GrapeApe Posted June 29, 2012 Share Posted June 29, 2012 Supposing we has a two flat tin trays, which were both an inch deep, but one was 12" square and the other 24" square. We leave both of them out in the torrential rain. Which would fill quicker? The 12" tray would of course. But eventually the other would too. So which tray would be representative of an inch of rainfall over time? They would both fill at the same time. Think of putting two 12" square trays together. Link to comment Share on other sites More sharing options...
PeteMorris Posted June 29, 2012 Author Share Posted June 29, 2012 They would both fill at the same time. Think of putting two 12" square trays together. No they wouldn't fill at the same rate. One would take twice as long to fill as the other. Surely? Bigger area to fill? Link to comment Share on other sites More sharing options...
truman Posted June 29, 2012 Share Posted June 29, 2012 No they wouldn't fill at the same rate. One would take twice as long to fill as the other. Surely? Bigger area to fill? No they'll take the same time..we're talking about depth..the rain falls over all the area so there's twice as much going into the bigger tray..as grape ape says try thinking of the 24 inch tray as 2 12 inch trays.. Link to comment Share on other sites More sharing options...
cgksheff Posted June 29, 2012 Share Posted June 29, 2012 ........ Which would fill quicker? The 12" tray would of course. But eventually the other would too. So which tray would be representative of an inch of rainfall over time? No. The water level in each would rise at the same rate. Different volumes, but the same volume per unit of surface area. Link to comment Share on other sites More sharing options...
Phanerothyme Posted June 29, 2012 Share Posted June 29, 2012 Standardisation, without it it would mean many hours work trying to replace or convert stuff. Like other people have said, the collection area of the rain gauge is irrelevant provided it's sufficiently large to catch rain. A 5" gauge is a convention. A 20cm rain gauge will give the same result as a 5" gauge. Link to comment Share on other sites More sharing options...
cgksheff Posted June 29, 2012 Share Posted June 29, 2012 .......... I know that the bucket I mentioned in my original post has about 6" of water in it, but it's more than 5" diameter and tapers outwards. ....... Roughly 6" of rain will have fallen between it being empty and you measuring it (assuming no evaporation and no-one drinking it or peeing in it. Because of the taper, the reading of 6" is slightly high, so somewhere near 5" is probably more accurate. If there was no taper, then 6" of rain would have fallen. Link to comment Share on other sites More sharing options...
PeteMorris Posted June 29, 2012 Author Share Posted June 29, 2012 No they'll take the same time..we're talking about depth..the rain falls over all the area so there's twice as much going into the bigger tray..as grape ape says try thinking of the 24 inch tray as 2 12 inch trays.. Hmmmm, yes. I see your point. So it's purely down to what makes the most efficient collector, and 5" seems to be the standard. Oh and before anyone else says, I know height from the ground makes a difference, as does where it's sited (ie not under a tree etc) Thanks for all you input. I can sleep easy now tonight knowing this! Link to comment Share on other sites More sharing options...
cgksheff Posted June 29, 2012 Share Posted June 29, 2012 Now for the good one ......... If it starts raining, you run home to get out of the rain quicker. However, by running, you will intercept more raindrops horizontally, than those that would have just fallen vertically onto your head and shoulders (and, in my case, ... belly). At what speed do you get just as wet as you would have if you stood still? Link to comment Share on other sites More sharing options...
PeteMorris Posted June 29, 2012 Author Share Posted June 29, 2012 Roughly 6" of rain will have fallen between it being empty and you measuring it (assuming no evaporation and no-one drinking it or peeing in it. Because of the taper, the reading of 6" is slightly high, so somewhere near 5" is probably more accurate. If there was no taper, then 6" of rain would have fallen. I think the dog has been having a crafty drink of it now and again!!!! Link to comment Share on other sites More sharing options...
Teddybare Posted June 29, 2012 Share Posted June 29, 2012 Now for the good one ......... If it starts raining, you run home to get out of the rain quicker. However, by running, you will intercept more raindrops horizontally, than those that would have just fallen vertically onto your head and shoulders (and, in my case, ... belly). At what speed do you get just as wet as you would have if you stood still? Chick Norris stays bone-dry even in a tropical storm and Usain bolt is faster than rain. So I'd say it depends who you are. Link to comment Share on other sites More sharing options...
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