Influence of preceding North Atlantic Oscillation on the spring precipitation in the middle and lower reaches of the Yangtze River valley
Jinping Han, Renhe Zhang
Abstract
Abstract The relationship between the spring precipitation in the middle and lower reaches of the Yangtze River valley and the North Atlantic Oscillation in the preceding winter is investigated based on data diagnosis. Through affecting the dynamics and thermodynamics in near‐surface atmosphere over Eurasia, the North Atlantic Oscillation in January can exert significant influence on the Eurasian snow cover to form a dipole pattern of snow anomalies. The dipole pattern of snow anomalies stimulates the Rossby wave train in the middle and high latitudes of the Northern Hemisphere in the following spring. Two activity centres associated with the wave train, one in the middle latitudes of Northwest Pacific with an anomalous anticyclone circulation and another in Mongolia with an anomalous cyclone circulation, bring the water vapour from the south and converge over the middle and lower reaches of the Yangtze River, resulting in the excessive precipitation over there. The results indicate that the North Atlantic Oscillation in January can act as a precursor signal for predicting the spring rainfall anomalies in the middle and lower reaches of the Yangtze River.