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Keywords:

  • meteorological thresholds;
  • extreme event;
  • decile method;
  • Gaussian curve of frequency;
  • destructive wind

Abstract

The extreme values of meteorological elements and weather phenomena (extreme events) have a profound influence on human activity. It has long been accepted as part of a weather forecaster's task to predict their occurrence and severity, but without any accepted scales. Here, measuring scales of daily temperature extremes, precipitation and wind velocity have been defined and described. The scales are: standard frequency distribution for daily temperature extremes, decile method for precipitation and the Beaufort scale for wind velocity. Their units are: standard deviation, decile of frequency and unit of the Beaufort scale, respectively. The step ‘normal’ and three steps for each threshold scale of positive departure from normal are defined: above normal, well above normal and extraordinarily above normal. Also, three steps for each threshold scale of negative departure from normal are defined: below normal, well below normal and extraordinarily below normal. The scales of standard frequency distribution and the decile method can be applied to other extreme values of meteorological elements and weather phenomena if they follow these types of frequency distributions. Examples drawn from the observations of the Meteorological Observatory in Belgrade for the climate period 1961–1990 are presented. Copyright © 2012 Royal Meteorological Society