Download or read book Variability on Decadal Scales in Pacific Sea Surface Temperatures and Atmosphere Ocean Interaction in the Coupled General Circulation Model ECHAM4 OPYC3 written by Andreas Bacher and published by . This book was released on 1998 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Examensarbeit written by and published by . This book was released on 2002 with total page 538 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Impact of Internal Atmospheric Variability on the North Pacific Decadal SST Variability written by Sang-Wook Yeh and published by . This book was released on 2003 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Ocean atmosphere Coupled Modes of Decadal Variability in the Southern Hemisphere written by Gang Wang and published by . This book was released on 2015 with total page 171 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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).

Download or read book Pacific Decadal Variability and ENSO Amplitude Modulation written by Sang-Wook Yeh and published by . This book was released on 2004 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Global Climate Anomalies and Decadal North Pacific SST Variability in a Coupled GCM written by Sang-Wook Yeh and published by . This book was released on 2004 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Madden Julian Oscillation in ECHAM4 Coupled and Uncoupled General Circulation Models written by and published by . This book was released on 2005 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Madden-Julian oscillation (MJO) dominates tropical variability on timescales of 30-70 days. During the boreal winter/spring, it is manifested as an eastward propagating disturbance, with a strong convective signature over the eastern hemisphere. The space-time structure of the MJO is analyzed using simulations with the ECHAM4 atmospheric general circulation model run with observed monthly mean sea-surface temperatures (SSTs), and coupled to three different ocean models. The coherence of the eastward propagation of MJO convection is sensitive to the ocean model to which ECHAM4 is coupled. For ECHAM4/OPYC and ECHO-G, models for which ~100 years of daily data is available, Monte Carlo sampling indicates that their metrics of eastward propagation are different at the 1% significance level. The flux-adjusted coupled simulations, ECHAM4/OPYC and ECHO-G, maintain a more realistic mean-state, and have a more realistic MJO simulation than the nonadjusted scale interaction experiment (SINTEX) coupled runs. The SINTEX model exhibits a cold bias in Indian Ocean and tropical West Pacific Ocean sea-surface temperature of ~0.5°C. This cold bias affects the distribution of time-mean convection over the tropical eastern hemisphere. Furthermore, the eastward propagation of MJO convection in this model is not as coherent as in the two models that used flux adjustment or when compared to an integration of ECHAM4 with prescribed observed SST. This result suggests that simulating a realistic basic state is at least as important as air-sea interaction for organizing the MJO. While all of the coupled models simulate the warm (cold) SST anomalies that precede (succeed) the MJO convection, the interaction of the components of the net surface heat flux that lead to these anomalies are different over the Indian Ocean. The ECHAM4/OPYC model in which the atmospheric model is run at a horizontal resolution of T42, has eastward propagating zonal wind anomalies and latent heat flux anomalies. However, the integrations with ECHO-G and SINTEX, which used T30 atmospheres, produce westward propagation of the latent heat flux anomalies, contrary to reanalysis. Furthermore, it is suggested that the differing ability of the models to represent the near-surface westerlies over the Indian Ocean is related to the different horizontal resolutions of the atmospheric model employed.

Download or read book Understanding the Role of Stochastic Atmospheric Forcing in Tropical Pacific Decadal Variability and ENSO Modulation written by Tianyi Sun (Ph. D.) and published by . This book was released on 2019 with total page 262 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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

Download or read book Tropical Pacific Decadal Variability and ENSO Amplitude Modulation in a CGCM written by Sang-Wook Yeh and published by . This book was released on 2004 with total page 74 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Climate Change 2013 The Physical Science Basis written by Intergovernmental Panel on Climate Change (IPCC) and published by Cambridge University Press. This book was released on 2014-03-24 with total page 1554 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) will again form the standard scientific reference for all those concerned with climate change and its consequences, including students and researchers in environmental science, meteorology, climatology, biology, ecology and atmospheric chemistry. It provides invaluable material for decision makers and stakeholders at international, national and local level, in government, businesses, and NGOs. This volume provides: • An authoritative and unbiased overview of the physical science basis of climate change • A more extensive assessment of changes observed throughout the climate system than ever before • New dedicated chapters on sea-level change, biogeochemical cycles, clouds and aerosols, and regional climate phenomena • Extensive coverage of model projections, both near-term and long-term climate projections • A detailed assessment of climate change observations, modelling, and attribution for every continent • A new comprehensive atlas of global and regional climate projections for 35 regions of the world

Download or read book Decadal Variability of the Pacific Subtropical Cells and Equatorial Sea Surface Temperature written by Carina Saxton Young and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis investigates possible dynamical pathways through which variability in the extra-tropical Pacific Ocean influences decadal fluctuations of tropical Pacific sea surface temperatures (SST). Specifically, we examine the hypothesis that low-frequency changes in the Pacific‟s meridional subtropical cells (STCs), which transport subsurface water masses equatorward from the extra-tropical into the tropical Pacific upwelling system, modulate decadal variations of the equatorial SST. The relationship between the STCs and equatorial Pacific SST anomalies is explored statistically using the monthly hindcast output from the Ocean General Circulation Model (OGCM) for the Earth Simulator (OFES). We find that decadal variability of the subsurface heat transport of the southern branch of the STC is more closely correlated (R = -0.74) with eastern equatorial SST anomalies on timescales longer than 8 years. The northern branch of the STC is overall not well correlated with equatorial SSTa; however, we find that in the period before the 1976 climate shift, the northern cell is more strongly and significantly correlated with equatorial SSTa (R = -0.89,>99%), while the southern cell is not (R = -0.32). The physical significance of these findings remain unclear and requires isolating mechanisms that could lead to an asymmetry in the role of the northern and southern STC in modulating eastern equatorial SSTa during different states of the Pacific climate. This will be a critical step to attribute physical significance to the statistical changes observed before and after the 1976 climate shift.

Download or read book Pacific Decadal Variability and Recent Tropical Expansion written by Michael Rollings and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "The latitudinal extent of the tropics is of great consequence because it affects agricultural production, water supply, storm frequency, and other factors of socioeconomic importance. The tropics can be defined by climatological metrics such as Hadley cell width, and observations show that the tropics have been expanding poleward since 1979.Tropical width is influenced by both anthropogenic forcing and patterns of large-scale internal climate variability, and the tropics have been expanding faster than coupled models forced with historic levels of anthropogenic forcing. The relative importance of each expansion mechanism has remained unclear since it is difficult to separate the signals of long-term variability, short-term variability, and climate change. Here, we have used statistically-separate patterns of sea surface temperature variability to analyze observations and design general circulation model experiments that isolate the respective roles of internal variability and climate change in recent tropical expansion, allowing us to quantify the influence of Pacific variability on Hadley cell width by timescale. When global warming is defined as independent of natural variability, we find an observed sensitivity of tropical width to global warming that agrees with coupled model experiments. Wealso find a strong correlation between long-term North Pacific variability and Southern Hemisphere Hadley cell extent in observations which cannot be reproduced in prescribed sea surface temperature general circulation model experiments. Conversely, we find a weaker observed relation between El Niño and the Hadley circulation when compared to simulations run with El Niño-like sea surface temperature boundary conditions. The dynamical relation between the Hadley cell and El Niño is generally well understood, but the relative importance of long-term oceanic variability for the general circulationremains unclear because it is difficult to produce the observed trends in simulations with prescribed sea surface temperature"--

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 The Characteristics of Signal Versus Noise SST Variability in the North Pacific and the Tropical Pacific Ocean written by Sang-Wook Yeh and published by . This book was released on 2002 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Internal Ocean Dynamics and Climate Variability written by Ben P. Kirtman and published by . This book was released on 2006 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Understanding the Impacts of the Indian Ocean on ENSO Variability in a Coupled GCM written by Renguang Wu and published by . This book was released on 2003 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Coupled Atmosphere Ocean Dynamics written by Shang-Ping Xie and published by Elsevier. This book was released on 2022-12-21 with total page 433 pages. Available in PDF, EPUB and Kindle. Book excerpt: Coupled Atmosphere-Ocean Dynamics of Climate Variability and Climate Change presents the patterns, mechanisms, and predictability of climate variability and anthropogenic climate change. Based on a graduate course the author has taught over 25 years, this book provides the physical foundation for those who are interested in fundamental questions such as: why climate varies from one year to another; how predictable climate is; and how climate will change in the face of increasing greenhouse gases in the atmosphere. This is the first comprehensive and systematic treatment of this subject that simultaneously draws on the latest research and is accessible for graduate students. The book takes a step-by-step systematic approach to coupled ocean-atmosphere interactions. This allows a wide range of comparative views: climate modes among and across different tropical ocean basins, ocean feedback on the atmosphere (in and out of the tropics), and spontaneous internal oscillation versus externally forced climate change. Such comparative views offer unprecedented insight into the dynamics of climate variability and predictability. This book can be used as supplementary reading for advanced undergraduate students, as coursework in climate dynamics, modeling, variability, and change, and as a reference book and research monograph for researchers in ocean, atmospheric, climate, and earth system sciences. - Delivers the first authored textbook on ocean-atmosphere interactions that give rise to climate variability/predictability and shape regional patterns of anthropogenic climate change - Contains historical accounts of major breakthroughs in the field - Includes homework questions, helping to reinforce key concepts and applications