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 year when buying, processing, or selling for their businesses. Pat provides services and resources for many different trades, crafts, and professions for commercial, industrial and government metrication leaders in Asia, Europe, and in the USA. Pat's clients include the Australian Government, Google, NASA, NIST, and the metric associations of Canada, the UK, and the USA. See http://www.metricationmatters.com for more metrication information, contact Pat at [email protected] or to get the free 'Metrication matters' newsletter go to: http://www.metricationmatters.com/newsletter to subscribe.
