# gsw_sigma1_CT_exact

    potential density anomaly with reference pressure
    of 1000 dbar, this being this particular potential
    density minus 1000 kg/m^3

## Contents

- USAGE:
- DESCRIPTION:
- INPUT:
- OUTPUT:
- EXAMPLE:
- AUTHOR:
- VERSION NUMBER:
- REFERENCES:

## USAGE:

    sigma1_CT_exact = gsw_sigma1_CT_exact(SA,CT)

## DESCRIPTION:

    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.

    Note that this function uses the full Gibbs function.  There is an
    alternative to calling this function, namely gsw_sigma1(SA,CT), which
    uses the computationally efficient 48-term expression for density in
    terms of SA, CT and p (McDougall et al., 2011).

    Note that the 48-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. (2011).  The GSW library function
    "gsw_infunnel(SA,CT,p)" is avaialble to be used if one wants to test if
    some of one's data lies outside this "funnel".

    Click for a more detailed description of potential
    density anomaly with p_ref of 1000 dbar (sigma_1).

## INPUT:

    SA  =  Absolute Salinity                                        [ g/kg ]
    CT  =  Conservative Temperature                                [ deg C ]

    SA & CT need to have the same dimensions.

## OUTPUT:

    sigma1_CT_exact  =  potential density anomaly with                     [ kg/m^3 ]
               respect to a reference pressure of 1000 dbar,
               that is, this potential density - 1000 kg/m^3.

## EXAMPLE:

    SA = [34.7118; 34.8915; 35.0256; 34.8472; 34.7366; 34.7324;]
    CT = [28.8099; 28.4392; 22.7862; 10.2262;  6.8272;  4.3236;]

    sigma1_CT_exact = gsw_sigma1_CT_exact(SA,CT)

    sigma1_CT_exact =

      25.955551924297879
      26.213079338959005
      28.125625321852112
      31.120452618127047
      31.637685737359789
      32.002400877214541

## AUTHOR:

    Trevor McDougall & Paul Barker     [ help@teos-10.org ]

## VERSION NUMBER:

    3.01 (26th May, 2011)

## 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 the TEOS-10 web site.
      See Eqn. (A.30.1) of this TEOS-10 Manual.

    McDougall T.J., P.M. Barker, R. Feistel and D.R. Jackett, 2011:  A
     computationally efficient 48-term expression for the density of
     seawater in terms of Conservative Temperature, and related properties
     of seawater.  To be submitted to Ocean Science Discussions.

    The software is available from http://www.TEOS-10.org