CR prepress abstract  -  DOI: https://doi.org/10.3354/cr01542

Linkage between the Arctic Oscillation and summer climate extreme events over the middle reaches of Yangtze River Valley

Lu Liu, Tong Zhou, Liang Ning, Jain Liu, Mi Yan, Chunhan Jin, Weiyi Sun

*Email: ningliangnnu@126.com

ABSTRACT: The Arctic Oscillation (AO) is commonly recognized as a dominant large-scale mode influencing climate over the northern hemisphere. The influences of May AO on summer (JJA) extreme precipitation events and summer extreme warm days over the middle reaches of Yangtze River Valley for the period 1961-2014 are investigated. Following a positive May AO, there are usually fewer summer extreme precipitation events but more summer extreme warm days over the middle reaches of Yangtze River Valley. Composite analyses show that positive May AO induces the north displacements of East Asian jet stream (EAJS) and northeastward of western Pacific subtropical high (WPSH), and causes a stronger, more northwestern subtropical northwest Pacific cyclone/anticyclone anomaly and an anticyclonic circulation anomaly in the north side of the South China Sea, resulting in northward shift of rainfall belt and enhancement of East Asia summer monsoon. . Therefore, the CDF (Cumulative Distribution Probability) of daily precipitation values to shift significantly to the left sides (lower precipitation value), resulting lower probabilities of summer extreme precipitation event occurrences following positive May AO. Weakening of WPSH induce anomalous sinking motion over the middle reaches of Yangtze River Valley. The 850hPa wind field shows the southerly wind anomalies over the Jiang-Huai River Basin, which cause a decrease in total cloud cover, resulting in an increase in solar radiation flux. Significant shift of the daily maximum temperature probability distribution towards to the larger values results higher probabilities of summer extreme warm day occurrences following positive May AO.