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Book Simulation and Prediction of North Pacific Sea Surface Temperature

Download or read book Simulation and Prediction of North Pacific Sea Surface Temperature written by Fabian Lienert and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The first part of this thesis is an assessment of the ability of global climate models to reproduce observed features of the leading Empirical Orthogonal Function (EOF) mode of North Pacific sea surface temperature (SST) anomalies known as the Pacific Decadal Oscillation (PDO). The simulations from 13 global climate models I am analyzing were performed under phase 3 of the coupled model intercomparison project (CMIP3). In particular, I am investigating whether these climate models capture tropical influences on the PDO, and the influences of the PDO on North American surface temperature and precipitation. My results are that 1) the models as group produce a realistic pattern of the PDO. The simulated variance of the PDO index is overestimated by roughly 30%. 2)The tropical influence on North Pacific SSTs is biased systematically in these models. The simulated response to El Nino-Southern Oscillation (ENSO) forcing is delayed compared to the observed response. This tendency is consistent with model biases toward deeper oceanic mixed layers in winter and spring and weaker air-sea feedbacks in the winter half-year. Model biases in mixed layer depths and air-sea feedbacks are also associated with a model mean ENSO-related signal in the North Pacific whose amplitude is overestimated by roughly 30%. Finally, model power spectra of the PDO signal and its ENSO-forced component are?redder? than observed due to errors originating in the tropics and extratropics. 3) The models are quite successful at capturing the influence of both the tropical Pacific related and the extratropical part of the PDO on North American surface temperature. 4) The models capture some of the influence of the PDO on North American precipitation mainly due to its tropical Pacific related part. In the second part of this thesis, I investigate the ability of one such coupled ocean-atmosphere climate model, carefully initialized with observations, to dynamically predict the future evolution of the PDO on seasonal to decadal time scales. I am using forecasts produced by the Canadian climate data assimilation and prediction system employing the Canadian climate model CanCM3 for seasonal (CHFP2) and CanCM4 for decadal (DHFP1) predictions. The skill of this system in predicting the future evolution of the PDO index is then inferred from a set of historical?forecasts? called hindcasts. In this manner, hindcasts are issued over the past 30 years (seasonal), or over the past 50 years (decadal) when they can be verified against the observed historical evolution of the PDO index. I find that 1) CHFP2 is successful at predicting the PDO at the seasonal timescale measured by mean-square skill score and correlation skill. Weather?noise? unpredictable at the seasonal time scale generated by substantial North Pacific stormtrack activity that coincides with a shallow oceanic mixed layer in May and June appear to pose a prediction barrier for the PDO. PDO skill therefore depends on the start season of the forecast. PDO skill also varies as a function of the target month. Variations in North Pacific storminess appear to impact PDO skill by means of a lagged response of the ocean mixed layer to weather noise. In CHFP2, times of increasing North Pacific storm track activity are followed by times of reduced PDO skill, while the North Pacific midwinter suppression of storm track ...

Book Simulation of the Tropical Pacific Using a Simplified Ocean Model

Download or read book Simulation of the Tropical Pacific Using a Simplified Ocean Model written by Magdalena A. Balmaseda and published by . This book was released on 1994 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Making Climate Forecasts Matter

Download or read book Making Climate Forecasts Matter written by National Research Council and published by National Academies Press. This book was released on 1999-05-27 with total page 189 pages. Available in PDF, EPUB and Kindle. Book excerpt: El Nino has been with us for centuries, but now we can forcast it, and thus can prepare far in advance for the extreme climatic events it brings. The emerging ability to forecast climate may be of tremendous value to humanity if we learn how to use the information well. How does society cope with seasonal-to-interannual climatic variations? How have climate forecasts been usedâ€"and how useful have they been? What kinds of forecast information are needed? Who is likely to benefit from forecasting skill? What are the benefits of better forecasting? This book reviews what we know about these and other questions and identifies research directions toward more useful seasonal-to-interannual climate forecasts. In approaching their recommendations, the panel explores: Vulnerability of human activities to climate. State of the science of climate forecasting. How societies coevolved with their climates and cope with variations in climate. How climate information should be disseminated to achieve the best response. How we can use forecasting to better manage the human consequences of climate change.

Book Indo pacific Climate Variability And Predictability

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.World Scientific Series on Asia-Pacific Weather and Climate is indexed in SCOPUS.

Book Controls of Tropical Pacific Rainfall and SST Biases in Global Climate Models

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.

Book Flexible Global Ocean Atmosphere Land System Model

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.

Book Assessment of Intraseasonal to Interannual Climate Prediction and Predictability

Download or read book Assessment of Intraseasonal to Interannual Climate Prediction and Predictability written by National Research Council and published by National Academies Press. This book was released on 2010-09-08 with total page 193 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Book New techniques for improving climate models predictions and projections

Download or read book New techniques for improving climate models predictions and projections written by Matthew Collins and published by Frontiers Media SA. This book was released on 2022-01-24 with total page 178 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Vulnerability of Tropical Pacific Fisheries and Aquaculture to Climate Change

Download or read book Vulnerability of Tropical Pacific Fisheries and Aquaculture to Climate Change written by Johann D. Bell and published by Pacific Community. This book was released on 2011-01-01 with total page 941 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Sources of Uncertainty in the Tropical Pacific Warming Pattern under Global Warming Projected by Coupled Ocean Atmosphere Models

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.

Book Simulation of Tropical Pacific and Atlantic Oceans Using a HYbrid Coordinate Ocean Model

Download or read book Simulation of Tropical Pacific and Atlantic Oceans Using a HYbrid Coordinate Ocean Model written by and published by . This book was released on 2005 with total page 31 pages. Available in PDF, EPUB and Kindle. Book excerpt: The climatological annual cycle of the tropical Pacific and Atlantic Oceans is simulated using the HYbrid Coordinate Ocean Model (HYCOM) configured in a non-uniform horizontal grid spanning 30 deg S-65.5 deg N and 102 deg E-15 deg E. The model is initialized with climatological summer temperature and salinity and is forced by climatological atmospheric fields derived from the COADS and ECMWF ERA-15 reanalysis. The model is spun up for 20 years to reach a reasonable steady state in the primary region of interest from 20 deg S to 20 deg N, and year 20 is analyzed. The COADS simulation is primarily analyzed because it is slightly better in more respects than the ECMWF simulation, particularly in the representation of upper-ocean thermal structure. Model evaluation is complicated by the fact that the different climatologies, including the atmospheric reanalysis climatologies that drive the model, are averaged over different time intervals. In the tropics, the model thermocline reproduces the observed zonal slopes and meridional ridges/troughs in the thermocline. The simulated Equatorial Undercurrent compares favorably to observations, but is slightly deeper than observed. The model overestimates temperature in the Pacific warm pool regions, both west and east, by more than 1 deg C when compared to all observed climatologies. The model also tends to overestimate temperature in the eastern equatorial cold tongues in both the Atlantic and Pacific, with this overestimate being confined to a very small region of the far eastern Pacific during winter. This overestimate varies substantially depending on which observed climatology is used for the comparison, so model limitations are only partly responsible for the simulated observed temperature differences in the cold tongues.

Book Empirical Approaches for Near term Climate Predictions

Download or read book Empirical Approaches for Near term Climate Predictions written by Daniela Faggiani Dias and published by . This book was released on 2020 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt: Climate variations on seasonal to decadal time scales can have enormous social, economical and environmental impacts. As such, the ability to make skilful and reliable climate predictions at these time scales offers many benefits for climate preparedness, adaptation and resilience. In the recent years, major progress has been made in the development of such predictions with the advent of simulations with global climate models that are initialized from the current climate state. However, many challenges remain including an understanding of the underlying physical mechanisms for skilful predictions and whether such predictions could be improved. The purpose of this thesis is to establish new benchmarks for seasonal to decadal predictions in diverse components of the climate system and to provide some pieces of evidence that help to understand what are the drivers for these predictable patterns. Specifically, we use a suite of empirical models to perform predictions of oceanic and atmospheric variables together with initialized climate predictions to: 1. Understand the contribution of remote and local factors to the predictability of North and Tropical Pacific Oceans Sea Surface Temperature and Land Surface Temperature over Western North America; 2. Provide a higher baseline level skill for the state-of-art global prediction systems, from seasonal to decadal time scales; 3. Explore possible sources of errors in the global climate model simulations using statistical predictive models. First, we isolate contributions to the forecast skill from different spatial and time scales in the Pacific Ocean using a Liner Inverse Modelling (LIM) approach, showing the importance of temporal scale interactions in improving the predictions on decadal time scales. Specifically, we show that the Extratropical North Pacific is a source of predictability for the tropics on seasonal to interannual time scales, while the tropics enhance the forecast skill for the decadal component. We then show that the skill for an empirically-built LIM is comparable to and sometimes better than that from two state-of-art global prediction systems, from seasonal to decadal timescales and for several regions around the globe. These results indicate that the evolution of the system in those areas may not be not fully driven by unpredictable dynamics and that there may be some room for improvement in the dynamical models predictions, given that a low-dimensional linear model is able to generate better skill than the fully-coupled nonlinear model. Bearing that in mind, we use the LIM linear feedback matrix to explore possible sources of errors in the dynamical model simulations and we find that some of the simulated atmospheric and oceanic local and remote feedbacks differ in several key regions from that obtained with observations. These results may indicate sources of error in the dynamical models and therefore in its prediction skill that merit focused attention. We then investigate the role of remote and local predictors in seasonal predictors of minimum and maximum air temperatures over the Western North America, using a Canonical Correlation Analysis approach. We show that remote predictors, in the form of Pacific climate modes, provide the best predictive skill for temperature over land, particularly during wintertime. Lastly, considering that persistence is the widely-used measure when evaluating the predictive skill for dynamical models, we suggest the use of CCA as a much higher benchmark for seasonal predictions of land surface air temperatures.