Imperial College London
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Professor SirBrianHoskins

Faculty of Natural Sciences, The Grantham Institute for Climate Change

Visiting Professor (Chair of Grantham Institute)
 
 
 
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Contact

 

+44 (0)20 7594 9667b.hoskins

 
 
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Assistant

 

Ms Gosia Gayer +44 (0)20 7594 9666

 
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Location

 

Electrical EngineeringSouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@article{Hoskins:2016:10.1175/JAS-D-15-0167.1,
author = {Hoskins, BJ and Yang, G-Y},
doi = {10.1175/JAS-D-15-0167.1},
journal = {Journal of the Atmospheric Sciences},
pages = {605--620},
title = {The Longitudinal Variation of Equatorial Waves due to Propagation on a Varying Zonal Flow},
url = {http://dx.doi.org/10.1175/JAS-D-15-0167.1},
volume = {73},
year = {2016}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - The general 1D theory of waves propagating on a zonally varying flow is developed from basic wave theory, and equations are derived for the variation of wavenumber and energy along ray paths. Different categories of behavior are found, depending on the sign of the group velocity cg and a wave property B. For B positive, the wave energy and the wavenumber vary in the same sense, with maxima in relative easterlies or westerlies, depending on the sign of cg. Also the wave accumulation of Webster and Chang occurs where cg goes to zero. However, for B negative, they behave in opposite senses and wave accumulation does not occur. The zonal propagation of the gravest equatorial waves is analyzed in detail using the theory. For nondispersive Kelvin waves, B reduces to 2, and an analytic solution is possible. For all the waves considered, B is positive, except for the westward-moving mixed Rossby–gravity (WMRG) wave, which can have negative B as well as positive B.Comparison is made between the observed climatologies of the individual equatorial waves and the result of pure propagation on the climatological upper-tropospheric flow. The Kelvin wave distribution is in remarkable agreement, considering the approximations made. Some aspects of the WMRG and Rossby wave distributions are also in qualitative agreement. However, the observed maxima in these waves in the winter westerlies in the eastern Pacific and Atlantic Oceans are generally not in accord with the theory. This is consistent with the importance of the sources of equatorial waves in these westerly duct regions due to higher-latitude wave activity.
AU  - Hoskins,BJ
AU  - Yang,G-Y
DO  - 10.1175/JAS-D-15-0167.1
EP  - 620
PY  - 2016///
SN  - 1520-0469
SP  - 605
TI  - The Longitudinal Variation of Equatorial Waves due to Propagation on a Varying Zonal Flow
T2  - Journal of the Atmospheric Sciences
UR  - http://dx.doi.org/10.1175/JAS-D-15-0167.1
UR  - http://hdl.handle.net/10044/1/40173
VL  - 73
ER  -
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