Jump to content

Zonal wavenumber

From Wikipedia, the free encyclopedia
500mb geopotential height averaged between October 9–21, 2010 illustrating Rossby wave pattern with the zonal wavenumber 4. DOE AMIP reanalysis data.

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]

where λ is the wavelength, r = 6378 km 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 2π = 360°. Wavenumber 2 has two ridges and two troughs around 360°.

Wavenumber 0 corresponds to zonal (symmetric) flow. Wavenumbers 1–3 are called long waves and are often synonymous in meteorological literature with the mid-latitude planetary Rossby waves, while wavenumbers 4–10 are often referred to as "synoptic" waves.[2] In the Northern Hemisphere, wavenumbers 1 and 2 are important for the time-mean circulation due to topography (Tibetan Plateau and Rocky Mountains),[3][4] whereas in the Southern Hemisphere, tropical convection is responsible for the presence of mainly zonal wavenumber 3.[5]


See also

[edit]

References

[edit]
  1. ^ "AMS Glossary". Glossary.ametsoc.org. 2015-07-28. Retrieved 2016-12-01.
  2. ^ Vallis, Geoffrey K (2006). Atmospheric and Oceanic Fluid Dynamics - Fundamentals and Large-scale Circulation. Cambridge, UK: Cambridge University Press. ISBN 9780521849692.
  3. ^ Held, I; Ting, M; Wang, H (2002). "Northern winter stationary waves: Theory and modeling". Journal of Climate. 15 (16): 2125–2144. Bibcode:2002JCli...15.2125H. doi:10.1175/1520-0442(2002)015<2125:NWSWTA>2.0.CO;2.
  4. ^ Garfinkel, C; White, I; Gerber, E; Jucker, M; Erez, M (2020). "The building blocks of Northern Hemisphere wintertime stationary waves". Journal of Climate. 33 (13): 5611–5633. Bibcode:2020JCli...33.5611G. doi:10.1175/JCLI-D-19-0181.1. S2CID 214141950.
  5. ^ Goyal, Rishav; Jucker, Martin; Sen Gupta, Alex; Hendon, Harry; England, Matthew (2021). "Zonal wave 3 pattern in the Southern Hemisphere generated by tropical convection". Nature Geoscience. 14 (10): 732–738. Bibcode:2021NatGe..14..732G. doi:10.1038/s41561-021-00811-3. hdl:1959.4/unsworks_79009. S2CID 237310074.