Calculation of Climatology

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The calculation of climatology is done for each weather indicator and for each individual geographical feature on a daily basis. For each grid cell, administrative region or agri-environmental region there are 366 values per indicator; for each day of the year one.

For the following basic parameters average values are calculated:

  • Precipitation
  • Temperature (daily maximum, daily minimum and daily average)
  • Dewpoint temperature (forecasted weather only)
  • Vapour pressure
  • Wind speed
  • Snow depth
  • Calculated radiation at surface (observed), global radiation (forecasted)
  • E0 (daily transpiration of water surface)
  • ES0 (daily transpiration of wet bare soil)
  • ET0 (daily transpiration of crop canopy; evapotranspiration)

Besides the average also minimum, maximum, standard deviation and count are calculated (observed weather only).These data are stored in:

To properly compare threshold-indicators like rainy days, hot days, cold days and tempature sums (above or below a minimum threshold), calculated over a certain period, with the long term average these long term average values should not be derived from climatology. This would lead to underestimation of the extremes. In stead first the threshold-indicator must be calculated for each historic year and the outcome must be averaged over all historic years. To enhance performance in visualization additional data are stored on the long term average tables that express the chance of an event e.g. the chance that a certain day has a rainfall event larger than 5 mm. Similary the average temperature above a threshold is stored. Using these additional data 'average' values of threshold-indicators can be calculated properly without accessing data of all historic years. In detail:

  • fraction of days with daily maximum temperature greater than 25 °C
  • fraction of days with daily maximum temperature greater than 30 °C
  • fraction of days with daily maximum temperature greater than 35 °C
  • fraction of days with daily maximum temperature greater than 40 °C
  • fraction of days with daily minimum temperature less than 0 °C
  • fraction of days with daily minimum temperature less than -8 °C
  • fraction of days with daily minimum temperature less than -10 °C
  • fraction of days with daily minimum temperature less than -18 °C
  • fraction of days with daily minimum temperature less than -20 °C
  • fraction of days with rainfall greater than 1 mm
  • fraction of days with rainfall greater than 3 mm
  • fraction of days with rainfall greater than 5 mm
  • fraction of days with rainfall greater than 10 mm
  • fraction of days with rainfall greater than 15 mm
  • fraction of days with rainfall greater than 30 mm
  • average temperature above 0 degrees Celsius
  • average temperature above 2 degrees Celsius
  • average temperature above 4 degrees Celsius
  • average temperature above 6 degrees Celsius
  • average temperature above 8 degrees Celsius
  • average temperature above 10 degrees Celsius

The data are stored in separate tables:


Reference weather

Long term average values of daily station observations are calculated and stored in table WEATHER_OBS_STATION_LTA (see also interpolation of observed weather).

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More information
ReferenceWeather