Monday, 10 February 2003
Influence of Arctic Oscillation on the East Asian summer monsoon (Formerly paper number 3.3)
The present study shows that the Arctic Oscillation (AO) for the month of May significantly influences year-to-year variations in the East Asian summer monsoon rainfall. Large-scale atmospheric circulation patterns in East Asia in association with the AO are also evident. A positive phase of the AO in late spring is found to lead to a northward shift in the summertime upper tropospheric jet stream over East Asia. This northward shift of the jet stream is closely related to an anomalous sinking motion in 20-40N and a rising motion in surrounding regions. These changes give rise to drier conditions over the region extending from central China to southern Japan and wetter conditions in southern China. A series of simulations using the atmospheric circulation model have been carried out to understand the influence of AO on the climate variations in East Asia. Results suggest the importance of strong influence of AO on the surface climate in mid- and high latitudes in winter and spring; the AO-related boundary anomalies impact the atmospheric circulation and give rise to the anomalous East Asian summer monsoon.