Global Warming–Induced Changes in El Niño Teleconnections over the North Pacific and North America

2014 ◽  
Vol 27 (24) ◽  
pp. 9050-9064 ◽  
Author(s):  
Zhen-Qiang Zhou ◽  
Shang-Ping Xie ◽  
Xiao-Tong Zheng ◽  
Qinyu Liu ◽  
Hai Wang
Keyword(s):  
Global Warming ◽  
North America ◽  
Spatial Pattern ◽  
Climate Warming ◽  
North American ◽  
El Niño ◽  
El Nino ◽  
Pacific North American ◽  
Sst Warming ◽  
The Mean

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.

Role of Climate Feedback in El Niño–Like SST Response to Global Warming

2014 ◽  
Vol 27 (19) ◽  
pp. 7301-7318 ◽  
Author(s):  
Xiaoliang Song ◽  
Guang J. Zhang
Keyword(s):  
Global Warming ◽  
Water Vapor ◽  
El Niño ◽  
El Nino ◽  
Eastern Pacific ◽  
Climate Feedback ◽  
Central Pacific ◽  
Water Vapor Feedback ◽  
Sst Warming ◽  
The Mean

Abstract Under global warming from the doubling of CO2, the equatorial Pacific experiences an El Niño–like warming, as simulated by most global climate models. A new climate feedback and response analysis method (CFRAM) is applied to 10 years of hourly output of the slab ocean model (SOM) version of the NCAR Community Climate System Model, version 3.0, (CCSM3-SOM) to determine the processes responsible for this warming. Unlike the traditional surface heat budget analysis, the CFRAM can explicitly quantify the contributions of each radiative climate feedback and of each physical and dynamical process of a GCM to temperature changes. The mean bias in the sum of partial SST changes due to each feedback derived with CFRAM in the tropical Pacific is negligible (0.5%) compared to the mean SST change from the CCSM3-SOM simulations, with a spatial pattern correlation of 0.97 between the two. The analysis shows that the factors contributing to the El Niño–like SST warming in the central Pacific are different from those in the eastern Pacific. In the central Pacific, the largest contributor to El Niño–like SST warming is dynamical advection, followed by PBL diffusion, water vapor feedback, and surface evaporation. In contrast, in the eastern Pacific the dominant contributor to El Niño–like SST warming is cloud feedback, with water vapor feedback further amplifying the warming.

scholarly journals Winter 2015/16 Atmospheric and Precipitation Anomalies over North America: El Niño Response and the Role of Noise

2018 ◽  
Vol 146 (3) ◽  
pp. 909-927 ◽  
Author(s):  
Mingyue Chen ◽  
Arun Kumar
Keyword(s):  
North America ◽  
El Niño ◽  
El Nino ◽  
Internal Variability ◽  
Precipitation Response ◽  
Sst Forcing ◽  
Precipitation Anomalies ◽  
The Mean ◽  
The U.S

Abstract The possible causes for the observed winter 2015/16 precipitation anomalies, which were opposite to the mean El Niño signal over the U.S. Southwest, are analyzed based on the ensemble of forecasts from the NCEP Climate Forecast System, version 2 (CFSv2). The analysis focuses on the role of anomalous sea surface temperature (SST) forcing and the contributions of atmospheric internal variability. The model-predicted ensemble mean forecast for December–January–February 2015/16 (DJF 2015/16) North American atmospheric anomalies compared favorably with the El Niño composite, although some difference existed. The predicted pattern was also like that in the previous strong El Niño events of 1982/83 and 1997/98. Therefore, the model largely predicted the teleconnection and precipitation response pattern in DJF 2015/16 like the mean El Niño signal. The observed negative precipitation anomalies over the U.S. Southwest in DJF 2015/16 were not consistent either with the observed or with the model-predicted El Niño composite. Analysis of the member-to-member variability in the ensemble of forecast anomalies allowed quantification of the contribution of atmospheric internal variability in shaping seasonal mean anomalies. There were considerable variations in the outcome of DJF 2015/16 precipitation over North America from one forecast to another even though the predicted SSTs were nearly identical. The observed DJF 2015/16 precipitation anomalies were well within the envelope of possible forecast outcomes. Therefore, the atmospheric internal variability could have played a considerable role in determining the observed DJF 2015/16 negative precipitation anomalies over the U.S. Southwest, and its role is discussed in the context of differences in response.

scholarly journals Impact of the El Niño type and PDO on the winter sub-seasonal North American zonal temperature dipole via the variability of positive PNA patterns

2021 ◽  
Author(s):  
Yao Ge ◽  
Dehai Luo
Keyword(s):  
North America ◽  
North American ◽  
El Niño ◽  
El Nino ◽  
Hadley Cell ◽  
Height Anomaly ◽  
Central Pacific ◽  
The West ◽  
Anticyclonic Anomaly ◽  
The Impact

Abstract In recent years, the winter (from December to February, DJF) North American surface air temperature (SAT) anomaly in midlatitudes shows a “warm west/cold east” (WWCE) dipole pattern. To some extent, the winter WWCE dipole can be considered as being a result of the winter mean of sub-seasonal WWCE events. In this paper, the Pacific SST condition linked to the sub-seasonal WWCE SAT dipole is investigated. It is found that while the sub-seasonal WWCE dipole is related to the positive Pacific North American (PNA+) pattern, the impact of the PNA+ on the WWCE dipole depends on the El Niño SST type and the phase of Pacific decadal Oscillation (PDO). For a central-Pacific (CP) type El Niño, the positive (negative) height anomaly center of PNA+ is located in the west (east) part of North America to result in an intensified WWCE dipole, though the positive PDO favors the WWCE dipole. In contrast, the WWCE dipole is suppressed under an Eastern-Pacific (EP) type El Niño because the PNA+ anticyclonic anomaly dominates the whole North America.Moreover, the physical cause of why the type of El Niño influences the PNA+ is further examined. It is found that the type of El Niño can significantly influence the location of PNA+ through changing North Pacific midlatitude westerly winds (NPWWs). For the CP-type El Niño, the eastward migration of PNA+ is suppressed to favor its anticyclonic (cyclonic) anomaly appearing in the west (east) region of North American owing to reduced NPWWs. But for the EP-type El Niño, NPWWs are intensified to cause the appearance of the PNA+ anticyclonic anomaly over the whole North America due to enhanced Hadley cell and Ferrell cell.

North American Warm-west/Cold-East air temperature pattern and its linkage to different El Nino types

2020 ◽  
Author(s):  
Yao Ge ◽  
Dehai Luo
Keyword(s):  
North America ◽  
North American ◽  
El Niño ◽  
North Pacific ◽  
El Nino ◽  
Anticyclonic Anomaly ◽  
The North ◽  
Westerly Winds ◽  
Dipole Pattern ◽  
Midlatitude Westerly

<p><strong> </strong></p><p>In recent years, the surface air temperature (SAT) anomalies in winter over North America show a “warm-West/cool-East” (WWCE) dipole pattern. The underlying mechanism of the North American WWCE dipole pattern has been an important research topic. This study examines the physical cause of the WWCE dipole generation.</p><p>It is found that the positive phase (PNA<sup>+</sup>) of the Pacific North American (PNA) pattern can lead to the generation of the WWCE SAT dipole. However, the impact of the PNA<sup>+ </sup>on the WWCE SAT dipole over North America depends on the type of the El Nino SST anomaly. When an Eastern-Pacific (EP) type El Nino occurs, the anticyclonic anomaly center of the PNA<sup>+ </sup>over the North American continent is displaced eastward near 100°W due to intensified midlatitude westerly winds over North Pacific so that its anticyclonic anomaly dominates the whole North America. In this case, the cyclonic anomaly of the PNA<sup>+</sup> almost disappears over the North America. Thus, the WWCE SAT dipole over the North America is weakened. In contrast, when a central-Pacific (CP) type El Nino appears, the anticyclonic anomaly center of the associated PNA<sup>+</sup> is located over the North America west coast due to reduced midlatitude westerly winds over North Pacific. As a result, the cyclonic anomaly of the PNA<sup>+</sup> can appear over the east United States to result in an intensified WWCE SAT dipole over the North America</p>

scholarly journals Impact of the El Niño type and PDO on the Winter Sub-seasonal North American Zonal Temperature Dipole via the Variability of Positive PNA Events

2021 ◽  
Author(s):  
Yao Ge ◽  
Dehai Luo
Keyword(s):  
North America ◽  
North American ◽  
El Niño ◽  
El Nino ◽  
Hadley Cell ◽  
Height Anomaly ◽  
Anticyclonic Anomaly ◽  
The Pacific ◽  
Westerly Winds ◽  
Midlatitude Westerly

Abstract In recent years, the winter (from December to February, DJF) North American surface air temperature (SAT) anomaly in midlatitudes shows a “warm west/cold east” (WWCE) dipole pattern. To some extent, the winter WWCE dipole can be considered as being a result of the winter mean of sub-seasonal WWCE events. In this paper, the Pacific SST condition linked to the WWCE SAT dipole is investigated. It is found that while the sub-seasonal WWCE dipole is related to the positive Pacific North American (PNA+) pattern, the impact of the PNA+ on the WWCE dipole depends on the El Niño SST type and the phase of Pacific decadal Oscillation (PDO). For a central-Pacific (CP) type El Niño, the positive (negative) height anomaly center of PNA+ is located in the western (eastern) North America to result in an intensified WWCE dipole, though the positive PDO favors the WWCE dipole. In contrast, the WWCE dipole is suppressed under an Eastern-Pacific (EP) type El Niño because the PNA+ anticyclonic anomaly dominates the whole North America. Moreover, the physical cause of why the El Niño type influences PNA+ is further examined. It is found that the type of El Niño can significantly influence the location of PNA+ through changing North Pacific midlatitude westerly winds associated with the Pacific Hadley cell change. For the CP-type El Niño, the eastward migration of PNA+ is suppressed to favor its anticyclonic (cyclonic) anomaly appearing in the west (east) region of North American owing to reduced midlatitude westerly winds. But for the EP-type El Niño, midlatitude westerly wind is intensified to cause the appearance of PNA+ anticyclonic anomaly over the whole North America due to enhanced Hadley cell.

scholarly journals Enhanced North American carbon uptake associated with El Niño

2019 ◽  
Vol 5 (6) ◽  
pp. eaaw0076 ◽  
Author(s):  
Lei Hu ◽  
Arlyn E. Andrews ◽  
Kirk W. Thoning ◽  
Colm Sweeney ◽  
John B. Miller ◽  
...  
Keyword(s):  
North America ◽  
North American ◽  
Water Availability ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Surface Air Temperature ◽  
Net Ecosystem Exchange ◽  
Carbon Uptake ◽  
Annual Nee

Long-term atmospheric CO2mole fraction and δ13CO2observations over North America document persistent responses to the El Niño–Southern Oscillation. We estimate these responses corresponded to 0.61 (0.45 to 0.79) PgC year−1more North American carbon uptake during El Niño than during La Niña between 2007 and 2015, partially offsetting increases of net tropical biosphere-to-atmosphere carbon flux around El Niño. Anomalies in derived North American net ecosystem exchange (NEE) display strong but opposite correlations with surface air temperature between seasons, while their correlation with water availability was more constant throughout the year, such that water availability is the dominant control on annual NEE variability over North America. These results suggest that increased water availability and favorable temperature conditions (warmer spring and cooler summer) caused enhanced carbon uptake over North America near and during El Niño.

scholarly journals Implications of the permanent El Niño teleconnection "blueprint" for past global and North American hydroclimatology

2011 ◽  
Vol 7 (3) ◽  
pp. 723-743 ◽  
Author(s):  
A. Goldner ◽  
M. Huber ◽  
N. Diffenbaugh ◽  
R. Caballero
Keyword(s):  
United States ◽  
North America ◽  
North American ◽  
El Niño ◽  
Climate Model ◽  
El Nino ◽  
Global Climate Model ◽  
Future Climate Change ◽  
Analogue Model ◽  
Change In Mean

Abstract. Substantial evidence exists for wetter-than-modern continental conditions in North America during the pre-Quaternary warm climate intervals. This is in apparent conflict with the robust global prediction for future climate change of a northward expansion of the subtropical dry zones that should drive aridification of many semiarid regions. Indeed, areas of expected future aridification include much of western North America, where extensive paleoenvironmental records are documented to have been much wetter before the onset of Quaternary ice ages. It has also been proposed that climates previous to the Quaternary may have been characterized as being in a state with warmer-than-modern eastern equatorial sea surface temperatures (SSTs). Because equatorial Pacific SSTs exert strong controls on midlatitude atmospheric circulation and the global hydrologic cycle, the teleconnected response from this permanent El Niño-like mean state has been proposed as a useful analogue model, or "blueprint", for understanding global climatological anomalies in the past. The present study quantitatively explores the implications of this blueprint for past climates with a specific focus on the Miocene and Pliocene, using a global climate model (CAM3.0) and a nested high-resolution climate model (RegCM3) to study the hydrologic impacts on global and North American climate of a change in mean SSTs resembling that which occurs during modern El Niño events. We find that the global circulation response to a permanent El Niño resembles a large, long El Niño event. This state also exhibits equatorial super-rotation, which would represent a fundamental change to the tropical circulations. We also find a southward shift in winter storm tracks in the Pacific and Atlantic, which affects precipitation and temperature over the mid-latitudes. In addition, summertime precipitation increases over the majority of the continental United States. These increases in precipitation are controlled by shifts in the subtropical jet and secondary atmospheric feedbacks. Based on these results and the data proxy comparison, we conclude that a permanent El Niño like state is one potential explanation of wetter-than-modern conditions observed in paleoclimate-proxy records, particularly over the western United States.

scholarly journals The North American Spring Coldness Response to the Persistent Weak Stratospheric Vortex Induced by Extreme El Niño Events

2021 ◽  
Vol 9 ◽  
Author(s):  
Xin Zhou ◽  
Quanliang Chen ◽  
Yang Li ◽  
Yawei Yang ◽  
Shaobo Zhang ◽  
...  
Keyword(s):  
North America ◽  
North American ◽  
El Niño ◽  
Climate Model ◽  
El Nino ◽  
Southern Oscillation ◽  
Stationary Waves ◽  
El Niño Events ◽  
Extreme El Niño ◽  
El Nino Events

The stratospheric pathway is a major driver of El Niño–Southern Oscillation (ENSO) impacts on mid-latitude tropospheric circulation and winter weather. The weak vortex induced by El Niño conditions has been shown to increase the risk of cold spells, especially over Eurasia, but its role for North American winters is less clear. This study involved idealized experiments with the Whole Atmosphere Community Climate Model to examine how the weak winter vortex induced by extreme El Niño events is linked to North American coldness in spring. Contrary to the expected mid-latitude cooling associated with a weak vortex, extreme El Niño events do not lead to North American cooling overall, with daily cold extremes actually decreasing, especially in Canada. The expected cooling is absent in most of North America because of the advection of warmer air masses guided by an enhanced ridge over Canada and a trough over the Aleutian Peninsula. This pattern persists in spring as a result of the trapping of stationary waves from the polar stratosphere and troposphere, implying that the stratospheric influence on North America is sensitive to regional downward wave activities.

scholarly journals A New Paradigm for Continental U.S. Summer Rainfall Variability: Asia–North America Teleconnection

2016 ◽  
Vol 29 (20) ◽  
pp. 7313-7327 ◽  
Author(s):  
Zhiwei Zhu ◽  
Tim Li
Keyword(s):  
North America ◽  
East Asia ◽  
North American ◽  
El Niño ◽  
Monsoon Rainfall ◽  
El Nino ◽  
Rainfall Variability ◽  
East Asian ◽  
Summer Rainfall ◽  
Boreal Summer

Abstract The present study reveals a close relationship between the leading mode of continental U.S. (CONUS) summer rainfall and the East Asian subtropical monsoon rainfall (viz., mei-yu in China, baiu in Japan, and changma in the Korean peninsula). The East Asian subtropical monsoon rainfall and the CONUS dipole rainfall patterns are connected by an upper-level Asia–North America (ANA) teleconnection. The Rossby wave energy propagates along the path of the westerly jet stream (WJS) from East Asia to North America, affecting the CONUS summer rainfall. Mechanisms through which East Asian summer monsoon heating influence North American rainfall are illustrated by idealized anomaly atmospheric general circulation model experiments. In boreal winter, because of the southward shift of the WJS, the Pacific–North American (PNA) pattern can be excited by the tropical central/eastern Pacific heating associated with El Niño, affecting the rainfall over CONUS. In boreal summer, because the WJS is weaker and locates farther to the north, an equatorial heating anomaly cannot directly perturb the WJS. A perturbation heating over subtropical East Asia, however, can trigger an ANA pattern along the path of the WJS, affecting the rainfall over North America. The season-dependent teleconnection scenario illustrates that the predictability source of CONUS rainfall variability is different between winter and summer. While the PNA pattern generated by El Niño is critical for CONUS rainfall in northern winter, the CONUS dipole rainfall variation in boreal summer is mainly governed by the remote forcing over subtropical East Asia via the ANA teleconnection.

scholarly journals An Investigation of the Differences between the North American Dipole and North Atlantic Oscillation

Atmosphere ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 58 ◽  
Author(s):  
Xuejing Zhou ◽  
Wei Wang ◽  
Ruiqiang Ding ◽  
Jianping Li ◽  
Zhaolu Hou ◽  
...  
Keyword(s):  
North Atlantic ◽  
North American ◽  
El Niño ◽  
El Nino ◽  
Tropical Pacific ◽  
Central Pacific ◽  
The North ◽  
El Niño Event ◽  
Sst Warming ◽  
The Tropical Pacific

This study examines the differences between the North American dipole (NAD) and the North American Oscillation (NAO) in terms of their spatial structure, temporal variations, and climate impacts. The results indicate that the sea level pressure anomalies associated with the NAD are located in more western and southern areas than those associated with the NAO, and that the NAD has its own temporal variability. In addition, the NAD has a greater influence on sea surface temperature (SST) and precipitation anomalies in the northern tropical Atlantic (NTA) than the NAO does in the North Atlantic. In the tropical Pacific, the NAD tends to be more effective in forcing SST warming during spring in the northeastern subtropical Pacific (NESP). This can extend equatorward to reach the equatorial central Pacific in the autumn, finally leading to a central Pacific (CP)-type El Niño event. In contrast, the NAO induces only weak SST warming over the NESP, so that a CP-type El Niño event does not occur. Additional analysis indicates that the influence of the NAO can pass to the tropical Pacific only when the NAD and NAO have the same sign, suggesting that the NAD may serve as an important bridge linking the NAO to El Niño–Southern Oscillation (ENSO).

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