Abstract
The impact of satellite wind data on the analysis and forecast is examined by applying the normal mode theory.
It is demonstrated that the impact of satellite wind data on the analysis appears largely in the external Rossby modes with low meridional index, especially 5-day wave.
Significant impact on the forecast is found in the mid-latitude in the northern hemisphere, part of which is the propagation of the initial impact on the Rossby mode. This impact may be classified as that of the planetary scale and that of the synoptic scale. The former is related to the tropical data effect (Daley et al., 1981), and can be enhanced by applying the appropriate broad vertical prediction error correlation. The latter, on the other hand, may be related to the baroclinic instability, and be dependent on the vertical shear of basic current. The shear is the difference of the wind between upper and lower level, and can be modified by the insertion of the satellite wind data.
Finally, it is concluded that, in order to make the maximum use of satellite wind data in the data assimilation cycle, the estimation of the vertical prediction error correlation of the model and the reliability of satellite wind data is essential.
