Empirical Orthogonal Function Analysis of Various Angular Momentum Waves

Empirical Orthogonal Function Analysis of Various Angular Momentum Waves

Ernesto W. Findlay, Paul Roundy

University at Albany, Albany, New York

The angular momentum (AM) with respect to the earth’s axis of rotation is one of the fundamental parameters used to characterize the general circulation of the atmosphere and the climate (Peioxoto and Oort 1992). Although AM in the earth-atmosphere system is nearly conserved, AM is constantly exchanged between the atmosphere and the solid earth, and variations in atmospheric AM (AAM) are often associated with particular types of atmospheric circulation patterns. A power spectrum in the zonal wave number and frequency domain across 15°N-15°S was computed to understand the sources of AAM variability. Results show that Rossby-Haurwitz (King et al. 2015) waves produce the largest power in terms of AAM variability in the spectrum of data filtered for symmetry across the equator. There are also a few other signals such as one centered around wavenumber 6 which spans periods of 3-30 days. In addition, in the spectrum of signals antisymmetric across the equator, there is signal that is of similar shape as the expression of Rossby-Haurwitz waves found in the spectrum of symmetric signals, located in longer timescales of 6-30 days. In this particular project, we perform an Empirical Orthogonal Function (EOF) analysis on the different waveguides included in the power spectrum. The resulting Principal Components (PCs) will be computed and binned in an 8 phase diagram. Finally, a composite wave structure during each phase will be computed to diagnose significant circulation patterns that may occur at each phase.