What's the difference between VAR and VAR_SSO

[Qianqian Huang]

Hi,
I noticed that there are VAR and VAR_SSO in geo_em*.nc file. May I ask, what's the difference between those two?
The description of VAR is "stdev of subgrid-scale orographic height", and the description of VAR_SSO is "Variance of Subgrid Scale Orography". So except that one is stdev and the other is variance, is there any other difference? I have calculated that VAR is not equal to sqrt(VAR_SSO).

Thanks in advance.
Qianqian

 

[Ming Chen]

These two variables have the same physical meaning. The only difference is that VARSSO is based on higher resolution terrain than VAR.

 

[Qianqian Huang]

Thank you for your reply.

I want to run some simulation with 1km and 333m resolution, using topo_wind. The default data path for VAR_SSO is varsso_10m written in GEOGRID.TBL. That is almost 20km resolution, a very low resolution for mesoscale simulation. I wonder why the default value setup like this? Is there any profound meaning in doing this? I noticed that the default value for other variable is high resolution data, for example HGT_M is 30sec.

So when I perform simulation with 1km and 333m resolution, should I use VARSSO_1sec ?

Thanks.
Qianqian