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

与十年尺度气候变化相关的大尺度大气环流系统的基本机制

基本信息

批准号：
12640418
负责人：
NAKAMURA Hisashi
金额：
$ 2.5万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12640418/
关键词：
Decadal-scale climate variability Storm tracks Siberian High Subtropical jet stream East Asian winter monsoon Subtropical High Stationary Rossby wave train Blocking 移動性高低気圧傾圧不安定亜熱帯ジェット冬季極東モンスーンアリューシャン低気圧アイスランド低気圧定常ロスビー波 /

项目摘要

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

1）已经确认了冬季冬季的两种不同阶段气候变化的不同模式，其中一种与异常的亚热带高度有关。发现异常的高度在其中纬度部分，而其亚热带部分明显是斜压。发现这种复杂的结构适合于产生异常的沉降，可以紧密相连的表面和上层异常圆。2）发现西伯利亚高中和东亚冬季季风的十年阶段弱化，从而导致北部太平洋目的地的风暴轨道的系统性增强，而北部太平洋目的地的背景宽松的背景baroclocinicity。这种增强显然与斜压不稳定性预测的线性理论相反。在存在极强的亚热带喷气机与1980年代中期强的季风相关的情况下，天气尺度的涡流质量在……通过亚洲大陆上的中纬度地区传播到北太平洋，在亚洲大陆上（9 km的海拔高度为9 km），倾向于从45°的核心中移动，同时又被置于1000张核心，同时又被置于Quiv中，同时又转移到了3 km的范围内。斜线区位于40°N，沿着亚热带和亚热带海洋循环之间的边界。因此，涡流与表面斜压区的垂直耦合削弱了，因此不利于涡流的斜压生长。相比之下，自1980年代后期放松的亚热带喷气机以来，涡流诱捕的可能性较小。涡流在表面斜压区域上方的纬度对流层面上更有可能传播，从而导致其有效的斜压生长。在涡流捕获中观察到的十年变化表现为这些涡流的结构变化。3）第一次得出了波动通量的特定形式，它可以代表rossby波小包的三维组速度传播，即固定或迁移的逼真的西风。通过我们应用这种通量，已经揭示了从每个强大的对流层异常（包括阻塞）中散发出的固定的Rossby波列，该序列（包括阻塞）可以到达较低的平流层，从而沿极地夜间射流形成波浪列。发现这些波列在冬季较低的平流层中观察到的下季节变异性大大贡献。较少的