摘要
亚洲夏季风按照气候带可以分为东亚副热带夏季风和亚洲热带夏季风。就气候平均而言,东亚副热带夏季风于4月初在我国江南（泛称＂华南＂）地区建立,而亚洲热带夏季风首先于5月初在孟加拉湾东北部建立,之后向东推进,于5月第4候到达南海,然而夏季风无法直接西传至印度地区,因此印度夏季风的爆发表现为热带对流在阿拉伯海上空自赤道向北逐步推进的特征。东亚副热带夏季风与亚洲热带夏季风的爆发机制和时空变率都存在明显差异。亚洲夏季风的建立与青藏高原的动力和热力强迫作用联系紧密,其中东亚副热带夏季风的建立又与东亚大陆-西北太平洋的纬向海陆热力差异的季节转换紧密联系,而亚洲热带夏季风的爆发则与亚洲南部地区对流层中上部经向温度梯度的季节变化有关。同时,亚洲热带夏季风的建立过程还与亚洲南部高、低空环流的垂直耦合密切相关。就季节内变化而言,东亚副热带夏季风在4月份表现出10~20天季节内振荡,这与青藏高原表面感热的季节内变化有关,而盛夏的东亚副热带夏季风则存在准双周和21~30天两种振荡信号。亚洲热带夏季风的季节内振荡包含30~60天的北传信号和10~20天的西传信号,其中北传信号与环境气流的垂直切变、边界层辐合以及暖SST下垫面有关。亚洲夏季风年际变率的主要外强迫是ENSO事件,同时印度洋和大西洋海温异常、南极海冰以及青藏高原的冬、春季积雪和感热异常也影响着亚洲夏季风的年际变率。而亚洲夏季风的年代际变化既与气候系统的自然变率有关,又受热带海温强迫、人为排放气溶胶浓度和青藏高原表面热状况长期变化影响。
The Asian Summer Monsoon（ASM） can be divided into the East Asian subtropical summer monsoon and the Asian tropical summer monsoon based on the climate belt. In climatology the East Asian subtropical summer monsoon builds up over the south of Yangtze River（referred to South China in general） in early April. The Asian tropical summer monsoon has onsets over the northeastern Bay of Bengal in early May, and then advances eastward to reach the South China Sea in Pentad 28, but the summer monsoon onset is blocked over the eastern waters of Indian Peninsula. Thus the establishment of Indian summer monsoon is featured by the northward shifting of tropical convection from the equator over the Arabian Sea. The ASM is closely associated with both mechanical and thermal forcing of Tibetan Plateau. Besides, the seasonal transition of zonal land-sea thermal contrast contributes to the onset of East Asian subtropical summer monsoon, whereas the Asian tropical summer monsoon is attributed to the seasonal changes in the mean temperature gradient in the middle and upper troposphere. In the meantime, vertical coupling of circulation between the upper and lower troposphere is important for the Asian tropical summer monsoon. For the intraseasonal variability, in April the East Asian subtropical summer monsoon shows a 10~20 day oscillation, which is attributed to the intraseasonal changes in the surface sensible heating over Tibetan Plateau. In boreal summer the East Asian subtropical summer monsoon manifests both bi-weekly and 21~30 day oscillation. Both the northward propagation of 30~60 day and the westward propagation of 10~20 day oscillation is significant for the Asian tropical summer monsoon, and the former is associated with the vertical shear of basic flow, the convergence in the boundary layer and the warm SST. The ENSO events are the major forcing for the interannual variability of ASM, which is modulated by the sea surface temperature anomaly（SSTA） in the Indian Ocean and Atlantic Ocean, the Antarctic sea-ice c
出处
《热带气象学报》
CSCD
北大核心
2015年第6期869-880,共12页
Journal of Tropical Meteorology
基金
国家重点基础研究发展计划973项目(2013CB430202)
公益性行业(气象)科研专项经费项目(GYHY201306030
GYHY201406018)
长江学者和创新团队发展计划资助(PCSIRT)
江苏高校优势学科建设工程资助项目(PAPD)共同资助
关键词
季风动力学
亚洲夏季风爆发
季节内变率
年际变率
年代际变率
monsoon dynamics
onset of Asian summer monsoon
intraseasonal variability
interannual variability
interdecadal changes
