--- - attrs: .reference_type: 0 Abstract: 'El Niño–Southern Oscillation (ENSO) induces climate anomalies around the globe. Atmospheric general circulation model simulations are used to investigate how ENSO-induced teleconnection patterns during boreal winter might change in response to global warming in the Pacific–North American sector. As models disagree on changes in the amplitude and spatial pattern of ENSO in response to global warming, for simplicity the same sea surface temperature (SST) pattern of ENSO is prescribed before and after the climate warming. In a warmer climate, precipitation anomalies intensify and move eastward over the equatorial Pacific during El Niño because the enhanced mean SST warming reduces the barrier to deep convection in the eastern basin. Associated with the eastward shift of tropical convective anomalies, the ENSO-forced Pacific–North American (PNA) teleconnection pattern moves eastward and intensifies under the climate warming. By contrast, the PNA mode of atmospheric internal variability remains largely unchanged in pattern, suggesting the importance of tropical convection in shifting atmospheric teleconnections. As the ENSO-induced PNA pattern shifts eastward, rainfall anomalies are expected to intensify on the west coast of North America, and the El Niño–induced surface warming to expand eastward and occupy all of northern North America. The spatial pattern of the mean SST warming affects changes in ENSO teleconnections. The teleconnection changes are larger with patterned mean warming than in an idealized case where the spatially uniform warming is prescribed in the mean state. The results herein suggest that the eastward-shifted PNA pattern is a robust change to be expected in the future, independent of the uncertainty in changes of ENSO itself.' Author: Zhen-Qiang Zhou; Shang-Ping Xie; Xiao-Tong Zheng; Qinyu Liu; Hai Wang DOI: 10.1175/JCLI-D-14-00254.1 Issue: 24 Journal: Journal of Climate Keywords: 'Teleconnections,ENSO,Greenhouse gases,Pacific-North American pattern/oscillation,Climate change' Pages: 9050-9064 Title: Global warming–induced changes in El Niño teleconnections over the North Pacific and North America Volume: 27 Year: 2014 _record_number: 19664 _uuid: 0cc23089-0001-453b-b3f7-99b53325f44b reftype: Journal Article child_publication: /article/10.1175/JCLI-D-14-00254.1 href: https://data.globalchange.gov/reference/0cc23089-0001-453b-b3f7-99b53325f44b.yaml identifier: 0cc23089-0001-453b-b3f7-99b53325f44b uri: /reference/0cc23089-0001-453b-b3f7-99b53325f44b - attrs: .reference_type: 0 Abstract: 'Forced atmospheric teleconnections during 1979–2014 are examined using a 50-member ensemble of atmospheric general circulation model (AGCM) simulations subjected to observed variations in sea surface temperatures (SSTs), sea ice, and carbon dioxide. Three primary modes of forced variability are identified using empirical orthogonal function (EOF) analysis of the ensemble mean wintertime extratropical Northern Hemisphere 500-hPa heights. The principal component time series of the first and second modes are highly correlated with Niño-3.4 and trans-Niño (TNI) SST indices, respectively, indicating mostly tropical sources. Their impacts are largely confined to the Pacific–North American (PNA) sector. The leading mode describes the canonical atmospheric teleconnection associated with El Niño–Southern Oscillation (ENSO) resembling the tropical/Northern Hemisphere pattern. The second mode describes a wave train resembling the classic PNA pattern resulting from atmospheric sensitivity to ENSO asymmetry and from sensitivity to a tropical precursor SST for ENSO development. The third mode is characterized by a hemisphere-scale increasing trend in heights. Based on a comparison with 50-member coupled ocean–atmosphere model simulations, it is argued that this mode is strongly related to radiatively forced climate change, while the other two forced teleconnections are principally related to internal coupled variability. A trend in the leading forced mode is related to ENSO-like decadal variability and dominates the overall observed 500-hPa height trend since 1979. These model results indicate that the trend in the first mode is due to internal variability rather than external radiative forcing.' Author: Tao Zhang; Martin P. Hoerling; Judith Perlwitz; Taiyi Xu DOI: 10.1175/jcli-d-15-0226.1 Issue: 7 Journal: Journal of Climate Keywords: 'Circulation/ Dynamics,Atmosphere-ocean interaction,Atmospheric circulation,ENSO,Variability,Climate variability' Pages: 2333-2357 Title: Forced atmospheric teleconnections during 1979–2014 Volume: 29 Year: 2016 _record_number: 20910 _uuid: 0eca3f20-4ffe-4d20-baaa-2d605941578d reftype: Journal Article child_publication: /article/10.1175/jcli-d-15-0226.1 href: https://data.globalchange.gov/reference/0eca3f20-4ffe-4d20-baaa-2d605941578d.yaml identifier: 0eca3f20-4ffe-4d20-baaa-2d605941578d uri: /reference/0eca3f20-4ffe-4d20-baaa-2d605941578d - attrs: .reference_type: 0 Author: 'Lee, Tong; McPhaden, Michael J.' DOI: 10.1029/2010GL044007 ISSN: 1944-8007 Issue: 14 Journal: Geophysical Research Letters Keywords: El Niño; 1616 Climate variability; 4231 Equatorial oceanography; 4522 ENSO Pages: L14603 Title: Increasing intensity of El Niño in the central-equatorial Pacific Volume: 37 Year: 2010 _record_number: 19629 _uuid: 20e157eb-e2b4-4201-8422-1a0dc8cd499f reftype: Journal Article child_publication: /article/10.1029/2010GL044007 href: https://data.globalchange.gov/reference/20e157eb-e2b4-4201-8422-1a0dc8cd499f.yaml identifier: 20e157eb-e2b4-4201-8422-1a0dc8cd499f uri: /reference/20e157eb-e2b4-4201-8422-1a0dc8cd499f - attrs: .reference_type: 0 Abstract: 'The “typical” global and large-scale regional temperature patterns associated with the low (warm) and high (cold) phases of the Southern Oscillation (SO) are investigated. A total of 12 separate regions were found to have consistent temperature patterns associated with low phase of the SO, while 11 areas were found to have temperature patterns associated with the high phase. Of these areas, 9 have expected temperature patterns during both phases of the SO. In the tropics, temperature anomalies are of the same sign as the SO-related sea surface temperature (SST) anomaly in all land regions except for one area in the west Pacific. Three extratropical responses to the low phase of the SO are found over North America and one is found in Japan. High SO-temperature patterns were found in the extratropies for Japan, western Europe, and northwestern North America. The identified temperature responses are more consistent in tropical regions than in the extratropies. The SO can influence the estimation of global surface temperature anomalies.' Author: Michael S. Halpert; Chester F. Ropelewski DOI: 10.1175/1520-0442(1992)005<0577:STPAWT>2.0.CO;2 Issue: 6 Journal: Journal of Climate Pages: 577-593 Title: Surface temperature patterns associated with the Southern Oscillation Volume: 5 Year: 1992 _record_number: 19617 _uuid: 20e48aa7-625b-4527-8639-e0bcd469b79d reftype: Journal Article child_publication: /article/10.1175/1520-0442(1992)005%3C0577:STPAWT%3E2.0.CO;2 href: https://data.globalchange.gov/reference/20e48aa7-625b-4527-8639-e0bcd469b79d.yaml identifier: 20e48aa7-625b-4527-8639-e0bcd469b79d uri: /reference/20e48aa7-625b-4527-8639-e0bcd469b79d - attrs: .reference_type: 0 Abstract: 'Analysis of a suite of atmospheric GCM experiments for 1950–94 shows that both the tropical and the extratropical wintertime climate respond nonlinearly with respect to opposite phases of ENSO. Such behavior is found to be reproducible among four different GCMs studied and confirms that several observed asymmetries in wintertime anomalies with respect to ENSO phases are symptomatic of nonlinearity rather than sampling error. Nonlinearity in the tropical Pacific rainfall response is related to an SST threshold for convection that leads to saturation at modestly cold SST forcing but a linear increase for warmer SST forcing. A spatial shift in the rainfall response is also a feature of the various GCMs’ nonlinear behavior, that is, accentuated by the large zonal gradient of climatological SSTs across the equatorial Pacific and the fact that convection responds to the total rather than the anomalous SST. Regarding upper-tropospheric teleconnection responses over the Pacific–North American region, nonlinearity exists in both the strength of the midlatitude response and its spatial phase. The four GCMs are found to be unanimous in having a 500-mb height response whose amplitude is roughly double for extreme warm tropical Pacific SSTs as compared with extreme cold SST forcing. The longitudinal phase of the GCMs’ teleconnections is also shifted eastward during warm events as compared with cold events, though this displacement is smaller than that observed. Further analysis of model simulations reveals that nonlinearity in climate responses emerges mainly for stronger ENSO events, and a predominantly linear response is found for weaker tropical Pacific SST forcing. In particular, climate simulations using both realistic and idealized SSTs indicate that tropical Pacific SST anomalies greater than one standard deviation of the interannual variation are required for initiating an appreciable nonlinear climate response.' Author: Martin P. Hoerling; Arun Kumar; Taiyi Xu DOI: 10.1175/1520-0442(2001)014<1277:ROTNCR>2.0.CO;2 Issue: 6 Journal: Journal of Climate Pages: 1277-1293 Title: Robustness of the nonlinear climate response to ENSO’s extreme phases Volume: 14 Year: 2001 _record_number: 19620 _uuid: 26e7ebff-78f5-4697-8203-cfc9586c6a0c reftype: Journal Article child_publication: /article/10.1175/1520-0442(2001)014%3C1277:ROTNCR%3E2.0.CO;2 href: https://data.globalchange.gov/reference/26e7ebff-78f5-4697-8203-cfc9586c6a0c.yaml identifier: 26e7ebff-78f5-4697-8203-cfc9586c6a0c uri: /reference/26e7ebff-78f5-4697-8203-cfc9586c6a0c - attrs: .reference_type: 0 Abstract: 'The two leading modes of North Pacific sea surface temperature (SST) and sea level pressure (SLP), as well as their connections to tropical variability, are explored in the 24 coupled climate models used in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) to evaluate North Pacific decadal variability (NPDV) in the past [twentieth century; climate of the twentieth century (20C3M) scenario] and future [twenty-first century; Special Report on Emissions Scenarios (SRES) A1B scenario] climate. Results indicate that the two dominant modes of North Pacific oceanic variability, the Pacific decadal oscillation (PDO) and the North Pacific Gyre Oscillation (NPGO), do not exhibit significant changes in their spatial and temporal characteristics under greenhouse warming. However, the ability of the models to capture the dynamics associated with the leading North Pacific oceanic modes, including their link to the corresponding atmospheric forcing patterns and to tropical variability, is questionable.The temporal and spatial statistics of the North Pacific Ocean modes exhibit significant discrepancies from observations in their twentieth-century climate, most visibly for the second mode, which has significantly more low-frequency power and higher variance than in observations. The dynamical coupling between the North Pacific Ocean and atmosphere modes evident in the observations is very strong in the models for the first atmosphere–ocean coupled mode, which represents covariability of the PDO pattern with the Aleutian low (AL). However, the link for the second atmosphere–ocean coupled mode, describing covariability of an NPGO-like SST pattern with the North Pacific Oscillation (NPO), is not as clearly reproduced, with some models showing no relationship between the two.Exploring the tropical Pacific–North Pacific teleconnections reveals more issues with the models. In contrast with observations, the atmospheric teleconnection excited by the El Niño–Southern Oscillation in the models does not project strongly on the AL–PDO coupled mode because of the displacement of the center of action of the AL in most models. Moreover, most models fail to show the observational connection between El Niño Modoki–central Pacific warming and NPO variability in the North Pacific. In fact, the atmospheric teleconnections associated with El Niño Modoki in some models have a significant projection on, and excite the AL–PDO coupled mode instead. Because of the known links between tropical Pacific variability and NPDV, these analyses demonstrate that focus on the North Pacific variability of climate models in isolation from tropical dynamics is likely to lead to an incomplete view, and inadequate prediction, of NPDV.' Author: Jason C. Furtado; Emanuele Di Lorenzo; Niklas Schneider; Nicholas A. Bond DOI: 10.1175/2010JCLI3584.1 Issue: 12 Journal: Journal of Climate Keywords: 'Climate change,North Pacific Ocean,Decadal variability,Sea surface temperature,Sea level,Pressure,Pacific decadal oscillation,Coupled models' Pages: 3049-3067 Title: North Pacific decadal variability and climate change in the IPCC AR4 models Volume: 24 Year: 2011 _record_number: 19612 _uuid: 2f2d945e-b0fe-43d7-a521-2a9219236862 reftype: Journal Article child_publication: /article/10.1175/2010JCLI3584.1 href: https://data.globalchange.gov/reference/2f2d945e-b0fe-43d7-a521-2a9219236862.yaml identifier: 2f2d945e-b0fe-43d7-a521-2a9219236862 uri: /reference/2f2d945e-b0fe-43d7-a521-2a9219236862 - attrs: .reference_type: 0 Abstract: 'Distinct biases are found in the pattern and teleconnections of the Arctic Oscillation (AO) in 32 climate models that participate the Coupled Model Intercomparison Project Phase 5 (CMIP5). Compared with observations, the Pacific (Atlantic) center of AO is excessively strong (weak) in most of the 32 CMIP5 models, and the AO-related surface air temperature anomalies are generally weak over the Eurasian continent and North America. These biases are closely tied to the excessively strong linkage, which is marginal in observations, between AO and the North Pacific mode (NPM)—the leading variability of the North Pacific sea level pressure. It implies that the AO in CMIP5 models may be compounded with some regional mode over the North Pacific. Accordingly, a bias-correction method was proposed via correcting the AO index (AOI) to improve the diagnostic estimates of the AO teleconnections. The results suggest that the biases in the pattern and teleconnections of AO can be significantly reduced when the NPM variability is linearly removed from the AOI.' Author: Hainan Gong; Lin Wang; Wen Chen; Xiaolong Chen; Debashis Nath DOI: 10.1088/1748-9326/12/1/014001 Issue: 1 Journal: Environmental Research Letters Pages: 014001 Title: Biases of the wintertime Arctic Oscillation in CMIP5 models Volume: 12 Year: 2017 _record_number: 20879 _uuid: 33619644-54fd-43b3-9fa8-e7ac5ddec196 reftype: Journal Article child_publication: /article/10.1088/1748-9326/12/1/014001 href: https://data.globalchange.gov/reference/33619644-54fd-43b3-9fa8-e7ac5ddec196.yaml identifier: 33619644-54fd-43b3-9fa8-e7ac5ddec196 uri: /reference/33619644-54fd-43b3-9fa8-e7ac5ddec196 - attrs: .reference_type: 0 Abstract: 'In this study, the nature and causes for observed regional precipitation trends during 1977-2006 are diagnosed. It is found that major features of regional trends in annual precipitation during 1977-2006 are consistent with an atmospheric response to observed sea surface temperature (SST) variability. This includes drying over the eastern Pacific Ocean that extends into western portions of the Americas related to a cooling of eastern Pacific SSTs, and broad increases in rainfall over the tropical Eastern Hemisphere, including a Sahelian rainfall recovery and increased wetness over the Indo West Pacific related to North Atlantic and Indo West Pacific ocean warming. It is further determined that these relationships between SST and rainfall change are generally not symptomatic of human-induced emissions of greenhouse gases (GHGs) and aerosols. The intensity of regional trends simulated in climate models using observed time variability in green house gases, tropospheric sulfate aerosol, and solar and volcanic aerosol forcing are appreciably weaker than those observed and also weaker than those simulated in atmospheric models using only observed SST forcing. The pattern of rainfall trends occurring in response to such external radiative forcing also departs significantly from observations, especially a simulated increase in rainfall over the tropical Pacific and southeastern Australia that are opposite in sign to the actual drying in these areas. Additional experiments illustrate that the discrepancy between observed and GHG-forced rainfall changes during 1977-2006 results mostly from the differences between observed and externally forced SST trends. Only weak rainfall sensitivity is found to occur in response to the uniform distribution of SST warming that is induced by GHG and aerosol forcing, whereas the particular pattern of the observed SST change that includes an increased SST contrast between the east Pacific and the Indian Ocean, and strong regional warming of the North Atlantic Ocean, was a key driver of regional rainfall trends. The results of this attribution study on the causes for 1977-2006 regional rainfall changes are used to discuss prediction challenges including the likelihood that recent rainfall trends might persist.' Author: 'Hoerling, M.; Eischeid, J.; Perlwitz, J.' DOI: 10.1175/2009jcli3420.1 Date: Apr Issue: 8 Journal: Journal of Climate Keywords: sea-surface temperatures; southern-oscillation; sahel rainfall; climate; model; el-nino; attribution; prediction; atlantic; gpcp Language: English Pages: 2131-2145 Title: 'Regional precipitation trends: Distinguishing natural variability from anthropogenic forcing' Volume: 23 Year: 2010 _record_number: 7051 _uuid: 39a41162-bda6-4606-9561-37e3e1839913 reftype: Journal Article child_publication: /article/10.1175/2009jcli3420.1 href: https://data.globalchange.gov/reference/39a41162-bda6-4606-9561-37e3e1839913.yaml identifier: 39a41162-bda6-4606-9561-37e3e1839913 uri: /reference/39a41162-bda6-4606-9561-37e3e1839913 - attrs: .reference_type: 0 Abstract: 'The accurate representation of precipitation is a recurring issue in climate models. El Niño–Southern Oscillation (ENSO) precipitation teleconnections provide a test bed for comparison of modeled to observed precipitation. The simulation quality for the atmospheric component of models in the Coupled Model Intercomparison Project (CMIP) phase 5 (CMIP5) is assessed here, using the ensemble of runs driven by observed sea surface temperatures (SSTs). Simulated seasonal precipitation teleconnection patterns are compared to observations during 1979–2005 and to the ensemble of CMIP phase 3 (CMIP3). Within regions of strong observed teleconnections (equatorial South America, the western equatorial Pacific, and a southern section of North America), there is little improvement in the CMIP5 ensemble relative to CMIP3 in amplitude and spatial correlation metrics of precipitation. Spatial patterns within each region exhibit substantial departures from observations, with spatial correlation coefficients typically less than 0.5. However, the atmospheric models do considerably better in other measures. First, the amplitude of the precipitation response (root-mean-square deviation over each region) is well estimated by the mean of the amplitudes from the individual models. This is in contrast with the amplitude of the multimodel ensemble mean, which is systematically smaller (by about 30%–40%) in the selected teleconnection regions. Second, high intermodel agreement on teleconnection sign provides a good predictor for high model agreement with observed teleconnections. The ability of the model ensemble to yield amplitude and sign measures that agree with the observed signal for ENSO precipitation teleconnections lends supporting evidence for the use of corresponding measures in global warming projections.' Author: Baird Langenbrunner; J. David Neelin DOI: 10.1175/jcli-d-12-00542.1 Issue: 13 Journal: Journal of Climate Keywords: 'El Nino,ENSO,Teleconnections,Climate models,Ensembles,Model evaluation/performance' Pages: 4431-4446 Title: Analyzing ENSO teleconnections in CMIP models as a measure of model fidelity in simulating precipitation Volume: 26 Year: 2013 _record_number: 20886 _uuid: 3c2004f1-4f51-4b84-8ec0-64a5e2c3a790 reftype: Journal Article child_publication: /article/10.1175/jcli-d-12-00542.1 href: https://data.globalchange.gov/reference/3c2004f1-4f51-4b84-8ec0-64a5e2c3a790.yaml identifier: 3c2004f1-4f51-4b84-8ec0-64a5e2c3a790 uri: /reference/3c2004f1-4f51-4b84-8ec0-64a5e2c3a790 - attrs: .reference_type: 0 Abstract: 'In what is arguably one of the most dramatic phenomena possibly associated with climate change or natural climate variability, the location of El Niño has shifted more to the central Pacific in recent decades. In this study, we use statistical analyses, numerical model experiments and case studies to show that the Central-Pacific El Niño enhances the drying effect, but weakens the wetting effect, typically produced by traditional Eastern-Pacific El Niño events on the US winter precipitation. As a result, the emerging Central-Pacific El Niño produces an overall drying effect on the US winter, particularly over the Ohio–Mississippi Valley, Pacific Northwest and Southeast. The enhanced drying effect is related to a more southward displacement of tropospheric jet streams that control the movements of winter storms. The results of this study imply that the emergence of the Central-Pacific El Niño in recent decades may be one factor contributing to the recent prevalence of extended droughts in the US.' Author: Jin-Yi Yu; Yuhao Zou DOI: 10.1088/1748-9326/8/1/014019 Issue: 1 Journal: Environmental Research Letters Pages: 014019 Title: The enhanced drying effect of Central-Pacific El Niño on US winter Volume: 8 Year: 2013 _record_number: 20325 _uuid: 4e933785-f080-4cc8-86a0-5259159292e0 reftype: Journal Article child_publication: /article/10.1088/1748-9326/8/1/014019 href: https://data.globalchange.gov/reference/4e933785-f080-4cc8-86a0-5259159292e0.yaml identifier: 4e933785-f080-4cc8-86a0-5259159292e0 uri: /reference/4e933785-f080-4cc8-86a0-5259159292e0 - attrs: .reference_type: 7 Author: J.H. Christensen; K. Krishna Kumar; E. Aldrian; S.-I. An; I.F.A. Cavalcanti; M. de Castro; W. Dong; P. Goswami; A. Hall; J.K. Kanyanga; A. Kitoh; J. Kossin; N.-C. Lau; J. Renwick; D.B. Stephenson; S.-P. Xie; T. Zhou Book Title: 'Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change' Editor: T.F. Stocker; D. Qin; G.-K. Plattner; M. Tignor; S.K. Allen; J. Boschung; A. Nauels; Y. Xia; V. Bex; P.M. Midgley ISBN: ISBN 978-1-107-66182-0 Pages: 1217–1308 Place Published: 'Cambridge, United Kingdom and New York, NY, USA' Publisher: Cambridge University Press Title: Climate phenomena and their relevance for future regional climate change URL: http://www.climatechange2013.org/report/full-report/ Year: 2013 _record_number: 16449 _uuid: 541fc57b-d7ad-4617-97de-2df91f99afc0 reftype: Book Section child_publication: /report/ipcc-ar5-wg1/chapter/wg1-ar5-chapter14-final href: https://data.globalchange.gov/reference/541fc57b-d7ad-4617-97de-2df91f99afc0.yaml identifier: 541fc57b-d7ad-4617-97de-2df91f99afc0 uri: /reference/541fc57b-d7ad-4617-97de-2df91f99afc0 - attrs: .reference_type: 0 Abstract: 'Greenland ice-core data have revealed large decadal climate variations over the North Atlantic that can be related to a major source of low-frequency variability, the North Atlantic Oscillation. Over the past decade, the Oscillation has remained in one extreme phase during the winters, contributing significantly to the recent wintertime warmth across Europe and to cold conditions in the northwest Atlantic. An evaluation of the atmospheric moisture budget reveals coherent large-scale changes since 1980 that are linked to recent dry conditions over southern Europe and the Mediterranean, whereas northern Europe and parts of Scandinavia have generally experienced wetter than normal conditions.%U ' Author: 'Hurrell, James W.' DOI: 10.1126/science.269.5224.676 Issue: 5224 Journal: Science Pages: 676-679 Title: 'Decadal trends in the North Atlantic oscillation: Regional temperatures and precipitation' Volume: 269 Year: 1995 _record_number: 20547 _uuid: 56bdd0b7-8658-48c1-9814-24ea5a5c2fc9 reftype: Journal Article child_publication: /article/10.1126/science.269.5224.676 href: https://data.globalchange.gov/reference/56bdd0b7-8658-48c1-9814-24ea5a5c2fc9.yaml identifier: 56bdd0b7-8658-48c1-9814-24ea5a5c2fc9 uri: /reference/56bdd0b7-8658-48c1-9814-24ea5a5c2fc9 - attrs: .reference_type: 0 Abstract: 'The potential of recent Arctic changes to influence hemispheric weather is a complex and controversial topic with considerable uncertainty, as time series of potential linkages are short (<10 yr) and understanding involves the relative contribution of direct forcing by Arctic changes on a chaotic climatic system. A way forward is through further investigation of atmospheric dynamic mechanisms. During several exceptionally warm Arctic winters since 2007, sea ice loss in the Barents and Kara Seas initiated eastward-propagating wave trains of high and low pressure. Anomalous high pressure east of the Ural Mountains advected Arctic air over central and eastern Asia, resulting in persistent cold spells. Blocking near Greenland related to low-level temperature anomalies led to northerly flow into eastern North America, inducing persistent cold periods. Potential Arctic connections in Europe are less clear. Variability in the North Pacific can reinforce downstream Arctic changes, and Arctic amplification can accentuate the impact of Pacific variability. The authors emphasize multiple linkage mechanisms that are regional, episodic, and based on amplification of existing jet stream wave patterns, which are the result of a combination of internal variability, lower-tropospheric temperature anomalies, and midlatitude teleconnections. The quantitative impact of Arctic change on midlatitude weather may not be resolved within the foreseeable future, yet new studies of the changing Arctic and subarctic low-frequency dynamics, together with additional Arctic observations, can contribute to improved skill in extended-range forecasts, as planned by the WMO Polar Prediction Project (PPP).' Author: James Overland; Jennifer A. Francis; Richard Hall; Edward Hanna; Seong-Joong Kim; Timo Vihma DOI: 10.1175/JCLI-D-14-00822.1 Issue: 20 Journal: Journal of Climate Keywords: 'Arctic,Arctic Oscillation,Atmospheric circulation,Blocking,Teleconnections,Climate variability' Pages: 7917-7932 Title: 'The melting Arctic and midlatitude weather patterns: Are they connected?' Volume: 28 Year: 2015 _record_number: 19858 _uuid: 655f721c-7b5f-4f69-a788-fa1ee8a2488e reftype: Journal Article child_publication: /article/10.1175/JCLI-D-14-00822.1 href: https://data.globalchange.gov/reference/655f721c-7b5f-4f69-a788-fa1ee8a2488e.yaml identifier: 655f721c-7b5f-4f69-a788-fa1ee8a2488e uri: /reference/655f721c-7b5f-4f69-a788-fa1ee8a2488e - attrs: .reference_type: 0 Abstract: 'Time series of U.S. daily heavy precipitation (95th percentile) are analyzed to determine factors responsible for regionality and seasonality in their 1979–2013 trends. For annual conditions, contiguous U.S. trends have been characterized by increases in precipitation associated with heavy daily events across the northern United States and decreases across the southern United States. Diagnosis of climate simulations (CCSM4 and CAM4) reveals that the evolution of observed sea surface temperatures (SSTs) was a more important factor influencing these trends than boundary condition changes linked to external radiative forcing alone. Since 1979, the latter induces widespread, but mostly weak, increases in precipitation associated with heavy daily events. The former induces a meridional pattern of northern U.S. increases and southern U.S. decreases as observed, the magnitude of which closely aligns with observed changes, especially over the south and far west. Analysis of model ensemble spread reveals that appreciable 35-yr trends in heavy daily precipitation can occur in the absence of forcing, thereby limiting detection of the weak anthropogenic influence at regional scales.Analysis of the seasonality in heavy daily precipitation trends supports physical arguments that their changes during 1979–2013 have been intimately linked to internal decadal ocean variability and less so to human-induced climate change. Most of the southern U.S. decrease has occurred during the cold season that has been dynamically driven by an atmospheric circulation reminiscent of teleconnections linked to cold tropical eastern Pacific SSTs. Most of the northeastern U.S. increase has been a warm season phenomenon, the immediate cause for which remains unresolved.' Author: Martin Hoerling; Jon Eischeid; Judith Perlwitz; Xiao-Wei Quan; Klaus Wolter; Linyin Cheng DOI: 10.1175/jcli-d-15-0441.1 Issue: 7 Journal: Journal of Climate Keywords: 'Geographic location/entity,North America,Physical Meteorology and Climatology,Atmosphere-ocean interaction,Climate change,Climate variability,Variability,Trends' Pages: 2313-2332 Title: Characterizing recent trends in U.S. heavy precipitation Volume: 29 Year: 2016 _record_number: 20882 _uuid: 6782b38a-17f4-40d2-9cff-da07da38f76a reftype: Journal Article child_publication: /article/10.1175/jcli-d-15-0441.1 href: https://data.globalchange.gov/reference/6782b38a-17f4-40d2-9cff-da07da38f76a.yaml identifier: 6782b38a-17f4-40d2-9cff-da07da38f76a uri: /reference/6782b38a-17f4-40d2-9cff-da07da38f76a - attrs: .reference_type: 0 Abstract: 'El Niño–Southern Oscillation (ENSO) is a naturally occurring mode of tropical Pacific variability, with global impacts on society and natural ecosystems. While it has long been known that El Niño events display a diverse range of amplitudes, triggers, spatial patterns, and life cycles, the realization that ENSO’s impacts can be highly sensitive to this event-to-event diversity is driving a renewed interest in the subject. This paper surveys our current state of knowledge of ENSO diversity, identifies key gaps in understanding, and outlines some promising future research directions.' Author: Antonietta Capotondi; Andrew T. Wittenberg; Matthew Newman; Emanuele Di Lorenzo; Jin-Yi Yu; Pascale Braconnot; Julia Cole; Boris Dewitte; Benjamin Giese; Eric Guilyardi; Fei-Fei Jin; Kristopher Karnauskas; Benjamin Kirtman; Tong Lee; Niklas Schneider; Yan Xue; Sang-Wook Yeh DOI: 10.1175/BAMS-D-13-00117.1 Issue: 6 Journal: Bulletin of the American Meteorological Society Pages: 921-938 Title: Understanding ENSO diversity Volume: 96 (12) Year: 2015 _record_number: 19601 _uuid: 7f094c4f-301c-422c-8fba-371b5502767c reftype: Journal Article child_publication: /article/10.1175/BAMS-D-13-00117.1 href: https://data.globalchange.gov/reference/7f094c4f-301c-422c-8fba-371b5502767c.yaml identifier: 7f094c4f-301c-422c-8fba-371b5502767c uri: /reference/7f094c4f-301c-422c-8fba-371b5502767c - attrs: .reference_type: 0 Author: 'Gillett, N. P.; Fyfe, J. C.' DOI: 10.1002/grl.50249 Issue: 6 Journal: Geophysical Research Letters Keywords: annular modes; NAM; SAM; NAO; CMIP5; 1626 Global climate models; 1627 Coupled models of the climate system; 1620 Climate dynamics; 3305 Climate change and variability; 3337 Global climate models Pages: 1189-1193 Title: Annular mode changes in the CMIP5 simulations Volume: 40 Year: 2013 _record_number: 19614 _uuid: 94d52b54-b40c-4447-a525-b79062fcedf1 reftype: Journal Article child_publication: /article/10.1002/grl.50249 href: https://data.globalchange.gov/reference/94d52b54-b40c-4447-a525-b79062fcedf1.yaml identifier: 94d52b54-b40c-4447-a525-b79062fcedf1 uri: /reference/94d52b54-b40c-4447-a525-b79062fcedf1 - attrs: .reference_type: 0 Abstract: 'The North Atlantic Oscillation (NAO) and the closely related Arctic Oscillation (AO) strongly affect Northern Hemisphere (NH) surface temperatures with patterns reported similar to the global warming trend. The NAO and AO were in a positive trend for much of the 1970s and 1980s with historic highs in the early 1990s, and it has been suggested that they contributed significantly to the global warming signal. The trends in standard indices of the AO, NAO, and NH average surface temperature for December–February, 1950–2004, and the associated patterns in surface temperature anomalies are examined. Also analyzed are factors previously identified as relating to the NAO, AO, and their positive trend: North Atlantic sea surface temperatures (SSTs), Indo–Pacific warm pool SSTs, stratospheric circulation, and Eurasian snow cover. Recently, the NAO and AO indices have been decreasing; when these data are included, the overall trends for the past 30 years are weak to nonexistent and are strongly dependent on the choice of start and end date. In clear distinction, the wintertime hemispheric warming trend has been vigorous and consistent throughout the entire period. When considered for the whole hemisphere, the NAO/AO patterns can also be distinguished from the trend pattern. Thus the December–February warming trend may be distinguished from the AO and NAO in terms of the strength, consistency, and pattern of the trend. These results are insensitive to choice of index or dataset. While the NAO and AO may contribute to hemispheric and regional warming for multiyear periods, these differences suggest that the large-scale features of the global warming trend over the last 30 years are unrelated to the AO and NAO. The related factors may also be clearly distinguished, with warm pool SSTs linked to the warming trend, while the others are linked to the NAO and AO.' Author: Judah Cohen; Mathew Barlow DOI: 10.1175/jcli3530.1 Issue: 21 Journal: Journal of Climate Pages: 4498-4513 Title: 'The NAO, the AO, and global warming: How closely related?' Volume: 18 Year: 2005 _record_number: 20545 _uuid: 99d2a237-b811-4c42-9bc3-cfd6cbb76504 reftype: Journal Article child_publication: /article/10.1175/jcli3530.1 href: https://data.globalchange.gov/reference/99d2a237-b811-4c42-9bc3-cfd6cbb76504.yaml identifier: 99d2a237-b811-4c42-9bc3-cfd6cbb76504 uri: /reference/99d2a237-b811-4c42-9bc3-cfd6cbb76504 - attrs: .publisher: Macmillan Publishers Limited. All rights reserved .reference_type: 0 Author: 'Yeh, Sang-Wook; Kug, Jong-Seong; Dewitte, Boris; Kwon, Min-Ho; Kirtman, Ben P.; Jin, Fei-Fei' DOI: 10.1038/nature08316 Date: 09/24/print Issue: 7263 Journal: Nature Pages: 511-514 Title: El Niño in a changing climate Volume: 461 Year: 2009 _record_number: 19662 _uuid: a3771226-1458-474e-ba3b-f046d4351558 reftype: Journal Article child_publication: /article/10.1038/nature08316 href: https://data.globalchange.gov/reference/a3771226-1458-474e-ba3b-f046d4351558.yaml identifier: a3771226-1458-474e-ba3b-f046d4351558 uri: /reference/a3771226-1458-474e-ba3b-f046d4351558 - attrs: .reference_type: 7 Author: G. Flato; J. Marotzke; B. Abiodun; P. Braconnot; S.C. Chou; W. Collins; P. Cox; F. Driouech; S. Emori; V. Eyring; C. Forest; P. Gleckler; E. Guilyardi; C. Jakob; V. Kattsov; C. Reason; M. Rummukainen Book Title: 'Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change' Editor: T.F. Stocker; D. Qin; G.-K. Plattner; M. Tignor; S.K. Allen; J. Boschung; A. Nauels; Y. Xia; V. Bex; P.M. Midgley ISBN: ISBN 978-1-107-66182-0 Pages: 741–866 Place Published: 'Cambridge, United Kingdom and New York, NY, USA' Publisher: Cambridge University Press Title: Evaluation of climate models URL: http://www.climatechange2013.org/report/full-report/ Year: 2013 _record_number: 16454 _uuid: a46eaad1-5c17-46f7-bba6-d3fee718a092 reftype: Book Section child_publication: /report/ipcc-ar5-wg1/chapter/wg1-ar5-chapter09-final href: https://data.globalchange.gov/reference/a46eaad1-5c17-46f7-bba6-d3fee718a092.yaml identifier: a46eaad1-5c17-46f7-bba6-d3fee718a092 uri: /reference/a46eaad1-5c17-46f7-bba6-d3fee718a092 - attrs: .reference_type: 0 Abstract: 'The North Atlantic Oscillation (NAO) is the primary mode of atmospheric variability over the Atlantic Ocean and plays an important role in climate variability over eastern North America. The frequency of extreme climate events and the associated social and economic impacts is also tied to the strength and phase of the NAO. In this study, seasonal phases of the NAO are compared to changes in the frequency and distribution of winter season (December–March) precipitation-type observations for the years 1961–2001 in the eastern U.S. Statistically significant increases in the frequency of rain observations across the study region are associated with positive NAO phases. Additionally, significant increases in the occurrence of snow are confined to the northern portion of the eastern U.S. during positive NAO phases. Connections between the phase of the NAO and the prevailing synoptic-scale circulation, at least partially, explain the inter-seasonal distribution of precipitation types across the eastern U.S. Using an intra-seasonal or intra-monthly NAO index may reveal a more robust relationship between snowfall observations across the eastern U.S. and surface pressure variability over the North Atlantic.' Author: 'Durkee, J. D.; Frye, J. D.; Fuhrmann, C. M.; Lacke, M. C.; Jeong, H. G.; Mote, T. L.' DOI: 10.1007/s00704-007-0345-x Issue: 1 Journal: Theoretical and Applied Climatology Pages: 51-65 Title: Effects of the North Atlantic Oscillation on precipitation-type frequency and distribution in the eastern United States Volume: 94 Year: 2008 _record_number: 20278 _uuid: b35b1dec-2d93-42a8-8a85-ba1a2cfa76b9 reftype: Journal Article child_publication: /article/10.1007/s00704-007-0345-x href: https://data.globalchange.gov/reference/b35b1dec-2d93-42a8-8a85-ba1a2cfa76b9.yaml identifier: b35b1dec-2d93-42a8-8a85-ba1a2cfa76b9 uri: /reference/b35b1dec-2d93-42a8-8a85-ba1a2cfa76b9