Four-dimensional variational data assimilation of heterogeneous mesoscale observations for a strong convective case

In terms of the assimilation model's ability to recover the vertical structure of moisture and in reproducing the rainfall pattern and amount, the wind profiler data have the maximum impact. The ground-based GPS data have a significant impact on the rainfall prediction, but have relatively small influence on the recovery of moisture structure. On the contrary, the surface dewpoint data are very useful for the recovery of the moisture structure, but have relatively small impact on rainfall prediction.

The assimilation of rainfall data is very important in preserving the precipitation structure of the squall line. All the data are found to be useful in this mesoscale data assimilation experiment. Issues related to the assimilation time window, weighting of different types of observations, and the use of accurate observation operator are also discussed.