Convective precip without using CU scheme?

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Convective precip without using CU scheme?

Postby Basit » Fri Jul 18, 2014 11:29 pm

Hi everyone,

A while ago there was some discussion on RAINC and RAINNC. I also have a question about this. I am running a high resolution simulation (<500m) with cumulus scheme turned off since i want to resolve convective precipitation explicitly. We know that RAINC (convective precip) comes from the cumulus scheme and RAINNC(non-convective precip) from microphysics scheme. If we turn off the cumulus scheme, RAINC would only have 0 values. I wonder if the model can resolve convective precipitation explicitly without using a cumulus parametrization at all? Or would the total resolved precip in RAINNC include both convective and non-convective precip?

Many thanks in advance for your much appreciated help.

Best
Basit
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Re: Convective precip without using CU scheme?

Postby mfearon » Tue Dec 09, 2014 5:42 pm

Basit,
Did you learn how to compute convective precipitation exclusively with the cumulus scheme turned off, eg, having the model resolve convection explicitly? I'm curious about the same thing.
thanks,
Matt
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Re: Convective precip without using CU scheme?

Postby alainaketh » Tue Oct 04, 2016 1:31 pm

Hi everyone,

As Basit well points out, RAINC comes from the convective scheme while RAINNC comes from the microphysics scheme.

To run the model with the cumulus scheme turned off, you simply have to specify "0" in the cu_physics option in the &physics section of your namelist.input, for example a simulation with four domains, where the innermost two have a resolution higher than 10 km:

&domains
max_dom = 4
dx = 54000, 18000, 6000, 2000,
dy = 54000, 18000, 6000, 2000,

&physics
cu_physics = 1, 1, 0, 0,

When you do this, the RAINC for the two innermost domains is always ZERO, so that the only rainfall comes from RAINNC. In this case, the values of RAINNC without cumulus (of the two innermost domains) are slightly higher than the values of RAINNC with cumulus. Actually, when computing statistics (POD, FAR, RMSE, BIAS), not using cumulus in domains with resolution higher than 10 km yields better results than when using cumulus. Paper to come ;)

Cheers,

Alaina.
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