Fig. 3: Mechanisms for the increased low-frequency VM variability.
From: Enhanced North Pacific Victoria mode in a warming climate
a The 23-year running correlation coefficients between the NDJFMA CP SST, NDJFMA Hawaii_SLP and DJFMAM VM indices for the period 1920–2021 in observations. b The 23-year running root-mean-square (RMS) of the NDJFMA Hawaii_SLP (blue line) and DJFMAM VM (red line) indices for the period 1920–2021. c The low-frequency fluctuations of DJFMAM observed (OBS) VM index (red line) and reconstructed (REC) VM index (blue line) using an AR1 model forced by the Hawaii_SLP index for the period 1920–2021. The units are in standard deviations (s.d.). d The 23-year running RMS of the DJFMAM OBS VM (red line) and REC VM (blue line) indices. e The low-frequency of DJFMAM OBS VM index (red line) and the ensemble mean reconstructed (EREC) VM index (blue line) using an AR1 model forced by the simulated Hawaii_SLP index for the period 1920–2019. f The 23-year running RMS of the DJFMAM OBS VM (red line) and EREC VM (blue line) indices. In a, b, d, f, linear fits are displayed together with p values based on the Mann–Kendall test and the shaded areas indicate the two-sided 95% confidence levels of the slopes. In c, e, the correlation coefficients are given in the lower left corner of each panel, significant at a 95% confidence level. The shaded area in e represents the standard error.
