Wednesday, 18 April 2018: 11:30 AM
Masters E (Sawgrass Marriott)
The presence of External Rossby (ER) waves has been documented throughout the literature. Many studies have found that these phenomena can affect the large-scale flow, one of these ways includes the possibility of exiting stationary forcing by resonance. In recent studies, resonance from westward moving Rossby waves has been found to be a possible mechanism to explain the occasional formation of blocking ridges over the Northern Atlantic Ocean. Little has been done on the effect of these modes on the large-scale circulation of the tropics. An Empirical Orthogonal Function (EOF) analysis was performed on the 15-30 day filtered vertically average geopotential height anomalies to extract its spatial patterns. The second and third EOFs are in quadrature with each other, representing a westward moving signal with an average period of around 16 days and a phase velocity of, closely resembling the 16-day ER mode. The Principal Components (PCs) from these eigenvectors were used to construct an External Rossby Wave Index (ERWI), which was used as a tool to monitor and track this 16-day ER wave. A composite analysis of each phase was performed to analyze the spatial structure of this wave. 100-day running average Outgoing Longwave Radiation (OLR) composites showed a westward moving active convection anomalies initiating in phase 5 over the eastern Pacific, moving west though phases 6-8 to the Maritime continent. Further investigation is needed to find a possible mechanism for the formation of these anomalies.
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