北半球夏季大气活动中心与海平面气压场的气候基本态及变率特征

Study on climate base state of northern summer atmospheric action center and SLP with its climate variability

研究了近 1 0 0多年北半球夏季大气活动中心强度与北半球海平面气压场的气候基本态及气候变率特征及时间演变规律。指出 ,夏季太平洋高压区与印度低压区基本态的改变最大。基本态的变化表现为两个基本模态 :第一模态主要反映印度低压的变化 ;第二模态主要表现太平洋高压及大西洋高压的特征。它们都有明显的长期变化。近百年来 ,印度低压与太平洋高压已明显地加强了 ,大西洋高压也有所加强。印度低压的低频强度具有大约 80年周期变化特征。而太平洋高压及大西洋高压则表现为明显的正趋势 ,它们的突变加强发生在本世纪初 ,在此以前两个高压都很弱 ,以后高压增强 ,2 0世纪 1 0～ 30年代最强。此外 ,东亚夏季风的强度与夏季太平洋高压、北半球海平面气压第二模态在气候尺度上有明显的正相关。

Study is undertaken of the climate base state of northern summer atmospheric action centers and sea level pressure (SLP) with its climate variability and temporal evolution in the past 100 years, indicating that the base state has its high value region of mean square deviation in the Pacific High and Indian Low. The climate base state of the summer SLP exhibits two modes for its variation.The first eigenvector of the base state displays Indian Low, the second Pacific High and Atlantic High.They have secular variation .The Indian Low and Pacific High is enhanced,with the Atlantic High being slightly enhanced in the past 100 years .The climate base state of the Indian Low displays oscillations at periods 80 years.Evidence suggests that the Pacific High and Atlantic High display a remarkably positive trend .They abruptly enhanced in the early 1900s,before that they are considerably weak and after that they become the strongest in 1910s～1930s.Further, the east Asian summer monsoon is closely positively related with the summer Pacific High intensity and with the second mode of northern SLP on the scale of more than 30 years.