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

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.

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.

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.

Tropical and Extratropical Air-Sea Interactions: Modes of Climate Variations provides a thorough introduction to global atmospheric and oceanic processes, as well as tropical, subtropical and mid-latitude ocean-atmosphere interactions. Written by leading experts in the field, each chapter is dedicated to a specific topic of air-sea interactions (such as ENSO, IOD, Atlantic Nino, ENSO Modoki, and newly discovered coastal Niños/Niñas) and their teleconnections. As the first book to cover all topics of tropical and extra-tropical air-sea interactions and new modes of climate variations, this book is an excellent resource for researchers and students of ocean, atmospheric and climate sciences. - Presents case studies on the ocean-atmosphere phenomena, including El Nino Southern Oscillation (ENSO), Indian Ocean Dipole and different Nino/Nina phenomena - Provides a clear description of air-sea relationships across the world's ocean with an analysis of air-sea relations in different time scales and a focus on climate change - Includes prospects for air-sea interaction research, thus benefiting young researchers and students

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.

Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 189. Climate Dynamics: Why Does Climate Vary? presents the major climate phenomena within the climate system to underscore the potency of dynamics in giving rise to climate change and variability. These phenomena include deep convection over the Indo-Pacific warm pool and its planetary-scale organization: the Madden-Julian Oscillation, the monsoons, the El Niño-Southern Oscillation, the Pacific Decadal Oscillation, and the low-frequency variability of extratropical circulations. The volume also has a chapter focusing on the discussion of the causes of the recent melting of Arctic sea ice and a chapter devoted to the discussion of the causes of recent changes in the frequency and intensity of tropical cyclones. On each topic, the basic material of climate dynamics is covered to aid the understanding of the forefront research, making the volume accessible to a broad spectrum of readers. The volume highlights include Diabatic and nonlinear aspects of the El Niño-Southern Oscillation Causes of sea ice melting in the Arctic Impact of global warming on tropical cyclone activity Origins of the Pacific Decadal Oscillation Causes of climate variability of Asian monsoons The volume will be of particular interest to graduate students and young researchers in atmospheric and oceanic sciences and related disciplines such as geology and geography. The book will also be a good read for those who have a more general interest in the Earth's climate and why it varies.