How to plot spatial distribution of roughness length Z0

Questions related to the use of new landuse, or geographical static data, or to modifications to the existing data
Post Reply
Liliputian_123
Posts: 37
Joined: Sat Jan 18, 2020 4:04 pm

How to plot spatial distribution of roughness length Z0

Post by Liliputian_123 » Fri Apr 23, 2021 4:47 pm

Dear WRF-experts,

I cant seem to find any tutorial online on how I can plot the roughness length (Z0).

This is also not located in the geo_em files.

Any ideas on how to plot this?

I'll appreciate any help on this.

Lyndz.

kwerner
Posts: 2287
Joined: Wed Feb 14, 2018 9:21 pm

Re: How to plot spatial distribution of roughness length Z0

Post by kwerner » Fri Apr 23, 2021 5:22 pm

Roughness length is something that is calculated in the PBL scheme - depending on which one you use. MYJ calculates that, but you would need to set it to be output. You can do so by using the run-time I/O namelist option.
NCAR/MMM

Liliputian_123
Posts: 37
Joined: Sat Jan 18, 2020 4:04 pm

Re: How to plot spatial distribution of roughness length Z0

Post by Liliputian_123 » Fri Apr 23, 2021 5:32 pm

@kwerner,

Thank you for the fast response.

I want to plot the USGS and MODIS roughness lengths before running WRF.

Is it the one from VEGPARM.TBL?
But Im confused. There are four in this TBL:

USGS (with Z0min and Z0max)
MODIFIED_IGBP_MODIS_NOAH (with Z0min and Z0max)
USGS-RUC (Z0 only)
MODI-RUC (Z0 only)

Which one should I use here?

If I use the first two, is it correct to take the average of Z0min and Z0max to get the Z0?

kwerner
Posts: 2287
Joined: Wed Feb 14, 2018 9:21 pm

Re: How to plot spatial distribution of roughness length Z0

Post by kwerner » Thu Apr 29, 2021 11:24 pm

I apologize for the delay. I wanted to run this by our physics specialist to ensure I was giving the appropriate response.

The roughness length is computed only when WRF starts running because it uses Z0min and Z0max and the seasonally varying VEGFRA, so it varies slowly with time, according to the season. Over water it varies with wind speed. ZNT in the output shows its latest value.
NCAR/MMM

Post Reply

Return to “New/Modified Static Data”