Liu, Zhiquan, Hui-Chuan Lin, Craig S. Schwartz, and
Ying-Hwa Kuo, National Center for Atmospheric Research
Bias correction (BC) is
crucial to properly assimilate radiance data and obtain the positive impact. At
the operational NWP centers, BC is usually applied to both global and regional
data assimilation system through a global set of BC coefficients. For community research applications
using a limited-area model such as WRF, a straight way is to apply BC
coefficients obtained over the domain under investigation through the advanced
scheme such as Variational BC (VarBC).
In this study, several 4-month long (August ~ November, 2008)
experiments were conducted to investigate the sensitivity of radiance data
impact on the BC strategy.
Firstly, we found that using a set of pre-trained BC coefficients at the
beginning of data assimilation cycles is beneficial when comparing to start
cycling from no knowledge of BC coefficients (i.e., cold-start BC). Moreover, we found that the global
statistics of BC coefficients are different from the regional ones over the
Northern or Southern high-latitude regions ASR or Antarctic-centered domain,
and radiance data assimilation with applying global BC coefficients outperforms
those using regional BC coefficients.