Nonstationary impact of the winter North Atlantic Oscillation and the response of mid-latitude Eurasian climate.

The North Atlantic Oscillation (NAO), although a local atmospheric mode over the North Atlantic Ocean, plays an important remote role in the Eurasian climate. However, the link between the NAO and Eurasian climate might be unstable. Here, we present a study on the relationship between the winter NAO and mid-latitude Eurasian climate, especially the mid-latitude East Asian precipitation, mainly based on meteorological data and output from an 1155-year-long coupled ocean-atmosphere model simulation. The results show that the winter NAO exerts a remarkable effect on the changes in mid-latitude Eurasian climate; however, the impact of the NAO is nonstationary. According to the model output, the impact of the NAO varies synchronously with the NAO variance with a period of around 150 years. During the high NAO variance period, the NAO has significant correlation with mid-latitude East Asian precipitation; low NAO variance periods do not. The variation of the NAO-precipitation teleconnection may arise from the changing influence of NAO on the local temperature. The NAO signal moves eastward by a zonally oriented wave train, where it modulates the atmospheric circulation structure, and thus results in the nonstationary relationship between the NAO and mid-latitude East Asian precipitation. [ABSTRACT FROM AUTHOR]