Global S&T Development Trend Analysis Platform of Resources and Environment
DOI | 10.1175/JAS-D-17-0184.1 |
Linking African Easterly Wave Activity with Equatorial Waves and the Influence of Rossby Waves from the Southern Hemisphere | |
Yang, Gui-Ying1,2; Methven, John2; Woolnough, Steve1,2; Hodges, Kevin2; Hoskins, Brian2 | |
2018-06-01 | |
发表期刊 | JOURNAL OF THE ATMOSPHERIC SCIENCES |
ISSN | 0022-4928 |
EISSN | 1520-0469 |
出版年 | 2018 |
卷号 | 75期号:6页码:1783-1809 |
文章类型 | Article |
语种 | 英语 |
国家 | England |
英文摘要 | A connection is found between African easterly waves (AEWs), equatorial westward-moving mixed Rossby-gravity (WMRG) waves, and equivalent barotropic Rossby waves (RWs) from the Southern Hemisphere (SH). The amplitude and phase of equatorial waves is calculated by projection of broadband-filtered ERA-Interim data onto a horizontal structure basis obtained from equatorial wave theory. Mechanisms enabling interaction between the wave types are identified. AEWs are dominated by a vorticity wave that tilts eastward below the African easterly jet and westward above: the tilt necessary for baroclinic wave growth. However, a strong relationship is identified between amplifying vorticity centers within AEWs and equatorial WMRG waves. Although the waves do not phase lock, positive vorticity centers amplify whenever the cross-equatorial motion of the WMRG wave lies at the same longitude in the upper troposphere (southward flow) and east of this in the lower troposphere (northward flow). Two mechanisms could explain the vorticity amplification: vortex stretching below the upper-tropospheric divergence and ascent associated with latent heating in convection in the lower-tropospheric moist northward flow. In years of strong AEW activity, SH and equatorial upper-tropospheric zonal winds are more easterly. Stronger easterlies have two effects: (i) they Doppler shift WMRG waves so that their period varies little with wavenumber (3-4 days) and (ii) they enable westward-moving RWs to propagate into the tropical waveguide from the SH. The RW phase speeds can match those of WMRG waves, enabling sustained excitation of WMRG. The WMRG waves have an eastward group velocity with wave activity accumulating over Africa and invigorating AEWs at similar frequencies through the vorticity amplification mechanism. |
领域 | 地球科学 |
收录类别 | SCI-E |
WOS记录号 | WOS:000434942300003 |
WOS关键词 | ATLANTIC TROPICAL SYSTEMS ; WEST-AFRICA ; 3-DIMENSIONAL STRUCTURE ; PART II ; PROPAGATION ; DISTURBANCES ; CONVECTION ; VARIABILITY ; REANALYSIS ; HURRICANES |
WOS类目 | Meteorology & Atmospheric Sciences |
WOS研究方向 | Meteorology & Atmospheric Sciences |
引用统计 | |
文献类型 | 期刊论文 |
条目标识符 | http://119.78.100.173/C666/handle/2XK7JSWQ/29285 |
专题 | 地球科学 |
作者单位 | 1.Univ Reading, Natl Ctr Atmospher Sci, Reading, Berks, England; 2.Univ Reading, Dept Meteorol, Reading, Berks, England |
推荐引用方式 GB/T 7714 | Yang, Gui-Ying,Methven, John,Woolnough, Steve,et al. Linking African Easterly Wave Activity with Equatorial Waves and the Influence of Rossby Waves from the Southern Hemisphere[J]. JOURNAL OF THE ATMOSPHERIC SCIENCES,2018,75(6):1783-1809. |
APA | Yang, Gui-Ying,Methven, John,Woolnough, Steve,Hodges, Kevin,&Hoskins, Brian.(2018).Linking African Easterly Wave Activity with Equatorial Waves and the Influence of Rossby Waves from the Southern Hemisphere.JOURNAL OF THE ATMOSPHERIC SCIENCES,75(6),1783-1809. |
MLA | Yang, Gui-Ying,et al."Linking African Easterly Wave Activity with Equatorial Waves and the Influence of Rossby Waves from the Southern Hemisphere".JOURNAL OF THE ATMOSPHERIC SCIENCES 75.6(2018):1783-1809. |
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