Fig. 2: Comparison of detectability of the Walker circulation intensity change at different tropospheric levels.
From: Early emergence and determinants of human-induced Walker circulation weakening
a Signal-to-noise ratio of the Walker circulation intensity change relative to the 1980–2014 baseline calculated based on the sea-level pressure gradient (dSLP). Blue (red) thick line denotes the ensemble mean of models under the SSP2-4.5 (SSP5-8.5) scenario, while blue (red) shading indicates the model spread. The gray dashed lines denote the signal-to-noise ratio of 1 or -1. b Time of emergence (ToE) for annual-mean Walker circulation intensity change based on the dSLP index, under the SSP2-4.5 (blue bars) and SSP5-8.5 (red bars) scenarios. Lighter blue and red bars indicate models in which no emergence of the forced Walker circulation intensity change is detected by the end of the 21st century for the respective scenarios. c–f are the same as (a–b) but based on the 500 hPa vertical velocity gradient (dW500) and the maximum absolute value in the 200 hPa velocity potential over the western tropical Pacific (VPmax), respectively.
