The MM5 model is used to simulate a typhoon Omar, which occurred on September 2-5, 1992 in the western Pacific region. Model output from different times will be inserted into a nonlinear radiance transfer model to calculate brightness temperatures. These brightness temperatures will then be compared with SSM/I brightness temperatures to evaluate the MM5 performance over the ocean region. Statistical comparison between model predicted and observed radiances will also be utilized to evaluate the potential benefit of SSM/I raw data in mesoscale models.

A linearized radiance transfer model has been developed from the nonlinear one. The MM5 output will also be fed into the linear radiance transfer model. The new generated brightness temperatures will be compared with those obtained from nonlinear radiance transfer model. Sensitivity studies will be carried out with the tangent linear and adjoint operators of the radiative transfer model to asses the impact of linearization on incremental variational data assimilation schemes.