Convectively Coupled Kelvin Waves over Tropical South America Region

Rainfall over the Amazon is known to both modulated by and also trigger convectively coupled Kelvin waves. In this work, the origin of South American Kelvin waves is revisited by analyzing empirical orthogonal functions (EOFs) of 4 times daily Kelvin-filtered brightness temperature over different tropical during boreal spring,

Consistent with prior studies, two main types of Kelvin waves over tropical South America are detected: Kelvin waves with a Pacific precursor that propagates into South America and Kelvin waves with a South American precursor. The events with precursors in the eastern Pacific account for about 45% of the total events. The cases with South America precursor are associated with either pressure surges from extratropical wave trains activity (“pressure surges”) or “in situ” convection that locally excites Kelvin waves. Kelvin waves associated with pressure surges are responsible for 32% of total events. Interestingly, only 30% of these extratropical disturbances that reach the equatorial region develop into a Kelvin wave.

To advance our understanding of forcing mechanisms related to the various types of Kelvin waves over tropical South America, a comprehensive analysis of their vertical structure, propagation characteristics and potential interactions with the basic state is presented.