scholarly journals Observed Atmospheric Responses to Global SST Variability Modes: A Unified Assessment Using GEFA*

2010 ◽  
Vol 23 (7) ◽  
pp. 1739-1759 ◽  
Author(s):  
Na Wen ◽  
Zhengyu Liu ◽  
Qinyu Liu ◽  
Claude Frankignoul
Keyword(s):  
North Atlantic ◽  
Wave Train ◽  
Tropical Indian Ocean ◽  
Tropical Pacific ◽  
Atmospheric Response ◽  
The North ◽  
Sst Variability ◽  
The North Atlantic ◽  
The North Atlantic Oscillation ◽  
The Tropical Pacific

Abstract The authors present a comprehensive assessment of the observed atmospheric response to SST variability modes in a unified approach using the Generalized Equilibrium Feedback Analysis (GEFA). This study confirms a dominant atmospheric response to the tropical SST variability associated with ENSO. A further analysis shows that the classical response to ENSO consists of two parts, one responding to the tropical Pacific ENSO mode and the other to the tropical Indian Ocean monopole (IOM) mode. The Pacific ENSO generates a significant baroclinic Rossby wave response locally over the tropical Pacific as well as equivalent barotropic wave train responses remotely into the extratropics. The IOM mode forces a strongly zonally symmetric response throughout the tropics and the extratropics. Furthermore, modest atmospheric responses to other oceanic modes were identified. For example, the North Pacific SST variability mode appears to generate an equivalent barotropic warm SST-ridge response locally over the Aleutian low with significant downstream influence on the North Atlantic Oscillation (NAO), whereas the North Atlantic tripole SST mode tends to force a local response on NAO. Finally, this pilot study serves as a demonstration of the potential utility of GEFA in identifying multiple surface feedbacks to the atmosphere in the observation.

scholarly journals An Observed Connection between the North Atlantic Oscillation and the Madden–Julian Oscillation

2009 ◽  
Vol 22 (2) ◽  
pp. 364-380 ◽  
Author(s):  
Hai Lin ◽  
Gilbert Brunet ◽  
Jacques Derome
Keyword(s):  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Wave Train ◽  
Intraseasonal Variability ◽  
Winter Season ◽  
Tropical Indian Ocean ◽  
Madden Julian Oscillation ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract Based on the bivariate Madden–Julian oscillation (MJO) index defined by Wheeler and Hendon and 25 yr (1979–2004) of pentad data, the association between the North Atlantic Oscillation (NAO) and the MJO on the intraseasonal time scale during the Northern Hemisphere winter season is analyzed. Time-lagged composites and probability analysis of the NAO index for different phases of the MJO reveal a statistically significant two-way connection between the NAO and the tropical convection of the MJO. A significant increase of the NAO amplitude happens about 5–15 days after the MJO-related convection anomaly reaches the tropical Indian Ocean and western Pacific region. The development of the NAO is associated with a Rossby wave train in the upstream Pacific and North American region. In the Atlantic and African sector, there is an extratropical influence on the tropical intraseasonal variability. Certain phases of the MJO are preceded by the occurrence of strong NAOs. A significant change of upper zonal wind in the tropical Atlantic is caused by a modulated transient westerly momentum flux convergence associated with the NAO.

scholarly journals Hydrological variations in central China over the past millennium and their links to the tropical Pacific and North Atlantic oceans

2020 ◽  
Vol 16 (2) ◽  
pp. 475-485
Author(s):  
Fucai Duan ◽  
Zhenqiu Zhang ◽  
Yi Wang ◽  
Jianshun Chen ◽  
Zebo Liao ◽  
...  
Keyword(s):  
North Atlantic ◽  
Atmospheric Precipitation ◽  
Tropical Pacific ◽  
Meridional Overturning Circulation ◽  
Central China ◽  
Ice Age ◽  
The North ◽  
Future Global Warming ◽  
The North Atlantic ◽  
The Tropical Pacific

Abstract. Variations of precipitation, also called the Meiyu rain, in the East Asian summer monsoon (EASM) domain during the last millennium could help enlighten the hydrological response to future global warming. Here we present a precisely dated and highly resolved stalagmite δ18O record from the Yongxing Cave, central China. Our new record, combined with a previously published one from the same cave, indicates that the Meiyu rain has changed dramatically in association with the global temperature change. In particular, our record shows that the Meiyu rain was weakened during the Medieval Climate Anomaly (MCA) but intensified during the Little Ice Age (LIA). During the Current Warm Period (CWP), our record indicates a similar weakening of the Meiyu rain. Furthermore, during the MCA and CWP, our records show that the atmospheric precipitation is similarly wet in northern China and similarly dry in central China, but relatively wet during the CWP in southern China. This spatial discrepancy indicates a complicated localized response of the regional precipitation to the anthropogenic forcing. The weakened (intensified) Meiyu rain during the MCA (LIA) matches well with the warm (cold) phases of Northern Hemisphere surface air temperature. This Meiyu rain pattern also corresponds well to the climatic conditions over the tropical Indo-Pacific warm pool. On the other hand, our record shows a strong association with the North Atlantic climate as well. The reduced (increased) Meiyu rain correlates well with positive (negative) phases of the North Atlantic Oscillation. In addition, our record links well to the strong (weak) Atlantic meridional overturning circulation during the MCA (LIA) period. All abovementioned localized correspondences and remote teleconnections on decadal to centennial timescales indicate that the Meiyu rain was coupled closely with oceanic processes in the tropical Pacific and North Atlantic oceans during the MCA and LIA.

Atmospheric Teleconnections of Tropical Atlantic Variability: Interhemispheric, Tropical–Extratropical, and Cross-Basin Interactions

2007 ◽  
Vol 20 (5) ◽  
pp. 856-870 ◽  
Author(s):  
Lixin Wu ◽  
Feng He ◽  
Zhengyu Liu ◽  
Chun Li
Keyword(s):  
North Atlantic ◽  
Southern Oscillation ◽  
Wave Train ◽  
Seasonal Migration ◽  
Atmospheric Response ◽  
Tropical Atlantic ◽  
The North ◽  
Atmospheric Teleconnections ◽  
Ocean Atmosphere ◽  
The North Atlantic

Abstract In this paper, the atmospheric teleconnections of the tropical Atlantic SST variability are investigated in a series of coupled ocean–atmosphere modeling experiments. It is found that the tropical Atlantic climate not only displays an apparent interhemispheric link, but also significantly influences the North Atlantic Oscillation (NAO) and the El Niño–Southern Oscillation (ENSO). In spring, the tropical Atlantic SST exhibits an interhemispheric seesaw controlled by the wind–evaporation–SST (WES) feedback that subsequently decays through the mediation of the seasonal migration of the ITCZ. Over the North Atlantic, the tropical Atlantic SST can force a significant coupled NAO–dipole SST response in spring that changes to a coupled wave train–horseshoe SST response in the following summer and fall, and a recurrence of the NAO in the next winter. The seasonal changes of the atmospheric response as well as the recurrence of the next winter’s NAO are driven predominantly by the tropical Atlantic SST itself, while the resulting extratropical SST can enhance the atmospheric response, but it is not a necessary bridge of the winter-to-winter NAO persistency. Over the Pacific, the model demonstrates that the north tropical Atlantic (NTA) SST can also organize an interhemispheric SST seesaw in spring in the eastern equatorial Pacific that subsequently evolves into an ENSO-like pattern in the tropical Pacific through mediation of the ITCZ and equatorial coupled ocean–atmosphere feedback.

scholarly journals Sensitivity study of the tropical Pacific precipitation anomalies

2016 ◽  
Author(s):  
Shouwen Zhang ◽  
Hua Jiang ◽  
Hui Wang ◽  
Ling Du ◽  
Dakui Wang
Keyword(s):  
Pacific Ocean ◽  
Sea Ice ◽  
North Atlantic ◽  
Climate Model ◽  
Tropical Pacific ◽  
Tropical Pacific Ocean ◽  
The North ◽  
Precipitation Anomalies ◽  
The North Atlantic ◽  
The Tropical Pacific

Abstract. Climate model results have shown that precipitation in the tropical Pacific Ocean will change up to 15 % and 25 % in one century. In this paper, both reanalysis data and climate model are used to study the response of global ocean and atmosphere to precipitation anomalies in the tropical Pacific Ocean. It shows that positive precipitation anomalies could trigger an El Nino-like SSTA response, with warmer SST in the east tropical Pacific Ocean and slightly cooler SST in the west tropical Pacific Ocean. The zonal tropical ocean currents change significantly, of which the magnitudes and directions are mainly relying on the intensity of the precipitation anomalies. Through a wave train encompassing the whole Northern Hemisphere named as the Circumglobal Waveguide Pattern (CWP), the North Atlantic atmospheric circulation responds to the freshwater anomalies in a NAO-like pattern. The anomalous atmospheric circulation transport sea ice to the North Atlantic Ocean. The sea ice melts in summer and freshen the upper ocean, which makes the ocean more stable. It thus constrains vertical heat transport and makes the upper water cooler, forming a significant positive feedback mechanism.

scholarly journals Portraying the Impact of the Tibetan Plateau on Global Climate

2020 ◽  
Vol 33 (9) ◽  
pp. 3565-3583 ◽  
Author(s):  
Haijun Yang ◽  
Xingchen Shen ◽  
Jie Yao ◽  
Qin Wen
Keyword(s):  
Tibetan Plateau ◽  
North Atlantic ◽  
Thermohaline Circulation ◽  
Global Climate ◽  
Tropical Pacific ◽  
The Tibetan Plateau ◽  
The North ◽  
The North Atlantic ◽  
The Impact ◽  
The Tropical Pacific

AbstractAs the most extensive highland in the world, the Tibetan Plateau (TP) plays an important role in shaping the global climate. Quantifying the effect of the TP on global climate is the first step for a full understanding of the TP’s standing on planet Earth. Through coupled model sensitivity experiments, we draw a panorama of the TP’s global impact in this paper. Our model results show that the absence of the TP would result in a 4°C colder and 10% drier climate in the Northern Hemisphere (NH). The TP has a striking remote effect on the North Atlantic. Removing the TP would enhance the westerlies in the mid- to high latitudes of the NH and weaken the easterlies over the tropical Pacific. More moisture would be relocated from the tropical Pacific to the North Atlantic, shutting down the Atlantic thermohaline circulation, which would eventually result in more than 15°C colder and 20% drier climate over the North Atlantic. Our model results suggest that the presence of the TP may have contributed greatly to the hospitable modern climate in the NH, by promoting the establishment of the thermohaline circulation in the Atlantic, and therefore enhancing the northward ocean heat transport and atmosphere moisture transport across the equator.

scholarly journals The Variability of the Atlantic Meridional Overturning Circulation, the North Atlantic Oscillation, and the El Niño–Southern Oscillation in the Bergen Climate Model

2005 ◽  
Vol 18 (13) ◽  
pp. 2361-2375 ◽  
Author(s):  
Juliette Mignot ◽  
Claude Frankignoul
Keyword(s):  
North Atlantic ◽  
Climate Model ◽  
Deep Convection ◽  
Meridional Overturning Circulation ◽  
Tropical Atlantic ◽  
The North ◽  
Meridional Overturning ◽  
The North Atlantic ◽  
The North Atlantic Oscillation ◽  
The Tropical Pacific

Abstract The link between the interannual to interdecadal variability of the Atlantic meridional overturning circulation (AMOC) and the atmospheric forcing is investigated using 200 yr of a control simulation of the Bergen Climate Model, where the mean circulation cell is rather realistic, as is also the location of deep convection in the northern North Atlantic. The AMOC variability has a slightly red frequency spectrum and is primarily forced by the atmosphere. The maximum value of the AMOC is mostly sensitive to the deep convection in the Irminger Sea, which it lags by about 5 yr. The latter is mostly forced by a succession of atmospheric patterns that induce anomalous northerly winds over the area. The impact of the North Atlantic Oscillation on deep convection in the Labrador and Greenland Seas is represented realistically, but its influence on the AMOC is limited to the interannual time scale and is primarily associated with wind forcing. The tropical Pacific shows a strong variability in the model, with too strong an influence on the North Atlantic. However, its influence on the tropical Atlantic is realistic. Based on lagged correlations and the release of fictitious Lagrangian drifters, the tropical Pacific seems to influence the AMOC with a time lag of about 40 yr. The mechanism is as follows: El Niño events induce positive sea surface salinity anomalies in the tropical Atlantic that are advected northward, circulate in the subtropical gyre, and then subduct. In the ocean interior, part of the salinity anomaly is advected along the North Atlantic current, eventually reaching the Irminger and Labrador Seas after about 35 yr where they destabilize the water column and favor deep convection.

scholarly journals The Development of a Statistical Forecast Model for Changma

2013 ◽  
Vol 28 (6) ◽  
pp. 1304-1321 ◽  
Author(s):  
Seung-Eon Lee ◽  
Kyong-Hwan Seo
Keyword(s):  
Wave Propagation ◽  
North Atlantic ◽  
North Pacific ◽  
Forecast Model ◽  
Tropical Pacific ◽  
The North ◽  
Sst Anomaly ◽  
The North Atlantic ◽  
The North Pacific ◽  
The Tropical Pacific

Abstract Forecasting year-to-year variations in East Asian summer monsoon (EASM) precipitation is one of the most challenging tasks in climate prediction because the predictors are not sufficiently well known and the forecast skill of the numerical models is poor. In this paper, a statistical forecast model for changma (the Korean portion of the EASM system) precipitation is proposed that was constructed with three physically based predictors. A forward-stepwise regression was used to select the predictors that included sea surface temperature (SST) anomalies over the North Pacific, the North Atlantic, and the tropical Pacific Ocean. Seasonal predictions with this model showed high forecasting capabilities that had a Gerrity skill score of ~0.82. The dynamical processes associated with the predictors were examined prior to their use in the prediction scheme. All predictors tended to induce an anticyclonic anomaly to the east or southeast of Japan, which was responsible for transporting a large amount of moisture to the southern Korean Peninsula. The predictor in the North Pacific formed an SST front to the east of Japan during the summertime, which maintained a lower-tropospheric baroclinicity. The North Atlantic SST anomaly induced downstream wave propagation in the upper troposphere, developing anticyclonic activity east of Japan. Forcing from the tropical Pacific SST anomaly triggered a cyclonic anomaly over the South China Sea, which was maintained by atmosphere–ocean interactions and induced an anticyclonic anomaly via northward Rossby wave propagation. Overall, the model used for forecasting changma precipitation performed well (R = 0.85) and correctly predicted information for 16 out of 19 yr of observational data.

Influence of Tropical Pacific Sea Surface Temperature on the Genesis of Gulf Stream Cyclones

2016 ◽  
Vol 73 (10) ◽  
pp. 4203-4214 ◽  
Author(s):  
Sebastian Schemm ◽  
Laura M. Ciasto ◽  
Camille Li ◽  
Nils Gunnar Kvamstø
Keyword(s):  
North Atlantic ◽  
El Niño ◽  
Gulf Stream ◽  
El Nino ◽  
Tropical Pacific ◽  
Cp El Niño ◽  
The North ◽  
Sst Variability ◽  
Ep El Niño ◽  
The North Atlantic

Abstract This study investigates the relationship between tropical Pacific sea surface temperature (SST) variability and cyclogenesis over the Gulf Stream region of the North Atlantic. A cyclone identification scheme and Lagrangian trajectories are used to compare preferred cyclogenesis locations and precyclogenesis flow paths associated with three patterns of tropical Pacific SST variability: eastern Pacific (EP) El Niño, central Pacific (CP) El Niño, and La Niña. During EP El Niño and La Niña winters, the upper-level precyclogenesis flow takes a subtropical path over North America and Gulf Stream cyclogenesis predominantly occurs under the North Atlantic jet entrance, which is the climatologically preferred location. In contrast, during CP El Niño winters, when the warmest SST anomalies occur in the central tropical Pacific, the precyclogenesis flow takes a northern path across North America and Gulf Stream cyclogenesis tends to occur farther north under the jet exit. The shift in preferred cyclogenesis is consistent with changes in transient upstream flow perturbations, detected using potential vorticity (PV) streamer frequencies, which are associated with the stationary wave response. Compared to EP El Niño winters, CP El Niño winters exhibit fewer southward-extending streamers and cyclonic (LC2) flow behavior, resulting in precyclogenesis air bypassing the right entrance of the North Atlantic jet. Downstream, Gulf Stream cyclones penetrate deeper into high Arctic latitudes during CP El Niño winters than in other cases. The results highlight distinct signatures of tropical SST anomalies on synoptic-scale atmospheric features and could help constrain future changes in the North Atlantic storm track and the associated poleward heat transport.

scholarly journals The North Atlantic Oscillation Response to Large-Scale Atmospheric Anomalies in the Northeastern Pacific

2013 ◽  
Vol 70 (9) ◽  
pp. 2854-2874 ◽  
Author(s):  
Marie Drouard ◽  
Gwendal Rivière ◽  
Philippe Arbogast
Keyword(s):  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Wave Breaking ◽  
Large Scale ◽  
Wave Train ◽  
Low Frequency ◽  
The North ◽  
Northeastern Pacific ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract Ingredients in the North Pacific flow influencing Rossby wave breakings in the North Atlantic and the intraseasonal variations of the North Atlantic Oscillation (NAO) are investigated using both reanalysis data and a three-level quasigeostrophic model on the sphere. First, a long-term run is shown to reproduce the observed relationship between the nature of the synoptic wave breaking and the phase of the NAO. Furthermore, a large-scale, low-frequency ridge anomaly is identified in the northeastern Pacific in the days prior to the maximum of the positive NAO phase both in the reanalysis and in the model. A large-scale northeastern Pacific trough anomaly is observed during the negative NAO phase but does not systematically precede it. Then, short-term linear and nonlinear simulations are performed to understand how the large-scale ridge anomaly can act as a precursor of the positive NAO phase. The numerical setup allows for analysis of the propagation of synoptic waves in the eastern Pacific in the presence of a large-scale ridge or trough anomaly and their downstream impact onto the Atlantic jet when they break. The ridge acts in two ways. First, it tends to prevent the downstream propagation of small waves compared to long waves. Second, it deflects the propagation of the wave trains in such a way that they mainly propagate equatorward in the Atlantic. The two modes of action favor the anticyclonic wave breaking and, therefore, the positive NAO phase. With the trough, the wave train propagation is more zonal, disturbances are more meridionally elongated, and cyclonic wave breaking is more frequent in the Atlantic than in the ridge case.

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