Yes, I use those rules of thumb. Also, for agriculture in our area, we
would like crops (in general) to receive 25 mm of rain weekly. If not
the rest must be made up by irrigation. I have a flow totalizer that
enables me to apply just the right amount, based on the rainfall records
from my personal weather station. Unfortunately, I have to convert the
number of liters needed to gallons, since that is what the dial reads
out in.
Jim
On 2011-05-28 1411, Pat Naughtin wrote:
On 2011/05/29, at 03:43 , James R. Frysinger wrote:
I've just started looking at FEMA 320, "Taking Shelter from the Storm".
http://www.fema.gov/library/viewRecord.do?id=1536
I stumbled and looked twice when I got to a statement on page 1, referring to a figure (map) on
page 3. On both pages, values are given of the number of "EF3, EF4, and EF5 tornadoes per
2,470 square miles" during the period 1950-2006, which isn't an example of a "round
number" in the denominator.
A little playing around with my calculator has convinced me that this data arises from a
geographically oriented data field with 80 km grid spacings. So, that "2,470 square
miles" is actually (80 km)^2. The squares are either 49.70 miles on a side or 79.98
km on a side, and I think the latter is more likely.
Grid sizes based on "round" numbers of kilometers are the norm in meteorology,
for example in circulation models, storm modeling, etc.
Jim
Dear Jim,
And flood modelling is so simple to do using metric system inits that it can be
described as a 'doddle'. This is an example of how the Bureau of Meteorology
does it in Australia.
1 millimetres of rain on 1 square metre is a litre of water.
1 millimetres of rain on 1 hectare is 10 000 litres (10 kilolitres) of water.
1 millimetres of rain on 1 square kilometre is 1 000 000 litres (1 megalitre)
of water.
So if 43 millimetres of rain falls on an area of 426 square kilometres of
sodden soil then you have 18 318 megalitres of water to contend with downstream.
Cheers,
Pat Naughtin LCAMS
Author of the ebook, Metrication Leaders Guide, see
http://metricationmatters.com/MetricationLeadersGuideInfo.html
Hear Pat speak at: http://www.youtube.com/watch?v=_lshRAPvPZY
PO Box 305 Belmont 3216,
Geelong, Australia
Phone: 61 3 5241 2008
Metric system consultant, writer, and speaker, Pat Naughtin, has helped
thousands of people and hundreds of companies upgrade to the modern metric
system smoothly, quickly, and so economically that they now save thousands each
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--
James R. Frysinger
632 Stony Point Mountain Road
Doyle, TN 38559-3030
(C) 931.212.0267
(H) 931.657.3107
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