Scale Selective Bias Correction

Scale Selective Bias Correction (SSBC) reduces the large scale error in the regional model.

The scheme cosnsitst of three components:
1) Nudging of the large scale part of the wind perturbation to zero,which is accomplished by adding a term in the momentum equation to reduce the tendency of the large scalepart of the perturbation.
2) Removing the area average perturbation of temperature and moisture at every model level.
3) Adjusting the area mean perturbation logarithm of surface pressure to the corresponding difference of logarithm of surface pressure due to the area mean difference in the global and regional topography.

SSBC is turned on by default in G-RSM. Default damping scale is 1000km and damping coefficient is 0.9.
1) and 2) are done in stdamp.F and 3) is done in stdamp3.F. Both subroutines are located in rsm/src/rsml or rsm/src/rsml_par (in the case of MPI code).

You can turn on/off the SSBC options in rsm/def/misc.h. STDAMP and STDAMP3 correspond to stdamp.F and stdamp3.F, respectively.

Reference
Kanamaru, H. and M. Kanamitsu, 2007: Scale-Selective Bias Correction in a Downscaling of Global Analysis using a Regional Model. Monthly Weather Review, 135 (2), 334–350.