{
  "url": "https://openlegislation.uk/air-quality-ozone-wales-regulations-2003/schedule-8/part-II",
  "json_url": "https://openlegislation.uk/air-quality-ozone-wales-regulations-2003/schedule-8/part-II.json",
  "legislation": "wsi/2003/1848",
  "legislation_title": "The Air Quality (Ozone) (Wales) Regulations 2003",
  "legislation_url": "https://openlegislation.uk/air-quality-ozone-wales-regulations-2003",
  "path": "schedule/8/part/II",
  "kind": "part",
  "number": "II",
  "heading": "Criteria for aggregating data and calculating statistical parameters",
  "text": "In this Part, percentiles are to be calculated using the method specified in Council Directive 97/101/EC.\nThe following criteria are to be used for checking validity when aggregating data and calculating statistical parameters:\nParameter\nRequired proportion of valid data\n(a)in cases where all possible measured data are not available, the following factor must be used to calculate AOT40 values:\nAOT40(estimate)=AOT40(measured)×totalpossiblenumberofhours*number of measured hourly values *being the number of hours within the time period of AOT40 definition (that is, 8:00 to 20:00 Central European Time from 1 May to 31 July each year, for vegetation protection and from 1 April to 30 September each year for forest protection).\n1 hour values\n75% (45 minutes)\n8 hour values\n75% of values (6 hours)\nMaximum daily 8 hours mean from hourly running 8 hours averages\n75% of the hourly running 8 hour averages (8 hours per day)\nAOT40\n90% of the 1 hour values over the time period defined for calculating the AOT40\nAnnual mean\n75% of the 1 hour values over summer (April to September) and winter (January to March, October to December) seasons separately\nNumber of exceedances and maximum values per month\n90% of the daily maximum 8 hours mean value (27 available daily values per month) 90% of the 1 hour values between 8:00 and 20:00 Central European Time\nNumber of exceedances and maximum values per year\nFive out of six summer months over the summer season (April to September)",
  "extent": null,
  "status": null,
  "version": "current",
  "annotations": [
    {
      "type": "footnote",
      "label": "f1",
      "text": "OJ L 35, 5.2.1997, p.14"
    },
    {
      "type": "footnote",
      "label": "f2",
      "text": "(a)in cases where all possible measured data are not available, the following factor must be used to calculate AOT40 values: AOT40(estimate)=AOT40(measured)×totalpossiblenumberofhours*number of measured hourly values *being the number of hours within the time period of AOT40 definition (that is, 8:00 to 20:00 Central European Time from 1 May to 31 July each year, for vegetation protection and from 1 April to 30 September each year for forest protection)."
    }
  ],
  "outstanding_effects": [],
  "provenance": {
    "source": "legislation.gov.uk",
    "source_url": "https://www.legislation.gov.uk/wsi/2003/1848/schedule/8/part/II",
    "retrieved_at": "2026-10-29T00:10:44.777755+00:00"
  },
  "licence": "Open Government Licence v3.0",
  "licence_url": "https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/",
  "attribution": "Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives."
}