HR: 1340h
AN: G33B-1248    [Abstracts]
TI: Modes of variability of atmospheric excitation functions for polar motion
AU: * Salstein, D A
EM: salstein@aer.com
AF: Atmospheric and Environmental Research, Inc., 131 Hartwell Ave., Lexington, MA 02421, United States
AU: Nastula, J
EM: nastula@cbk.waw.pl
AF: Space Research Center of the PAS, Bartycka 18a, Warsaw, 00-716, Poland
AB: We undertake a study to examine the modes of atmospheric regional variability that drive polar motion. From atmospheric surface pressure fields in the NCAR-NCEP reanalysis we have calculated atmospheric-mass polar motion excitations on a fine-resolution network of sectors over the extended 60-year period 1948-2007. Earlier work demonstrated the intramonthly variability in these sectors, and highlighted regions that were particularly important to polar motion excitation, like the atmosphere over central Eurasia, but was based typically on a shorter period and a coarser network. Here we expand the study as well to examine monthly and interannual time scales. We utilize the complex empirical orthogonal function method to select the vector modes that explain independently the most variance of polar motion excitation. Modes comprise a measure of variance explained (the eigenvalue), a geographical structure (the eigenvector), and a time series (mode loadings), so that the regional and temporal importance of the atmosphere with respect to the polar motion function are revealed. Regionally, only the atmosphere over land is important, as the Inverted Barometer model, which greatly reduces all variability over the ocean, is appropriate at the time scales considered here. The variability appears strong over portions of Eurasia and North America in particular for most modes, but has some southern hemisphere variability as well for the first mode too. The time series of these modes, especially when seasonally stratified, may reveals some influence of climate patterns like the El Nino/Southern Oscillation, North Atlantic, Arctic, Antarctic, and Pacific-North American Oscillations, based on their indices.
DE: 1239 Earth rotation variations
DE: 3305 Climate change and variability (1616, 1635, 3309, 4215, 4513)
DE: 3319 General circulation (1223)
SC: Geodesy [G]
MN: 2007 Fall Meeting