5 of this TEOS-10 Manual.

McDougall, T.J., D.R. Jackett, F.J. Millero, R. Pawlowicz and P.M. Barker, 2012: A global algorithm for estimating Absolute Salinity. Ocean Science, 8, 1123-1134. https://os.copernicus.org/articles/8/1123/2012/os-8-1123-2012.pdf

gsw.conversions.adiabatic_lapse_rate_from_CT(SA, CT, p)[source]

Calculates the adiabatic lapse rate of sea water from Conservative Temperature.

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:

adiabatic_lapse_ratearray-like, K/Pa: adiabatic lapse rate

References

IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. Available from https://www.teos-10.org/. See Eqn. (2.22.1) of this TEOS-10 Manual.

gsw.conversions.deltaSA_from_SP(SP, p, lon, lat)[source]

Calculates Absolute Salinity Anomaly from Practical Salinity. Since SP is non-negative by definition, this function changes any negative input values of SP to be zero.

Parameters:

SParray-like: Practical Salinity (PSS-78), unitless
parray-like: Sea pressure (absolute pressure minus 10.1325 dbar), dbar
lonarray-like: Longitude, -360 to 360 degrees
latarray-like: Latitude, -90 to 90 degrees

Returns:

deltaSAarray-like, g/kg: Absolute Salinity Anomaly

References

IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. Available from https://www.teos-10.org/ See section 2.5 and appendices A.4 and A.5 of this TEOS-10 Manual.

McDougall, T.J., D.R. Jackett, F.J. Millero, R. Pawlowicz and P.M. Barker, 2012: A global algorithm for estimating Absolute Salinity. Ocean Science, 8, 1117-1128. https://os.copernicus.org/articles/8/1117/2012/os-8-1117-2012.pdf

gsw.conversions.entropy_from_pt(SA, pt)[source]

Calculates specific entropy of seawater as a function of potential temperature.

Parameters:

SAarray-like: Absolute Salinity, g/kg
ptarray-like: Potential temperature referenced to a sea pressure, degrees C

Returns:

entropyarray-like, J/(kg*K): specific entropy

References

IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. Available from https://www.teos-10.org/ See appendix A.10 of this TEOS-10 Manual.

gsw.conversions.entropy_from_t(SA, t, p)[source]

Calculates specific entropy of seawater from in-situ temperature.

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:

entropyarray-like, J/(kg*K): specific entropy

References

IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. Available from https://www.teos-10.org/

gsw.conversions.p_from_z(z, lat, geo_strf_dyn_height=0, sea_surface_geopotential=0)[source]

Calculates sea pressure from height using computationally-efficient 75-term expression for density, in terms of SA, CT and p (Roquet et al., 2015). Dynamic height anomaly, geo_strf_dyn_height, if provided, must be computed with its p_ref = 0 (the surface). Also if provided, sea_surface_geopotental is the geopotential at zero sea pressure. This function solves Eqn.(3.32.3) of IOC et al. (2010) iteratively for p.

Parameters:

zarray-like

Depth, positive up, m

latarray-like

Latitude, -90 to 90 degrees

geo_strf_dyn_heightarray-like

dynamic height anomaly, m^2/s^2: Note that the reference pressure, p_ref, of geo_strf_dyn_height must be zero (0) dbar.

sea_surface_geopotentialarray-like

geopotential at zero sea pressure, m^2/s^2

Returns:

parray-like, dbar: sea pressure ( i.e. absolute pressure - 10.1325 dbar )

Notes

Note. Height (z) is NEGATIVE in the ocean. Depth is -z. Depth is not used in the GSW computer software library.

Note that this 75-term equation has been fitted in a restricted range of parameter space, and is most accurate inside the “oceanographic funnel” described in McDougall et al. (2003). The GSW library function “gsw_infunnel(SA,CT,p)” is available to be used if one wants to test if some of one’s data lies outside this “funnel”.

References

IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. Available from https://www.teos-10.org/

McDougall, T.J., D.R. Jackett, D.G. Wright and R. Feistel, 2003: Accurate and computationally efficient algorithms for potential temperature and density of seawater. J. Atmosph. Ocean. Tech., 20, pp. 730-741.

McDougall, T.J., and S.J. Wotherspoon, 2013: A simple modification of Newton’s method to achieve convergence of order 1 + sqrt(2). Applied Mathematics Letters, 29, pp. 20-25.

Moritz, H., 2000: Geodetic reference system 1980. J. Geodesy, 74, pp. 128-133.

Roquet, F., G. Madec, T.J. McDougall, P.M. Barker, 2015: Accurate polynomial expressions for the density and specific volume of seawater using the TEOS-10 standard. Ocean Modelling, 90, pp. 29-43.

Saunders, P.M., 1981: Practical conversion of pressure to depth. Journal of Physical Oceanography, 11, pp. 573-574.

This software is available from https://www.teos-10.org/

gsw.conversions.pt0_from_t(SA, t, p)[source]

Calculates potential temperature with reference pressure, p_ref = 0 dbar. The present routine is computationally faster than the more general function “gsw_pt_from_t(SA,t,p,p_ref)” which can be used for any reference pressure value. This subroutine calls “gsw_entropy_part(SA,t,p)”, “gsw_entropy_part_zerop(SA,pt0)” and “gsw_gibbs_pt0_pt0(SA,pt0)”.

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:

pt0array-like, deg C: potential temperature with reference sea pressure (p_ref) = 0 dbar.

References

IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. Available from https://www.teos-10.org/ See section 3.1 of this TEOS-10 Manual.

McDougall T. J. and S. J. Wotherspoon, 2013: A simple modification of Newton’s method to achieve convergence of order 1 + sqrt(2). Applied Mathematics Letters, 29, 20-25.

gsw.conversions.pt_from_CT(SA, CT)[source]

Calculates potential temperature (with a reference sea pressure of zero dbar) from Conservative Temperature. This function uses 1.5 iterations through a modified Newton-Raphson (N-R) iterative solution procedure, starting from a rational-function-based initial condition for both pt and dCT_dpt.

Parameters:

SAarray-like: Absolute Salinity, g/kg
CTarray-like: Conservative Temperature (ITS-90), degrees C

Returns:

ptarray-like, deg C: potential temperature referenced to a sea pressure of zero dbar (ITS-90)

References

IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. Available from https://www.teos-10.org/ See sections 3.1 and 3.3 of this TEOS-10 Manual.

McDougall, T.J., and S.J. Wotherspoon, 2014: A simple modification of Newton’s method to achieve convergence of order 1 + sqrt(2). Applied Mathematics Letters, 29, 20-25.

gsw.conversions.pt_from_entropy(SA, entropy)[source]

Calculates potential temperature with reference pressure p_ref = 0 dbar and with entropy as an input variable.

Parameters:

SAarray-like: Absolute Salinity, g/kg
entropyarray-like: Specific entropy, J/(kg*K)

Returns:

ptarray-like, deg C: potential temperature with reference sea pressure (p_ref) = 0 dbar.

References

IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. Available from https://www.teos-10.org/ See appendix A.10 of this TEOS-10 Manual.

McDougall T. J. and S. J. Wotherspoon, 2013: A simple modification of Newton’s method to achieve convergence of order 1 + sqrt(2). Applied Mathematics Letters, 29, 20-25.

gsw.conversions.pt_from_t(SA, t, p, p_ref)[source]

Calculates potential temperature with the general reference pressure, p_ref, from in-situ temperature, t. This function calls “gsw_entropy_part” which evaluates entropy except for the parts which are a function of Absolute Salinity alone. A faster gsw routine exists if p_ref is indeed zero dbar. This routine is “gsw_pt0_from_t(SA,t,p)”.

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
p_refarray-like: Reference pressure, dbar

Returns:

ptarray-like, deg C: potential temperature with reference pressure, p_ref, on the ITS-90 temperature scale

References

IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. Available from https://www.teos-10.org/ See section 3.1 of this TEOS-10 Manual.

McDougall T. J. and S. J. Wotherspoon, 2013: A simple modification of Newton’s method to achieve convergence of order 1 + sqrt(2). Applied Mathematics Letters, 29, 20-25.

gsw.conversions.t90_from_t68(t68)[source]

ITS-90 temperature from IPTS-68 temperature

This conversion should be applied to all in-situ data collected between 1/1/1968 and 31/12/1989.

gsw.conversions.t_from_CT(SA, CT, p)[source]

Calculates in-situ temperature from the Conservative Temperature of seawater.

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:

tarray-like, deg C: in-situ temperature (ITS-90)

References

IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. Available from https://www.teos-10.org/ See sections 3.1 and 3.3 of this TEOS-10 Manual.

gsw.conversions.z_from_p(p, lat, geo_strf_dyn_height=0, sea_surface_geopotential=0)[source]

Calculates height from sea pressure using the computationally-efficient 75-term expression for specific volume in terms of SA, CT and p (Roquet et al., 2015). Dynamic height anomaly, geo_strf_dyn_height, if provided, must be computed with its p_ref = 0 (the surface). Also if provided, sea_surface_geopotental is the geopotential at zero sea pressure. This function solves Eqn.(3.32.3) of IOC et al. (2010).

Parameters:

parray-like

Sea pressure (absolute pressure minus 10.1325 dbar), dbar

latarray-like

Latitude, -90 to 90 degrees

geo_strf_dyn_heightarray-like

dynamic height anomaly, m^2/s^2: Note that the reference pressure, p_ref, of geo_strf_dyn_height must be zero (0) dbar.

sea_surface_geopotentialarray-like

geopotential at zero sea pressure, m^2/s^2

Returns:

zarray-like, m: height

Notes

Note. Height z is NEGATIVE in the ocean. i.e. Depth is -z. Depth is not used in the GSW computer software library.

Note that this 75-term equation has been fitted in a restricted range of parameter space, and is most accurate inside the “oceanographic funnel” described in McDougall et al. (2003). The GSW library function “gsw_infunnel(SA,CT,p)” is available to be used if one wants to test if some of one’s data lies outside this “funnel”.

References

IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of seawater - 2010: Calculation and use of thermodynamic properties. Intergovernmental Oceanographic Commission, Manuals and Guides No. 56, UNESCO (English), 196 pp. Available from https://www.teos-10.org/

McDougall, T.J., D.R. Jackett, D.G. Wright and R. Feistel, 2003: Accurate and computationally efficient algorithms for potential temperature and density of seawater. J. Atmosph. Ocean. Tech., 20, pp. 730-741.

Moritz, H., 2000: Geodetic reference system 1980. J. Geodesy, 74, pp. 128-133.

Roquet, F., G. Madec, T.J. McDougall, P.M. Barker, 2015: Accurate polynomial expressions for the density and specific volume of seawater using the TEOS-10 standard. Ocean Modelling, 90, pp. 29-43.

This software is available from https://www.teos-10.org/