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4.1. Outdoor Thermal Comfort: ExtremeFinder

  • Contributor
    Name Institution
    Bei Huang Reading
    Andy Gabey Reading
    Fredrik Lindberg Gothenburg
  • Current Options

    Identifies extreme high events (e.g. Heat waves) and low events (e.g. Cold Waves). Designed primarily for temperature data (heat waves identified from daily maximum and mean T; cold waves from daily minimum), but can also be used to indicate potential high and low extremes in other meteorological variables.

  • Data must be provided by the user, and can be
    • Previously-downloaded ERA5 data in a NetCDF (* file (this can be obtained from the ERA5 downloader)
    • Other NetCDF (.nc) file containing sub-daily measurements, or daily maximum/mean/minimum values. Must contain a ‘time’ dimension, and variable(s) with name(s) matching those being analysed using the ExtremeFinder.
    • Text (.txt) file, daily Tmax, Tavg or Tmin (file sample: 1979-01-01 to 2009-12-31). Only temperature analysis can be performed using a text file.
  • Method
    Basis for thresholds - set into Input.nml (namelist)
  • Dialog box

    Fig. 4.1 The interface for the ExtremeFinder plugin

  • Steps to use
    1. Select climate data: The ExtremeFinder will use all the data available in its analysis. You will be prompted for a text (.txt) or NetCDF (.nc) file:
      • NetCDF file: The latitude, longitude, start and end date boxes will be populated automatically, if the data is available in the NetCDF file.
      • Text file: The latitude, longitude, start and end date boxes must be filled in by the user, as the information is needed in calculations:
        • Latitude (degrees N) and Longitude (degrees E) are WGS84 co-ordinates
        • Start and end date are inclusive and must match the data extent
    2. Select the extreme event type and the calculation method:
      • Event types are either Extreme high (e.g. Heat wave) or low (e.g. Cold wave)
      • There are several different ways to identify extremes, depending on the event type
      • Choose the meteorological variable to analyse for extremes
        • Note: The methods in the Extreme Finder are based on Tair and may not be appropriate for other variables
    3. Select Output File: A list of extreme events will be written to the file
      • Note: this will be overwritten if not a new name
    4. Run: Performs the analysis
  • Output: Extreme events (heat waves used as example below)
    1. Daily Tmax (or Tavg / Tmin) with time (Y=Year, X=Month)

      • Colour gives Temperature (see key)

      • Yellow Box Highlights Heatwave (Coldwave) periods This loads the model interface dialog box:


        Fig. 4.2 Heat/Cold wave periods

    2. Box plot of distribution of heat (cold) wave by year.

      • whiskers =1.5* IQR

      • outliers - any data beyond the whiskers


        Fig. 4.3 Box-and-whisker plot of Heat/Cold wave days each year

    3. Number of heat (cold) waves days per year


      Fig. 4.4 Histogram showing number of Heat/Cold wave days each year