1990年代初夏季东北亚低压的年代际转变

夏季东亚地区对流层低层受到一个陆地低压系统控制；该低压中心位于东亚的北部地区，文中称之为东北亚低压。基于NCEP/DOE、NCEP/NCAR、ERA-40和ERA-Interim四种不同的再分析数据，本文分析了夏季东北亚低压的年代际变化特征，并进一步探讨了其转变的可能物理机理。研究结果表明夏季东北亚低压在1990年代初期存在一次显著的年代际转变， 之后低压强度减弱。对应此次年代际转变，东北亚地区对流层位势高度呈现为正压结构的正异常，其南侧的高空西风急流中心强度减弱。进一步，基于观测和简单线性斜压模式模拟结果，我们提出环贝加尔湖地区夏季气温增加可能是导致1990年代初期之后夏季东北亚低压减弱的原因。

Inter-decadal Change in the Summertime Northeast Asia Low-Pressure System in the Early 1990s

East Asian summer climate is controlled by a low pressure system centered over continental northern East Asia in the lower troposphere, which is named as the Northeast Asia low pressure (NEAL). Based on the NCEP-DOE, NCEP-NCAR, ERA-40, and ERA-Interim reanalysis data, we investigate the inter-decadal change of the summertime Northeast Asia Low-pressure system and discuss the possible physical mechanism associated with this change. Results show that NEAL experienced a significant decadal change in the early 1990s. The intensity of NEAL has decreased since 1991. Corresponding to the weakened NEAL, the tropospheric geopotential height field over Northeast Asia presents a barotropic-structure positive anomaly and the intensity of upper-tropospheric westerly jet to the south decreases. Based on results from the observational analysis and simulations of a linear baroclinic model, it is found that the surface warming around the Lake Baikal in the summer may be responsible for the weakening of the NEAL after the early 1990s.