When the wind really is freezing
QUESTION How is the wind chill factor of temperature measured? THE human body has a core temperature of about 37C. The surrounding air is usually below 37C, so we lose heat from anywhere not covered by clothing.
The principal mode of heat transfer is convection to the surrounding air. Convective heat transfer rises with increasing air velocity. As the wind increases, it draws heat from the body, driving down skin temperature and, eventually, internal body temperature.
The temperature given with the ‘wind chill factor’ is equivalent to the air temperature needed to produce the same cooling effect under calm conditions. It’s not an actual temperature, but an index that helps relate the cooling effect of the wind to calm air temperature.
Wind chill factor was first quantified in 1941 by Major Paul Siple of the US Army and geographer Charles Passel while working in Antarctica. They measured the cooling rate of water in a container left hanging outside and developed the basic Siple- Passel index for wind chill based on this data. Later experiments tested naked humans in wind tunnels in an effort to apply these indices to personal physiology.
In 2008, Britain adopted the (Joint Action Group For Temperature Indices) formula developed by federal agencies in the US and Canada. It incorporates wind speed calculated at the average height 1.5m of a human face (instead of the 10m used earlier) and modern theories of heat loss, based on a clothed person walking at 5km/h, using consistent standard skin tissue resistance and the worst case for solar radiation in a complex equation.
Under this system, 0C feels like –5C in a 16km/h wind and –8C in a 48km/h wind. It’s an important measure in cold climates as the risk of frostbite increases rapidly when values go below 27C.
Dr Ken Warrem, Glasgow. QUESTION How many Irish people have won Academy Awards? YOUR earlier answers omitted Greer Garson, who won a best actress Oscar in 1942 for Mrs Miniver.
Although Eileen Evelyn Garson claimed all her life to have been born to George and Nina Sophia Garson i n Gilford, Co. Down, on September 29, 1908, her birth certificate (discovered shortly before her death) revealed she had been fooling the world for decades.
Her birth actually took place four years earlier, in 1904, in London. Her father died when she was only four months old and little Eileen remained with her mother in London.
Martha Young, Dublin 4. QUESTION What is the most amusing piece of sporting advice heard from a spectator? FURTHER to earlier answers, at a cricket match a few seasons ago, an opening batsman employed by a well- known supermarket chain was clean bowled having scored only a handful of runs.
As he made his way disconsolately to the pavilion, a local character on the boundary shouted: ‘Never mind – Every Little Helps!’