Scheduled Downtime
On Friday 21 April 2023 @ 5pm MT, this website will be down for maintenance and expected to return online the morning of 24 April 2023 at the latest

regarding Cumulus parameterization schemes

This post was from a previous version of the WRF&MPAS-A Support Forum. New replies have been disabled and if you have follow up questions related to this post, then please start a new thread from the forum home page.

deva_wrf

Member
hello everyone,
i have to ask you a question regarding the cu_physics for innermost domain having resolution 3km, i want to know is this important to set the cu physics for inner most domain for such fine resolution domain.
 
Hi,
No, we actually don't recommend using a cumulus scheme for grid resolutions <= 3km. We do recommend using one for anything >= 10km, and between 3km and 10km is somewhat of a gray zone, meaning it's not clear whether a cumulus scheme should be used - users should either refrain from using domains with that grid resolution, or do some simple testing to determine if using a cumulus scheme is ideal for their particular run.
 
Hi,

I have a follow-up question on this, I compared a 12km run with KF cumulus parameterization (let's call it CP), a 12km without any CP, and a 4km without any CP. As expected, the 12km with KF did show larger bias than the 4km without CP; however, I saw the 12km without CP did better than 12km with CP, in fact the 12km without CP does an equally good job as the 4km without CP. I am talking about precipitation, compared to PRISM 4km, one-month total precip amount.

My question is, the CP is not perfect anyways, why do we need it, even for the 12km? Is there anyway that I can approve that 12km without CP is bad and one SHOULD use a CP when running 12km?

Attached please see 3 figures for bias of these 3 model setup. again the bias is for 2017 Jun monthly total precip. unit: mm/month
 

Attachments

  • 2017_Jun.zip
    257.8 KB · Views: 66
Top