Fig. 2: Visualization of assimilation results.

The estimated states of two upper-air variables (Z500 and T850) and two surface variables (2 m-temperature and 10-m wind speed). For each case, the background field (first column), 4DVarNet (second column), ViT (third column), 4DVarFormer (fourth column), and the ERA5 ground truth (fifth column) are shown. For all illustrated cases, the time is 00:00 UTC on 19 July 2021, for there is a tropical cyclone at this time in the East China region.