Could the North Pacific Oscillation be modified by the initiation of the East Asian Winter Monsoon?
The North Pacific Oscillation (NPO) is the second leading mode of winter sea level pressure anomalies over the North Pacific. It can significantly influence downstream weather and climate conditions over North America during the boreal winter. Most previous studies have stated that the variability of the NPO is due to stochastic processes in the atmosphere. Prof. Yu-heng Tseng and his colleagues find that the initiation of East Asian Winter Monsoon (EAWM) in the Philippine Sea strongly connects to the southern lobe variability of the NPO in January. No apparent connection was found for the northern lobe of the NPO. The strengthening of the EAWM in November interacts with the Kuroshio front and generates a low-level heating source in the Philippine Sea. This forms significant Rossby wave sources in the lower to mid troposphere, which propagate eastward to affect the NPO. This is a breakthrough study confirming the modulation of the NPO variability may be partially deterministic and associated with the initiation of EAWM from the western North Pacific. Further information about the detailed pathway and dynamical process can be found in Prof. Tseng’s recent paper published in Journal of Climate (Tseng et al., 2020).
Tseng, Y.H., Ding, R., Zhao, S., Kuo, Y.C., Liang, Y.C. (2020), “Could the North Pacific Oscillation be modified by the initiation of the East Asian Winter Monsoon?” J. Clim., https://doi.org/10.1175/JCLI-D-19-0112.1.