Article Type:
Research Article

Inconsistencies in the “New” Windchill Chart at Low Wind Speeds

Avraham Shitzer Department of Mechanical Engineering, Technion, Israel Institute of Technology, Haifa, Israel

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Richard de Dear Division of Environmental and Life Sciences, Macquarie University, Sydney, New South Wales, Australia

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Print Publication:
01 May 2006
DOI:
https://doi.org/10.1175/JAM2373.1
Page(s):
787–790
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Abstract

An apparent error was detected in the calculation of windchill equivalent temperatures (WCETs) in the “new” chart and corresponding equation that were adopted in 2001 by the weather services in the United States and Canada. The problem is caused by significant discontinuities in WCETs at the assumed “calm” wind speed condition of 1.34 m s−1. As a result, published WCETs are not equal to, as they should be by definition, but are lower than air temperatures at the assumed calm wind speed condition. This inconsistency further propagates to higher wind speeds beyond the assumed calm condition. In this paper, a straightforward correction is proposed to circumvent these inconsistencies of the new windchill. The proposed correction makes this transition gradual rather than abrupt by applying it to the expression used for estimating the effects of wind on the convective heat exchange coefficient between humans and their cold and windy environment.

Corresponding author address: Avraham Shitzer, Department of Mechanical Engineering, Technion, Israel Institute of Technology, Haifa 32000, Israel. Email: mersasa@tx.technion.ac.il

Abstract

An apparent error was detected in the calculation of windchill equivalent temperatures (WCETs) in the “new” chart and corresponding equation that were adopted in 2001 by the weather services in the United States and Canada. The problem is caused by significant discontinuities in WCETs at the assumed “calm” wind speed condition of 1.34 m s−1. As a result, published WCETs are not equal to, as they should be by definition, but are lower than air temperatures at the assumed calm wind speed condition. This inconsistency further propagates to higher wind speeds beyond the assumed calm condition. In this paper, a straightforward correction is proposed to circumvent these inconsistencies of the new windchill. The proposed correction makes this transition gradual rather than abrupt by applying it to the expression used for estimating the effects of wind on the convective heat exchange coefficient between humans and their cold and windy environment.

Corresponding author address: Avraham Shitzer, Department of Mechanical Engineering, Technion, Israel Institute of Technology, Haifa 32000, Israel. Email: mersasa@tx.technion.ac.il

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