线性定常响应有效强迫与遥相关型动力学

EFFICIENT FORCINGS FOR LINEAR STEADY RESPONSES AND DYNAMICS OF ATMOSPHERIC TELECONNECTIONS

中文关键词:  定常响应  有效强迫  遥相关型

英文关键词:Steady response  Efficient forcing  Teleconnection pattern

中文摘要:

      对线性定常强迫问题,本文发展了具有能量意义的内积空间中建立一组完备正交强迫模的动力学方法,其中这组正交强迫模是正定对称阵的特征矢量,相应的特征值则决定了强迫模产生的大气响应强度.以冬季300hPa气候平均流为基本状态进行具体计算.结果表明,有实际意义的遥相关型只是由很少几个使大气产生大响应的最有效强迫模产生.这些最有效的强迫模产生的大气响应同实际观测到的遥相关型有很好的对应关系.能量分析表明,有利强迫模建立遥相关型,基本流向大气响应提供的动能比强迫产生的动能更大.所以,强迫建立遥相关型不只依赖于外源产生的动能的传播,更主要依赖于大气响应能否从基本流吸取动能.

英文摘要:

      For linear steady forcing problems,a method is developed to provide a set of forcing modes which form a set of complete orthonormal basis in the energetics inner product space.The forcing modes are found by calculating eigenvectors of a positive symmetric matrix determined from given equations of motion.The amplitude of responses to forcing modes is given in term of the associated eigenvalues.This method is used in a nondivergent barotropic model linearized about the 300 hPa tonally-varying climatological flow for northern wintertime.The results show that only a few of forcing modes associated with the leading eigenvalues can excite sufficiently large response comparable with realistic teleconnection patterns,and those preferred responses to these efficient forcing modes are in good agreement with realistic teleconnection patterns.Energetics analyses are performed.The primary source of energy of responses to the most efficient forcing modes is the conversion of basic state kinetic energy to the response kinetic energy,rather than directly from the forcing itself.It is suggested that teleconnection patterns produced by external source are not determined only by Rossby wave dispersion from external sources,but mainly depend on the efficient extraction of energy of the forced perturbation from the basic state.