Summer Rain Band Pattern in Mid-Lower Reaches of Yangtze Riverand Its Inter-decadal Variability

摘要

Since the summer rainfall over Yangtze River and Huaihe River often leads to the occurrence of floods, with inconsistent distribution among those years, it is important to investigate the characteristics and the causes of rainfall anomalies. Therefore, REOF analysis is performed on 1951-1998 monthly mean precipitation from both CMA-(China Meteorological Administration)-provided 160 weather stations and NCEP/NCAR re-analyses. Results show that: 1) summer rainfall over the mid-lower reaches of Yangtze River (MLRYR) can be divided into two rain belts in the south and north of the study region, called as the southern and northern branch of rain belt, respectively. In detail, the southern belt is located in south of the MLRYR, i.e. regions of Jiangxi, Hunan and Zhejiang, and the other is located in regions of Chongqing, southeast Shaanxi, Hubei, south Henan and Anhui, with east-west zonal distributions for the both; 2) both the rain belts are marked by conspicuous intra-annual and inter-decadal oscillations, with remarkable 14-/8-yr periods on the inter-decadal scale for the southern/northern belt. Besides, two belts are different in the amount of precipitation during the same stage, which is closely related to the large-scale circulation, especially the strength of summer monsoon and subtropical high, both impacting greatly on amount and distribution of the precipitation in two belts.