Impact of the Pacific mean SST bias to the Atlantic-Pacific teleconnection

2020 ◽  
Author(s):  
Chen Li ◽  
Dietmar Dommenget ◽  
Shayne McGregor
Keyword(s):  
Decadal Variability ◽  
Atmospheric Stability ◽  
Low Frequency ◽  
Trade Wind ◽  
Atmospheric Teleconnection ◽  
Surface Warming ◽  
Sst Bias ◽  
Pacific Decadal Variability ◽  
The Pacific ◽  
Low Frequency Variability

<p><span>A robust eastern tropical Pacific surface temperature cooling trend along with the strengthening of Pacific trade wind is evident across different observations since late 1990s, which is considered as a pronounced contributor to the slowdown in global surface warming. However, most CMIP5 historical simulations failed to reproduce this La Ni</span>ñ<span>a-like change. Previous studies have attributed this discrepancy between the multi-model simulations and the observations to the underrepresentation of Pacific low-frequency variability together with the misrepresentation of inter-basin forcing response. The underlying reasons remain unclear. Here, we investigate a hypothesis that common Pacific mean SST bias may diminish the Pacific-Atlantic atmospheric teleconnection and further contribute to the underestimated eastern Pacific cooling. Model results suggest that the CMIP5-like Pacific bias acts to reduce the Atlantic heating response by strengthening the atmospheric stability over the Atlantic region and therefore weaken the trans-basin variability. In addition, </span>the Pacific bias simulation with a strong SST cold tongue substantially undermined the positive zonal wind feedback, which also contributes to the underestimated Pacific cooling response. Future efforts aim at reducing the model mean state biases may significantly help to improve the simulation skills of the trans-basin teleconnection, Pacific decadal variability, and the associated Pacific dynamics.      </p>

Multi-decadal climate variability in the tropical stratosphere coupled to the Pacific

2021 ◽  
Author(s):  
Fernando Iglesias-Suarez ◽  
Oliver Wild ◽  
Douglas E. Kinnison ◽  
Rolando R. Garcia ◽  
Daniel R. Marsh ◽  
...  
Keyword(s):  
Climate Model ◽  
Decadal Variability ◽  
Stratospheric Ozone ◽  
Low Frequency ◽  
Decadal Climate Variability ◽  
The Pacific ◽  
Low Frequency Variability ◽  
The Pacific Ocean ◽  
Climate Model Simulations ◽  
Decadal Climate

<p><span>Recent studies have noted that tropical mid-stratospheric ozone decreased in the 1990s and has remained persistently low since. Current analyses suggest that these observations are linked to dynamical processes rather than being chemically-driven, although this has not been fully explored. Using measurements and chemistry-climate model simulations, we show that 50 ± 10% of these observed trends can be accounted for through multi-decadal variability in the Brewer-Dobson circulation (BDC) tied to the Pacific Ocean sea surface temperatures (the Interdecadal Pacific Oscillation, or IPO), via dynamical and chemical couplings. Moreover, accounting for this low frequency variability in the BDC can also help interpret previous observationally-derived changes in that circulation since year 1979. Overall, these findings demonstrate strong links between stratosphere-troposphere variability at decadal time scales and their potential importance for future ozone recovery detection.</span></p>

Interactions between Decadal to Multidecadal Ocean Variability and Stratospheric Sudden Warmings

2021 ◽  
Author(s):  
Blanca Ayarzagüena ◽  
Elisa Manzini ◽  
Natalia Calvo ◽  
Daniela Matei
Keyword(s):  
Decadal Variability ◽  
Low Frequency ◽  
Max Planck ◽  
Near Surface ◽  
Multidecadal Variability ◽  
Pacific Decadal Variability ◽  
Surface Circulation ◽  
Low Frequency Variability ◽  
First Time ◽  
Observational Record

<p>Major sudden stratospheric warmings (SSWs) are largest instances of the boreal polar stratospheric variability. Their effects extend farther from the polar stratosphere, affecting for example near-surface circulation. According to observations, SSWs are not equally distributed along time, with decades with almost no events and decades with SSWs happening almost every winter. This suggests the existence of multidecadal variability of SSWs. Some previous studies have pointed to phenomena in the ocean surface as the main precursors of this low-frequency variability. However, the relatively short observational record and the need of long model simulations with daily output have not enabled an analysis of the influences of these oceanic phenomena on SSWs</p><p>The goal of this study is to investigate the effects of Atlantic Multidecadal Variability (AMV) and Pacific Decadal Variability (PDV) on SSWs. To do so, we use for the first time a large ensemble of historical experiments (Max Planck Grand Ensemble) that allows us to examine the modulation of the frequency, precursors and surface impact of SSWs by both types of oceanic variability. Our results reveal that PDV has an impact on the frequency of SSWs, with a significant higher rate of SSWs for its positive than the negative phase. As for AMV, the main effect of AMV is centered on the tropospheric response to SSWs, with almost no modulation in the occurrence of the event. This last finding would be useful in order to predict the tropospheric fingerprint of SSWs.</p>

scholarly journals Atmospheric Circulation Regimes in a Nonlinear Quasi-Geostrophic Model

2015 ◽  
Vol 2015 ◽  
pp. 1-19 ◽  
Author(s):  
Henriette Labsch ◽  
Dörthe Handorf ◽  
Klaus Dethloff ◽  
Michael V. Kurgansky
Keyword(s):  
Atmospheric Circulation ◽  
Arctic Oscillation ◽  
Significant Contribution ◽  
Decadal Variability ◽  
Low Frequency ◽  
The Arctic ◽  
Satisfactory Model ◽  
Low Frequency Variability ◽  
Interannual And Decadal Variability ◽  
The Arctic Oscillation

Atmospheric low-frequency variability and circulation regime behavior are investigated in the context of a quasi-geostrophic (QG) three-level T63 model of the wintertime atmospheric circulation over the Northern Hemisphere (NH). The model generates strong interannual and decadal variability, with the domination of the annular mode of variability. It successfully reproduces a satisfactory model climatology and the most important atmospheric circulation regimes. The positive phase of the Arctic Oscillation is a robust feature of the quasi-geostrophic T63 model. The model results based on QG dynamics underlie atmospheric regime behavior in the extratropical NH and suggest that nonlinear internal processes deliver significant contribution to the atmospheric climate variability on interannual and decadal timescales.

scholarly journals Analogous Pacific and Atlantic Meridional Modes of Tropical Atmosphere–Ocean Variability*

2004 ◽  
Vol 17 (21) ◽  
pp. 4143-4158 ◽  
Author(s):  
John C. H. Chiang ◽  
Daniel J. Vimont
Keyword(s):  
Decadal Variability ◽  
Trade Wind ◽  
Tropical Atmosphere ◽  
Tropical Atlantic ◽  
Cold Tongue ◽  
Ocean Variability ◽  
The Pacific ◽  
The Mean ◽  
Meridional Mode ◽  
Subtropical Oceans

Abstract From observational analysis a Pacific mode of variability in the intertropical convergence zone (ITCZ)/cold tongue region is identified that possesses characteristics and interpretation similar to the dominant “meridional” mode of interannual–decadal variability in the tropical Atlantic. The Pacific and Atlantic meridional modes are characterized by an anomalous sea surface temperature (SST) gradient across the mean latitude of the ITCZ coupled to an anomalous displacement of the ITCZ toward the warmer hemisphere. Both are forced by trade wind variations in their respective northern subtropical oceans. The Pacific meridional mode exists independently of ENSO, although ENSO nonlinearity projects strongly on it during the peak anomaly season of boreal spring. It is suggested that the Pacific and Atlantic modes are analogous, governed by physics intrinsic to the ITCZ/ cold tongue complex.

scholarly journals Atmospheric Stability in a Generalized Barotropic Model

2005 ◽  
Vol 62 (2) ◽  
pp. 476-491 ◽  
Author(s):  
Christos M. Mitas ◽  
Walter A. Robinson
Keyword(s):  
Quantitative Description ◽  
Atmospheric Stability ◽  
Low Frequency ◽  
Initial Value ◽  
Modified Model ◽  
Barotropic Model ◽  
Upper Troposphere ◽  
Low Frequency Variability ◽  
Short Times ◽  
Better Than

Abstract An empirical modification of conventional barotropic dynamics is implemented to study the low-frequency variability (LFV) of the upper troposphere. Using the conservation of potential vorticity, generalized spectral barotropic operators that apply at single isentropic levels are constructed. In initial value calculations the empirical model shows improvement in skill compared to the conventional barotropic model, but it does not do significantly better than persistence. For short times, however, the empirically modified model shows a much closer resemblance to the observed streamfunction tendency. Overall, it is a significantly more accurate representation of the atmosphere than the conventional barotropic model. Normal, optimal, and singular modes of the modified model are calculated. The modes of the empirically modified model are more stable and more difficult to excite than those of the barotropic model. These results are consistent with previous studies that found barotropic dynamics deficient for the quantitative description of LFV. The singular modes of the modified operator have very similar patterns but explain less variance than those of the barotropic operator, which is consistent with the difficulty in detecting optimal patterns in observations. The modified barotropic operator is also more normal than the barotropic operator, and thus less variable.

scholarly journals Global oscillatory modes in high-end climate modeling and reanalyses

2021 ◽  
Author(s):  
Yizhak Feliks ◽  
Justin Small ◽  
Michael Ghil
Keyword(s):  
Sea Level ◽  
Climate Modeling ◽  
Singular Spectrum Analysis ◽  
Low Frequency ◽  
Sea Level Pressure ◽  
The North ◽  
The Pacific ◽  
Low Frequency Variability ◽  
Community Earth System Model ◽  
Spatio Temporal

AbstractInterannual oscillatory modes, atmospheric and oceanic, are present in several large regions of the globe. We examine here low-frequency variability (LFV) over the entire globe in the Community Earth System Model (CESM) and in the NCEP-NCAR and ECMWF ERA5 reanalyses. Multichannel singular spectrum analysis (MSSA) is applied to these three datasets. In the fully coupled CESM1.1 model, with its resolution of $$0.1 \times 0.1$$ 0.1 × 0.1 degrees in the ocean and $$0.25 \times 0.25$$ 0.25 × 0.25 degrees in the atmosphere, the fields analyzed are surface temperatures, sea level pressures and the 200-hPa geopotential. The simulation is 100-year long and the last 66 yr are used in the analysis. The two statistically significant periodicities in this IPCC-class model are 11 and 3.4 year. In the NCEP-NCAR reanalysis, the fields of sea level pressure and of 200-hPa geopotential are analyzed at the available resolution of $$2.5 \times 2.5$$ 2.5 × 2.5 degrees over the 68-years interval 1949–2016. Oscillations with periods of 12 and 3.6 years are found to be statistically significant in this dataset. In the ECMWF ERA5 reanalysis, the 200-hPa geopotential field was analyzed at its resolution of $$0.25 \times 0.25$$ 0.25 × 0.25 degrees over the 71-years interval 1950–2020. Oscillations with periods of 10 and 3.6 years are found to be statistically significant in this third dataset. The spatio-temporal patterns of the oscillations in the three datasets are quite similar. The spatial pattern of these global oscillations over the North Pacific and North Atlantic resemble the Pacific Decadal Oscillation and the LFV found in the Gulf Stream region and Labrador Sea, respectively. We speculate that such regional oscillations are synchronized over the globe, thus yielding the global oscillatory modes found herein, and discuss the potential role of the 11-year solar-irradiance cycle in this synchronization. The robustness of the two global modes, with their 10–12 and 3.4–3.6 years periodicities, also suggests potential contributions to predictability at 1–3 years horizons.

The Pacific Decadal Oscillation less predictable under greenhouse warming

2020 ◽  
Author(s):  
Shujun Li
Keyword(s):  
Pacific Decadal Oscillation ◽  
Decadal Variability ◽  
Coupled Model ◽  
Influential Factor ◽  
Growth Time ◽  
Greenhouse Warming ◽  
Surface Warming ◽  
The North ◽  
Global Mean Temperature ◽  
The Pacific

<p><strong>The Pacific Decadal Oscillation (PDO) is the most prominent form of decadal variability over the North Pacific, characterized by its horseshoe-like sea surface temperature (SST) anomaly pattern. The PDO exerts a substantial influence on marine ecosystems, fisheries, and agriculture. Through modulating global mean temperature, the phase shift of the PDO at the end of the 20th century is suggested to be an influential factor in the recent surface warming hiatus. Therefore, determining the predictability of the PDO in a warming climate is of great importance. By analyzing future climate under different emission scenarios simulated by the Coupled Model Intercomparison Project phase 5 (CMIP5), we show that the prediction lead time and the associated amplitude of the PDO decreases sharply under greenhouse warming conditions. This decrease is largely attributable to a warming-induced intensification of oceanic stratification, which accelerates propagation of Rossby waves, shortening the PDO lifespan and suppressing its amplitude by limiting its growth time. Our results suggest that greenhouse warming will make prediction of the PDO more challenging, with far-reaching ramifications.   </strong></p>

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