Hua-Lu Pan wrote:

>
>    Interestingly, the 2-meter variables are actually created during the
> model integration. This is what is done:
>
>   The similarity profile function is evaluated at the first sigma level and
> at 2 meters. The ratio is then used to derive the 2-meter temperature. The
> derivation assumes that the heat flux is constant between surface and the
> first sigma level. For moisture, the procedure is slightly different. When
> there is upward moisture flux, the surface humidity is computed inversely
> from the land surface model derived evaporation rate. When there is dew
> formation, the surface specific humidity is assumed to be the saturation
> value at the skin temperature and the constant flux assumption is used to
> derive the 2-meter q.  Relative humidity is then computed in the post. I
> hope this description makes some sense to you. Basically, the formula for
> surface fluxes are used such that the same flux will be obtained whether
> the computation is with sigma level one fields or the 2-meter fields. On
> the other hand, the 1000 hPa fields are obtained simply from sigma level
> interpolations (or extrapolations).
>
> Hua-Lu