Surface winds with reversed sign

[joanballester_ic3@gmail_com]

Hi all,I am performing my first simulation, and I am a bit puzzled about the output I got.The surface zonal wind stress (UWS), the zonal wind at 10m (U10m) and the zonal wind at the lowest atmospheric level (U993hPa) look very similar, but U993hPa has opposite sign with respect to UWS and U10m. Up to my knowledge, the three variables should look relatively similar.I attach 6 figures, corresponding to raw values of the 3 variables for an El Niño December and for a La Niña December. All the figures correspond to the same domain, the tropical Pacific. I additionally computed the interannual anomalies (not attached), and U993hPa shows anomalies that are coherent with the temperature values (El Niño and La Niña patterns), while UWS and U10m seem to have the wrong sign. The same applies to the meridional counterparts of wind stress and winds.Am I doing something wrong?Thanks.joan

 

[santos]

The "U10" is a speed, not the zonal component of velocity, which is why it doesn't match the lowest level zonal wind. Notice that your 993 hPa plot has negative values, while the U10 plot does not.I'm not sure what specific variable you are plotting as the "wind stress". However, note that CAM is usually concerned with the drag that the surface exerts on the lowest level, rather than the stress exerted by the atmosphere on the surface. So unless the surface drag is anisotropic somehow, it should always point in the exact opposite direction from the lowest level wind.