We focus on a regional analysis of the equatorial components of the Effective Atmospheric Angular Momentum (EAAM) functions that are responsible for excitation of polar motion. These functions are computed from the NCEP/NCAR 40-Year Reanalysis Project data both globally and in 108 geographic sectors for the period from 1968 to 1997. We investigate regional contributions of these atmospheric angular momentum functions to the short period oscillations of geodetically-determined polar motion directly and to the global EAAM excitation functions themselves. We examine two excitation terms in parallel, both excluding and including the inverted barometer (IB) formulation which adjusts the atmosphere to account for an isostatic equilibrium response from the ocean to overlying pressure; the IB formulation tends to decrease effective atmospheric variability. In the case of pressure terms without IB the largest contributions to the equatorial components of EAAM functions originate in the South Pacific, North Atlantic and North Pacific regions. However, application of the IB correction may result in the dominance of Eurasia and North America instead, with nearly all southern hemisphere contributions disappearing. Oscillations of the polar motion excitation function are mainly coherent with variations of the pressure term of the EAAM excitation functions over northern mid-latitude land areas. Distinct oscillations appear to occur in two frequency bands: 25 - 75 days and 75 - 125 days, in both prograde and retrograde directions which correspond to counterclockwise and clockwise polar motion, respectively. Coherence and cross-spectral analyses are performed to determined degree of agreement and common amplitude, respectively. We examine the atmospheric functions with respect to one important region in Eurasia and note a propagating horizontal influence within the atmosphere.
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