Journal ArticleDOI
Convectively Coupled Equatorial Waves: Analysis of Clouds and Temperature in the Wavenumber–Frequency Domain
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In this article, a wavenumber-frequency spectrum analysis is performed for all longitudes in the domain 158S−158N using a long (;18 years) twice-daily record of satellite-observed outgoing longwave radiation (OLR), a good proxy for deep tropical convection.Abstract:
A wavenumber-frequency spectrum analysis is performed for all longitudes in the domain 158S‐158N using a long (;18 years) twice-daily record of satellite-observed outgoing longwave radiation (OLR), a good proxy for deep tropical convection. The broad nature of the spectrum is red in both zonal wavenumber and frequency. By removing an estimated background spectrum, numerous statistically significant spectral peaks are isolated. Some of the peaks correspond quite well to the dispersion relations of the equatorially trapped wave modes of shallow water theory with implied equivalent depths in the range of 12‐50 m. Cross-spectrum analysis with the satellite-based microwave sounding unit deep-layer temperature data shows that these spectral peaks in the OLR are ‘‘coupled’’ with this dynamical field. The equivalent depths of the convectively coupled waves are shallower than those typical of equatorial waves uncoupled with convection. Such a small equivalent depth is thought to be a result of the interaction between convection and the dynamics. The convectively coupled equatorial waves identified correspond to the Kelvin, n 5 1 equatorial Rossby, mixed Rossby-gravity, n 5 0 eastward inertiogravity, n 5 1 westward inertio-gravity (WIG), and n 5 2 WIG waves. Additionally, the Madden‐Julian oscillation and tropical depression-type disturbances are present in the OLR spectra. These latter two features are unlike the convectively coupled equatorial waves due to their location away from the equatorial wave dispersion curves in the wavenumber-frequency domain. Extraction of the different convectively coupled disturbances in the time‐longitude domain is performed by filtering the OLR dataset for very specific zonal wavenumbers and frequencies. The geographical distribution of the variance of these filtered data gives further evidence that some of the spectral peaks correspond to particular equatorial wave modes. The results have implications for the cumulus parameterization problem, for the excitation of equatorial waves in the lower stratosphere, and for extended-range forecasting in the Tropics.read more
Citations
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Journal ArticleDOI
Madden-Julian Oscillation analog and intraseasonal variability in a multicloud model above the equator
TL;DR: An MJO analog is produced by using the recent multicloud model of Khouider and Majda in an appropriate intraseasonal parameter regime for flows above the equator so that rotation is ignored.
Journal ArticleDOI
Synoptic variability of the monsoon flux over West Africa prior to the onset
Fleur Couvreux,Françoise Guichard,Olivier Bock,B. Campistron,Jean-Philippe Lafore,Jean-Luc Redelsperger +5 more
TL;DR: In this paper, the authors investigated the synoptic variability of the monsoon flux during the establishment of the West African monsoon using observations and ECMWF analyses, highlighting variability at a 3-5-day time scale.
Book ChapterDOI
The Influence of Natural Climate Variability on Tropical Cyclones, and Seasonal Forecasts of Tropical Cyclone Activity
Journal ArticleDOI
Observed Structure of Convectively Coupled Waves as a Function of Equivalent Depth: Kelvin Waves and the Madden–Julian Oscillation
TL;DR: In this article, the view that convectively coupled Kelvin waves and the Madden-Julian oscillation (MJO) are distinct modes is tested by regressing data from the Climate Forecast System Reanalysis against satellite outgoing longwave radiation data filtered for particular zonal wavenumbers and frequencies by wavelet analysis.
Journal ArticleDOI
Temperature and tropopause characteristics from reanalyses data in the tropical tropopause layer
Susann Tegtmeier,James Anstey,Sean M. Davis,Rossana Dragani,Yayoi Harada,Ioana Ivanciu,Robin Pilch Kedzierski,Kirstin Krüger,Bernard Legras,Craig S. Long,James S. Wang,Krzysztof Wargan,Jonathon S. Wright +12 more
TL;DR: In this paper, the authors presented an evaluation of the tropical tropopause layer (TTL) and its characteristics in the reanalysis data sets ERA-Interim, ERA5, JRA-25, ERA-55, MERRA-2, NCEP-NCAR (R1), and CFSR.
References
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Journal ArticleDOI
The NCEP/NCAR 40-Year Reanalysis Project
Eugenia Kalnay,Masao Kanamitsu,Robert Kistler,William D. Collins,D.G. Deaven,L. S. Gandin,M. Iredell,Suranjana Saha,Glenn H. White,John S. Woollen,Yuejian Zhu,Muthuvel Chelliah,Wesley Ebisuzaki,Wayne Higgins,John E. Janowiak,Kingtse C. Mo,Chester F. Ropelewski,Julian X. L. Wang,Ants Leetmaa,Richard W. Reynolds,Roy L. Jenne,Dennis Joseph +21 more
TL;DR: The NCEP/NCAR 40-yr reanalysis uses a frozen state-of-the-art global data assimilation system and a database as complete as possible, except that the horizontal resolution is T62 (about 210 km) as discussed by the authors.
Journal ArticleDOI
Quasi-geostrophic motions in the equatorial area
TL;DR: In this article, a single layer of homogeneous incompressible fluid with free surface is treated, where the Coriolis parameter is assumed to be proportional to the latitude, and a strong east-west current was formed along the equator.
Journal ArticleDOI
Observations of the 40-50-day tropical oscillation - a review
Roland A. Madden,Paul R. Julian +1 more
TL;DR: The 40-50-day cyclone oscillation is the result of large-scale circulation cells oriented in the equatorial plane that move eastward from at least the Indian Ocean to the central Pacific as discussed by the authors.
Journal ArticleDOI
TOGA COARE: The Coupled Ocean-Atmosphere Response Experiment.
Peter J. Webster,Roger Lukas +1 more
TL;DR: In this article, the authors present a simulation of the western Pacific warm pool, the region of the warmest sea surface temperature in the open oceans, which coexists with the largest annual precipitation and latent heat release in the atmosphere.