Download or read book The Equatorial Pacific Cold Tongue Bias in a Coupled Climate Model written by and published by . This book was released on 2007 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Controls of Tropical Pacific Rainfall and SST Biases in Global Climate Models written by Matthew D. Woelfle and published by . This book was released on 2018 with total page 117 pages. Available in PDF, EPUB and Kindle. Book excerpt: Despite continual improvements in both model physics and resolution, accurate simulation of the tropical Pacific mean state has been an elusive goal for many coupled global climate models (GCMs) for decades. Because temperature and pressure gradients are weak in the deep tropics, small errors in simulating these fields can lead to large circulation biases. Any initial bias may be further amplified through feedbacks involving ocean circulations, cloud radiative forcings, and surface turbulent heat or momentum fluxes. The interrelated nature of these processes in the deep tropics has long complicated our ability to understand and correct the initial source of a given model bias. In this dissertation, we examine two persistent tropical biases within the National Center for Atmospheric Research's Community Earth System Model (CESM): the Pacific cold tongue bias and the double-Intertropical Convergence Zone (ITCZ) bias. The Pacific cold tongue bias refers to the tendency for coupled GCMs to simulate sea surface temperatures (SSTs) which are too cold along the equator in the tropical Pacific. The double-ITCZ bias refers the tendency for coupled GCMs to simulate too much precipitation in a zonal band south of the equator. In Chapter 2, a series of six-month coupled hindcasts show the strength of the rapidly developing Pacific cold tongue bias in CESM version 1 (CESM1) to be sensitive to the convective parameterization employed. In the standard configuration of the model, too strong equatorial surface easterlies drive cooling of up to 1~K in the first two months of coupled integration. In a simulation wherein the deep convective parameterization is disabled, the cold tongue bias intensifies due to an increase in the zonal pressure gradient and associated easterlies. Superparameterized hindcasts show improvements in the cold tongue bias and reduced surface easterlies despite an increase in the zonal pressure gradient. The superparameterized model neglects convective momentum fluxes as the embedded two dimensional cloud resolving models are unable to accurately simulate turbulent momentum flux tendencies. Thus, rather than increasing near-surface wind speeds, the increased zonal pressure gradient drives anomalously strong easterly jet at 1-1.5~km elevation as surface drag effects are incorrectly concentrated in the lowest model levels. A series of sensitivity tests confirm the role of shallow convective momentum transport in determining the low-level zonal wind shear. The simulations presented in this chapter suggest shallow convective momentum fluxes may be an underappreciated mechanism for controlling both the equatorial cold tongue strength and the relationship between the large scale surface pressure gradient and surface easterlies. Despite differences in central Pacific SST of nearly 2~K across these hindcasts, the double-ITCZ bias persists in all model configurations. While the double-ITCZ bias is robust across all simulations presented in Chapter 2, the simulations presented in Chapter 3 show the east Pacific manifestation of the double-ITCZ bias to be greatly improved in the newest version of CESM: CESM version~2 (CESM2). In Chapter 3, we examine the state of the double-ITCZ bias across ten versions of CESM created as part of the development process for CESM2. In CESM1, a warm SSTs bias in the southeast Pacific forces zonal and meridional surface pressure gradients that are favorable for increased convergence and convection in this region. This SST bias is reduced in CESM2 due to an increase in overlying low cloud fraction and a corresponding strengthening of the shortwave cloud forcing (SWCF). Between two model versions with similar configurations but differing ITCZ bias strengths, this cloud change is driven by the removal of the dependence of liquid autoconversion and accretion rates on cloud water variance and by the removal of a secondary condensation scheme. These changes reduce the drizzle production rate in the low liquid clouds of the southeast Pacific which in turn delays their breakup and dissipation. As a result, cloud fraction and SWCF increase to more realistic values in the stratocumulus to trade cumulus transition region. The improvements in SWCF and the double-ITCZ bias persist through subsequent modifications to the liquid microphysics parameterizations. Despite the local improvement in the east Pacific rainfall climatology, neither the Pacific cold tongue bias nor global measures of the double-ITCZ bias show a consistent improvement across the model development process from CESM1 to CESM2.
Download or read book El Ni o Southern Oscillation in a Changing Climate written by Michael J. McPhaden and published by John Wiley & Sons. This book was released on 2020-11-24 with total page 528 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Sources of Uncertainty in the Tropical Pacific Warming Pattern under Global Warming Projected by Coupled Ocean Atmosphere Models written by Jun Ying and published by Springer Nature. This book was released on 2019-09-06 with total page 81 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book discusses the sources of uncertainty in future model projections of the tropical Pacific SST warming pattern under global warming. It mainly focuses on cloud radiation feedback and ocean dynamical effect, which reveal to be the two greatest sources of uncertainty in the tropical Pacific SST warming pattern. Moreover, the book presents a correction for model projections of the tropical Pacific SST warming pattern based on the concept of “observational constraints”; the corrected projection exhibits a more El Niño-like warming pattern.
Download or read book Indo Pacific Climate Variability and Predictability written by Swadhin Kumar Behera and published by World Scientific. This book was released on 2015-12-09 with total page 323 pages. Available in PDF, EPUB and Kindle. Book excerpt: "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."--
Download or read book Numerical and Assimilative Studies of the Equatorial Pacific Cold Tongue written by Renellys Christine Perez and published by . This book was released on 2005 with total page 514 pages. Available in PDF, EPUB and Kindle. Book excerpt: Numerical model and assimilation experiments were conducted in the tropical Pacific Ocean to obtain a better understanding of the processes that control the cold tongue surface mixed layer temperature balance during August 1999 to July 2004. The numerical model was first applied to test two hypotheses (asymmetric background currents and asymmetric wind forcing) for the observed asymmetry of annual equatorial Rossby waves. The model with asymmetric background currents perturbed with symmetric annually-varying winds consistently produced asymmetric Rossby waves, and simulations with symmetric background currents perturbed by asymmetric annually-varying winds failed to produce the observed Rossby wave structure unless the perturbation winds were strong enough for nonlinear interactions to become important. The observed latitudinal asymmetry of the westward phase speed was found to be critically dependent on the inclusion of realistic coastline boundaries. To measure the cold tongue sensitivity to errors in wind forcing, the next study compared the seasonal cycle response of the model driven by different wind stress products. The FSU wind stress produced the least realistic cold tongue, and both the ECMWF and QuikSCAT wind stress driven model runs exhibited cold tongue annual cycles, tropical instability waves, and annual equatorial Rossby waves that compared well with observations. The highest realism, however, was obtained with QuikSCAT wind forcing. In the final modeling study, mean dynamic height biases resulting from climatological drift away from the Levitus initialization were discovered in the waveguide. The assimilation experiments combined the model driven by 5-day QuikSCAT winds with 5-day Tropical Atmosphere Ocean dynamic height anomalies via a reduced state space Kalman filter. Assimilation improved the interannual and intraseasonal variability of sea surface height, reduced the cold tongue bias in the waveguide, increased the core strength of the Equatorial Undercurrent, and produced more realistic albeit weak tropical instability waves. An autoregressive model added to the innovation sequence further optimized the assimilation scheme, but did not correct the pre-existing cold tongue thermal biases. Despite the decrease in positive (warming) high-frequency horizontal advection associated with TIWs, the assimilation run with the autoregressive model did not alter the mean balance significantly as there was a compensatory decrease in magnitude of the cooling by the low-frequency horizontal advection. Based on comparisons with observations, the annual cycle of the model tendency was too weak in the eastern Pacific giving rise to sea surface temperatures that were too cold in the spring and summer months and during the 2002-2003 El Nino event. Errors in the simulated net surface heat flux, vertical entrainment, and diffusion were identified as sources for the unrealistically low annual amplitudes of sea surface temperature and tendency in the model cold tongue.
Download or read book Flexible Global Ocean Atmosphere Land System Model written by Tianjun Zhou and published by Springer Science & Business Media. This book was released on 2013-11-19 with total page 468 pages. Available in PDF, EPUB and Kindle. Book excerpt: Coupled climate system models are of central importance for climate studies. A new model known as FGOALS ( the Flexible Global Ocean-Atmosphere-Land System model), has been developed by the Sate Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences (LASG/IAP, CAS), a first-tier national geophysical laboratory. It serves as a powerful tool, both for deepening our understanding of fundamental mechanisms of the climate system and for making decadal prediction and scenario projections of future climate change. "Flexible Global Ocean-Atmosphere-Land System Model: A Modeling Tool for the Climate Change Research Community” is the first book to offer systematic evaluations of this model’s performance. It is comprehensive in scope, covering both developmental and application-oriented aspects of this climate system model. It also provides an outlook of future development of FGOALS and offers an overview of how to employ the model. It represents a valuable reference work for researchers and professionals working within the related areas of climate variability and change. Prof. Tianjun Zhou, Yongqiang Yu, Yimin Liu and Bin Wang work at LASG, the Institute of Atmospheric Physics, Chinese Academy of Sciences, China.
Download or read book El Nino La Nina and the Southern Oscillation written by S. George Philander and published by Academic Press. This book was released on 1989-12-14 with total page 309 pages. Available in PDF, EPUB and Kindle. Book excerpt: El Nino and the Southern Oscillation is by far the most striking phenomenon caused by the interplay of ocean and atmosphere. It can be explained neither in strictly oceanographic nor strictly meteorological terms. This volume provides a brief history of the subject, summarizes the oceanographic and meteorological observations and theories, and discusses the recent advances in computer modeling studies of the phenomenon. Includes a comprehensive and up-to-date research survey Discusses in detail sophisticated computer models Provides a clear exposition of the major problems which prevent more accurate predictions of El Nino
Download or read book The Ocean Heat Budget written by J. Warren Hill and published by . This book was released on 1987 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: Methods are assembled for calculating the components of ocean heating/cooling from above, viz. short-wave radiation, albedo, long-wave radiation, and evaporative and sensible heat exchange with the atmosphere.
Download or read book Decade to Century Scale Climate Variability and Change written by National Research Council and published by National Academies Press. This book was released on 1998-12-24 with total page 161 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Climate Extremes written by S.-Y. Simon Wang and published by John Wiley & Sons. This book was released on 2017-06-15 with total page 436 pages. Available in PDF, EPUB and Kindle. Book excerpt: Although we are seeing more weather and climate extremes, individual extreme events are very diverse and generalization of trends is difficult. For example, mid-latitude and subtropical climate extremes such as heat waves, hurricanes and droughts have increased, and could have been caused by processes including arctic amplification, jet stream meandering, and tropical expansion. This volume documents various climate extreme events and associated changes that have been analyzed through diagnostics, modeling, and statistical approaches. The identification of patterns and mechanisms can aid the prediction of future extreme events. Volume highlights include: Compilation of processes and mechanisms unique to individual weather and climate extreme events Discussion of climate model performance in terms of simulating high-impact weather and climate extremes Summary of various existing theories, including controversial ones, on how climate extremes will continue to become stronger and more frequent Climate Extremes: Patterns and Mechanisms is a valuable resource for scientists and graduate students in the fields of geophysics, climate physics, natural hazards, and environmental science. Read an interview with the editors to find out more: https://eos.org/editors-vox/how-does-changing-climate-bring-more-extreme-events
Download or read book Natural Climate Variability on Decade to Century Time Scales written by National Research Council and published by National Academies Press. This book was released on 1996-08-30 with total page 645 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume reflects the current state of scientific knowledge about natural climate variability on decade-to-century time scales. It covers a wide range of relevant subjects, including the characteristics of the atmosphere and ocean environments as well as the methods used to describe and analyze them, such as proxy data and numerical models. They clearly demonstrate the range, persistence, and magnitude of climate variability as represented by many different indicators. Not only do natural climate variations have important socioeconomic effects, but they must be better understood before possible anthropogenic effects (from greenhouse gas emissions, for instance) can be evaluated. A topical essay introduces each of the disciplines represented, providing the nonscientist with a perspective on the field and linking the papers to the larger issues in climate research. In its conclusions section, the book evaluates progress in the different areas and makes recommendations for the direction and conduct of future climate research. This book, while consisting of technical papers, is also accessible to the interested layperson.
Download or read book Next Generation Earth System Prediction written by National Academies of Sciences, Engineering, and Medicine and published by National Academies Press. This book was released on 2016-08-22 with total page 351 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Ocean Circulation Theory written by Joseph Pedlosky and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 463 pages. Available in PDF, EPUB and Kindle. Book excerpt: An overview of the advances made in the last decade and a half in this field. Based on an advanced graduate level course, the book represents fundamental insights into the structure of the physical theory of the large-scale dynamics of the oceans. The author has maintained throughout a blend of analytical and numerical results so as to achieve as deep a physical understanding of the dynamics of the large-scale circulations as possible. The results of the theories are compared with observations and the success or inadequacies of the theories are highlighted. Topics of particular interest are: theory of the wind-driven circulation, the thermocline, the equatorial circulation and the abyssal circulation. Much of the material - previously scattered throughout the literature - has been collated here for the first time.
Download or read book Near annual SST Variability in the Equatorial Pacific in a Coupled General Circulation Model written by Renguang Wu and published by . This book was released on 2004 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Coral Reefs of the Eastern Tropical Pacific written by Peter W. Glynn and published by Springer. This book was released on 2016-08-12 with total page 666 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book documents and examines the state of health of coral reefs in the eastern tropical Pacific region. It touches on the occurrence of coral reefs in the waters of surrounding countries, and it explores their biogeography, biodiversity and condition relative to the El Niño southern oscillation and human impacts. Additionally contained within is a field that presents information on many of the species presented in the preceding chapters.
Download or read book Climate Response of the Equatorial Pacific to Global Warming written by Pedro N. Di Nezio and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The climate response of the equatorial Pacific to increased greenhouse gases is investigated using numerical experiments from five climate models participating in the Intergovernmental Panel on Climate Change Fourth Assessment Report. Changes in the heat budget of the surface layer in response to CO2 doubling (2xCO2) are analyzed in experiments with full-coupled ocean dynamics; and compared to experiments with uncoupled ocean dynamics. In full-coupled experiments, weaker ocean zonal currents driven by a slowing down of the Walker circulation reduce the ocean heat flux divergence throughout the equatorial Pacific. The resulting ocean dynamical heating enhances the surface warming due to increased clear-sky surface radiation in response to 2xCO2. The total radiative plus ocean dynamical heating are stabilized by evaporation and cloud feedbacks over the warm pool and by increased ocean vertical heat transport over the cold tongue. Increased near-surface thermal stratification enhances vertical heat transport in the cold tongue despite a reduction in vertical velocity. This ocean dynamical cooling is the dominant negative term in the heat budget changes over the eastern Pacific; and represents a strengthening of the processes leading to the annual cycle of the cold tongue, which increases by 0.4 K as a result. The stratification response is found to be a permanent feature of the equilibrium climate potentially linked to both thermodynamical and dynamical changes within the equatorial Pacific. To conclude, the relationship between the heat budget changes and the SST response is discussed along with implications for detecting these signals in the modern observational record.
