Ocean Atmosphere Coupled Modes Of Decadal Variability In The Southern Hemisphere
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| Author | : Gang Wang |
| Publisher | : |
| Total Pages | : 171 |
| Release | : 2015 |
| Genre | : |
| ISBN | : |
The Southern Ocean has a critical influence on the global climate, and any long-term variability in the Southern Ocean can have both regional and global impacts significantly. However, sparse observations limit the study of the long-term variation. To test the quality of models simulating the natural sea surface temperature (SST) variability, the SST variability in the global oceans is evaluated in simulations of the Climate Model Intercomparison Project Phase 3 (CMIP3) and CMIP5 models. The result shows that some models demonstrate good skill in simulating the observed spatial structure of the SST variability in the tropical domains and less so in the extra-tropical domains. The CMIP5 ensemble exhibits some improvement over the CMIP3 ensemble, mostly in the tropical domains on SST variability simulation. Further, the spatial structure of the SST modes of the CMIP3 and CMIP5 super ensemble is more realistic than any single model, which is mostly used for the following study. Several SST leading modes in the Southern Ocean are discussed on decadal and even larger time scales using CMIP5 data set based on EOF analysis. We compare the modes against several simple null hypotheses, such as isotropic diffusion (red noise) and a Slab Ocean model, to investigate the sources of decadal variability and the factors affecting the propagation and decay of long-term anomalies. The result reveals that the annular mode with largest amplitudes in the Pacific, the basin-wide monopole mode and South Pacific dipole are the principle patterns with low-frequency variability, which contain the dual effects of internal intrinsic processes as well as external forcing and teleconnections. The annular mode is mostly affected by El Niño Southern Oscillation (ENSO) via teleconnection especially in the South Pacific domain and by local Southern Annular Mode (SAM) over the whole Southern Ocean. The monopole mode and South Pacific dipole mode, while they both demonstrate pronounced multi-decadal and longer time scales variability, are firstly inducted by the Wave-3 patterns in the atmosphere and further developed via ocean dynamics. The causes and characteristics of interannual-decadal SST variability in the Southern Ocean are further investigated with an ocean general circulation model and a simplified band ocean model. Possible factors are examined affecting the generation, propagation and decay of long-term anomalies with a series of sensitivity experiments. We found that the atmospheric forcing not only affects the SST modes on shorter time-scales directly, but also shows its influence on longer time scales via air-sea interaction, amplification and oceanic feedback. The deep mixed layer in the Southern Ocean is an essential element to maintain the long-term SST variability. The ocean dynamics connect the entire ocean and create the homogeneous-like spatial patterns. The ocean advection is the key factor to create SST spectral structure, which concentrates the spectrum on interannnual scale synchronizing with the transport of Antarctic Circumpolar Current (ACC).
| Author | : National Academies of Sciences, Engineering, and Medicine |
| Publisher | : National Academies Press |
| Total Pages | : 92 |
| Release | : 2016-07-22 |
| Genre | : Science |
| ISBN | : 0309444640 |
Many factors contribute to variability in Earth's climate on a range of timescales, from seasons to decades. Natural climate variability arises from two different sources: (1) internal variability from interactions among components of the climate system, for example, between the ocean and the atmosphere, and (2) natural external forcings, such as variations in the amount of radiation from the Sun. External forcings on the climate system also arise from some human activities, such as the emission of greenhouse gases (GHGs) and aerosols. The climate that we experience is a combination of all of these factors. Understanding climate variability on the decadal timescale is important to decision-making. Planners and policy makers want information about decadal variability in order to make decisions in a range of sectors, including for infrastructure, water resources, agriculture, and energy. In September 2015, the National Academies of Sciences, Engineering, and Medicine convened a workshop to examine variability in Earth's climate on decadal timescales, defined as 10 to 30 years. During the workshop, ocean and climate scientists reviewed the state of the science of decadal climate variability and its relationship to rates of human-caused global warming, and they explored opportunities for improvement in modeling and observations and assessing knowledge gaps. Frontiers in Decadal Climate Variability summarizes the presentations and discussions from the workshop.
| Author | : National Research Council |
| Publisher | : National Academies Press |
| Total Pages | : 161 |
| Release | : 1998-12-24 |
| Genre | : Science |
| ISBN | : 0309060982 |
Society today may be more vulnerable to global-scale, long-term, climate change than ever before. Even without any human influence, past records show that climate can be expected to continue to undergo considerable change over decades to centuries. Measures for adaption and mitigation will call for policy decisions based on a sound scientific foundation. Better understanding and prediction of climate variations can be achieved most efficiently through a nationally recognized "dec-cen" science plan. This book articulates the scientific issues that must be addressed to advance us efficiently toward that understanding and outlines the data collection and modeling needed.
| Author | : Claude Abiven |
| Publisher | : |
| Total Pages | : 76 |
| Release | : 2007 |
| Genre | : |
| ISBN | : |
The mechanisms of variability of a coupled atmosphere-ocean model are investigated through the study of two coupled configurations: an aquaplanet in which gyres are absent, and an aquaplanet in which a ridge extending from pole to pole supports gyres. Empirical Orthogonal Functions (EOFs) are used to explore the main features of variability exhibited by extended integrations of both configurations. In the aquaplanet a decadal variability is observed in the atmosphere and the ocean. Stochastic driving of the annular modes in the atmosphere generates an anomalous Sea Surface Temperature (SST) dipole through latent heat fluxes and Ekman pumping. A feedback of this SST dipole on the atmosphere enables a damping slow enough for anomalies to persist over decadal time scales. This air-sea feedback combined with a slow advection of the anomalies by mean ocean currents result in the observed decadal oscillation. A simple stochastic model captures the essence of this mechanism. In the ridge decadal variability is absent but centennial variability is observed in the atmosphere and the ocean. Stochastic driving of the annular modes in the atmosphere generates a weak SST tripole due to latent heat fluxes. The weak amplitude of this tripole prevents the existence of any significant air-sea feedback, implies a stronger damping than in the aquaplanet, and ultimately results in the absence of oscillations. The classic stochastic model of Hasselmann [19] explains the evolution of the SST anomaly through time. Within a delay of one year stochastic atmospheric variability additionally generates a baroclinic streamfunction as well as baroclinic Rossby waves at the eastern boundary of the basin. The former is slowly advected by the mean flow while the latter propagates towards the western boundary, inducing a feedback on the atmosphere with a delay of sixty years. A simple model is found to capture the essence of this mechanism. The results of the aquaplanet and the ridge are used to interpret the Drake, a third configuration in which a band of land extends from the North Pole to the line of -45' of latitude. In the northern hemisphere of the Drake mean state and variability are similar to the ones observed in the ridge. The observed centennial oscillation would correspond to a decadal oscillation in the Atlantic. In the southern hemisphere of the Drake, mean state and variability have elements of both the ridge and the aquaplanet.
| Author | : Jacques C. J. Nihoul |
| Publisher | : Elsevier Publishing Company |
| Total Pages | : 800 |
| Release | : 1985 |
| Genre | : Electronic books |
| ISBN | : |
The exchange of momentum, heat, moisture, gases (such as CO 2 and O 2 ) and salt between the atmosphere and the ocean is a phenomenon of paramount importance for the dynamics of the atmosphere and the ocean. With the pressing need for reliable climate forecast (e.g. to deal with severe food and energy problems) interactive ocean-atmosphere models have become one of the main objectives of geophysical fluid dynamics. This volume provides the first state-of-the-art review of interactive ocean-atmosphere modelling and its application to climates. The papers are by active and eminent scientists from different countries and different disciplines. They provide a up-to-date survey of major recent discoveries and valuable recommendations for future research."
| Author | : Carlos R. Mechoso |
| Publisher | : Cambridge University Press |
| Total Pages | : 359 |
| Release | : 2020-11-26 |
| Genre | : Science |
| ISBN | : 1108492703 |
A comprehensive review of interactions between the climates of different ocean basins and their key contributions to global climate variability and change. Providing essential theory and discussing outstanding examples as well as impacts on monsoons, it a useful resource for graduate students and researchers in the atmospheric and ocean sciences.
| Author | : S. George Philander |
| Publisher | : Princeton University Press |
| Total Pages | : 292 |
| Release | : 2006-05-07 |
| Genre | : Nature |
| ISBN | : 9780691126227 |
Until 1997, few people had heard of the seasonal current that Peruvians nicknamed El Niño. But when meteorologists linked it to devastating floods in California, severe droughts in Indonesia, and strange weather everywhere, its name became entrenched in the common parlance faster than a typhoon making landfall. Bumper stickers appeared bearing the phrase "Don't blame me; blame El Niño." Stockbrokers muttered "El Niño" when the market became erratic. What's behind this fascinating natural phenomenon, and how did our perceptions of it change? In this captivating book, renowned oceanographer George Philander engages readers in lucid and stimulating discussions of the scientific, political, economic and cultural developments that shaped our perceptions of this force of nature. The book begins by outlining the history of El Niño, an innocuous current that appears off the coast of Peru around Christmastime--its name refers to the Child Jesus--and originally was welcomed as a blessing. It goes on to explore how our perceptions of El Niño were transformed, not because the phenomenon changed, but because we did. Philander argues persuasively that familiarity with the different facets of our affair with El Niño--our wealth of experience in dealing with natural hazards such as severe storms and prolonged droughts--can help us cope with an urgent and controversial environmental problem of our own making--global warming. Intellectually invigorating and a joy to read, Our Affair with El Niño is an important contribution to the debate about the relationship between scientific knowledge and public affairs.
| Author | : Vikram M. Mehta |
| Publisher | : CRC Press |
| Total Pages | : 356 |
| Release | : 2020-11-19 |
| Genre | : Nature |
| ISBN | : 1351052896 |
Natural decadal climate variability (DCV) and its interactions with anthropogenic climate change (ACC) are vitally important to understand to predict the future of the Earth’s climate. This book, after familiarizing readers with the importance of understanding and predicting DCV phenomena and its distinction from ACC phenomena, comprehensively explains the physics of DCV, integrating paleoclimate proxy and modern instrument-based data and simulations with climate models. Features of this book: Uniquely focuses on natural DCV, its physics, and its predictability Presents an integrated view of DCV phenomena based on approximately 700 peer-reviewed publications cited in the book Includes research on influences of decadal variability in solar emissions on the Earth’s climate, with a historical perspective going back several centuries Describes progress in decadal climate predictability and prediction research, with a historical perspective on weather and climate predictability research This book is an excellent resource for graduate students, faculty members and other teachers and researchers, and anyone who is interested in learning about a very important component of the puzzle of the changing climate. "This book provides a comprehensive review.... Highlighted throughout the book are potential links between DCV and solar variability, a fascinating topic that has engaged our minds for centuries. Written by an expert with more than 30 years’ experience, this book should be an invaluable resource for students and researchers interested in how our climate will evolve over the coming decades." Doug Smith, Decadal Climate Prediction Leader, Meteorological Office Hadley Centre, UK "This book is a tour de force by the author who has spent his career studying decadal climate variability. He brings new insights to the vast scope of this topic, providing clearly understandable descriptions of the various aspects." Gerald Meehl, Senior Scientist, National Center for Atmospheric Research, Colorado, USA
| Author | : Antonio Navarra |
| Publisher | : Springer Science & Business Media |
| Total Pages | : 412 |
| Release | : 2012-12-06 |
| Genre | : Science |
| ISBN | : 3642583695 |
The interest and level of research into climate variability has risen dramatically in recent years, and major breakthroughs have been achieved in the understanding and modelling of seasonal to interannual climate variability and prediction. At the same time, the documentation of longer term variability and its underlying mecha nisms have progressed considerably. Within the European Commission's Environment and Climate research programs several important projects have been supported in these areas - including the "Dec adal and Interdecadal Climate variability Experiment" (DICE) which forms the basis of this book. Within the EC supported climate research, we see an increasing importance of research into climate variability, as is evidenced in the upcoming Fifth Framework Programme's Key Action on Global Change, Climate and Biodi versity. This is because of the obvious potential socio-economic benefits from sea sonal to decadal scale climate prediction and equally important for the fundamental understanding of the climate system to help improve the quality and reliability of future climate change and mankind's current interference with it. The DICE group has performed important and pioneering work, and we hope this book will receive the wide distribution and recognition it deserves. We wel come the contributions from distinguished researchers from US, Japan and Canada to the EC's DICE group towards completing the scope of the book and as an exam ple of international cooperation which is essential in such a high-level scientific endeavor.
| Author | : Tianyi Sun (Ph. D.) |
| Publisher | : |
| Total Pages | : 262 |
| Release | : 2019 |
| Genre | : |
| ISBN | : |
Interdecadal variability of the tropical Pacific affects global hydroclimate and ecosystem and is suggested to modulate global mean temperature in the past century. It has been long acknowledged that Pacific decadal variability can be generated in the extratropics through integration of stochastic atmospheric forcing by the ocean mixed layer. However, it remains unclear how the extratropical signal propagates into the tropical Pacific and forms a basin-wide anomaly pattern and how the resultant tropical Pacific decadal variability (TPDV) interacts with the El Niño-Southern Oscillation (ENSO), the dominant mode of interannual climate variability. To answer this question, a suite of climate model experiments is conducted with small time-invariant surface heat flux anomalies associated with the leading atmospheric modes in the extratropical South and North Pacific. The results show that subtropical ocean-atmosphere anomalies driven by the surface heat flux forcing propagate into the tropical Pacific mainly through thermodynamic ocean-atmosphere interactions, with ocean dynamics playing an important role in modifying the equatorial sea surface temperature (SST) response. The associated changes in the tropical Pacific mean state not only extend climate anomalies into the other hemisphere through atmospheric teleconnections, but also significantly affect the properties of ENSO. In particular, the ENSO-like TPDV affects the relative frequency of El Niño and La Niña. To investigate the causality and mechanism of this linkage, a separate set of climate model experiments is conducted by imposing surface heat flux anomalies associated with the ENSO-like TPDV in the tropical Pacific. The forced mean state change affects the frequency of El Niño and La Niña events by modulating the SST contrast between the tropical Pacific and the Indian/Atlantic Oceans and associated zonal wind anomalies in the western Pacific. This study presents in detail the atmospheric and oceanic mechanisms by which extratropical atmospheric forcing induces basin-wide coherent patterns of TPDV that can further affect ENSO characteristics, which has not been systematically studied in fully coupled climate models. The results also show that the tropical Pacific is more strongly influenced by the South Pacific through both thermodynamic processes and ocean dynamics. The strong oceanic linkage to the South Pacific allows delayed negative oceanic feedback to effectively affect the equatorial Pacific SST, which may be important for setting up the time scales of TPDV
