Abstract
Characteristics of atmospheric equatorial Kelvin waves and mixed Rossby-Gravity (MRG) waves as well as their relationship with tropical convective activity associated with El Niño-Southern Oscillation (ENSO) were analyzed. Kelvin waves and MRG waves were identified by using a Space-Time Spectral Analysis (STSA) technique, where the differences in the strength of both waves were quantified by taking the wave spectrum differences for each ENSO phase. Our result showed that Kelvin wave activity is stronger during an El Nino years, whereas the MRG wave activity is stronger during the La Nina years. Seasonal variations of Kelvin wave activity occurs predominantly in MAM over the central to the east Pacific in the El Nino years, while the strongest seasonal variation of MRG wave activity occus in MAM and SON over the northern and southern Pacific during La Nina years. The local variation of Kelvin wave and MRG wave activities are found to be controlled by variation in lower level atmospheric convection induced by sea surface temperature in the tropical Pacific Ocean.
Highlights
Equatorial planetary waves (EPW) are one of the dominant modes of synoptic-to-subseasonal variability in the tropics
We have examined the impact of El Niño-Southern Oscillation (ENSO) on seasonal variation of Kelvin waves and Mixed Rossby-Gravity (MRG) waves by using National Oceanic and Atmospheric Administration (NOAA) outgoing longwave radiation (OLR) dataset and sea surface temperature anomalies (SST)
The Kelvin waves ad MRG waves have been isolated by using space-time spectral analysis (STSA) and composite analysis
Summary
Equatorial planetary waves (EPW) are one of the dominant modes of synoptic-to-subseasonal variability in the tropics. They are generated by diabatic heating due to organized tropical large-scale convective heating in the equatorial belt [1][2][3]. EPW causes predominant disturbances in the equatorial atmosphere such as inducing mean-meridional circulation that is important for the heat balance of the equatorial belt [4][5], affecting the patterns of low level moisture convergence, and controling the distribution of tropical convective heating and storms in large longitudinal distances [4]. Two dominant atmospheric equatorial waves has an important role in the region is equatorial Kelvin waves and Mixed RossbyGravity (MRG) waves. In this study our analysis will focus on understanding the nature of Kelvin waves and MRG waves during ENSO events
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