Zonal wavenumber
In meteorological applications, a zonal wavenumber or hemispheric wavenumber is the dimensionless number of wavelengths fitting within a full circle around the globe at a given latitude.[1]
![](../I/500mb_geopotential_height_wavenumber_4_Rossby_wave_(planetary_waves)_pattern._October_9-21%252C_2010_daily_average.jpg.webp)
500mb geopotential height averaged between October 9–21, 2010 illustrating Rossby wave pattern with the zonal wavenumber 4. DOE AMIP reanalysis data.
where λ is the wavelength, r is the Earth's radius, and is the latitude.
Zonal wavenumbers are typically counted on the upper level (say 500-millibar) geopotential maps by identifying troughs and ridges of the waves. Wavenumber 1 has one trough and one ridge, i.e. one wavelength fits degrees. Wavenumber 2 has two ridges and two troughs around 360 degrees.
Wavenumber 0 corresponds to zonal (symmetric) flow. Wavenumbers 1–6 are called long waves and often synonymous in meteorological literature with the mid-latitude planetary Rossby waves.
See also
References
- "AMS Glossary". Glossary.ametsoc.org. 2015-07-28. Retrieved 2016-12-01.
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