Wednesday, September 26, 2012

Soft and fluffy - need hard hats

The Gorse Fox has been considering the rain that has fallen this week. The Met Office tell us that the cloud was six miles deep. It seems incredible. Yet clouds seem so "fluffy" and innocuous. This got the Gorse Fox thinking, and it went something like this:

  • Co. Durham was badly affected and covers about 650,000 acres.
  • 1 inch of rain across 1 acre weighs 113.25 tons
  • It was estimated that they received 4 inches of rain
So this means that if evenly distribute across the County - 294,450,000 tons of rain fell.

Now spread this further - to Yorkshire and across Northumberland and across the South and the sums become ridiculous.

  • England is 130,400 sq. km, which is 32222541.6824 acres
  • Assume we only received 2 inches of rain, on average over the past couple of days; that's 226.5 tons/acre
  • That's a staggering 7,298,405,691 tons of rain in 48 hours or so
That's just been hanging around above our heads. Seems to the Gorse Fox that there is a case for wandering round in a hard hat.


a bad man said...

"1 inch of rain across 1 acre weighs 113.25 tons"

How do you come to that conclusion? My findings indicate that there are 4046.86 square meters in an acre. If that acre had a standing inch of water then on needs to multiply 4046.86 by 0.00254 to give the number of cubic metres of water resting on that area.

I make this to be 10.2790244 metres cubed.

If we assume the water is pure, then each cubic metre will contain 1000 litres and weigh one metric tonne.

This suggests that you are over calling the weight by more than a factor of ten.

I think you can take that hard hat off. It doesn't suit you :-)


bad man

The Gorse Fox said...

Well, let's check.
There are 43560 sq feet per acre.
With a depth of 1 inch there are 144 cubic inches per square foot. So that is 6,272,640 cu inches of rain per acre.
1 cu inch of pure water weighs 0.036127 pounds; and 2240 lbs in a ton.
6,272,640 x 0.036127 = 226611.66528 lbs and that divided by 2240 (lbs in a ton) is 101.16...

(difference from initial calc was due to use of US weights, and rounding).


The Gorse Fox said...

Ah ha... in your calculation you assume 1 inch is 0.00254m, it is actually .0254m

a bad man said...

Apologies - long day and hands up to the decimal error. Thanks heavens for peer review :-)