## Convective precip without using CU scheme?

Topics related to current and future physics in the WRF as well as any problems you may have.

### Convective precip without using CU scheme?

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?

Best
Basit
Basit

Posts: 8
Joined: Fri Aug 05, 2011 6:03 am

### Re: Convective precip without using CU scheme?

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
mfearon

Posts: 1
Joined: Tue Dec 09, 2014 5:37 pm

### Re: Convective precip without using CU scheme?

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.
alainaketh

Posts: 30
Joined: Fri Jun 26, 2015 12:30 pm