Characterizing Equatorial waves in the Atmosphere under different mean states

Abstract

Convectively coupled equatorial waves serves as the primary source of information for understanding the highly coupled ocean-atmosphere system. Since the spatiotemporal scales of equatorial waves fall conveniently between those of weather and climate, they can influence both the scales. In this study we plan to focus on the effect of mean states on equatorial waves to better understand the interaction of equatorial waves with weather and climate scales under different background conditions. They study may provide important insight on equatorial wave dynamics in a warming environment. Chapter 1: Space time spectral analysis was performed on daily OLR and U850 data to identify the spectral signatures of equatorial waves. Coherence-squared spectra was also performed on OLR with U850 to study the correlation between the equatorial wave signals in OLR and U850. Further wave-filtered OLR was used to locate the active regions of equatorial wave activity. Preferential peaking of equatorial wave activities during different phases of ENSO was identified. Chapter 2: Vertical propagation of equatorial waves under different background states was studied. Linear regression technique and Empirical Orthogonal Function analysis were used to identify the convective patterns of equatorial waves. Preferential vertical propagation of equatorial waves during different phases of QBO was identified. Chapter 3: OLR, U850 and U200 data from five global climate models that efficiently simulate MJO are compared with observation results to observe how well these models simulate convectively coupled equatorial waves in the troposphere, using the same analysis performed in Chapter 1.