Statistically equivalent systems for the determination of dispersion categories

Based on the meteorological data measured at the KARLSRUHE Nuclear Research Centre (KNRC) during a five year period statistically equivalent systems for the determination of dispersion were developed. The standard deviation of the vertical wind direction was chosen as a basic parameter, because this parameter was used to classify the turbulence conditions prevailing during the tracer experiments at the KNRC. The other systems are based on the following meteorological parameters: 1) standard deviation of the horizontal wind direction; 2) temperature gradient and wind speed; 3) radiation balance and wind speed; 4) wind profile exponent; 5) synoptic data. The calculation of the correlation between the basic system and the others allows a classification of the systems according to their reliability in individual meteorological situations. As expected, the more indirect systems 3, 4 and 5 have a noticeably lower correlation coefficient than the more direct systems 1 and 2. Therefore, the application of the more indirect systems is less appropriate, if the short-term environmental impact, as for example after an accidental release, has to be calculated. Finally, the transferability of the systems to other sites is discussed