Impact of Sea Surface Temperature Uncertainty on the Western North Pacific Subtropical High (WNPSH) and rainfall
The atmospheric model develops large uncertainty in the Korea and Japan area due to the fluctuation in horizontal pressure gradient caused by the location of the WNPSH. This, in turn, increases the variance of the low-level jet (LLJ) over southeast China, resulting in large differences in the moist transport flux from the tropical ocean and subsequent rainfall. Validation using bin-mean statistics shows that the ensemble forecast with the perturbed SST better distinguishes large forecast error variance from small forecast error variance. The results suggest that using the SST perturbation as proxy for the ocean ensemble in a coupled atmosphere and ocean ensemble system is feasible and can save computational time.