Friday, January 23, 2009
The effects of wind chill
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A recent Nordic Walk in bitterly cold conditions here in the UK gave me a sharp reminder of the effect that the wind can have on perceived temperatures. Even when the still air temperature is about average, a strong north-easterly wind can make it feel very cold. Indeed, such a wind is often described as being “lazy” as most people will have described it as having “gone straight though them”, rather than “around”!
The apparent cooling effect is called “wind chill” and can prove dangerous, particularly if your Nordic Walks take you into remote or upland territory. Even in your local park the effects at best can be uncomfortable. Of course, citizens in countries where exceptionally cold winters are commonplace will be well aware of the risks and have mitigation measures in place.
As a guide, it is suggested that if there is a wind of ten knots, a calm air temperature of 0 Celsius will feel like minus 5 Celsius. As the wind increases to 25 knots the wind chill falls to minus 12 Celsius, and so on.
The apparent cooling effect is called “wind chill” and can prove dangerous, particularly if your Nordic Walks take you into remote or upland territory. Even in your local park the effects at best can be uncomfortable. Of course, citizens in countries where exceptionally cold winters are commonplace will be well aware of the risks and have mitigation measures in place.
As a guide, it is suggested that if there is a wind of ten knots, a calm air temperature of 0 Celsius will feel like minus 5 Celsius. As the wind increases to 25 knots the wind chill falls to minus 12 Celsius, and so on.
Certain medical conditions can have an impact, eg. people with diabetes who have peripheral neuropathy may find that they sweat more on their face and neck, where we lose a large proportion of our body heat. Also, people taking Beta-Blockers (often used to manage high blood pressure) may have colder hands and feet owing to constriction of blood vessels. (Therefore, if you are an instructor, your medical screening questionnaire will be relevant).
Fortunately, if you are exercising hard the effects of wind chill are somewhat mitigated by the heat generated by metabolism. Of course, what you wear plays a key role, but this can prove difficult to gauge for the keen exerciser. Another article will follow soon which discusses the principles of the “layering system” of clothing.
In the meantime, keep well hydrated – both inside and out!
Malcolm Jarvis, Nordic Walker Leeds UK
