Details:

Journal Title:
Atmosphere
Personal Author:
Teruya, Andre S. W. ; Raphaldini, Breno ; Mayta, Victor C. ; Raupp, Carlos F. M. ; da Silva Dias, Pedro L.
Teruya, Andre S. W. ; Raphaldini, Breno ; Mayta, Victor C. ; Raupp, Carlos F. M. ; da Silva Dias, Pedro L. Less -
NOAA Program & Office:
OAR (Oceanic and Atmospheric Research)
Description:
The study of tropical tropospheric disturbances has led to important challenges from both observational and theoretical points of view. In particular, the observed wavenumber-frequency spectrum of tropical oscillations has helped bridge the gap between observations and the linear theory of equatorial waves. In this study, we obtained a similar wavenumber-frequency spectrum for each equatorial wave type by performing a normal mode function (NMF) decomposition of global Era–Interim reanalysis data. The NMF basis used here is provided by the eigensolutions of the primitive equations in spherical coordinates as linearized around a resting background state. In this methodology, the global multi-level horizontal velocity and geopotential height fields are projected onto the normal mode functions, characterized by a vertical mode, a zonal wavenumber, a meridional quantum index, and a mode type, namely, Rossby, Kelvin, mixed Rossby-gravity, and westward/eastward propagating inertio-gravity modes. The horizontal velocity and geopotential height fields associated with each mode type are then reconstructed in the physical space, as well as their corresponding filtered versions defined according to the vertical mode classes that exhibit barotropic and baroclinic structures within the troposphere. The results reveal expected structures, such as the dominant global-scale Rossby and Kelvin waves constituting the intraseasonal frequency associated with the Madden–Julian Oscillation. On the other hand, a number of unexpected features, such as eastward propagating westward inertio-gravity waves, are revealed by our observed 200 hPa zonal wind spectrum. Among all possible nonlinear processes, we focus on the analysis of the interaction between Kelvin and westward inertio-gravity waves, providing evidence for their coupling. Apart from the nonlinearity, we discuss the potential roles of a vertically/meridionally varying background state as well as the coupling with moist convection in explaining the departures of the observed spectra from the corresponding linear equatorial wave theory.
Keywords:
[+]
Atmospheric Science Environmental Science (miscellaneous)
Source:
Atmosphere, 14(4), 622
DOI:
https://doi.org/10.3390/atmos14040622
ISSN:
2073-4433
Format:
PDF
Publisher:
MDPI AG
Document Type:
Journal Article
Funding:
Grant no. NA22OAR4310611
License:
https://creativecommons.org/licenses/by/4.0/
Rights Information:
CC BY
Compliance:
Library
Main Document Checksum:
[+]
urn:sha256:f5e82ed640b727a023badfbbbafde491b4affc4199f4972fc54cf3fa71a3d6f4
Download URL:
https://repository.library.noaa.gov/view/noaa/58747/noaa_58747_DS1.pdf
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