{
  "key": "sigma_theta_ave",
  "slug": "sigma_theta_ave",
  "label": "Potential density anomaly (sigma-theta), sensor-pair average by the provider's flags",
  "short_label": "Potential density (sensor mean)",
  "description": "Potential density anomaly (sigma-theta), sensor-pair average by the provider's flags",
  "units": "kg/m3",
  "units_nerc_p06": "http://vocab.nerc.ac.uk/collection/P06/current/UKMC/",
  "nerc_p01": null,
  "category": {
    "key": null,
    "name": "Physical Oceanography",
    "icon": "cat-physical",
    "realm": "env",
    "order": 1
  },
  "is_unified": false,
  "derivation": "calcofi4db::ctd_sigma_theta_ave() = combine_sensor_pair() on sigma_theta_1/2: an 8/9-flagged sensor dropped, 1/2 select a sensor, else the mean; final and preliminary_with_bottle casts only",
  "climatology": true,
  "bounds": {
    "valid_min": 15,
    "valid_max": 35,
    "declared_by": [
      "sigma_theta_ave"
    ]
  },
  "totals": {
    "n_values": 682193,
    "n_samples": 9534,
    "n_roots": 9534,
    "n_datasets": 1,
    "year_min": 1993,
    "year_max": 2026,
    "depth_min_m": 1,
    "depth_max_m": 3630,
    "qual_ok_n": 682193,
    "n_flagged": 0
  },
  "series": [
    {
      "measurement_type": "sigma_theta_ave",
      "dataset_key": "calcofi_ctd-derived",
      "source_column": "sigma_theta_1; sigma_theta_2",
      "qual_column": null,
      "description": "Potential density anomaly (sigma-theta), sensor-pair average by the provider's flags",
      "units": "kg/m3",
      "nerc_p01": null,
      "is_canonical": true,
      "n_values": 682193,
      "n_samples": 9534,
      "n_roots": 9534,
      "n_cells": 113,
      "n_cruises": 138,
      "year_min": 1993,
      "year_max": 2026,
      "depth_min_m": 1,
      "depth_max_m": 3630,
      "years": {
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        "1994": 21986,
        "1995": 20610,
        "1996": 23083,
        "1997": 21826,
        "1998": 32352,
        "1999": 20617,
        "2000": 19723,
        "2001": 19476,
        "2002": 19710,
        "2003": 24257,
        "2004": 24832,
        "2005": 20574,
        "2006": 22492,
        "2007": 21605,
        "2008": 21265,
        "2009": 23763,
        "2010": 22484,
        "2011": 23349,
        "2012": 18926,
        "2013": 22093,
        "2014": 17537,
        "2015": 20791,
        "2016": 23887,
        "2017": 21363,
        "2018": 18652,
        "2019": 15177,
        "2020": 16306,
        "2021": 17352,
        "2022": 15531,
        "2023": 21964,
        "2024": 17860,
        "2025": 15172,
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      },
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        "10-50": 88860,
        "50-100": 108158,
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        "500-1000": 38020,
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      "qual": {
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      "qual_ok_n": 682193,
      "n_flagged": 0,
      "observed": {
        "min": 15.8835,
        "p05": 24.3376,
        "p50": 26.33695,
        "p95": 26.9727,
        "max": 30.5674
      },
      "out_of_bounds": {
        "n": 0,
        "min": null,
        "max": null
      },
      "flags": [
        "no_flag_at_grain",
        "no_p01"
      ]
    }
  ],
  "related": [],
  "flags": [
    "no_label"
  ],
  "face": {
    "kind": "standsin",
    "face_of": "sigma_theta",
    "stands_in_note": "stands in: sigma-theta's face (sensor-pair average by the provider's flags)",
    "source": "no NERC P01 on this key (D3)"
  },
  "method": [
    {
      "dataset_key": "calcofi_ctd-derived",
      "measurement_type": "sigma_theta_ave",
      "platform": "ctd",
      "instrument": "Computed from the two CTD sensors' salinity and potential temperature",
      "nerc_l22": null,
      "principle": "Potential density (sigma-theta) computed for each of the CTD's two sensor pairs and combined into one series by the provider's flags: a sensor flagged 8 or 9 is dropped, 1 or 2 select a sensor, otherwise the two are averaged. Published for final and preliminary_with_bottle casts only.",
      "steps": [],
      "wavelength_nm": null,
      "precision": null,
      "bibkeys": [],
      "calcofi_org_url": null,
      "text_fragment": null,
      "source": "the record's own derivation (measurement_type.csv)",
      "source_url": null
    }
  ],
  "why": [
    {
      "rank": 1,
      "kind": "authored",
      "text": "Potential density is what stacks the water column: the denser the surface layer is over the one below it, the less winter mixing and upwelling lift into the light, and off California stronger layering has gone with less zooplankton.",
      "bibkeys": [
        "roemmich1995"
      ],
      "source_url": null,
      "eov": null,
      "goos_doc": null
    },
    {
      "rank": 2,
      "kind": "authored",
      "text": "Density is computed from temperature, salinity and pressure, so it inherits both the warming and the freshening the record carries separately.",
      "bibkeys": [],
      "source_url": null,
      "eov": null,
      "goos_doc": null
    },
    {
      "rank": 3,
      "kind": "wikipedia",
      "text": "Potential density",
      "bibkeys": [],
      "source_url": "https://en.wikipedia.org/wiki/Potential_density",
      "eov": null,
      "goos_doc": null
    },
    {
      "rank": 4,
      "kind": "wikipedia",
      "text": "Thermocline",
      "bibkeys": [],
      "source_url": "https://en.wikipedia.org/wiki/Thermocline",
      "eov": null,
      "goos_doc": null
    }
  ],
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