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310/1749-9
ICTP-COST-CAWSES-INAF-INFNInternational Advanced School
on Space Weather2-19 May 2006
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Introduction to Middle AtmosphericDynamics
Kevin Peardon HAMILTONProfessor and Chair
Department of Meteorology, andInternational Pacific Research Center (IPRC)
University of Hawai`i at ManoaHonolulu, HI 96822
USA
___________________________________________________________________________These lecture notes are intended only for distribution to participants
310/1749-9
ICTP-COST-CAWSES-INAF-INFNInternational Advanced School
on Space Weather2-19 May 2006
���������������������������������������������������������������������
Introduction to Middle AtmosphericDynamics
Kevin Peardon HAMILTONProfessor and Chair
Department of Meteorology, andInternational Pacific Research Center (IPRC)
University of Hawai`i at ManoaHonolulu, HI 96822
USA
___________________________________________________________________________These lecture notes are intended only for distribution to participants
Introduction to Middle Atmospheric Dynamics
Kevin HamiltonInternational Pacific Research Center, and
Department of MeteorologyUniversity of Hawaii at Manoa
Zonal Mean and Eddy Components
" Overall the strongest gradients in circulation are north-south rather than east-west
So we describe circulation as zonal-mean(average around latitude circles) plus eddy(deviations form zonal-mean) components
Zonal-mean circulation consists of generally strong zonal flow and much weaker overturning circulation in the meridional plane (mean meridional circulation, MMC)
Zonal Mean and Eddy Components
" Overall the strongest gradients in circulation are north-south rather than east-west
" So we describe circulation as zonal-mean(average around latitude circles) plus eddy(deviations form zonal-mean) components
Zonal-mean circulation consists of generally strong zonal flow and much weaker overturning circulation in the meridional plane (mean meridional circulation, MMC)
Zonal Mean and Eddy Components
" Overall the strongest gradients in circulation are north-south rather than east-west
" So we describe circulation as zonal-mean(average around latitude circles) plus eddy(deviations form zonal-mean) components
" Zonal-mean circulation consists of generally strong zonal flow and much weaker overturning circulation in the meridional plane (mean meridional circulation, MMC)
Dominant Balances Determining the MMC
� Write nonlinear advection in terms of eddy flux convergences
� Look for steady state� Consider only dominant terms for extratropical
region
"Transformed-Eulerian" Equations
" Define a transformed MMC that is "forced" (mostly) by the diabatic heating
" Effects of eddy fluxes on the zonal mean takes the form of an "Eliassen-Palm (EP) flux divergence
" TE MMC is close to Lagrangian MMC
Tropical Middle Atmosphere
Quasi-biennial Oscillation
Semiannual Oscillation
Tropical Effects on Extratropics
Tropical Mean Flow DynamicsNear the equator the eddy forcing of zonal-
mean momentum (EP flux divergence) is not balanced by Coriolis torques, but directly forces mean flow accelerations
Sustained, but self-limiting eddy driven mean flow forcing comes from upward-propagating gravity waves (and related equatorial-planetary waves)
Tropical Mean Flow Dynamics
" Near the equator the eddy forcing of zonal-mean momentum (EP flux divergence) is not balanced by Coriolis torques, but directly forces mean flow accelerations
Sustained, but self-limiting eddy driven mean flow forcing comes from upward-propagating gravity waves (and related equatorial-planetary waves)
Tropical Mean Flow Dynamics
" Near the equator the eddy forcing of zonal-mean momentum (EP flux divergence) is not balanced by Coriolis torques, but directly forces mean flow accelerations
" Sustained, but self-limiting eddy driven mean flow forcing comes from upward-propagating gravity waves (and related equatorial-planetary waves)
