Fig. 5: Visualization of assimilation results.

The state estimation of two upper-air geopotential fields (Z500 and Z850) and two surface variables (MSLP and 10-m wind speed). For each case, the background field (first column), states estimated by 4DVarNet (second column), ViT (third column), 4DVarFormer (fourth column), and the ERA5 ground truth (fifth column) are shown. The results are generated by only assimilating 10 m wind observations. 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.