diagnostic qsurf

[fcheruy]

As described in ticket #480, the diagnostic of the near surface air humidity (used in LMD to diagnose the 2m values of q and T) is qsurf = beta*qsat + (1-beta)qair
However there is an error in the coded version [ Commit done in the trunk [6018] and in ORCHIDEE_2_2 [6019].] .
The correction is coded as qsurf = beta*qsat + (2-beta)qair.
To avoir problems we propose to use a variable betatot, with
betatot=
((vbeta1(ji)*(un - vbeta5(ji)) + vbeta5(ji))+ (un - vbeta1(ji))*(un - vbeta5(ji))*vbeta(ji)

and compute qsurf as betatot*qsat + (1-betatot)*qair

NB: The line below has to be maintained: when there is no turbulence and the wind is low, one imposes qsurf = qair, otherwise if the soil is not dry, the way the vbeta are evaluated leads to qsurf close to the saturation value [qsat_new], which was inducing irrealistics diagnostics for the 2m temperature and negative values for q2m.

IF ( qc .LE. min_qc ) qsurf(ji) = qair(ji) s

[jgipsl]

Correction done in

• branch ORCHIDEE_2_2 in rev [7084]
• in branch ORCHIDEE_Quest in rev [7086]
• in the trunk rev [7089]