Theoretical studies on the interaction between the general circulation and small-scale phenomena.

Research Project

Project/Area Number	60540261
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	気象・海洋・陸水学
Research Institution	Kyushu University
Principal Investigator	URYU Michiya Department of Physics, Faculty of Science, 理学部, 教授 (60037215)
Project Period (FY)	1985 – 1986
Project Status	Completed (Fiscal Year 1986)
Budget Amount *help	¥800,000 (Direct Cost: ¥800,000) Fiscal Year 1986: ¥800,000 (Direct Cost: ¥800,000)
Keywords	prameterization / non-linear / bifurcation / the stratosphere as a non-linear system / ヒステリシス
Research Abstract	In the so-called parameterization, we evaluate the effects of smaller scale phenomena on the large-scale motion considered, usually with use of the latter variables. However, if we treat the interaction correctly, the equations will become non-linear, including the feed-back effects of the large-scale motion modified by the smaller ones, and will lead us to somewhat difficult situation, because it is generally impossible to omit the feed-back, except the case where its time-scale is sufficiently longer. The non-linearity of equation may cause the bifurcation of solutions. The idea of parameterization does not necessarily involve such a consideration. Then, in this wotk, as the first step toward founding a reasonable idea of parameterization, we have a vertical one dimensional model of the stratosphere as a non-linear system in which the mean zonal flow and planetary waves are mutually affecting, and examined the bifurcation of the solutions and also the response to external forcing. As the result, we have succeeded to answer reasonably or soundly the problems such as why the planetary waves can amplify in late winter, why the sudden warmings prefer late winter or early spring to other seasons and so on. These phenomena can be interpreted as the transitions among stable equilibrium states, occuring in the stratosphere responding to the seasonal change in solar differential heating. We anticipate that similar situations may appear in the prblem of interaction between gravity wave and the mean circulation, which is being intensively studied in recent years with respect to the gravity wave parameterization.