## Formula to calculate CV2

Discussion of meteorological data.

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Rabah.Hachelaf
Posts: 2
Joined: Thu Feb 18, 2016 5:46 pm
Organization: UQAM

### Formula to calculate CV2

Hello,

Could you please give me the exactly formula used to calculate CV2_Sonic_<z>m.val
from u,v,w sonic anemometer measurements.

Thank you for your help.

Andy.Clifton
Posts: 83
Joined: Wed Feb 29, 2012 3:13 pm
Organization: NREL
Location: Boulder, CO
Contact:

### Re: Formula to calculate CV2

Hi Rabah,

if you look at items 2 and 3 on https://nwtc.nrel.gov/MetDataPublications, you should find what you are looking for. If you want to see the code, this is available through https://github.com/NREL/TITANIC.

Good luck,

Andy
Andy Clifton, Ph.D.
Senior Engineer

Rabah.Hachelaf
Posts: 2
Joined: Thu Feb 18, 2016 5:46 pm
Organization: UQAM

### Re: Formula to calculate CV2

Hi Andy,

I find this part of matlab code where cv2 is calculated

for li = 1:numel(L)
uplagged = [u_p NaN*ones(1,L(li)-1)];
Tplagged = [T_p NaN*ones(1,L(li)-1)];
u_p_zero = [NaN*ones(1,L(li)-1) u_p];
T_p_zero = [NaN*ones(1,L(li)-1) T_p];
DVV(L(li)) = nanmean((uplagged - u_p_zero).^2);
DTT(L(li)) = nanmean((Tplagged - T_p_zero).^2);
end

cv2 is the structure functions of velocity, i think it suppose include all the 3 components of air mouvement.
but looking at the code it seems cv2 is calculated only using the zonal component (u),Am i wrong ?
Also i need to know how U_ref is calculated, i didn't find any thing in all matlab codes.

Thank you

Rabah

Andy.Clifton
Posts: 83
Joined: Wed Feb 29, 2012 3:13 pm
Organization: NREL
Location: Boulder, CO
Contact:

### Re: Formula to calculate CV2

The code for the structure function is in SubDissipationRateStructureFunction.m. This function is called from [url =https://github.com/NREL/TITANIC/blob/master/firstlook/FirstLook.m] FirstLook[/url] as follows:

Code: Select all

`[epsilon_SF,lags,cv2,cv2m,DVV,cT2,cT2m,DTT] = ...            SubDissipationRateStructureFunction(SonicAdvectionSpeed,...            tower.daqfreq,u_p,T_p)`

You should note that u_p is the fluctuating component of the prevailing wind, and SonicAdvectionSpeed is the mean of that wind speed. It's not the zonal or meridional wind speed.

So, if the structure function is supposed to be from the fluctuations of the wind speed I think I'm doing that.
Andy Clifton, Ph.D.
Senior Engineer

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