A Simple Model for Transient Eddy Momentum Fluxes in the Upper Troposphere

Abstract A simple model for transient eddy momentum fluxes is constructed based on the hypothesis that planetary waves radiating from low-level baroclinic eddies act effectively as a random forcing of the upper troposphere. The response of the upper troposphere is modeled by the barotropic, nondivergent vorticity equation, linearized about a zonally symmetric flow. Rayleigh friction and scale-selective damping are included to crudely represent the effect of vertical diffusion and nonlinear equilibration mechanisms; the associated damping rates constitute the only tunable parameters of the model. A distinguishing feature of the model is that wave-activity theory is used to specify the statistics of the random forcing as a function of the background flow and low-level eddy heat fluxes. The resulting model simulates the annual cycle of momentum fluxes reasonably well, but tends to underestimate the eddy kinetic energy in midlatitudes. The results are interpreted in light of an analytic solution to the linear...

[1]  S. Ghan,et al.  Short-Term Fluctuations in the Eddy Heat Flux and Baroclinic Stability of the Atmosphere , 1982 .

[2]  T. DelSole.  Stochastic Models of Shear-Flow Turbulence with Enstrophy Transfer to Subgrid Scales , 1999 .

[3]  C. Leith.  Climate Response and Fluctuation Dissipation , 1975 .

[4]  J. G. Charney,et al.  Propagation of planetary‐scale disturbances from the lower into the upper atmosphere , 1961 .

[5]  J. G. Charney,et al.  THE DYNAMICS OF LONG WAVES IN A BAROCLINIC WESTERLY CURRENT , 1947 .

[6]  B. Hoskins,et al.  Eliassen-Palm Cross Sections for the Troposphere , 1980 .

[7]  R. Reynolds,et al.  The NCEP/NCAR 40-Year Reanalysis Project , 1996, Renewable Energy.

[8]  J. Peixoto,et al.  Physics of climate , 1992 .

[9]  D. G. Andrews,et al.  Planetary Waves in Horizontal and Vertical Shear: The Generalized Eliassen-Palm Relation and the Mean Zonal Acceleration , 1976 .

[10]  Prashant D. Sardeshmukh,et al.  The Diagnosis of Mechanical Dissipation in the Atmosphere from Large-Scale Balance Requirements , 1992 .

[11]  B. Hoskins,et al.  Energy Spectra Predicted by Semi-Geostrophic Theories of Frontogenesis , 1978 .

[12]  H. Kuo.  Dynamical Aspects of the General Circulation and the Stability of Zonal Flow , 1951 .

[13]  Edward N. Lorenz,et al.  The nature and theory of the general circulation of the atmosphere , 1967 .

[14]  J. Pedlosky.  Geophysical Fluid Dynamics , 1979 .

[15]  E. T. Eady,et al.  Long Waves and Cyclone Waves , 1949 .

[16]  Brian J. Hoskins,et al.  The Steady Linear Response of a Spherical Atmosphere to Thermal and Orographic Forcing , 1981 .

[17]  C. Gardiner.  Handbook of Stochastic Methods , 1983 .

[18]  K. Tung,et al.  On the Equilibrium Spectrum of Transient Waves in the Atmosphere , 1998 .

[19]  Peter H. Stone,et al.  Development of a two-dimensional zonally averaged statistical-dynamical model. II - The role of eddy momentum fluxes in the general circulation and their parameterization , 1987 .

[20]  A. E. Gill.  Atmosphere-Ocean Dynamics , 1982 .

[21]  J. Green,et al.  Transfer properties of the large‐scale eddies and the general circulation of the atmosphere , 1970 .

[22]  B. Hoskins,et al.  Large-Scale Eddies and the General Circulation of the Troposphere , 1985 .

[23]  J. Holton.  An introduction to dynamic meteorology , 2004 .

[24]  Brian F. Farrell,et al.  Stochastic Dynamics of Baroclinic Waves , 1993 .

[25]  A. White,et al.  Transfer coefficient eddy flux parametrizations in a simple model of the zonal average atmospheric circulation , 1984 .

[26]  Brian F. Farrell,et al.  A Stochastically Excited Linear System as a Model for Quasigeostrophic Turbulence:Analytic Results for One- and Two-Layer Fluids , 1995 .

[27]  M. McIntyre,et al.  Generalized Eliassen-Palm and Charney-Drazin Theorems for Waves on Axismmetric Mean Flows in Compressible Atmospheres , 1978 .

[28]  Brian F. Farrell,et al.  Optimal Excitation of Baroclinic Waves , 1989 .

[29]  I. Held,et al.  Phase Speed Spectra of Transient Eddy Fluxes and Critical Layer Absorption , 1991 .

[30]  Brian F. Farrell,et al.  Stochastic dynamics of the midlatitude atmospheric jet , 1995 .

[31]  I. Held.  Momentum Transport by Quasi-Geostrophic Eddies , 1975 .

[32]  Jeffrey S. Whitaker,et al.  A Linear Theory of Extratropical Synoptic Eddy Statistics , 1998 .

[33]  Matthew Newman,et al.  Stochastic Forcing of the Wintertime Extratropical Flow , 1997 .

[34]  I. Held,et al.  Linear and nonlinear barotropic decay on the sphere , 1987 .

[35]  Sukyoung Lee.  Why Are the Climatological Zonal Winds Easterly in the EquatorialUpper Troposphere , 1999 .