HR: 10:40h
AN: G21E-02 INVITED     [PDF]
TI: The Dynamics of Equatorial Atmospheric Angular Momentum
AU: * Feldstein, S B
EM: sbf@essc.psu.edu
AF: EMS Environment Institute The Pennsylvania State University, 2217 Earth-Engineering Science Building, University Park, PA 16802 United States
AB: The physical processes that drive intraseasonal equatorial atmospheric angular momentum (EAAM) fluctuations are examined with data from an aquaplanet GCM run and with NCEP/NCAR reanalysis data. The GCM has an all-ocean lower boundary with a zonally symmetric sea surface temperature field. The EAAM budget is dominated by the equatorial bulge torque in both the GCM and in observations. For the GCM and the atmosphere, both components of the EAAM vector exhibit a strong spectral peak near a period of 10 days. An analysis with the linearized shallow water model equations on the sphere shows that this 10-day period can be interpreted as arising from the westward propagation of a free, antisymmetric, zonal wavenumber one, Rossby wave. The amplitude fluctuations of the EAAM vector are found to be related to tropical convection in both the GCM and the atmosphere. For the GCM, this convection is associated with an equatorial mixed Rossby-gravity wave. In the atmosphere, in addition to mixed Rossby-gravity waves, EAAM amplitude fluctuations are also related to both the Madden-Julian Oscillation (MJO) and to constructive and destructive interference between the propagating and stationary components of EAAM vector. The latter two processes arise because of the large, nonzero, seasonal mean values of the components of the EAAM vector. The above findings collectively suggest that the latent heat release in the tropics excites poleward Rossby wave propagation which alters the amplitude of the EAAM vector.
DE: 1223 Ocean/Earth/atmosphere interactions (3339)
DE: 1239 Rotational variations
DE: 3319 General circulation
DE: 3384 Waves and tides
SC: Geodesy [G]
MN: 2003 Fall Meeting