Convectively Coupled Equatorial Waves: A New Methodology for Identifying Wave Structures in Observational Data

Abstract

Convectively coupled equatorial waves are fundamental components of the interaction between the physics and dynamics of the tropical atmosphere. A new methodology, which isolates individual equatorial wave modes, has been developed and applied to observational data. The methodology assumes that the horizontal structures given by equatorial wave theory can be used to project upper-and lower-tropospheric data onto equatorial wave modes. The dynamical fields are first separated into eastward-and westward-moving components with a specified domain of frequency-zonal wavenumber. Each of the components for each field is then projected onto the different equatorial modes using the y structures of these modes given by the theory. The latitudinal scale y o of the modes is predetermined by data to fit the equatorial trapping in a suitable latitude belt y Y. The extent to which the different dynamical fields are consistent with one another in their depiction of each equatorial wave structure determines the confidence in the reality of that structure. Comparison of the analyzed modes with the eastward-and westward-moving components in the convection field enables the identification of the dynamical structure and nature of convectively coupled equatorial waves.