Large-Scale Dynamical Fields Associated with Convectively Coupled Equatorial Waves

2000 ◽  
Vol 57 (5) ◽  
pp. 613-640 ◽  
Author(s):  
Matthew Wheeler ◽  
George N. Kiladis ◽  
Peter J. Webster
Keyword(s):  
Large Scale ◽  
Equatorial Waves ◽  
Convectively Coupled Equatorial Waves

The Diurnal Cycle of Rainfall and the Convectively Coupled Equatorial Waves over the Maritime Continent

2020 ◽  
Vol 33 (8) ◽  
pp. 3307-3331 ◽  
Author(s):  
Naoko Sakaeda ◽  
George Kiladis ◽  
Juliana Dias
Keyword(s):  
Diurnal Cycle ◽  
Large Scale ◽  
Vertical Motion ◽  
Equatorial Waves ◽  
Maritime Continent ◽  
Moisture Profile ◽  
Convectively Coupled Equatorial Waves ◽  
Large Scale Disturbance ◽  
Diurnal Rainfall ◽  
Equatorial Rossby Waves

AbstractPrecipitation variability over the Maritime Continent is predominantly explained by its diurnal cycle and large-scale disturbances such as the Madden–Julian oscillation (MJO) and convectively coupled equatorial waves (CCEWs). To advance our understanding of their interactions and physical processes, this study uses satellite data to examine changes in the diurnal cycle of rainfall associated with the MJO and CCEWs over the Maritime Continent. We find that diurnal cycle modulations associated with the passage of any type of large-scale disturbance are closely tied to changes in rain types and land–sea diurnal propagation of rainfall. When the amplitude of the diurnal cycle increases over the islands, the phase of the diurnal cycle is delayed by a few hours as clouds are more organized and rainfall from stratiform-anvil clouds increases. Enhanced amplitude of the diurnal cycle can alter the speed of land–sea diurnal propagation of rainfall, which then influences the timing of diurnal rainfall over coastal regions. These changes in the diurnal cycle occur asymmetrically across the island terrain associated with the MJO and equatorial Rossby waves, while such asymmetric modulations are not observed for other waves. Geographical and wave dependencies of the diurnal cycle are linked to differences in large-scale lower tropospheric wind, vertical motion, and moisture profile perturbations, which are in turn tied to differences in cloud population evolution. The results of this study highlight the importance of further improving our understanding of the sensitivity of cloud populations to varying large-scale phenomena.

The influence of observations propagated by convectively coupled equatorial waves

2011 ◽  
Vol 137 (656) ◽  
pp. 641-655 ◽  
Author(s):  
Qoosaku Moteki ◽  
Kunio Yoneyama ◽  
Ryuichi Shirooka ◽  
Hisayuki Kubota ◽  
Kazuaki Yasunaga ◽  
...  
Keyword(s):  
Equatorial Waves ◽  
Convectively Coupled Equatorial Waves

scholarly journals Convectively Coupled Equatorial Waves. Part I: Horizontal and Vertical Structures

2007 ◽  
Vol 64 (10) ◽  
pp. 3406-3423 ◽  
Author(s):  
Gui-Ying Yang ◽  
Brian Hoskins ◽  
Julia Slingo
Keyword(s):  
Composite Structures ◽  
Wave Structure ◽  
Wave Theory ◽  
Western Hemisphere ◽  
Equatorial Waves ◽  
Kelvin Wave ◽  
Ambient Flow ◽  
Convectively Coupled Equatorial Waves ◽  
Eastern Hemisphere ◽  
Equatorial Wave

Abstract Multilevel 15-yr ECMWF Re-Analysis (ERA-15) and satellite-observed brightness temperature (Tb) data for the period May–October 1992 are used to examine the horizontal and vertical structures of convectively coupled equatorial waves. Dynamical waves are isolated using a methodology developed previously. Composite structures of convectively coupled equatorial waves are obtained using linear regression/correlation between convection (Tb) and dynamical structures. It is found that the relationship depends on the ambient flow and the nature of the convective coupling, and varies between off-equatorial- and equatorial-centered convection, different hemispheres, and seasons. The Kelvin wave structure in the Western Hemisphere is generally consistent with classic equatorial wave theory and has its convection located in the region of low-level convergence. In the Eastern Hemisphere the Kelvin wave tends to have convection in the region of enhanced lower-tropospheric westerlies and a tilted vertical structure. The Kelvin wave also tends to have a third peak in zonal wind amplitude at 500 hPa and exhibits upward propagation into the lower stratosphere. Lower-tropospheric westward-moving mixed Rossby–gravity (WMRG) and n = 1 Rossby (R1) wave structures and their relationship with convection are consistent with classic equatorial wave theory and the implied lower-tropospheric convergences. In the Eastern Hemisphere the WMRG and R1 waves have first baroclinic mode structures in the vertical. However, in the Western Hemisphere, the R1 wave has a barotropic structure. In the Eastern Hemisphere the R1 wave, like the Kelvin wave, tends to have equatorial convection in the region of enhanced lower-level westerlies, suggesting that enhanced surface energy fluxes associated with these waves may play an important organizing role for equatorial convection in this warm-water hemisphere. In the upper troposphere, eastward-moving Rossby–gravity (EMRG) and n = 1 gravity waves are found in the Eastern Hemisphere, and eastward-moving WMRG and R1 waves are found in the Western Hemisphere, suggestive of Doppler shifting of waves by the ambient flow.

Uncertainties of Estimates of Inertia–Gravity Energy in the Atmosphere. Part II: Large-Scale Equatorial Waves

2009 ◽  
Vol 137 (11) ◽  
pp. 3858-3873 ◽  
Author(s):  
N. Žagar ◽  
J. Tribbia ◽  
J. L. Anderson ◽  
K. Raeder
Keyword(s):  
Large Scale ◽  
Normal Modes ◽  
Lower Troposphere ◽  
Physical Space ◽  
Significant Degree ◽  
Hadley Cell ◽  
Equatorial Waves ◽  
Kelvin Wave ◽  
Energy Propagation ◽  
Zonal Wavenumber

Abstract This paper analyzes the spectra and spatiotemporal features of the large-scale inertia-gravity (IG) circulations in four analysis systems in the tropics. Of special interest is the Kelvin wave (KW), which represents between 7% and 25% of the total IG wave (zonal wavenumber k ≠ 0) energy. The mixed Rossby–gravity (MRG) mode comprises between 4% and 15% of the IG wave energy. At the longest scales, the KW spectra are fitted by a law while the MRG energy spectrum appears flat. At shorter scales both modes follow a −3 law. Energy spectra of the total IG wave motion at long zonal scales (zonal wavenumber smaller than 7) have slopes close to −1. The average circulation associated with KW is characterized by reverse flows in the upper and lower troposphere consistent with the ideas behind simple tropical models. The inverse projection is used to quantify the role of Kelvin and MRG waves in current analysis systems in the upper troposphere over the Indian Ocean. At these levels, easterlies between 10°S and 30°N are represented by the KW to a significant degree while the cross-equatorial flow toward the descending branch of the Hadley cell at 10°S is associated with the MRG waves. The transient structure of equatorial waves is presented in the space of normal modes defined by the zonal wavenumbers, meridional Hough functions, and the vertical eigenfunctions. The difference in the depth of the model domain in DART–CAM and NCEP–NCAR on one hand and ECMWF and NCEP on the other appears to be one reason for different wave propagation properties. In the latter case the vertical energy propagation is diagnosed by filtering the propagating KW modes back to physical space. The results agree with the linear theory of vertically propagating equatorial waves.

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