Experimental ENSO Predictions with a CGCM PDF Download

Author: Zhengxin Zhu
Publisher:
ISBN:
Category : El Niño Current
Languages : en
Pages : 326

View

Book Description

Author: Michael J. McPhaden
Publisher: John Wiley & Sons
ISBN: 1119548128
Category : Science
Languages : en
Pages : 528

View

Book Description
Comprehensive and up-to-date information on Earth’s most dominant year-to-year climate variation The El Niño Southern Oscillation (ENSO) in the Pacific Ocean has major worldwide social and economic consequences through its global scale effects on atmospheric and oceanic circulation, marine and terrestrial ecosystems, and other natural systems. Ongoing climate change is projected to significantly alter ENSO's dynamics and impacts. El Niño Southern Oscillation in a Changing Climate presents the latest theories, models, and observations, and explores the challenges of forecasting ENSO as the climate continues to change. Volume highlights include: Historical background on ENSO and its societal consequences Review of key El Niño (ENSO warm phase) and La Niña (ENSO cold phase) characteristics Mathematical description of the underlying physical processes that generate ENSO variations Conceptual framework for understanding ENSO changes on decadal and longer time scales, including the response to greenhouse gas forcing ENSO impacts on extreme ocean, weather, and climate events, including tropical cyclones, and how ENSO affects fisheries and the global carbon cycle Advances in modeling, paleo-reconstructions, and operational climate forecasting Future projections of ENSO and its impacts Factors influencing ENSO events, such as inter-basin climate interactions and volcanic eruptions The American Geophysical Union promotes discovery in Earth and space science for the benefit of humanity. Its publications disseminate scientific knowledge and provide resources for researchers, students, and professionals. Find out more about this book from this Q&A with the editors.

Author:
Publisher:
ISBN:
Category : Climatic changes
Languages : en
Pages : 222

View

Book Description

Author: National Research Council
Publisher: National Academies Press
ISBN: 030915183X
Category : Science
Languages : en
Pages : 192

View

Book Description
More accurate forecasts of climate conditions over time periods of weeks to a few years could help people plan agricultural activities, mitigate drought, and manage energy resources, amongst other activities; however, current forecast systems have limited ability on these time- scales. Models for such climate forecasts must take into account complex interactions among the ocean, atmosphere, and land surface. Such processes can be difficult to represent realistically. To improve the quality of forecasts, this book makes recommendations about the development of the tools used in forecasting and about specific research goals for improving understanding of sources of predictability. To improve the accessibility of these forecasts to decision-makers and researchers, this book also suggests best practices to improve how forecasts are made and disseminated.

Author: National Academies of Sciences, Engineering, and Medicine
Publisher: National Academies Press
ISBN: 0309388805
Category : Science
Languages : en
Pages : 351

View

Book Description
As the nation's economic activities, security concerns, and stewardship of natural resources become increasingly complex and globally interrelated, they become ever more sensitive to adverse impacts from weather, climate, and other natural phenomena. For several decades, forecasts with lead times of a few days for weather and other environmental phenomena have yielded valuable information to improve decision-making across all sectors of society. Developing the capability to forecast environmental conditions and disruptive events several weeks and months in advance could dramatically increase the value and benefit of environmental predictions, saving lives, protecting property, increasing economic vitality, protecting the environment, and informing policy choices. Over the past decade, the ability to forecast weather and climate conditions on subseasonal to seasonal (S2S) timescales, i.e., two to fifty-two weeks in advance, has improved substantially. Although significant progress has been made, much work remains to make S2S predictions skillful enough, as well as optimally tailored and communicated, to enable widespread use. Next Generation Earth System Predictions presents a ten-year U.S. research agenda that increases the nation's S2S research and modeling capability, advances S2S forecasting, and aids in decision making at medium and extended lead times.

Author: Swadhin Kumar Behera
Publisher: World Scientific
ISBN: 9814696625
Category : Science
Languages : en
Pages : 323

View

Book Description
"This book aims to compile some of the important results from the latest research in climate variation and prediction studies with a focus on the role of the ocean, particularly in the Indo-Pacific region. Several new modes of ocean-atmosphere climate variations have been discovered in the last decade, and the advance of climate models have made it possible to predict some of these modes several seasons ahead. This has improved the society's ability to use model predictions to mitigate climate disaster risks. Leading experts in the field were invited to contribute to this book in order to compile a comprehensive review for the benefit of researchers as well as general readers interested in the subject."--

Author: William K.-M. Lau
Publisher: Springer Science & Business Media
ISBN: 3642139140
Category : Science
Languages : en
Pages : 642

View

Book Description
Improving the reliability of long-range forecasts of natural disasters, such as severe weather, droughts and floods, in North America, South America, Africa and the Asian/Australasian monsoon regions is of vital importance to the livelihood of millions of people who are affected by these events. In recent years the significance of major short-term climatic variability, and events such as the El Nino/Southern Oscillation in the Pacific, with its worldwide effect on rainfall patterns, has been all to clearly demonstrated. Understanding and predicting the intra-seasonal variability (ISV) of the ocean and atmosphere is crucial to improving long range environmental forecasts and the reliability of climate change projects through climate models. In the second edition of this classic book on the subject, the authors have updated the original chapters, where appropriate, and added a new chapter that includes short subjects representing substantial new development in ISV research since the publication of the first edition.

Author: Ian T. Jolliffe
Publisher: John Wiley & Sons
ISBN: 0470864419
Category : Science
Languages : en
Pages : 257

View

Book Description
This handy reference introduces the subject of forecastverification and provides a review of the basic concepts,discussing different types of data that may be forecast. Each chapter covers a different type of predicted quantity(predictand), then looks at some of the relationships betweeneconomic value and skill scores, before moving on to review the keyconcepts and summarise aspects of forecast verification thatreceive the most attention in other disciplines. The book concludes with a discussion on the most importanttopics in the field that are the subject of current research orthat would benefit from future research. An easy to read guide of current techniques with real life casestudies An up-to-date and practical introduction to the differenttechniques and an examination of their strengths andweaknesses Practical advice given by some of the world?s leadingforecasting experts Case studies and illustrations of actual verification and itsinterpretation Comprehensive glossary and consistent statistical andmathematical definition of commonly used terms

Author: Hosmay Lopez
Publisher:
ISBN:
Category :
Languages : en
Pages :

View

Book Description
There is an active research debate regarding how weather and climate interact -- this is particular noted in terms of understanding ENSO predictability and the influence of "weather noise". This weather noise view argues that the irregularity of ENSO and ultimately the loss of predictability are largely driven by stochastic forcing. If the stochastic forcing or noise is of primary importance then it is possible that the details (e.g., space-time structure and state dependence) of the noise are also important -- that is weather and climate interactions. The overarching goal of this dissertation research is to develop a framework to study the role, if any, that noise plays in sustaining/modifying/modulating ENSO and tropical Pacific climate variability and predictability. The methodology used here follows two different approaches: (a) assessing the impact of the noise in a non-phenomenological manner recognizing that it can occur on all temporal and spatial scales and (b) assuming the noise is associated with a specific phenomena with clear constrains on its location and spatial-temporal structure. A noise reduction technique, namely the interactive ensemble (IE) approach is adopted to reduce non-phenomenological noise at the air-sea interface due to internal atmospheric dynamics in a state-of-the-art coupled general circulation model (CGCM), namely the Community Climate System Model (CCSM3). To study the impact of weather noise and resolution in the context of a CGCM, two IE experiments are performed at different resolutions. Atmospheric resolution is an important issue since the noise statistics will depend on the spatial scales resolved. A simple formulation to extract atmospheric internal variability is presented. The results are compared to their respective control cases where internal atmospheric variability is left unchanged. The non-phenomenological noise reduction has a major impact on the coupled simulation and the magnitude of this effect strongly depends on the horizontal resolution of the atmospheric component model. Specifically, applying the noise reduction technique reduces the overall climate variability more effectively at higher resolution. This suggests that "weather noise" is more important in sustaining climate variability as resolution increases. ENSO statistics, dynamics, and phase asymmetry are all modified by the noise reduction, in particular ENSO becomes more regular with less phase asymmetry when noise is reduced. All these effects are more marked for the higher resolution case. In contrast, ENSO frequency is unchanged by the reduction in the weather noise, but its phase-locking to the annual cycle is strongly dependent on noise and resolution. At low resolution the noise structure is similar to the signal, whereas the spatial structure of the noise deviates from the spatial structure of the signal as resolution increases. It is also suggested that event-to-event differences are largely driven by atmospheric noise as opposed to chaotic dynamics within the context of the large-scale coupled system, suggesting that there is a well-defined "canonical" event. The next step is to study the importance of phenomenological noise forcing of the climate system. Here, westerly wind bursts or events (WWBs or WWEs) are taken as example of phenomenological noise forcing of the tropical Pacific Ocean. The impact of parameterized WWBs on ENSO variability in CCSM3 and CCSM4 is analyzed. To study the impact of WWBs three experiments are performed. In the first experiment, the model is integrated for several hundred years with no prescribed WWBs events (i.e., the control). In the second case, state-independent WWBs events are introduced. In other words, the occurrence, location, duration, and scale of the WWBs are determined (within bounds) randomly. For the third case, the WWBs are introduced but as multiplicative noise or state-dependent forcing, modulated by SST anomalies. State-dependent case produced larger ENSO. There is very little difference between the control and the state-independent WWB simulations suggesting that the deterministic component of the burst is responsible for reshaping the ENSO events. There is a shift towards a more self sustained mechanism as the experiments progress from the control to the state dependent WWBs. Overall, the parameterized WWBs have the capability to modify the ENSO regime in the CGCM, demonstrating the importance of sub-seasonal variability on interannual time scales. This study also investigates the effect of parameterized WWBs on the diversity of ENSO warm events, namely eastern Pacific (EP) and central Pacific (CP) ENSO in CCSM3 and CCSM4. It is found that parameterized WWBs tend to enhance EP variability more relatively to CP variability. This enhancement in the case of state-dependent WWBs forcing is due to an increase in the so-called thermocline feedback as opposed to the so-called zonal advective feedback. Lastly, we test whether phenomenological stochastic forcing of the form of WWBs impacts ENSO predictability. An ensemble ENSO prediction experiment is presented in which CCSM3 control and CCSM3 with state-dependent WWBs parameterization are used as both truth and as predictor systems. The inclusion of WWBs does not improve nor degrades ENSO predictability if the truth lacks WWBs activity. ENSO predictability increases substantially if a forecast system that produces WWBs activity is used to predict a truth that includes these wind events. It is also found that the so-called forecast spring prediction barrier (SPB) is partially caused by the lack of WWBs representation in the forecast system. The argument for the SPB is that the coupled system is more susceptible to noise forcing in spring. The signal-to-noise ratio (SNR) is larger with WWBs, so it must be that the increase in the signal due to state-dependent WWBs is more important that the added noise. These results were further validated with the more recent version of this model, namely CCSM4. It turned out that CCSM4, at least with the coarse resolution used here, has a much-reduced seasonality in the SNR and therefore reduced seasonality in the forecast skill of SSTA. To further test these results, CCSM3 with and without WWBs parameterization were used to make real predictions of observed tropical Pacific SSTA. It was demonstrated that predictability skill are enhanced when WWBs were included and these improvements were mostly over the low SNR season. These results were further validated by a case study of a warm event with considerable WWBs activity, mimicking the strong 1997-98 event. It was found that the presence of WWBs in the prediction system enhances the forecast ensemble spread, leading to a more reliable probabilistic forecast. But most importantly, the number of ensemble members depicting the correct "truth" increases considerably. This is best observed for those forecasts progressing through the SPB.

Author: Renguang Wu
Publisher:
ISBN:
Category : Atmospheric circulation
Languages : en
Pages : 68

View

Book Description