Fundamental Mechanisms of Large-Scale Atmospheric Circulation Systems Related to the Decadal-Scale Climate Variability

1)冬季北太平洋存在两种不同的年代际气候变率模态，其中一种与副热带高压异常有关。该异常高压在中纬度地区具有强正压性，而副热带地区则具有明显的斜压性。这种复杂的结构有利于异常沉降的产生，并通过这种结构将地面和高层异常环流紧密联系在一起。2）西伯利亚高压和东亚冬季风的年代际尺度减弱导致了北太平洋风暴轴活动的系统性增强，尽管背景斜压性减弱。这种增强显然与斜压不稳定的线性理论所预言的相反。80年代初至中期，在副热带急流与强季风相联系的情况下，天气尺度涡旋在 关于我们 经亚洲大陆（海拔9km，45°N）中纬度对流层顶向北太平洋输送的高压气流，往往被困在急流核心中，而被抬升到3km，并沿副极地和副热带海洋环流的边界沿着向赤道移动1000km，离开40°N的地面斜压带。涡与地面斜压区的垂直耦合减弱，不利于涡的斜压增长。相反，自80年代后期以来，在副热带急流松弛的情况下，涡卷捕获的可能性较小.涡更可能通过中纬度对流层顶正上方的地面斜压带传播，导致其有效的斜压增长的观察。3）首次导出了一种特殊形式的波活动通量，它可以代表Rossby波包在现实西风带中的三维群速度传播，无论是静止的还是移动的。它已被揭示，通过我们的应用程序，这一流量，一个固定的Rossby波列发出的每一个强大的亚季节对流层异常，包括阻塞可以达到平流层下部，形成一个波列沿着极夜急流。这些波列被发现大大有助于在冬季平流层下部观测到的亚季节变化。少

1) The presence of the two distinct modes of decadal-scale climate variability in the wintertime North Pacific has been confirmed, one of which is associated with the anomalous subtropical high. The anomalous high was found highly barotropic in its midlatitude portion, whereas its subtropical portion is distinctly baroclinic. This complex structure is found to be suited for the generation of anomalous subsidence, through which the surface and upper-level anomalous circulation can be tightly linked.2) The decadal-scale weakening of the Siberian High and the East Asian winter monsoon has been found to cause systematic enhancing of the storm track activity in the North Pacific despite the relaxed background baroclinicity. This enhancement is apparently opposite to what the linear theory of baroclinic instability predicts. In the presence of the excessively strong subtropical jet in association with the strong monsoon during the early through mid-1980s, synoptic-scale eddies propagating in … More to the North Pacific through the midlatitude tropopause over the Asian continent (9 km in altitude, 45°N) tend to be trapped into the jet core, while lifted up to 3 km and shifted equatorward by 1000 km away from the surface baroclinic zone at 40°N located along the boundary between the subpolar and subtropical oceanic gyres. The vertical coupling of the eddies with the surface baroclinic zone is thus weakened and thus unfavorable for the baroclinic growth of the eddies. In contrast, the eddy trapping has been less likely since the late 1980 s under the relaxed subtropical jet. The eddies were more likely to propagate through the midlatitude tropopause right above the surface baroclinic zone, resulting in their efficient baroclinic growth as observed. The decadal change observed in the eddy trapping is manifested as the structural changes of those eddies.3) A particular form of a wave-activity flux has been derived for the first time, which can represent three-dimensional group-velocity propagation of a Rossby wave packet, either stationary or migratory in the realistic westerlies. It has been revealed through our application of this flux that a stationary Rossby wave train emanated from each of the strong sub-seasonal tropospheric anomalies including blocking can reach into the lower stratosphere, forming a wave train along the polar-night jet. Those wave trains were found to contribute substantially to the observed sub-seasonal variability in the wintertime lower stratosphere. Less