• DOI:10.1175/JAS-D-16-0099.1
• Corpus ID: 1217777

The Linear Response Function of an Idealized Atmosphere. Part II: Implications for the Practical Use of the Fluctuation–Dissipation Theorem and the Role of Operator’s Nonnormality

@article{Hassanzadeh2015TheLR,
  title={The Linear Response Function of an Idealized Atmosphere. Part II: Implications for the Practical Use of the Fluctuation–Dissipation Theorem and the Role of Operator’s Nonnormality},
  author={Pedram Hassanzadeh and Zhiming Kuang},
  journal={Journal of the Atmospheric Sciences},
  year={2015},
  volume={73},
  pages={3441-3452}
}

• P. Hassanzadeh, Z. Kuang
• Published 18 June 2015
• Environmental Science, Physics
• Journal of the Atmospheric Sciences

AbstractA linear response function (LRF) relates the mean response of a nonlinear system to weak external forcings and vice versa. Even for simple models of the general circulation, such as the dry dynamical core, the LRF cannot be calculated from first principles owing to the lack of a complete theory for eddy–mean flow feedbacks. According to the fluctuation–dissipation theorem (FDT), the LRF can be calculated using only the covariance and lag-covariance matrices of the unforced system. However, efforts in calculating the LRFs for GCMs using FDT have produced mixed results, and the reason(s) behind the poor performance of the FDT remain(s) unclear. In Part I of this study, the LRF of an idealized GCM, the dry dynamical core with Held–Suarez physics, is accurately calculated using Green’s functions. In this paper (Part II), the LRF of the same model is computed using FDT, which is found to perform poorly for some of the test cases. The accurate LRF of Part I is used with a linear stochastic equation to s...