HR: 14:00h
AN: NG43A-02    [Abstracts]
TI: A Dynamic Closure of Synoptic Eddy and Low-frequency Flow (SELF) Interaction and the Self-organization of Low-frequency Modes
AU: * Jin, F
EM: jff@met.fsu.edu
AF: Dept. Meteorology, FSU, Love Building 404, Tallahassee, FL 32306 United States
AU: Pan, L
EM: lpan@met.fsu.edu
AF: Dept. Meteorology, FSU, Love Building 404, Tallahassee, FL 32306 United States
AU: Watanabe, M
AF: Graduate School of Environment Earth Science, Hokkaido University, Hokkaido, Japan, Japan
AB: The two-way interaction between synoptic eddy and low-frequency flow (SELF), which we will refer to as the SELF interaction, has been recognized for decades to play an important role in the dynamics of the low-frequency variability of the atmospheric circulation. We propose a new framework for studying the dynamics of the SELF interaction and the low-frequency variability in a stormy background flow. By considering a Gaussian flow as a surrogate for the stormy background flow, we expand the traditional climatological basic flow to a synthetic stochastic basic flow. Its ensemble mean is the observed climatological mean flow while its prescribed variance/covariance fields represent the climatological variance/covariance fields of the observed synoptic eddies. Low-frequency anomalies in the traditional month-to-seasonal mean flow and in the variance/covariance fields of the transient eddy flow are viewed as equivalent to the anomalies in the first and second moments of the quasi-stationary stochastic flow ensemble. The linear dynamics of SELF interaction are described by the coupling among the anomalies in first and second moments. Under the assumption that slow changes in the second moments are in quasi-equilibrium with the anomalies in the first moment, an analytical non-local dynamical closure for SELF interaction is obtained. Using this framework, we show that leading low-frequency modes earn their dominance because they can effective organizing the turbulent synoptic flow such that they get reinforced by positive SELF interaction.
DE: 3300 METEOROLOGY AND ATMOSPHERIC DYNAMICS
DE: 3319 General circulation
SC: Nonlinear Geophysics [NG]
MN: 2005 Joint Assembly