Abstract
The summer precipitation produced by the East Asian summer monsoon (EASM) is significantly affecting agriculture and socioeconomics. Based on the Precipitation Reconstruction dataset in East China from 1950 to 2017, we investigate the spatiotemporal variations of summer precipitation, influencing environmental factors and their relation with the EASM and the Pacific Decadal Oscillation (PDO) in both central Pacific (CP) El Niño developing and decaying years. Results indicate the following: (1) The evolutions of CP El Niño events modulate the summer precipitation anomalies in East China. In the cool PDO phase, CP El Niño causes enhanced precipitation anomalies in the decaying years but less precipitation anomalies in the developing years, and vice versa for the warm PDO phase. (2) Atmospheric circulation anomalies drive the moisture transportation and combine the motion of western Pacific subtropical high resulting in the variation of precipitation patterns. Anomalous cyclone over the western North Pacific and the sustained Western Pacific Subtropical High (WPSH) are favorable for the increment of summer precipitation. (3) The different CP El Niño-EASM relationship is caused by the influences of PDO on the evolution of CP El Niño. CP El Niño develops slowly (decays rapidly) and is associated with rapidly developing (slowly decaying) anomalous warming in the north Indian Ocean during the developing (decaying) years.
Highlights
Variations in the intensity of East Asian summer monsoon (EASM) greatly influence the summer precipitation distributions in East China
Feng et al [52] investigated the impact of central Pacific (CP) El Niño on China rainfall in the decaying phase and considered that classical El Niño combined with the western North Pacific anticyclone brings about plentiful moisture to southern China, while there is no obvious rainfall in CP El Niño resulting in weakened western North Pacific anticyclone
We found that weak precipitation anomalies happen in the decaying-warm Pacific Decadal Oscillation (PDO) phase, while the enhanced precipitation anomalies happen during the developing-warm PDO phase and decaying-cool PDO phase
Summary
Variations in the intensity of East Asian summer monsoon (EASM) greatly influence the summer precipitation distributions in East China. South Asian high influences extreme precipitation over eastern China by modulating the position and amplitude of western North Pacific subtropical high, which is identified as a semipermanent anticyclonic circulation pattern in the upper troposphere and cyclonic circulation in the lower troposphere over the Asian continent in the boreal summer [35,36,37]. During the developing El Niño summer, positive SST anomalies strengthen convective activities over the equatorial central and eastern Pacific and induce an anomalous cyclonic circulation in the lower troposphere over the western North Pacific through the Gill-Matsuno mechanism [39, 40]. For each CP El Niño event, we consider the developing summer as the JuneJuly-August (JJA) season before the event peak and the decaying summer as the JJA season following the peak
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