The phrase froid ressenti is appearing on the weather forecasts a lot these days. It translates literally as ‘cold felt/experienced’ but is pretty much the same as refroidissement éolien (wind chill factor) – nothing to do with windmills (éoliennes) this time!) Frequently the froid ressenti is 7 or 8 degrees colder than the actual temperature. I imagined that someone was estimating this, but the computation of wind chill factor is based on very sound science.
Wind chill is the felt air temperature on exposed skin. The first wind chill formula was created by Paul Siple and Charles Passel while working in Antartica. You can see what must have motivated them! They expressed wind chill in watts of heat lost per square metre of skin. This didn’t catch on terribly well, so the formula was revised a few times by other people and these days it reflects the notion of equivalent temperature. This is what the formula looks like:
Twc = 13.12 + 0.6215 Ta – 11.37 V+0.16 + 0.3965 TaV+0.16
where w is the wind chill index in Celsius, Ta is the air temp in Celsius V is the wind speed at 10 metres (standard anemometer height), in kilometres per hour (km/h).
Simple! So, the figures appearing on the météo each day have been carefully worked out after all.
There wasn’t too much noticeable wind chill today, which has been a balmy minus 4 actual temperature wise, although that’s dropping fast now that evening is coming. We fired up Rusty Deux the tractor to deliver hay bales to the llamas, sheep and goats. Then we drove down to the cabin to fetch the gas bottles. Our central heating is dodgy so we might need to get the gas heaters going.
I love the passenger seat on Rusty Deux. You get great views from up there. It’s quite deadly trying to take photos though, since it’s a bumpy ride and the seat is a small square of metal with a tiny bit of rail behind it so very easy to slip off!
And I did the famous End To End Ice Walk today – my death defying walk across our lake. It’s used to be a Christmas Eve tradition (the rest of the family were nobly prepared to share my pressies between them if I fall through the ice) but the last two years we haven’t been iced up by then. So it’s slipped back a bit. I don’t know how long the lake is exactly but it’s a 10 acre lake so it’s pretty big! It’s also pretty deep so I’m very careful on the way. Any cracks or strange sounds send me scuttling to the bank right away.
Tomorrow we’ll profit from the big freeze to do some tidying up along the banks. There are over hanging branches that need sawing off. It will be a lot easier doing them standing on the ice than from the rowing boat, which is what we’d thought we’d be having to do this winter since it started so mild.
Subscribe via RSS