By: Blonde Two
As you know, the Two Blondes encounter a fair amount of low cloud on their adventures. “Visibility Low” seems to be a key phrase in our walking log books. It was the same at home on Saturday but I couldn’t make up my mind what to call it – mist or fog seemed the two most likely options so I looked up the difference between them. Several interesting possibilities have been discovered;
1. You can see further in mist than in fog. In most places including shipping and aviation forecasts, if you can see less than 1km (which is nearly all the time on Dartmoor) it is fog. Mist allows you to see up to 2km. Apparently this wasn’t precise enough for the Brits and we use “fog” if visibility is less than 200 yards.
2. Mist/fog is caused by teeny water droplets hanging in the air. Light hits them and scatters and we humans can’t see. Mist has teeny weeny weeny droplets and fog has bigger ones (teeny). Light scatters within a shorter distance with bigger droplets hence fog is murkier. Sometimes there are bigger (tiny) droplets which start to fall towards the ground and are called drizzle.
3. Some people claim that fog is in touch with the ground and mist is floating around – the Two Blondes’ (note the correct apostrophe placement) breath on a cold day for example. This idea does not seem to have much support which is a shame because it would be the easiest to explain to kids.
4. The dew point is the temperature at which air cools enough to become water saturated (condensation). I think this is easier to understand when you imagine going to the loo behind a bush at midnight and coming back to a dry tent and then going again at dawn (when the air is at its coldest) and finding your tent covered in moisture. Of course, the unexpected moisture could be because someone else is going to the loo and mistakes your tent for a bush.
These different definitions and explanations are so confusing that I have decided to make my own naming rule up. It is quite simple – the name of the white hanging-around stuff depends on where you happen to be at the time. It has to be alliterative (check out my English knowledge). For example – if you are driving through Moretonhampstead (I never seem to stop there) then it is mist “Moretonhampstead Mist”. If you are at Fingle’s Bridge it is “Fingle’s Fog”. This game has endless possibilities for a cold night round the fire but here are a few that I have come up with so far:-
Drizzlecombe – Drizzle (easy I know but so true)
Corndon – Condensation
Lustleigh Cleave – Low Cloud
Clampitt – Clag (Cloud Low Aircraft Grounded)
Any other offerings? Please feel free to share, we could make a map of the UK with its new mist/cloud/fog/clag names. If you want to read some less confused info from the experts – here is fact sheet number three from the wonderful Met Office http://www.metoffice.gov.uk/media/pdf/f/c/Fact_sheet_No._3.pdf