# [ncl-talk] U and V components rotation

maxpalma at fastwebnet.it maxpalma at fastwebnet.it
Tue Oct 28 03:14:11 MDT 2014

I am writing because i have problem with a rotation of a u, v components.

I know that u and v must be rotated together, using something like this:
uNew = u*cos(rot) - v*sin(rot)
vNew = u*sin(rot) + v*cos(rot)
but in my case, i don't have the rotation angle (rot).

How can I rotate the components?

I found the function  wrf_uvmet,  but i did't understand it very well, and i don
't know if this function is the solution of my problem.

The result of the "ncdump -h" of my file "tauvo" ( v component for example, for
u is the same) is:

variables:

double lon(y, x) ;
lon:standard_name = "longitude" ;
lon:long_name = "Longitude" ;
lon:units = "degrees_east" ;
lon:_CoordinateAxisType = "Lon" ;

double lat(y, x) ;
lat:standard_name = "latitude" ;
lat:long_name = "Latitude" ;
lat:units = "degrees_north" ;
lat:_CoordinateAxisType = "Lat" ;

double time(time) ;
time:standard_name = "time" ;
time:units = "hours since 2012-01-01 00:00:00" ;
time:calendar = "standard" ;

double tauvo(time, y, x) ;
tauvo:standard_name = "tauvo" ;
tauvo:long_name = "surface_downward_y_stress" ;
tauvo:units = "N/m2" ;
tauvo:coordinates = "lon lat" ;

Can I use this wrf_uvmet function with these variables? I have only these..
How can I use this function? What is "cen_lon" and "cone"? I don't have these in
formations..

I would be most grateful if you could give me also a practical examples..

Thank you very much!

Yours faithfully

Massimiliano Palma