北半球阻塞高压的维持Ⅱ:瞬变扰动强迫和平均流位涡平流的形成

ON MAINTENANCE OF BLOCKING ANTICYCLONES OF NORTHERN HEMISPHERE PART 2: MECHANISM OF EDDY FORCING AND PV ADVECTION BY MEAN FLOW

摘要: 着重探讨大西洋阻高和东亚阻高个例中瞬变扰动位涡(涡度)输送强迫和太平洋阻高中平均流位涡平流的形成机理。结果表明,扰动在阻高西南部西风分流区因形变而产生的扰动拟能向更小尺度串级过程,并不是扰动位涡输送强迫形成的必要机理。扰-流相互作用在阻高西(北)部非分流气流中也十分显着。数值试验表明,这一相互作用也可能是扰动强迫作用形成的机理。而青藏高原和附近海陆对比的强迫作用则可能是太平洋阻高中平均流的位涡平流形成的重要因素。对比分析表明,阻高维持机制的地域性差别可能与其上游(如青藏高原地区、落基山脉)地形和热源强迫作用不同有关。

Abstract: In this paper, formation of the potential vorticity (PV) tranfer by eddy in the Atlantic and Asia blocking cases and the advection of PV by mean flow in the Pacific blocking cases are invested.It has been shown that the propagation of eddy in diffluent flow (Shutts.1983) is not necessary for the formation of the eddy forcing.The interaction between mean flow and eddy is also strong within non-diffluent flow of north eastern part of the anticyclones and numerical experments suggest that it may also contribute to the formation of the eddy forcing.The formation of the advection of mean flow in the Pacific blocking cases has been shown to be related to forcing of the Qinghai-Xizang Plateau.