Large-Scale Circulation Characteristics Corresponding to the Cold and Rainy Summer of 2014 in Zhejiang Province and the Relationship with SST Anomalies

Using NECP/NCAR reanalysis data, NCC (National Climate Center) and NOAA (National Oceanic and Atmospheric Administration) relevant data, large-scale circulation characteristics and sea surface temperature corresponding to the cold and rainy summer of 2014 in Zhejiang Province are analyzed. The results are as follows. The anomalous cyclonic circulation in the middle and low latitudes from eastern China to southern Japan was conducive to cold and rainy summer in Zhejiang, while the abnormally strong and southward expanding western Pacific subtropical high was also an important factor for the extremely cold and rainy August; EAP and EU were two main teleconnection patterns that affected the abnormal cold and rainy summer in Zhejiang Province. The negative EAP (East Asia-Pacific teleconnection pattern) phase and positive EU (Eurasian teleconnection pattern) phase were in favor of cold air accumulation and southward moving. The cold and warm air intersected over Zhejiang Province, leading to cold rainy weather. The rare cold rainy August was the synergistic result of negative EAP phase and positive EU phase. Further analysis reveals that the warm ENSO phase triggered a strong abnormal descending airflow and an anticyclone over the western Pacific in August, which forced the western Pacific subtropical high to move southward and become stronger, while EAP wave trains occurred over East Asia in response. The maintenance of the warm IOBW (Indian Ocean Basin Wide) phase further weakened convective activities over the Maritime continent in August. Intraseasonal SST changes in the central North Atlantic might be associated with the shifts of the EU phase.