Seawater Density (simplified EOS) mechanism

Model scope

The atmospheric-pressure UNESCO EOS-80 polynomial tested here is standard and gives the expected values. The instrument cannot be approved as specified because it advertises optional pressure without defining the pressure-dependent equation, units, range, or whether pressure is gauge or absolute. The honest-label statement is appropriate only if the exact EOS-80 approximation, validity range, and pressure limitation are displayed.

• The specification does not state the exact UNESCO EOS-80 density equation or its coefficients, so 'simplified linear/UNESCO-80-style polynomial' is not uniquely implementable.
• Pressure is listed as optional, but no pressure correction, pressure range, or pressure unit is specified. The atmospheric-pressure polynomial alone is not valid for nonzero pressure.
• The implementation should explicitly distinguish practical salinity S in PSU from mass-fraction salinity; PSU is dimensionless and should not be treated as g/kg without qualification.

Units and conventions

• Temperature is in degrees Celsius on the IPTS-68/ITS-90-compatible EOS-80 temperature scale.
• Salinity is practical salinity S in PSU, numerically dimensionless, with S^(3/2) interpreted as S multiplied by sqrt(S).
• The tested polynomial computes in-situ density at zero gauge pressure, conventionally P=0 dbar; pressure-dependent density requires the UNESCO pressure correction.
• Output density is in kg/m^3.
• The atmospheric EOS-80 polynomial is intended approximately for -2 <= T <= 40 degrees C and 0 <= S <= 42 PSU; these constraints should be enforced or documented.

Inspectable vector

One of 4 source-bound review vectors:

{
  "inputs": {
    "temperature_C": 0,
    "salinity_PSU": 0,
    "pressure_dbar": 0
  },
  "expected_outputs": {
    "density_kg_m3": 999.842594
  },
  "reference_data": {
    "rho_w_coefficients": {
      "a0": 999.842594,
      "a1": 0.06793952,
      "a2": -0.00909529,
      "a3": 0.0001001685,
      "a4": -0.000001120083,
      "a5": 6.536332e-9
    },
    "source_convention": "Widely tabulated standard value, UNESCO EOS-80/UNESCO Technical Papers in Marine Science 44 atmospheric pure-water density polynomial"
  },
  "working": "Use rho_w(T)=a0+a1*T+a2*T^2+a3*T^3+a4*T^4+a5*T^5. At T=0: rho_w=999.842594+0.06793952*0-0.00909529*0^2+0.0001001685*0^3-0.000001120083*0^4+0.000000006536332*0^5=999.842594 kg/m^3. At S=0, all salinity terms are zero, so rho=999.842594 kg/m^3."
}

Failure boundary

BREAK_CLAIMED · SELF_FLAGGED

The negative-salinity vector produces an undefined real result and must be rejected. The convention probe also exposes a unit-label hazard: interpreting an unlabeled temperature value of 10 as Celsius versus Fahrenheit changes the expected density substantially.

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche7/tranche7-results.json
• BOUNDARY_HAZARD_CATALOG.json