# [ncl-talk] Problem with calculate average wind speed at specific z level(eta level)

Dennis Shea shea at ucar.edu
Mon Dec 14 13:38:50 MST 2020

```Perhaps, I don't understand but
pblws_avg = *dim_avg_n*
<http://www.ncl.ucar.edu/Document/Functions/Built-in/dim_avg_n.shtml>(pblws,
0)
printVarSummary(pblws_avg)             ;   (y,x)

On Sun, Dec 13, 2020 at 11:54 PM 소윤영 via ncl-talk <ncl-talk at mailman.ucar.edu>
wrote:

> Dear NCL users,
>
> I want to draw a 'ventilation index' calculated with pblh(m), wind speed,
> z level.
>
>
> -------------------------------------------------------------------------------------------
> pblh=wrf_user_getvar(input_fils,"PBLH",-1)   ;PBL HEIGHT [m]
>
> uvm10 =wrf_user_getvar(input_fils,"uvmet10",-1)    ; 10m U and V
> components
> u10 = uvm10(0,:,:,:)
> v10 = uvm10(1,:,:,:)
> ws = sqrt(u10^2+v10^2)
>
> pblws:= pblh*ws         ; 3d[t,y,x]
>
> ----------------------------------------------------------------------------------------------
>
> this is the simple version of this idea. But i wnat to get a  average
> windspeed at  0~z level which means 0~pblh(m).
>
> I will be grateful for help
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