{
  "schema": "nephos.example-analysis.v1",
  "analysis_id": "NEP-EX-002",
  "object": {
    "title": "Cloud Study",
    "artist": "John Constable",
    "date": "1822-09-21",
    "inscription_verbatim": "Sep[br] 21. 1822. | ½ p’s[t] one o clock. | looking south. | wind very fresh at East, but warm.",
    "inscription_source": "YCBA LIDO catalogue transcription, printed on a label affixed to the stretcher.",
    "inscription_lido_url": "https://harvester-bl.britishart.yale.edu/oaicatmuseum/OAIHandler?verb=GetRecord&identifier=oai:tms.ycba.yale.edu:627&metadataPrefix=lido",
    "inscription_lido_oai_datestamp": "2026-08-25",
    "place": "Hampstead, London (series localization per YCBA curatorial text; coordinates are the analyst's, not the museum's)",
    "accession_number": "B1981.25.116",
    "collection": "Yale Center for British Art, Paul Mellon Collection",
    "medium": "Oil on paper laid on panel",
    "dimensions": "11 1/4 x 19 in (28.6 x 48.3 cm)",
    "rights": "Public Domain / CC0 1.0",
    "record_url": "https://collections.britishart.yale.edu/catalog/tms:627",
    "iiif_manifest": "https://manifests.collections.yale.edu/ycba/obj/627"
  },
  "claims_on_the_object": [
    {
      "id": "date",
      "claim": "Sep[br] 21. 1822."
    },
    {
      "id": "time",
      "claim": "½ p’s[t] one o clock."
    },
    {
      "id": "view",
      "claim": "looking south."
    },
    {
      "id": "wind",
      "claim": "wind very fresh at East,"
    },
    {
      "id": "warmth",
      "claim": "but warm."
    }
  ],
  "capture": {
    "capture_id": "ycba_627_recto_cropped",
    "source_asset": "assets/constable/source/cloud-study-1822-recto.jpg",
    "source_sha256": "45172bb63160087859f20e084060ed82acad991c1ee74c174cca9e1e7f3145f1",
    "source_dimensions": [
      3660,
      2167
    ],
    "source_iiif": "https://images.collections.yale.edu/iiif/2/ycba:a1a011a9-da67-4438-97e4-afe1151cd62b/full/full/0/default.jpg",
    "region_assets": {
      "upper_blue": "assets/constable/derived/constable-upper-blue.jpg",
      "cumulus_left": "assets/constable/derived/constable-cumulus-left.jpg",
      "grey_mass_right": "assets/constable/derived/constable-grey-mass-right.jpg",
      "haze_bed": "assets/constable/derived/constable-haze-bed.jpg"
    },
    "region_metrics": {
      "upper_blue": {
        "mean_rgb": [
          136,
          155,
          155
        ],
        "mean_hex": "#889b9b",
        "mean_saturation": 0.136,
        "mean_relative_luminance": 0.592,
        "luminance_standard_deviation": 0.033,
        "pixel_count": 798708
      },
      "cumulus_left": {
        "mean_rgb": [
          144,
          152,
          143
        ],
        "mean_hex": "#90988f",
        "mean_saturation": 0.1,
        "mean_relative_luminance": 0.586,
        "luminance_standard_deviation": 0.05,
        "pixel_count": 1427400
      },
      "grey_mass_right": {
        "mean_rgb": [
          161,
          160,
          143
        ],
        "mean_hex": "#a1a08f",
        "mean_saturation": 0.122,
        "mean_relative_luminance": 0.624,
        "luminance_standard_deviation": 0.055,
        "pixel_count": 732550
      },
      "haze_bed": {
        "mean_rgb": [
          159,
          159,
          142
        ],
        "mean_hex": "#9f9f8e",
        "mean_saturation": 0.118,
        "mean_relative_luminance": 0.619,
        "luminance_standard_deviation": 0.038,
        "pixel_count": 663507
      }
    },
    "painted_sky_fractions": {
      "opaque_cloud": 0.579,
      "thin_veil": 0.167,
      "clear_blue": 0.254
    },
    "cloud_mask_overlay": "assets/constable/derived/cloud-mask-overlay.png",
    "cloud_mask_note": "Capture-specific blueness heuristic (strongly blue paint reads as clear sky, weakly blue as thin veil, warm or neutral as opaque cloud); it measures this digitization's paint colors, not the 1822 atmosphere.",
    "x_radiograph_iiif": "https://images.collections.yale.edu/iiif/2/ycba:08a9dda3-efd8-428a-9751-541a9957dabe/full/full/0/default.jpg",
    "x_radiograph_note": "YCBA x-radiograph (7/19/2022, 30 kV, 5 mA, 105 s): lead-white cloud masses are radio-opaque and register bright."
  },
  "solar": {
    "library": "Skyfield 1.55",
    "ephemeris": "JPL DE440",
    "site_assumption": {
      "latitude_degrees_north": 51.56,
      "longitude_degrees_east": -0.165
    },
    "time_interpretation": "The catalogue's '½ p’s[t] one o clock.' is treated as approximately 13:30 local mean time. The stored 13:00 and 14:00 values are sensitivity samples around that primary point. No cited source establishes the clock basis; LMT at 0.165 W trails UTC by about 40 seconds.",
    "table": [
      {
        "local_mean_time": "13:00",
        "altitude_degrees": 37.308,
        "azimuth_degrees": 201.341
      },
      {
        "local_mean_time": "13:30",
        "altitude_degrees": 35.268,
        "azimuth_degrees": 210.301
      },
      {
        "local_mean_time": "14:00",
        "altitude_degrees": 32.616,
        "azimuth_degrees": 218.763
      }
    ],
    "summary": "At 13:30 LMT the sun stood 35.3 degrees above the horizon at azimuth 210.3 degrees. Across the stored sensitivity samples at 13:00 and 14:00, altitude ranges from 37.3 to 32.6 degrees and azimuth from 201 to 219 degrees.",
    "disposition": "unknown; the computed sun is consistent with early afternoon but cannot be tested against the horizonless painted sky",
    "limit": "A pure sky with no horizon yields no measurable painted solar direction, so no painted-versus-computed angular residual is reported."
  },
  "weather": {
    "dataset": "NOAA-CIRES-DOE 20th Century Reanalysis v3",
    "inputs_from_painting": 0,
    "grid_cell": {
      "latitude": 52.0,
      "longitude": 0.0,
      "resolution_degrees": 1.0,
      "approximate_dimensions_km_at_latitude": [
        111,
        68
      ]
    },
    "date": "1822-09-21",
    "utc_hours": [
      "06:00",
      "09:00",
      "12:00",
      "15:00",
      "18:00"
    ],
    "total_cloud_cover_percent": {
      "ensemble_mean": [
        51.0,
        57.0,
        60.0,
        63.0,
        57.0
      ],
      "ensemble_spread": [
        39.21,
        37.61,
        31.72,
        34.0,
        34.42
      ]
    },
    "u_wind_10m_ms": {
      "ensemble_mean": [
        -2.110466,
        -4.6705565,
        -4.9793115,
        -4.8147798,
        -3.3837693
      ],
      "ensemble_spread": [
        2.7707422,
        3.5591502,
        3.6187677,
        3.3017032,
        2.5360978
      ]
    },
    "v_wind_10m_ms": {
      "ensemble_mean": [
        -2.8453445,
        -2.6773949,
        -2.9898705,
        -3.5372376,
        -3.169906
      ],
      "ensemble_spread": [
        1.6746607,
        2.3651502,
        2.5429246,
        2.4677033,
        1.670438
      ]
    },
    "air_temperature_2m_K": {
      "ensemble_mean": [
        282.4222,
        285.5312,
        287.18015,
        287.0742,
        284.94043
      ],
      "ensemble_spread": [
        2.0250695,
        1.4225051,
        1.7017908,
        1.7868588,
        1.3687993
      ]
    },
    "at_target_1300_utc": {
      "cloud_cover_percent": 61.0,
      "cloud_cover_spread_pp": 32.5,
      "wind_speed_ms": 5.86,
      "wind_speed_range_1sigma_ms": [
        1.56,
        10.18
      ],
      "wind_from_degrees": 57.2,
      "wind_from_range_1sigma_degrees": [
        13.9,
        85.6
      ],
      "wind_from_compass": "ENE",
      "air_temperature_c": 14.0,
      "air_temperature_spread_k": 1.7
    },
    "query_urls": {
      "tcdc_mean": "https://psl.noaa.gov/thredds/dodsC/Datasets/20thC_ReanV3/miscSI/tcdc.eatm.1822.nc.ascii?tcdc%5B2106:1:2110%5D%5B142:1:142%5D%5B0:1:0%5D",
      "tcdc_spread": "https://psl.noaa.gov/thredds/dodsC/Datasets/20thC_ReanV3/spreads/miscSI/tcdc.eatm.1822.nc.ascii?tcdc%5B2106:1:2110%5D%5B142:1:142%5D%5B0:1:0%5D",
      "uwnd_mean": "https://psl.noaa.gov/thredds/dodsC/Datasets/20thC_ReanV3/10mSI/uwnd.10m.1822.nc.ascii?uwnd%5B2106:1:2110%5D%5B142:1:142%5D%5B0:1:0%5D",
      "uwnd_spread": "https://psl.noaa.gov/thredds/dodsC/Datasets/20thC_ReanV3/spreads/10mSI/uwnd.10m.1822.nc.ascii?uwnd%5B2106:1:2110%5D%5B142:1:142%5D%5B0:1:0%5D",
      "vwnd_mean": "https://psl.noaa.gov/thredds/dodsC/Datasets/20thC_ReanV3/10mSI/vwnd.10m.1822.nc.ascii?vwnd%5B2106:1:2110%5D%5B142:1:142%5D%5B0:1:0%5D",
      "vwnd_spread": "https://psl.noaa.gov/thredds/dodsC/Datasets/20thC_ReanV3/spreads/10mSI/vwnd.10m.1822.nc.ascii?vwnd%5B2106:1:2110%5D%5B142:1:142%5D%5B0:1:0%5D",
      "air_mean": "https://psl.noaa.gov/thredds/dodsC/Datasets/20thC_ReanV3/2mSI/air.2m.1822.nc.ascii?air%5B2106:1:2110%5D%5B142:1:142%5D%5B0:1:0%5D",
      "air_spread": "https://psl.noaa.gov/thredds/dodsC/Datasets/20thC_ReanV3/spreads/2mSI/air.2m.1822.nc.ascii?air%5B2106:1:2110%5D%5B142:1:142%5D%5B0:1:0%5D"
    },
    "limit": "A 1-degree pressure-assimilating ensemble covers about 111 by 68 km at London's latitude. It is regional context, not an observation at the assumed Hampstead site; the cloud-cover spread is comparable to its mean."
  },
  "instrumental": {
    "dataset": "Met Office Hadley Centre Central England Temperature, daily means",
    "source_url": "https://www.metoffice.gov.uk/hadobs/hadcet/data/meantemp_daily_totals.txt",
    "daily_mean_c": {
      "1822-09-17": 14.5,
      "1822-09-18": 12.9,
      "1822-09-19": 12.4,
      "1822-09-20": 11.6,
      "1822-09-21": 11.6,
      "1822-09-22": 12.4,
      "1822-09-23": 12.6,
      "1822-09-26": 9.5
    },
    "prior_50_year_calendar_date_mean_c": 12.552,
    "note": "CET is a regional daily composite, not a London station or a measurement at Constable's position. The 11.6 C daily mean on 1822-09-21 sat in a mild spell that collapsed toward 9.5 C by 1822-09-26, but it was slightly below the approximately 12.6 C average of the prior 50 September 21 readings. Neither CET nor the reanalysis defines the adjective 'warm'."
  },
  "written_record": {
    "observer": "Luke Howard, The Climate of London, 2nd edition, 3 vols, London: Harvey and Darton, 1833",
    "coverage": "Vol. III, Meteorological Observations made at Tottenham and at Stratford, near London, 1819-1827; Table CXCVI (September 1822), p. 90, notes pp. 90-91",
    "entry_1822_09_21": {
      "wind": "NE",
      "barometer_inches": [
        29.87,
        29.8
      ],
      "note": "Howard's note covering the 17th through the 21st reads: Fine."
    },
    "month_wind_tally_sept_1822": {
      "N": 3,
      "NE": 9,
      "E": 4,
      "SE": 1,
      "SW": 5,
      "W": 1,
      "NW": 7
    },
    "comparison_to_constable": {
      "constable_claim": "East at the assumed Hampstead site",
      "howard_reading": "NE at Howard's station",
      "disposition": "partial_agreement",
      "label": "partial agreement / near-agreement",
      "reasoning": "East and northeast are adjacent compass sectors, but they are not identical readings. The observations also refer to different locations across London, so Howard's NE supports only near-agreement with Constable's East, not a match."
    },
    "verification": {
      "status": "verified",
      "method": "Direct visual inspection of the scanned page image for Howard, The Climate of London, volume III, Table CXCVI, page 90.",
      "page_image_url": "https://archive.org/download/in.ernet.dli.2015.48048/page/n96.jpg",
      "checked_on": "2026-08-18",
      "notes": "The wind cells for 20, 21, and 22 September 1822 read SE, NE, and E, respectively. The notes line reads 17-21. Fine. Howard's NE on 21 September is not the same direction label as Constable's East."
    },
    "caveats": "Station attribution (Stratford register with parallel Tottenham figures) is inferred, not labelled per table. Table CXCVI, page 90, was checked directly against the page image on 2026-08-18. Howard's day-21 wind cell reads NE; Constable wrote East for the assumed Hampstead site, so this is partial or near-agreement rather than a match.",
    "constable_letters": {
      "source": "C.R. Leslie, Memoirs of the Life of John Constable, 2nd edition, London, 1845",
      "skying_letter": "I have done a good deal of skying, for I am determined to conquer all difficulties, and that among the rest. (To John Fisher, Hampstead, 23 October 1821, pp. 91-93)",
      "fifty_studies": "I have made about fifty careful studies of skies, tolerably large to be careful. (To John Fisher, Hampstead, 7 October 1822, p. 101)",
      "leslie_on_versos": "They are painted in oil, on large sheets of thick paper, and all dated, with the time of day, the direction of the wind, and other memoranda on their backs. (Leslie, p. 102)"
    },
    "scholarship": "John Thornes, Constable's Clouds, The Burlington Magazine 121 (1979), pp. 697-704: the weather notes on the 1821-22 studies are accurate enough that nine undated studies were assigned years from historical weather records alone. This painting is catalogued in Thornes, John Constable's Skies (1999) as no. 52, plate 123, per the YCBA bibliography."
  }
}