NOTES AND CORRESPONDENCE; Extraction of Major Teleconnection Patterns Possibly Associated with the Anomalous Summer Climate in Japan

Abstract

Four teleconnection patterns that are possibly associated with the anomalous summer climate in Japan and the surrounding regions, were extracted by applying empirical orthogonal function and regression analyses to stream function anomalies. The two teleconnection patterns prevailing over northern Eurasia, especially in early summer, called the Europe-Japan (EJ) 1 and EJ2, are linked with the variability of the Okhotsk high. The third teleconnection pattern, called the West Asia-Japan (WJ), is a stationary wave-train pattern along the upper-level subtropical jet from West Asia to the central North Pacific, which is possibly excited by the anomalous convective heating of the Indian summer monsoon. The final teleconnection pattern is identified with the Pacific-Japan (PJ), found by Nitta. Teleconnection indices that account for the variability of those patterns are also defined on a monthly basis. The PJ and WJ patterns, which are more influential teleconnection patterns than the others, are closely related to the summer temperature anomalies, especially in northern and western Japan, respectively. EJ1 and EJ2 were amplified in several extreme summers, and they played a vital role in the cool summer of 2003, along with PJ. A combination of two or three teleconnection patterns was also responsible for the occurrence of the recent extreme summers. Monitoring the major teleconnection patterns is very useful for understanding and forecasting the anomalous summer climate in East Asia.

Analysis on the Dynamics of a Wave-like Teleconnection Pattern along the Summertime Asian Jet Based on a Reanalysis Dataset and Climate Model Simulations

“…2), in agreement with the previous studies (Wakabayashi and Kawamura 2004;Sato and Takahashi 2006). The wavenumber of the observed wave train is overall consistent with the stationary Rossby wavenumber determined by the intensity of the jet.…”

“…A wave-like anomalous circulation pattern along the summertime Asian jet, which develops along the poleward flank of the upper-level Tibetan High, is one of the major low-frequency variability patterns that influence East Asian climate in summer (Wakabayashi and Kawamura 2004;Yasunaka and Hanawa 2006;Hsu and Lin 2007). In July, it induces the withdrawal of Baiu/Meiyu season in the East Asia (Enomoto et al 2003).…”

Impacts of tropical Indian Ocean SST on the meridional displacement of East Asian jet in boreal summer

“…Thus, the PJ teleconnection (Nitta, 1987) or the East AsianPacific (EAP) teleconnection (Huang and Sun, 1992) is prominent (Figures 1(b) and 6(c)). The correlation coefficients of the PJ index (Wakabayashi and Kawamura, 2004) and the EAP index (Huang and Yan, 1999) with the TIO SST index are −0.57 and −0.55, respectively, both exceeding the 99% confidence level.…”

Evaluation for the Seasonal Evolution of the Summer Monsoon over the Asian and Western North Pacific Sector in the WCRP CMIP3 Multi-model Experiments

“…The strength of the lower tropospheric wind over the WNP region is intimately connected with the latitudinal position of the NPSH ridge. Figure 2 shows an inter-model relationship between JJA mean 850 hPa zonal wind over (Wakabayashi and Kawamura 2004) including the Silk Road pattern (Enomoto et al 2003;Kosaka et al 2009), this inter-model relationship suggests that the climatological circulation in the CGCMs over the WNP-EA domain is at least partly influenced by the PJ (Pacific-Japan) teleconnection pattern (Nitta 1987). It should be emphasized here that the latitude of NPSH ridge in many CGCMs is higher than that in observation (denoted as a filled square in Fig.…”