LAGRANGIAN METHOD USED IN THE RESEARCH OF ATMOSPHERIC CIRCULATION_*

Based on the conservation of entropy and potential vorticity in adiabatic atmospheric motion without the consideration of friction,calculation is made of the trajectory of a particle on an isentropic surface by use of the data of FGGE Ⅲ-b.Results of several calculation schemes of the trajectory discussed show that the local data interpolation and Runge-Kutta time-integral scheme is the best.The calculated trajectory reflects the large-scale atmospheric motion only and the small-scale motion emerges as a deviation term of the calculated trajectory.And then the outbreak and propagation of planetary wave are studied by means of the deformation of a material line,with the result showing that the material line can be tracked in the troposphere only in a few days,beyond which the interaction between the small-scale waves and large-scale motion leads to its dramatical twisting and deformation.Therefore,the Lagrangian method is assumed to be an effective means of diagnostic research in the nonlinear interaction in atmospheric circulation,in addition to the general study of the atmospheric circulation.