Influence of Winter North Atlantic Oscillation on Spring Precipitation in China

Based on the precipitation data at 397 stations in China and the NCEP/NCAR monthly reanalysis data,the relations between the winter North Atlantic Oscillation(NAO) and the spring precipitation in China using the correlation analysis and composite analysis are studied.The results show that the NAO significantly influence on the variations of spring precipitation in China.Associated with the positive(negative) NAO,the precipitation in South China will increase(decrease) and the precipitation in North China will decrease(increase).Further analysis indicates that winter NAO can exert notable influence on the atmospheric circulation over East Asia by propagation of wave train.In strong positive(negative) NAO year,the East Asian subtropical westerly jet enhanced(weakened) and the East Asia polar-front jet weakened(enhanced).The NAO-related atmospheric circulation resulted in the abnormalities of temperatures on 500~200 hPa,cause corresponding variations in meridional gradients of temperature.Perhaps it is one of the reasons why NAO impacts on westerly jet stream over East Asia.The further analysis indicates that upper-level cooling(warming) is closely related to anomalous sinking(rising) motion in 30°-40° N and rising(sinking) motion in 20°-30°N.These changes result in a drier(wetter) condition in the northern China and a wetter(drier) condition in the southern China.