RiskWare  On-line Reference Manual

Release Level 1.9
Release Date 2000 06


Revision Level 1.0




Meteorological data

Meteorological data are stored in AirWare as standard time series data, with the notable exception of vertical profiles that use a different special format (in preparation).

The basic set of data required includes:

  • wind speed (in meter/second)
  • wind direction (in degrees indicating the direction the wind is coming from; N = 0, E = 90)
  • air temperature (in degree Centigrade)
  • stability class (Pasquill Stability Classes 1-6)
  • mixing height (in meters, relative to ground level).
The variables define the basic meteorological scenario for the ISC models.

Auxiliary variables that are used by other models or for some of the auxiliary estimation programs, e.g., wind field generator or estimation of mixing height) include:

  • precipitation (in mm/day)
  • cloud cover (in %)
  • solar radiation ()
Additional information required is the height (above ground) of the wind measurement to correct for vertical speed profiles. Please note that the wind field generation requires also geostrophic wind data.

Stability Class

Atmospheric stability can be used to derive values for the horizontal (transversal) and vertical dispersion coefficient of atmospheric dispersion models.

AirWare uses the stability class definitions from Pasquill (1961) The Meteorological Magazine, February 1961, HMSO.

In the Pasquill approach, six classes that are related (and can be derived from) basic meteorological parameters, namely wind speed, insolation, and cloud cover (for day and night conditions, respectively) are used.

The following table summarizes these relationships:

                         Day                Night
   wind speed         Insolation         Cloud Cover
    (m/sec)     strong  medium  slight   >4/8   <3/8
      <2          A      A-B      B        -     -
     2-3         A-B      B       C        E     F
     3-5          B      B-C      C        D     E
     5-6          C      C-D      D        D     D
      >6          C       D       D        D     D

Vertical Profiles

in preparation.


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