The combined effects of North Atlantic Oscillation and Western Pacific teleconnection on winter temperature in Eastern Asia during 1980–2021.

As important atmospheric circulation patterns in Northern Hemisphere (NH), the North Atlantic Oscillation (NAO) and the Western Pacific teleconnection (WP) affect the winter climate in Eurasia. In order to explore the combined effects of NAO and WP on East Asian (EA) temperature, the NAO and WP indices are divided into four phases from 1980–2021: the positive NAO and WP phase (NAO+/WP+), the negative NAO and WP phase (NAO−/WP−), the positive NAO and negative WP phase (NAO+/WP−), the negative NAO and positive WP phase (NAO−/WP+). In the phase of NAO+/WP+, the low geopotential height (GH) stays in north of EA at 50°–80°N; the surface air temperature anomaly (SATA) is 0.8–1 °C lower than Southern Asian. In the phase of NAO−/WP−, the center of high temperature and GH locate in the northeast of EA; the cold air spreads to Southern Asia, causing the SATA decreases 1–1.5 °C. In the phase of NAO+/WP−, the high GH belt is formed at 55°–80°N. Meanwhile, the center of high SATA locates in the north of Asia that increases 0.8–1.1 °C. The cold airflow causes temperature dropping 0.5–1 °C in the south of EA. The SATA improves 0.5–1.5 °C in south of EA in the phase of NAO−/WP+. The belt of high GH is formed at 25°–50°N, and blocks the cold air which from Siberia. The NAO and WP generate two warped plate pressure structures in NH, and affect the temperature by different pressure configurations. NAO and WP form different GH, and GH acts to block and push airflow by affecting the air pressure, then causes the temperature to be different from the north and south of EA. Finally, the multiple linear regression result shows that NAO and WP are weakened by each other such as the phase of NAO+/WP+ and NAO−/WP−. [ABSTRACT FROM AUTHOR]