Distinct intraseasonal periodicity of Siberian High as modulated by ENSO: dominance of Madden-Julian Oscillation

Abstract

Abstract While previous studies have demonstrated that the El Niño-Southern Oscillation (ENSO) can impact global climate systems on the intraseasonal timescale, how ENSO affects the intraseasonal variability of the Siberian High (SH) still remains unclear. Based on spectral analysis, the SH exhibits evident intraseasonal periodicity (ISP) differences, with 25–50 days during El Niño winters and 50–90 days during La Niña winters. The northward propagation of the Rossby wave from the tropics during the phase transition of the SH leads to the Madden Julian Oscillation (MJO) dominating the difference in the ISP of the SH. The faster eastward propagation of the MJO in El Niño winters leads to a quicker evolution of the SH. Accompanied by the eastward propagation of the MJO, when the tropical westerly in the lower troposphere is located over the Indian Ocean, it can deflect to the north and involved the Eurasian cyclonic circulation, which contributes to the negative phase of the SH. When the tropical westerly moves eastward and the easterly is occupied the Indian Ocean, the middle-to-high latitude northerly completely dominates the East Asia region, penetrates southward to the South China Sea, deflects westward, and involved the tropical easterly, acting as the positive peak stage of the SH. The upper-level tropical zonal wind overrides the low-level tropical zonal wind, forming a coupled circulation and air temperature pattern together with the low level. The faster propagation of the MJO in El Niño winters leads to the intraseasonal evolution of the El Niño-related SH to change from lagging behind the La Niña-related SH to exceeding it, thereby contributing to the ISP of the SH being much shorter during El Niño winters.