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Bin Wang - One of the best experts on this subject based on the ideXlab platform.
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Circulation Factors Determining the Propagation Speed of the Madden–Julian Oscillation
Journal of Climate, 2020Co-Authors: Guosen Chen, Bin WangAbstract:ABSTRACTThe eastward propagating Madden–Julian Oscillation (MJO) events exhibit various speeds ranging from 1 to 9 m s−1, but what controls the propagation speed remains elusive. This study attempt...
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Diversity of the Madden-Julian Oscillation
2020Co-Authors: Guosen Chen, Bin WangAbstract:<p>Madden-Julian Oscillation (MJO) is the dominant mode of atmospheric intraseasonal variability and the cornerstone for subseasonal prediction of extreme weather events. Climate modeling and prediction of MJO remain a big challenge, partially due to lack of understanding the MJO diversity. Here, we delineate observed MJO diversity by cluster analysis of propagation patterns of MJO events, which reveals four archetypes: standing, jumping, slow eastward propagation, and fast eastward propagation. Each type of MJO exhibits distinctive east-west asymmetric circulation and thermodynamic structures. Tight coupling between the Kelvin wave response and major convection is unique for the propagating events (slow and fast propagations), while the strength and length of Kelvin wave response distinguish slow and fast propagations. The Pacific sea surface temperature anomalies can affect MJO diversity by modifying the Kelvin wave response and its coupling to MJO convection. An El Ni&#241;o state tends to increase the zonal scale of Kelvin wave response, to amplify it, and to enhance its coupling to the convection, while a La Ni&#241;a state tends to decrease the zonal scale of Kelvin wave response, to suppress it, and to weaken its coupling to the major convection. This effect of background sea surface temperature on the MJO diversity has been verified by using a theoretical model. The results shed light on the mechanisms responsible for MJO diversity and provide potential precursors for foreseeing MJO propagation.</p>
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Diversity of the Madden-Julian Oscillation
Science Advances, 2019Co-Authors: Bin Wang, Guosen ChenAbstract:Madden-Julian Oscillation (MJO) is the dominant mode of atmospheric intraseasonal variability and the cornerstone for subseasonal prediction of extreme weather events. Climate modeling and prediction of MJO remain a big challenge, partially due to lack of understanding the MJO diversity. Here, we delineate observed MJO diversity by cluster analysis of propagation patterns of MJO events, which reveals four archetypes: standing, jumping, slow eastward propagation, and fast eastward propagation. Each type exhibits distinctive east-west asymmetric circulation and thermodynamic structures. Tight coupling between the Kelvin wave response and major convection is unique for the propagating events, while the strength and length of Kelvin wave response distinguish slow and fast propagations. The Pacific sea surface temperature anomalies can affect MJO diversity by modifying the Kelvin wave response and its coupling to MJO convection. The results shed light on the mechanisms responsible for MJO diversity and provide potential precursors for foreseeing MJO propagation.
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Dynamics-Oriented Diagnostics for the Madden–Julian Oscillation
Journal of Climate, 2018Co-Authors: Bin Wang, Duane E. Waliser, Eric D. Maloney, Tim Li, Xianan Jiang, Chidong Zhang, Adam H. Sobel, Kyung-ja HaAbstract:AbstractRealistic simulations of the Madden-Julian Oscillation (MJO) by global climate models (GCMs) remain a great challenge. To evaluate GCM simulations of the MJO, the U.S. CLIVAR MJO Working Group developed a standardized set of diagnostics, providing a comprehensive assessment of statistical properties of the MJO. Here, we develop a suite of complementary diagnostics that provide discrimination and assessment of MJO simulations based on the perception that the MJO propagation has characteristic dynamic and thermodynamic structures. The new dynamics-oriented diagnostics help to evaluate whether a model produces eastward propagating MJO for the right reasons. The diagnostics include (1) the horizontal structure of boundary layer moisture convergence (BLMC) that moistens the lower troposphere to the east of convection center; (2) the preluding eastward propagation of BLMC that leads the propagation of MJO precipitation by about 5 days; (3) the horizontal structure of 850 hPa zonal wind and its equatoria...
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the madden julian Oscillation detected in aquarius salinity observations
Geophysical Research Letters, 2013Co-Authors: Gary Grunseich, Bulusu Subrahmanyam, Bin WangAbstract:[1] The Madden-Julian Oscillation (MJO) impacts a wide range of weather and climate phenomena. Current global coupled ocean-atmospheric general circulation models exhibit considerable shortcomings in representing and predicting the MJO, specifically its initiation, due to a lack of in situ observations. Here we show, for the first time, that the MJO propagation can be detected from the newly launched NASA Aquarius Salinity mission. The magnitude and extent of sea surface salinity (SSS) variations during the MJO is established, providing a useful tool for data assimilation into models to correctly represent both oceanic and atmospheric processes during intraseasonal variations. Salinity observation allows for atmospheric conditions to be inferred from freshwater flux, on which surface salinity is highly dependent. Increased observations of global SSS from the Aquarius mission will be particularly valuable in remote regions of the tropics and will increase our dynamical understanding and advance prediction of the MJO through model improvement.
Harry H. Hendon - One of the best experts on this subject based on the ideXlab platform.
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Stratospheric Control of the Madden–Julian Oscillation
Journal of Climate, 2017Co-Authors: Harry H. HendonAbstract:AbstractInterannual variation of seasonal-mean tropical convection over the Indo-Pacific region is primarily controlled by El Nino–Southern Oscillation (ENSO). For example, during El Nino winters, seasonal-mean convection around the Maritime Continent becomes weaker than normal, while that over the central to eastern Pacific is strengthened. Similarly, subseasonal convective activity, which is associated with the Madden–Julian Oscillation (MJO), is influenced by ENSO. The MJO activity tends to extend farther eastward to the date line during El Nino winters and contract toward the western Pacific during La Nina winters. However, the overall level of MJO activity across the Maritime Continent does not change much in response to the ENSO. It is shown that the boreal winter MJO amplitude is closely linked with the stratospheric quasi-biennial Oscillation (QBO) rather than with ENSO. The MJO activity around the Maritime Continent becomes stronger and more organized during the easterly QBO winters. The QBO-rela...
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Visualizing and verifying probabilistic forecasts of the Madden‐Julian Oscillation
Geophysical Research Letters, 2016Co-Authors: Andrew G. Marshall, Harry H. Hendon, Debra HudsonAbstract:We describe a new approach for presenting probabilistic forecasts of the Madden-Julian Oscillation (MJO) based on the community standard Real-time Multivariate MJO (RMM) index, using forecasts from version 2 of the Predictive Ocean Atmosphere Model for Australia. This new display overcomes the difficulty of interpreting a dispersive ensemble plume and directly quantifies the probability for the MJO to occur in each of its eight RMM-defined phases as well as the weak phase. Beyond monitoring and interpreting predictions of the MJO, this new approach also provides a basis for forecast verification using probability-based skill scores. Here we present a clear and concise quantitative summary of this innovative method for accessing probability of the state of the MJO in an ensemble forecast. This new method compliments the traditional MJO ensemble forecast display and verification and will benefit global forecasting centers, international MJO working groups, and the World Meteorological Organization Subseasonal to Seasonal Project.
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Empirical Extended-Range Prediction of the Madden–Julian Oscillation
Monthly Weather Review, 2000Co-Authors: Fiona Lo, Harry H. HendonAbstract:Abstract An empirical model that predicts the evolution of the Madden–Julian Oscillation (MJO) in outgoing longwave radiation (OLR) and 200-mb streamfunction is developed. The model is based on the assumption that the MJO can be well represented by a pair of empirical orthogonal functions (EOFs) of OLR and three EOFs of streamfunction. With an eye toward using this model in real time, these EOFs are determined with data only subjected to filtering that can be applied in near–real time. Stepwise lag regression is used to develop the model on 11 winters of dependent data. The predictands are the leading two principal components (PCs) of OLR and the leading three PCs of streamfunction. The model is validated with five winters of independent data and is also compared to dynamic extended range forecasts (DERFs) made with the National Centers for Environmental Prediction’s Medium Range Forecast (MRF) model. Skillful forecasts of the MJO in OLR and streamfunction with the empirical model are achieved out to abou...
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Interannual Variation of the Madden–Julian Oscillation during Austral Summer
Journal of Climate, 1999Co-Authors: Harry H. Hendon, Chidong Zhang, John D. GlickAbstract:Interannual variability of the Madden‐Julian Oscillation (MJO), the dominant mode of intraseasonal variability in the Tropics, is investigated during the extended austral summer season November‐March, which is when the MJO is most prominent. Indexes of the level of MJO activity are developed using outgoing longwave radiation and zonal wind analyses at 850 mb for 1974‐98. Based on these indexes, interannual variations in the level of MJO activity are found to be primarily associated with changes in the number of discrete MJO events each year and with changes in the intensity of intraseasonal convection across the Indian and western Pacific Oceans, where the MJO is normally prominent. An eastward shift of MJO activity east of the date line does occur during
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Oceanic Kelvin Waves and the Madden–Julian Oscillation
Journal of the Atmospheric Sciences, 1998Co-Authors: Harry H. Hendon, Brant Liebmann, John D. GlickAbstract:Abstract The relationship between the Madden–Julian Oscillation (MJO), the dominant mode of intraseasonal variability in the tropical troposphere, and the Kelvin waves that dominate the variability of the equatorial thermocline in the central and eastern Pacific Oceans is explored. The Kelvin waves have period near 70 days, which is distinctly longer than the dominant period of the MJO (40–50 days). Their zonal wavelength is roughly the width of the Pacific basin, which is about twice the zonal scale of the zonal stress anomalies produced by the MJO across the western Pacific. Their eastward phase speed is about 2.3 m s−1, which is indistinguishable from the gravest baroclinic mode using the observed stratification in the Pacific. The stress anomalies that force the Kelvin waves are shown to be associated with the lower-frequency components of the MJO (i.e., periods greater than about 60 days). These stress anomalies move eastward at less than 5 m s−1 from the Indian Ocean to the date line, where their lo...
Chidong Zhang - One of the best experts on this subject based on the ideXlab platform.
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Dynamics-Oriented Diagnostics for the Madden–Julian Oscillation
Journal of Climate, 2018Co-Authors: Bin Wang, Duane E. Waliser, Eric D. Maloney, Tim Li, Xianan Jiang, Chidong Zhang, Adam H. Sobel, Kyung-ja HaAbstract:AbstractRealistic simulations of the Madden-Julian Oscillation (MJO) by global climate models (GCMs) remain a great challenge. To evaluate GCM simulations of the MJO, the U.S. CLIVAR MJO Working Group developed a standardized set of diagnostics, providing a comprehensive assessment of statistical properties of the MJO. Here, we develop a suite of complementary diagnostics that provide discrimination and assessment of MJO simulations based on the perception that the MJO propagation has characteristic dynamic and thermodynamic structures. The new dynamics-oriented diagnostics help to evaluate whether a model produces eastward propagating MJO for the right reasons. The diagnostics include (1) the horizontal structure of boundary layer moisture convergence (BLMC) that moistens the lower troposphere to the east of convection center; (2) the preluding eastward propagation of BLMC that leads the propagation of MJO precipitation by about 5 days; (3) the horizontal structure of 850 hPa zonal wind and its equatoria...
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madden julian Oscillation bridging weather and climate
Bulletin of the American Meteorological Society, 2013Co-Authors: Chidong ZhangAbstract:The Madden–Julian Oscillation exerts broad influences on global weather and climate as its center of convection moves from the tropical Indian Ocean into the Pacific. Weather events under the influence of the MJO include precipitation, surface temperature, tropical cyclones, tornadoes, flood, wildfire, and lightning, among others. Several climate phenomena are also affected by the MJO. They are the monsoons, El Nino–Southern Oscillation, the North Atlantic Oscillation, the Pacific and North American pattern, the Arctic and Antarctic Oscillations or northern and southern annual modes, the Indian Ocean dipole, the Wyrtki jets, and the Indonesian Through-flow. This article provides a brief summary of the connections between the MJO and these weather and climate phenomena. These connections demonstrate the critical role of the MJO in the weather–climate continuum and its prediction.
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Madden–Julian Oscillation: Bridging Weather and Climate
Bulletin of the American Meteorological Society, 2013Co-Authors: Chidong ZhangAbstract:The Madden–Julian Oscillation exerts broad influences on global weather and climate as its center of convection moves from the tropical Indian Ocean into the Pacific. Weather events under the influence of the MJO include precipitation, surface temperature, tropical cyclones, tornadoes, flood, wildfire, and lightning, among others. Several climate phenomena are also affected by the MJO. They are the monsoons, El Nino–Southern Oscillation, the North Atlantic Oscillation, the Pacific and North American pattern, the Arctic and Antarctic Oscillations or northern and southern annual modes, the Indian Ocean dipole, the Wyrtki jets, and the Indonesian Through-flow. This article provides a brief summary of the connections between the MJO and these weather and climate phenomena. These connections demonstrate the critical role of the MJO in the weather–climate continuum and its prediction.
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Tracking Pulses of the Madden–Julian Oscillation
Bulletin of the American Meteorological Society, 2013Co-Authors: Kunio Yoneyama, Chidong Zhang, Charles N. LongAbstract:An international field campaign aiming at atmospheric and oceanic processes associated with the Madden–Julian Oscillation (MJO) was conducted in and around the tropical Indian Ocean during October 2011–March 2012. The objective of the field campaign was to collect observations urgently needed to expedite the progress of understanding the key processes of the MJO, focusing on its convective initiation but also including propagation and maturation, and ultimately to improve skills of numerical simulation and prediction of the MJO. Primary targets of the field campaign included interaction of atmospheric deep convection with its environmental moisture, evolution of cloud populations, and air– sea interaction. Several MJO events were captured by ground-based, airborne, and oceanic instruments with advanced observing technology. Numerical simulations and real-time forecasts were integrated components of the field campaign in its design and operation. Observations collected during the campaign provide unprecede...
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Potential Vorticity of the Madden–Julian Oscillation
Journal of the Atmospheric Sciences, 2012Co-Authors: Chidong Zhang, Jian LingAbstract:AbstractThis study explores the extent to which the dynamical structure of the Madden–Julian Oscillation (MJO), its evolution, and its connection to diabatic heating can be described in terms of potential vorticity (PV). The signature PV structure of the MJO is an equatorial quadrupole of cyclonic and anticyclonic PV that tilts westward and poleward. This PV quadrupole is closely related to positive and negative anomalies in precipitation that are in a swallowtail pattern extending eastward along the equator and splitting into off-equatorial branches westward. Two processes dominate the generation of MJO PV. One is linear, involving MJO diabatic heating alone. The other is nonlinear, involving diabatic heating and relative vorticity of perturbations spectrally outside the MJO domain but spatially constrained to the MJO convective envelope. The MJO is thus partially a self-sustaining system and partially a consequence of scale interaction of MJO-constrained stochastic processes. Convective initiation of th...
Gary Grunseich - One of the best experts on this subject based on the ideXlab platform.
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the madden julian Oscillation detected in aquarius salinity observations
Geophysical Research Letters, 2013Co-Authors: Gary Grunseich, Bulusu Subrahmanyam, Bin WangAbstract:[1] The Madden-Julian Oscillation (MJO) impacts a wide range of weather and climate phenomena. Current global coupled ocean-atmospheric general circulation models exhibit considerable shortcomings in representing and predicting the MJO, specifically its initiation, due to a lack of in situ observations. Here we show, for the first time, that the MJO propagation can be detected from the newly launched NASA Aquarius Salinity mission. The magnitude and extent of sea surface salinity (SSS) variations during the MJO is established, providing a useful tool for data assimilation into models to correctly represent both oceanic and atmospheric processes during intraseasonal variations. Salinity observation allows for atmospheric conditions to be inferred from freshwater flux, on which surface salinity is highly dependent. Increased observations of global SSS from the Aquarius mission will be particularly valuable in remote regions of the tropics and will increase our dynamical understanding and advance prediction of the MJO through model improvement.
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The Madden‐Julian Oscillation detected in Aquarius salinity observations
Geophysical Research Letters, 2013Co-Authors: Gary Grunseich, Bulusu Subrahmanyam, Bin WangAbstract:[1] The Madden-Julian Oscillation (MJO) impacts a wide range of weather and climate phenomena. Current global coupled ocean-atmospheric general circulation models exhibit considerable shortcomings in representing and predicting the MJO, specifically its initiation, due to a lack of in situ observations. Here we show, for the first time, that the MJO propagation can be detected from the newly launched NASA Aquarius Salinity mission. The magnitude and extent of sea surface salinity (SSS) variations during the MJO is established, providing a useful tool for data assimilation into models to correctly represent both oceanic and atmospheric processes during intraseasonal variations. Salinity observation allows for atmospheric conditions to be inferred from freshwater flux, on which surface salinity is highly dependent. Increased observations of global SSS from the Aquarius mission will be particularly valuable in remote regions of the tropics and will increase our dynamical understanding and advance prediction of the MJO through model improvement.
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Detection of the Madden–Julian Oscillation in the Indian Ocean From Satellite Altimetry
IEEE Geoscience and Remote Sensing Letters, 2013Co-Authors: Gary Grunseich, Bulusu SubrahmanyamAbstract:The role of air-sea interaction on Madden-Julian Oscillation (MJO) propagations across the tropical Indian Ocean is analyzed using integrated multimission satellite measurements of sea surface height and outgoing longwave radiation (OLR). MJO-related activity is observed in both parameters in the eastern equatorial Indian Ocean indicating a unique interaction in this region. In the eastern Indian Ocean, atmospheric conditions appear to aid in the creation of equatorial Rossby waves, while in the central and western Indian Ocean, different phases of oceanic Rossby wave propagations seem to have a strong influence on atmospheric conditions associated with the MJO. The downwelling phase of equatorial Rossby waves corresponds to a strengthening of OLR anomalies in extent and magnitude across the equatorial Indian Ocean, while the upwelling phase appears to weaken atmospheric MJO activity. This study improves climate research by identifying the MJO signal in altimetry data.
Bulusu Subrahmanyam - One of the best experts on this subject based on the ideXlab platform.
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the madden julian Oscillation detected in aquarius salinity observations
Geophysical Research Letters, 2013Co-Authors: Gary Grunseich, Bulusu Subrahmanyam, Bin WangAbstract:[1] The Madden-Julian Oscillation (MJO) impacts a wide range of weather and climate phenomena. Current global coupled ocean-atmospheric general circulation models exhibit considerable shortcomings in representing and predicting the MJO, specifically its initiation, due to a lack of in situ observations. Here we show, for the first time, that the MJO propagation can be detected from the newly launched NASA Aquarius Salinity mission. The magnitude and extent of sea surface salinity (SSS) variations during the MJO is established, providing a useful tool for data assimilation into models to correctly represent both oceanic and atmospheric processes during intraseasonal variations. Salinity observation allows for atmospheric conditions to be inferred from freshwater flux, on which surface salinity is highly dependent. Increased observations of global SSS from the Aquarius mission will be particularly valuable in remote regions of the tropics and will increase our dynamical understanding and advance prediction of the MJO through model improvement.
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The Madden‐Julian Oscillation detected in Aquarius salinity observations
Geophysical Research Letters, 2013Co-Authors: Gary Grunseich, Bulusu Subrahmanyam, Bin WangAbstract:[1] The Madden-Julian Oscillation (MJO) impacts a wide range of weather and climate phenomena. Current global coupled ocean-atmospheric general circulation models exhibit considerable shortcomings in representing and predicting the MJO, specifically its initiation, due to a lack of in situ observations. Here we show, for the first time, that the MJO propagation can be detected from the newly launched NASA Aquarius Salinity mission. The magnitude and extent of sea surface salinity (SSS) variations during the MJO is established, providing a useful tool for data assimilation into models to correctly represent both oceanic and atmospheric processes during intraseasonal variations. Salinity observation allows for atmospheric conditions to be inferred from freshwater flux, on which surface salinity is highly dependent. Increased observations of global SSS from the Aquarius mission will be particularly valuable in remote regions of the tropics and will increase our dynamical understanding and advance prediction of the MJO through model improvement.
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Detection of the Madden–Julian Oscillation in the Indian Ocean From Satellite Altimetry
IEEE Geoscience and Remote Sensing Letters, 2013Co-Authors: Gary Grunseich, Bulusu SubrahmanyamAbstract:The role of air-sea interaction on Madden-Julian Oscillation (MJO) propagations across the tropical Indian Ocean is analyzed using integrated multimission satellite measurements of sea surface height and outgoing longwave radiation (OLR). MJO-related activity is observed in both parameters in the eastern equatorial Indian Ocean indicating a unique interaction in this region. In the eastern Indian Ocean, atmospheric conditions appear to aid in the creation of equatorial Rossby waves, while in the central and western Indian Ocean, different phases of oceanic Rossby wave propagations seem to have a strong influence on atmospheric conditions associated with the MJO. The downwelling phase of equatorial Rossby waves corresponds to a strengthening of OLR anomalies in extent and magnitude across the equatorial Indian Ocean, while the upwelling phase appears to weaken atmospheric MJO activity. This study improves climate research by identifying the MJO signal in altimetry data.
