Wind speed variables in CAM

[djamaya]

Hi all,

I have a question about the variable WSPDSRFAV or "Horizontal total wind speed average at the surface". Any ideas what it means by "total" wind speed?

The goal is to calculate wind speed cubed, and I know that should be done with as high-frequency output as possible. The model also outputs 10m wind speed, but only at monthly resolution while WSPDSRFAV has daily output. Just trying to figure out if WSPDSRFAV is what I want or if I have to use the monthly 10m wind speed output.

Best,

Dillon

 

[nusbaume]

Hi Dillon,

If you are doing your own model simulations, then you should be able to output any history variable in CAM at any time-scale you want, down to the model time step itself. This is done by modifying the "user_nl_cam" file before running your simulation. For example, if you wanted 10-meter wind speed every six hours, you would add:

fincl1 = 'U10'
nhtfrq = -6

to "user_nl_cam", and then the model will generate new "h1" files that contain U10 values for every six hours. Other namelist variables that might be helpful as well are mfilt, which controls the number of entries per history file, and ndens, which defines the numerical precision of the output. You can find descriptions of all of these namelist variables online here:

CESM2 CAM6.3 Namelist Definitions

Namelist definitions for CAM6.3 in CESM2

www.cesm.ucar.edu

Or just post any questions you have on this forum.

Finally, in terms of your specific question, the "total" wind speed described in WSPDSRFAV is the combined horizontal (u + v) wind speed. Essentially, the quantity is calculated in the model as:

WSPDSRFAV = sqrt(u^2 + v^2)

where u and v are at the lowest CAM model layer (pver).

Anyways, I hope that helps, and have a great weekend!

Jesse

 

[Yongwu]

Hi Jesse,

Thanks for your reply. I also have some similar questions on the wind speed in the CAM model.

In my case, I run the CAM model and output monthly. I compared the value of U10 with the sqrt(u^2 + v^2) in the lowest model layer. I found it's different. Do you know why?

By the way, if I want to calculate the zonal and meridional components of the wind at 10m level, could I use the cdo ml2hlx interpolation to get the result?

Best.
Yongwu

 

[yixia]

Hi Jesse,

Thanks for your reply. I also have some similar questions on the wind speed in the CAM model.

In my case, I run the CAM model and output monthly. I compared the value of U10 with the sqrt(u^2 + v^2) in the lowest model layer. I found it's different. Do you know why?

By the way, if I want to calculate the zonal and meridional components of the wind at 10m level, could I use the cdo ml2hlx interpolation to get the result?

Best.
Yongwu

Hi Yongwu,

I wonder did you figure out how to get V10? I also met the same problem.

Thanks,
Yi

 

[Yongwu]

Hi Yongwu,

I wonder did you figure out how to get V10? I also met the same problem.

Thanks,
Yi

Hi Yi,

I use the cdo ml2hlx to do the interpolation to get the V10. But I'm not sure if this method is suitable.

Best,
Yongwu