Equatorial modes observed in atmospheric variables

Kiranmayi, L. ; Bhat, G. S. (2009) Equatorial modes observed in atmospheric variables Journal of Earth System Science, 118 (3). pp. 181-192. ISSN 0253-4126

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Official URL: http://www.ias.ac.in/jess/jun2009/jed9-05.pdf

Related URL: http://dx.doi.org/10.1007/s12040-009-0015-8


Wavenumber-frequency spectral analysis of different atmospheric variables has been carried out using 25 years of data. The area considered is the tropical belt 25°S - 25° N. A combined FFT-wavelet analysis method has been used for this purpose. Variables considered are outgoing long-wave radiation (OLR), 850 hPa divergence, zonal and meridional winds at 850, 500 and 200 hPa levels, sea level pressure and 850 hPa geopotential height. It is shown that the spectra of different variables have some common properties, but each variable also has few features different from the rest. While Kelvin mode is prominent in OLR and zonal winds, it is not clearly observed in pressure and geopotential height fields; the latter two have a dominant wavenumber zero mode not seen in other variables except in meridional wind at 200 hPa and 850 hPa divergences. Different dominant modes in the tropics show significant variations on sub-seasonal time scales.

Item Type:Article
Source:Copyright of this article belongs to Indian Academy of Sciences.
Keywords:Tropical Intraseasonal Oscillation; Equatorial Modes; MJO; Equatorial Wave Theory
ID Code:2496
Deposited On:08 Oct 2010 07:09
Last Modified:16 May 2016 13:29

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