Propagation Characteristics of Rossby Wave Trains Associated with the North Atlantic Oscillation in Winter and Their Impacts on Downstream Climate

Using reanalysis products, we can divide the 45 winters from 1957/1958 to 2001/2002 into two types, i.e., high latitude (H) and low latitude (L), based on whether the quasi-stationary wave trains propagating downstream in the Northern Hemisphere in the winter are reflected in Europe. The wave reflection is related to the North Atlantic Oscillation (NAO). In the H (L) type winter, the Rossby wave trains associated with the NAO mainly propagate downstream along the high-latitude (low-latitude) path. We compared the relationships between the NAO and atmospheric circulation, surface air temperature (SAT), sea surface temperature (SST), and precipitation in the two types of winter. The results show that in the H-type winter, 300-hPa geopotential height anomalies are positively correlated with the NAO in western Siberia and western-central Siberia, while in L-type winter, 300-hPa geopotential height anomalies are positively correlated with the NAO in eastern coast of Asia (about 40°N) and North Pacific; meridional wind anomalies associated with the NAO in the H-type winter form wave trains in the mid-latitude, while in the L-type winter, meridional wind anomalies form wave trains in the subtropics; SAT anomalies in the H-type winter are positively correlated with the NAO in the high latitudes of inland Eurasia, while SAT anomalies in the L-type winter are relatively weak in the high latitudes of inland Eurasia, but the SAT anomalies caused by the NAO can extend to northeastern Asia. Main differences in precipitation between the H-type winter and L-type winter are found in China. In southern China, the relationship between the H-type winter precipitation anomalies and the NAO is relatively weak, while that between the L-type winter precipitation anomalies and NAO is positively correlated; SST anomalies are positively correlated with the NAO in the mid-latitude area of the North Atlantic during the same period, while the SST anomalies related to the NAO in the L-type winter are relatively weak in the mid-latitude area of the North Atlantic, and stronger in the northern and southern North Atlantic. Generally speaking, the NAO has different downstream effects in the H-type and L-type winters.