A key process of the nonstationary relationship between ENSO and the Western Pacific teleconnection pattern
There is intriguing nonstationary relationship between ENSO and the WP teleconnection pattern, with a regime-dependent interdecadal modulation of significant correlations for 1973-1987 (r = 0.68) and insignificant correlations for 1988-2002 (r = 0.14). The subject has nontrivial implications for ascertaining whether the WP is directly forced by ENSO or by midlatitude storm tracks-driven intrinsic processes. Based on EOF analysis of Rossby wave sources (RWS) in connection with the upper-level teleconnection patterns, the nonstationarity in question can be explained by the regime-dependent constructive or destructive interference in meridional overturning circulation between ENSO- and WP-related two leading EOF modes of RWS. The insignificant correlation between ENSO and the WP after the 1998 regime shift can be explained by interrupted teleconnection between the tropics and high latitudes due to the collapse of the subtropical bridge pillar in the jet entrance region, consequence of the destructive interference.