Global distribution of atmospheric waves in the equatorial uppertroposphere and lower stratosphere: AGCM simulation of sourcesand propagation

摘要

The global distribution, sources, and propagation of atmospheric waves in theequatorial upper troposphere and lower stratosphere were investigated using anatmospheric general circulation model with T 1 06L60 resolution (120-km horizontaland 550-m vertical resolution). The quasibiennial oscillation (QBO) with a period of–1.5-2 years was simulated well without gravity wave drag parameterization. Thezonal wave number versus the frequency spectra of simulated precipitation representrealistic signals of convectively coupled equatorial trapped waves (EQWs). Thetemperature spectra in the stratosphere also indicate dominant signals of EQWs. EQWswith equivalent depths in the range of 8-90 m from the n = –1 mode to n = 2 modewere extracted separately. Each EQW in the stratosphere generally corresponded wellwith the source of each convectively coupled EQW activity in the troposphere. Thepropagations of Kelvin waves and n = 0 eastward/westward propagating EQWs arestrongly influenced by the Walker circulation and the phase of the QBO. Potentialenergy associated with EQWs is generally larger in the westerly than in the easterlyshear phase of the QBO. EQWs with vertical wavelengths < 7 km contribute up to–30% of total potential energy < 7 km over the equator at an altitude of 20-30 krn.Gravity waves generated by cumulus convection with periods < 24 h are clearly visibleover areas of Africa, the Amazon, and around Indonesia, and result in localized PEdistributions in areas short distances from the source region. Comparisons of the modelresults and recent satellite observations are discussed.