# 20 Liters per cubic meter of rain???

by Chiclayo guy
Tags: cubic, liters, meter, rain
 P: 26 A weather report for Chiclayo Peru said we received 20 liters per cubic meter of rain yesterday. How many inches of rain would a New York weather report say we received? Thanks. Tom
 Sci Advisor P: 5,891 The report (as you stated) can't be translated. If it were liters per square meter, then you can calculate the height. Assuming my interpretation, you have 2x104 cc of rain on an area of 104 sq cm. This gives a height of 2 cm, approx. 0.8 in.
 P: 26 I just saw the report again and they did say 20 liters per cubic meter (which has caused wide-spread flooding here). But intuitively the figure you arrived at of 0.8 inches feels in the ball park. It fell in a 24 hour period and given conditions here could have caused the flooding. Thanks for your response. Tom
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## 20 Liters per cubic meter of rain???

 Quote by Chiclayo guy I just saw the report again and they did say 20 liters per cubic meter
Then the report had a typo
It doesn't make much sense to measure the height of a flooding rain in terms of cubic units.
Mentor
P: 20,431
 Quote by Mentallic Then the report had a typo It doesn't make much sense to measure the height of a flooding rain in terms of cubic units.
That's what I think, also.
Mentor
P: 14,243
 Quote by Mentallic It doesn't make much sense to measure the height of a flooding rain in terms of cubic units.
It makes even less sense to report the quantity of rainfall as 0.02 -- and that is what 20 liters/meters3 is. It is a unitless number. Both liters and cubic meters are a measure of volume.
 P: 26 You folks are correct...this internet article just showed up: "Rains fell on Tumbes during 21 hours, leaving 35.4 liters per square meter, that turned streets into rivers, but fortunately caused no personal injuries, according to Civil Defense reports. Chiclayo (Lambayeque) also suffered intense rains during six hours, that flooded the main avenues and affected some roads connecting to Cajamarca region." Thanks for the responses. Tom
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 Quote by D H It makes even less sense to report the quantity of rainfall as 0.02 -- and that is what 20 liters/meters3 is. It is a unitless number. Both liters and cubic meters are a measure of volume.
I disagree.
The public is only interested in a measurement of flooding that is simple to understand. 20mm rainfall makes sense as we only care how high the flooding is going to get. 20 L/m3 is less intuitive and only makes us have to do unnecessary mental calculations to convert this into something more understandable.
Of course we would get used to accepting the magnitude of such floods as 20L/m3 as we have with other non-intuitive measurements such as kilometres/hour, but again it's not a necessity to make these changes.

Also, what if the flooding were very intense and were to become over 1000mm? We would instead have something like 1500 Litres/metre3 and this makes even less sense.
 P: 986 0.8 inches is not that much. The area near my house got 5 inches in 4 days a few weeks ago. It was wet, but there were no major disruptions.
Mentor
P: 11,964
 Quote by Mentallic I disagree. ... 20 L/m3 is less intuitive and only makes us have to do unnecessary mental calculations to convert this into something more understandable.
Aren't there are always 1000 liters per m3, no matter how much rain has fallen? The m3 was clearly a typo, as the OP has confirmed.
P: 2,751
 Quote by Mentallic I disagree. The public is only interested in a measurement of flooding that is simple to understand. 20mm rainfall makes sense as we only care how high the flooding is going to get. 20 L/m3 is less intuitive and only makes us have to do unnecessary mental calculations to convert this into something more understandable. Of course we would get used to accepting the magnitude of such floods as 20L/m3 as we have with other non-intuitive measurements such as kilometres/hour, but again it's not a necessity to make these changes. Also, what if the flooding were very intense and were to become over 1000mm? We would instead have something like 1500 Litres/metre3 and this makes even less sense.
You misunderstand the post you're disagreeing with. The figure of 0.02 is most definitely not 20mm when the 0.02 is dimensionless (Vol/Vol). That was DH's point.
Mentor
P: 11,964
 Quote by uart You misunderstand the post you're disagreeing with.
Entirely possible.
 The figure of 0.02 is most definitely not 20mm when the 0.02 is dimensionless (Vol/Vol). That was DH's point.
That I agree with.
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Quote by D H
 Quote by Mentallic It doesn't make much sense to measure the height of a flooding rain in terms of cubic units.
It makes even less sense to report the quantity of rainfall as 0.02 -- ...
 Quote by uart You misunderstand the post you're disagreeing with. The figure of 0.02 is most definitely not 20mm when the 0.02 is dimensionless (Vol/Vol). That was DH's point.
Yes you're right uart, I did misunderstand DH's post simply because the misleading part in bold made me think he was implying that the way the current system of rainfall measured in L/m2 made less sense that L/m3. DH misunderstood me, I misunderstood him. I think we've settled the problem
 Mentor P: 11,964 And I misunderstood who uart was telling that they misunderstood. (I hope that sentence was understandable.)

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