[Wrf-users] Cold bias

[Juan José Ruiz]

Dear Wrfhelp, thank you for your answer,
In the following link
http://wrf.cima.fcen.uba.ar/tsoil_t2m_mapa.gif you will find an example of
the cold bias distribution over South America. The shaded fiel is the
difference between the top layer soil temperature at the beginning of the
forecast and the 48 hours forecast of the same variable. The contours
shows the difference (analysis - 48 hour forecast) for the 2 meter
temperatures. This is the result of averaging 2 months (15 December 2002 -
15 February 2003) of 48 hours forecasts over the region. The drop in the
temperature increases with the forecast time. This is an example of the
BIAS for the 850 hPa level comparing with a single RS station located
where the BIAS are larger in the figure (over central Argentina).
6 hour forecast: -1º
30 hour forecast: -1.68º
42 hour forecast: -2.42º
This BIASES has been computed over a month 01 January - 15 Febrary 2003.
The model configuration is 50km horizontal resolution with the following
sigma levels:
LEVELS = 1.000, 0.993, 0.980, 0.966, 0.950, 0.933,
               0.913, 0.892, 0.869, 0.844, 0.816, 0.786,
               0.753, 0.718, 0.680, 0.639, 0.596, 0.550,
               0.501, 0.451, 0.398, 0.345, 0.290, 0.236,
               0.188, 0.145, 0.108, 0.075, 0.046, 0.021,
               0.000,

PBL= Mellor and Yamada (some improvment is found with YSU but the problem
is still present), Grell, Noah LSM and RRTM.
The initial conditions are taken from the GDAS analysis and the initial
soil temperature and 2m temperature looks very similar to that finded in
the analysis.
There is also an improvment using the new version of the model (V2.2.0)
the bias is reduced but the spatial distribution remains aproximately the
same.
Thanks a lot for your help!
Best regards.
Juan.

> Can you quantify your cold bias? Does the model start with the right
> low level
> and surface temperatures (e.g. TSK)? If you use a LSM option, do you
> have the
> right soil temp and moisture?
>
> wrfhelp