Calculate u10 and v10 without Z from CAM output

[BenT]

Hello,

I have "output of opportunity" (so to speak) from CAM5, whereby I'd like, if possible, to compute u10 and v10 wind components (over the ocean).

In the output, we have U(time, lev, ncol); V(time, lev, ncol) but no Z variable(s). I guess ZBOT varies somewhat around ~60m which could be used to approximate u10 and v10 using a power law, but is there any other approach here?

I also wonder if the power law exponent, which is a function of flow stability, can in any way be estimated from CAM output. E.g. we have T(time, lev, ncol), that might be useful. But I don't have experience with this.

Many thanks.

 

[mdfowler]

Hi Ben,

In theory you can interpolate the bottom-level U and V down to 10m, though without ZBOT I think that might be a little challenging. Do you have PS? I'd point you to a few other discussions on this topic though:

U10m wind computed by CAM5

Can I get u, v wind components at 10m from U10 (10m wind speed), TAUX, and TAUY?

Hello, I'd like to calculate u, v wind components at 10m using 10m wind speed, and zonal and meridional wind stress components. This is because u, v wind components at 10m do not save in our runs. Theoretically, zonal and meridional wind stress components can be explained as follows. TAUX =...

bb.cgd.ucar.edu

calculation of meridional wind at 10m

I am trying to calculate meridional wind at 10m(V10). The zonal wind at 10m (U10) is directly available in CAM history file but this is not the case for V10. could anyone help me to calculate V10?Thanks in advance!

bb.cgd.ucar.edu

Normally, U10 (which is just the speed at 10m, not the zonal component) is computed using Monin-Obukhov Similarity Theory. The model doesn't actually compute the components of that wind speed, so your only option would be to interpolate to that level, but it wouldn't account for things like friction, surface roughness, etc.

Cheers,

 

[BenT]

Hi Meg, many thanks for your suggestions! I had not seen the first discussion.

In this case, I do have PS. Can I use this to estimate a scaling relationship?

I am interested in generating ocean surface waves. I have previously interpolated (where Z information was available) to find u10 and v10 but I am not sure there is any particularly satisfactory way forward because the surface waves to be generated, in turn create surface drag.

I do have access to some output where U10 (wind speed) is available, along with Z, and I wonder if it would be instructive to compared U10 (from CAM) with U'10 = sqrt(u10^2 + v10^2) generated from power law scaling using UBOT and VBOT.

In point of fact, I'm interested in understanding whether near-surface conditions (moisture / heat flux, sea-spray, ... ) in CAM might be appreciably affected if waves, and wave-breaking in particular, were better incorporated (through some suitable parameterization etc).

 

[peverley]

Hi Ben,

Can you post your question and the corresponding context to the ocean forum? Assuming you are using POP, the forum is here: POP

They will be better situated to help with the wave stuff. If you have additional atmosphere questions, feel free to come back to us. Keeping the threads separate will (hopefully) make things searchable for people who have your same questions in the future.

Thanks!
Courtney