1.Nanjing University of Information Science and Technology;2.Anhui Meteorological Observatory
Based on the daily precipitation over Huaihe River basin and reanalysis datasets from 1961 to 2016, the spatial patterns of the summer extreme precipitation frequency over Huaihe River basin are objectively classified through K-means cluster, rotated empirical orthogonal function analysis (REOF), and their formation mechanisms are investigated via observational diagnosis and numerical simulations. The results show that: (1) the spatial distribution of summer extreme precipitation frequency over Huaihe River basin can be objectively divided into three types: S-Type, C-type, and N-type, in which the extreme precipitation mainly falls in south of 33°N, 31°-36°N and north of 34°N, respectively. (2) The S-Type is related to the anomalous southwestward shift of north western Pacific subtropical high (NWPSH). The cyclonic anomalies north of NWPSH hinder the water vapor further to the north, resulting in more extreme precipitation in south of Huaihe River basin. For the C-Type, the Huaihe River basin is controlled by saddle circulation anomalies pattern, therefore, extreme precipitation is mainly confined to the central Huaihe River basin. The N-Type is associated with the northwestward shift of the NWPSH. The southerly wind could transport water vapor to the north of Huaihe River basin, resulting in more extreme precipitation in the region. (3) The formation and the related circulation anomalies of S-Type and N-Type are closely associated with the El Ni?o-like and La Ni?a-like SST anomalies, whilst the C-Type related saddle circulation pattern is linked to two southward-propagated stationary Rossby waves over Eurasian Continent induced by the Arctic sea ice anomalies over Barents Sea/Kara Sea.