# 20 Liters per cubic meter of rain?

1. Feb 7, 2010

### Chiclayo guy

20 Liters per cubic meter of rain???

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

2. Feb 7, 2010

### mathman

Re: 20 Liters per cubic meter of rain???

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.

3. Feb 7, 2010

### Chiclayo guy

Re: 20 Liters per cubic meter of rain???

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

4. Feb 8, 2010

### Mentallic

Re: 20 Liters per cubic meter of rain???

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.

5. Feb 8, 2010

### Staff: Mentor

Re: 20 Liters per cubic meter of rain???

That's what I think, also.

6. Feb 8, 2010

### D H

Staff Emeritus
Re: 20 Liters per cubic meter of rain???

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.

7. Feb 8, 2010

### Chiclayo guy

Re: 20 Liters per cubic meter of rain???

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

8. Feb 8, 2010

### Mentallic

Re: 20 Liters per cubic meter of rain???

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.

9. Feb 9, 2010

### hamster143

Re: 20 Liters per cubic meter of rain???

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.

10. Feb 12, 2010

### Redbelly98

Staff Emeritus
Re: 20 Liters per cubic meter of rain???

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.

11. Feb 12, 2010

### uart

Re: 20 Liters per cubic meter of rain???

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.

12. Feb 12, 2010

### Redbelly98

Staff Emeritus
Re: 20 Liters per cubic meter of rain???

Entirely possible.
That I agree with.

13. Feb 12, 2010

### Mentallic

Re: 20 Liters per cubic meter of rain???

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 :tongue:

14. Feb 13, 2010

### Redbelly98

Staff Emeritus
Re: 20 Liters per cubic meter of rain???

And I misunderstood who uart was telling that they misunderstood. (I hope that sentence was understandable.)