Thursday, 21 April 2016: 8:00 AM
Ponce de Leon B (The Condado Hilton Plaza)
Convectively coupled equatorial waves (CCEWs) are often identiﬁed by space-time ﬁltering techniques which make use of the eigenvalues of linear shallow water theory. Here, instead, a method is presented for identifying CCEWs by projection onto the eigenvectors of the theory. This method does not use space-time ﬁltering; instead, wave signals corresponding to the ﬁrst baroclinic Kelvin, Rossby, and mixed Rossby-gravity (MRG) waves are constructed from reanalysis data by a series of projections onto (i) vertical and meridional modes and (ii) the wave eigenvectors. In accordance with the theory, only dry variables, i.e. winds and geopotential height, are used; no proxy for convection is used. Using lag-lead regression, composites of the structures associated with each eigenvector signal during boreal summer are shown to contain all the features of the theory as well as some additional features seen in previous observational studies, such as vertical tilts. In addition, these composites exhibit propagation in good agreement with the theory; for the Kelvin and MRG composites, this agreement is strongest over the Paciﬁc ITCZ, while the Rossby composite exhibits strongest agreement over the Paciﬁc warm pool. The eigenvector signals are also in good agreement with space-time ﬁltered outgoing longwave radiation (OLR) for the Kelvin wave, and reasonable agreement for the Rossby and MRG waves, and it is shown that the eigenvector projections used here contribute to this agreement. Finally, a space-time ﬁltered version of the eigenvector projection is brieﬂy discussed, as are potential applications of the method.
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