Interannual and Interdecadal Variabilities of Circulation over Lake Baikal Region in Late Spring and Their Association with Temperature and Precipitation over China

Characteristics of the circulation over the Lake Baikal region in late spring and its association withtemperature and precipitation over China are investigated on interannual and interdecadal time scales by using reanalysis and observational data from 1951-2011. It is determined that a ridge over Lake Baikal (LBR) was in a weak phase during 1951-1979 but was amplified during 1980-1999. Since the beginning of this century, the amplitude of the LBR showed a significant decreasing trend. In addition, a strong (weak) LBR led to a temperature increase (decrease) over northern China and a temperature decrease (increase) over southwestern China. The temperature influences of the LBR over the northern part of China were most significant during 1951-1979 and became significant over southwestern China after 1980. An out-of-phase relationship existed between LBR intensity and the precipitation over the lower reaches of the Yangtze River valley during 1951-1999. Conversely, the LBR intensity was strongly correlated with the precipitation over southwestern China since the beginning of this century, with a positive correlation coefficient of 0.74 at the 0.01 significance level. Moreover, the strong LBR was characterized by the eastward propagation of a stationary planetary-scale wave that originated from the North Atlantic/European sector, and the weak LBR featured a ridge with a zonally elongated structure along the sub-arctic coast of Eurasia. However, among the various interdecadal time periods, the characteristics of the Northern Hemisphere circulation associated with the anomalous LBR show differences. Further, the North Atlantic Oscillation, the East Atlantic Oscillation, and the weakened East Asian major trough persisting in February-April may be considered as precursory signals of the strong LBR in May. For the weak LBR in May, anomalous cyclonic circulation over the Ural Mountains may be considered as a precursory signal.