MEANINGFUL WIND CHILL INDICATORS DERIVED FROM HEAT-TRANSFER PRINCIPLES

The wind chill index (WCI) and the more widely used wind chill equival ent temperature represent an attempt to combine several weather-relate d variables (temperature, wind velocity and solar radiation) into a si ngle index which can indicate human comfort. Since its introduction in 1945, the WCI has been criticized mainly on the ground that the under lying model does not comply with modern heat transfer theory. In spite of that, the WCI, ''calibrated'' to human comfort, has proven to be s uccessful in predicting discomfort and tolerance of man to the cold. N evertheless, neither the WCI nor the wind chill equivalent temperature can be actually measured and, therefore, without the additional 'cali bration' they are meaningless. In this study we have shown that the WC I represents the instantaneous rate of heat loss from bare skin at the moment of exposure to the cold, and as such, it correlates reasonably well with measurable variables that represent a feeling of cold. Two new wind chill indicators have been introduced: exposed skin temperatu re and maximum exposure time. These indicators yield more information than the WCI provides, are measurable, have physical meaning and are b ased on established heat transfer principles.