scholarly journals Response of the Midlatitude Jets, and of Their Variability, to Increased Greenhouse Gases in the CMIP5 Models

2013 ◽  
Vol 26 (18) ◽  
pp. 7117-7135 ◽  
Author(s):  
Elizabeth A. Barnes ◽  
Lorenzo Polvani
Keyword(s):  
Climate Change ◽  
Greenhouse Gases ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
North Atlantic ◽  
North Pacific ◽  
Cmip5 Models ◽  
The North ◽  
The North Atlantic ◽  
The North Pacific

Abstract This work documents how the midlatitude, eddy-driven jets respond to climate change using model output from phase 5 of the Coupled Model Intercomparison Project (CMIP5). The authors consider separately the North Atlantic, the North Pacific, and the Southern Hemisphere jets. The analysis is not limited to annual-mean changes in the latitude and speed of the jets, but also explores how the variability of each jet changes with increased greenhouse gases. All jets are found to migrate poleward with climate change: the Southern Hemisphere jet shifts poleward by 2° of latitude between the historical period and the end of the twenty-first century in the representative concentration pathway 8.5 (RCP8.5) scenario, whereas both Northern Hemisphere jets shift by only 1°. In addition, the speed of the Southern Hemisphere jet is found to increase markedly (by 1.2 m s−1 between 850 and 700 hPa), while the speed remains nearly constant for both jets in the Northern Hemisphere. More importantly, it is found that the patterns of jet variability are a strong function of the jet position in all three sectors of the globe, and as the jets shift poleward the patterns of variability change. Specifically, for the Southern Hemisphere and the North Atlantic jets, the variability becomes less of a north–south wobbling and more of a pulsing (i.e., variation in jet speed). In contrast, for the North Pacific jet, the variability becomes less of a pulsing and more of a north–south wobbling. These different responses can be understood in terms of Rossby wave breaking, allowing the authors to explain most of the projected jet changes within a single dynamical framework.

scholarly journals Diversity of the Wintertime Arctic Oscillation Pattern among CMIP5 Models: Role of the Stratospheric Polar Vortex

2019 ◽  
Vol 32 (16) ◽  
pp. 5235-5250 ◽  
Author(s):  
Hainan Gong ◽  
Lin Wang ◽  
Wen Chen ◽  
Renguang Wu ◽  
Wen Zhou ◽  
...  
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
Arctic Oscillation ◽  
Climate Models ◽  
Polar Vortex ◽  
Cmip5 Models ◽  
Stratospheric Polar Vortex ◽  
The North ◽  
The North Atlantic ◽  
The North Pacific

AbstractThe wintertime Arctic Oscillation (AO) pattern in phase 5 of the Coupled Model Intercomparison Project (CMIP5) climate models displays notable differences from the reanalysis. The North Pacific center of the AO pattern is larger in the ensemble mean of 27 models than in the reanalysis, and the magnitude of the North Pacific center of the AO pattern varies largely among the models. This study investigates the plausible sources of the diversity of the AO pattern in the models. Analysis indicates that the amplitude of the North Pacific center is associated with the coupling between the North Pacific and North Atlantic, which in turn is primarily modulated by the strength of the stratospheric polar vortex. A comparative analysis is conducted for the strong polar vortex (SPV) and weak polar vortex (WPV) models. It reveals that a stronger stratospheric polar vortex induces more planetary waves to reflect from the North Pacific to the North Atlantic and more wave activity fluxes to propagate from the North Pacific to the North Atlantic in the SPV models than in the WPV models. Thus, the coupling of atmospheric circulation between the North Pacific and North Atlantic is stronger in the SPV models, which facilitates more North Pacific variability to be involved in the AO variability and induces a stronger North Pacific center in the AO pattern. The increase in vertical resolution may improve the simulation of the stratospheric polar vortex and thereby reduces the model biases in the North Pacific–North Atlantic coupling and thereby the amplitude of the North Pacific center of the AO pattern in models.

scholarly journals Evaluation of Northern Hemisphere Blocking Climatology in the Global Environment Multiscale Model

2013 ◽  
Vol 141 (2) ◽  
pp. 707-727 ◽  
Author(s):  
Etienne Dunn-Sigouin ◽  
Seok-Woo Son ◽  
Hai Lin
Keyword(s):  
Northern Hemisphere ◽  
North Atlantic ◽  
North Pacific ◽  
Detection Algorithm ◽  
Late Winter ◽  
Stationary Waves ◽  
The North ◽  
Zonal Wavenumber ◽  
The North Atlantic ◽  
The North Pacific

Abstract The performance of the Global Environmental Multiscale (GEM) model, the Canadian operational numerical model, in reproducing atmospheric low-frequency variability is evaluated in the context of Northern Hemisphere blocking climatology. The validation is conducted by applying a comprehensive but relatively simple blocking detection algorithm to a 20-yr (1987–2006) integration of the GEM model in climate mode. The comparison to reanalysis reveals that, although the model can reproduce Northern Hemisphere blocking climatology reasonably well, the maximum blocking frequency over the North Atlantic and western Europe is generally underestimated and its peak season is delayed from late winter to spring. This contrasts with the blocking frequency over the North Pacific, which is generally overestimated during all seasons. These misrepresentations of blocking climatology are found to be largely associated with the biases in climatological background flow. The modeled stationary waves show a seasonal delay in zonal wavenumber 1 and an eastward extension in zonal wavenumber-2 components consistent with blocking frequency biases. High-frequency eddies are, however, consistently underestimated both in the North Atlantic and Pacific, indicating that the biases in eddy fields might not be the main reason for the blocking biases in the North Pacific.

scholarly journals Relative Importance of Northern Hemisphere Circulation Modes in Predicting Regional Climate Change

2004 ◽  
Vol 17 (21) ◽  
pp. 4180-4189 ◽  
Author(s):  
Monika Rauthe ◽  
Heiko Paeth
Keyword(s):  
Climate Change ◽  
Northern Hemisphere ◽  
North Atlantic ◽  
North Pacific ◽  
Regional Climate ◽  
Regional Climate Change ◽  
Relative Importance ◽  
Near Surface ◽  
The North ◽  
The North Pacific

Abstract The Northern Hemisphere annular mode (NAM), North Atlantic Oscillation (NAO), and Aleutian low (AL) are known to be the most prominent components of Northern Hemisphere (NH) near-surface climate variability. In a tremendous number of studies, the impact of these circulation features on regional climate has been demonstrated. More recently, research has gone into the connection between the NAO and NAM and into the physical meaning of the latter. However, the relevance of those circulation modes for climatological issues may also be inferred from another nondynamical point of view: their statistical relationship to various climate parameters. This study comprises two steps: 1) qualifying and quantifying the relative importance of NH circulation modes with respect to twentieth-century near-surface temperature and precipitation, using stepwise multiple regression with cross validation; and 2) using predictor–predictand relationships to access the contributions of each circulation mode to regional climate change in the middle of the twenty-first century, given multimodel predictions of the circulation modes' responses to increasing greenhouse gas (GHG) and sulfate aerosol (SUL) concentrations. Altogether, the NAM, NAO, and AL account locally for up to 75% of the total interannual temperature and rainfall variability over NH continents. Over the major part of the NH, the NAM appears to be the most important predictor. In some parts of the North Atlantic, temperature and rainfall are more closely linked to the NAO, while the North Pacific is clearly dominated by the AL dynamics. In general, the NAO and AL have a more regionally confined influence. Climate change experiments mostly predict an intensification of the NAM and AL under GHG+SUL forcing, while the NAO response is much less consistent with different models and generally undergoes no long-term changes. This leads to substantial contributions to temperature and rainfall anomalies, especially over the NH landmasses. Temperature changes amount to ±1 K over large parts of Russia, North America, and the North Pacific. The major precipitation changes occur over the North Pacific, the North Atlantic, and Scandinavia. This circulation-induced contribution accounts for a considerable part of total expected change in these regions. Given its distinct trend, the NAM plays the main role, except over the Pacific Ocean and North America, where the AL is driving regional climate anomalies. Thus, whether physically relevant or not, the NAM is an appropriate statistical indicator of NH regional climate change.

scholarly journals The Impact of Land-Ocean Contrast on The Seasonal To Decadal Variability of The Northern Hemisphere Jet Stream

2021 ◽  
Author(s):  
Samantha Hallam ◽  
Simon Josey ◽  
Gerard McCarthy ◽  
Joel Hirschi
Keyword(s):  
North America ◽  
Northern Hemisphere ◽  
North Atlantic ◽  
North Pacific ◽  
Jet Stream ◽  
Latitude Range ◽  
The North ◽  
Regional Basis ◽  
The North Atlantic ◽  
The North Pacific

Abstract Seasonal to decadal variations in Northern Hemisphere jet stream latitude and speed over land (Eurasia, North America) and oceanic (North Atlantic, North Pacific) regions are presented for the period 1871 – 2011 from the Twentieth Century Reanalysis dataset. Significant regional differences are seen on seasonal to decadal timescales. The ocean acts to reduce the seasonal jet latitude range from 20° over Eurasia to 10° over the North Atlantic where the ocean meridional heat transport is greatest. The mean jet latitude range is at a minimum in winter (DJF), along the western boundary of the North Pacific and North Atlantic, where the land-sea contrast and SST gradients are strongest. The 141-year trends in jet latitude and speed show differences on a regional basis. The North Atlantic has significant increasing jet latitude trends in all seasons, up to 3° in winter. Eurasia has significant increasing trends in winter and summer, however, no increase is seen across the North Pacific or North America. Jet speed shows significant increases evident in winter (up to 4.7ms -1 ), spring and autumn over the North Atlantic, Eurasia and North America however, over the North Pacific no increase is observed. Long term trends are generally overlaid by multidecadal variability, particularly evident in the North Pacific, where 20-year variability in jet latitude and jet speed are seen, associated with the Pacific Decadal Oscillation which explains 50% of the winter variance in jet latitude since 1940. Northern hemisphere jet variability and trends differ on a regional basis (North Atlantic, North Pacific, Eurasia and America) on seasonal to decadal timescales, indicating different mechanisms are influencing the jet latitude and speed. It is important that the differing regional trends and mechanisms are incorporated into climate models and predictions.

scholarly journals Connectivity of climatic variations in the North Atlantic and North Pacific

Trudy VNIRO ◽  
2020 ◽  
Vol 180 ◽  
pp. 23-43
Author(s):  
A. S. Krovnin
Keyword(s):  
Northern Hemisphere ◽  
North Atlantic ◽  
North Pacific ◽  
Northwestern Part ◽  
Teleconnection Patterns ◽  
Climatic Variations ◽  
The North ◽  
The North Atlantic ◽  
The Impact ◽  
The North Pacific

Based on the analysis of changes in the spatial structure of climatic variations in the Northern Hemisphere before and after the climatic regime shift in the 1980s, the modes of interaction between climatic processes in the North Atlantic and North Pacific have been identified. The first (“western”) mode prevailed until the late 1980s, reflected the impact of the North Pacific climatic processes on the North Atlantic climate as a result of interaction of two mutually independent Pacific teleconnection patterns (Pacific/North American and Tropical/Northern Hemisphere patterns) with the West Atlantic pattern. The pronounced eastward shift of the North Atlantic Oscillation (NAO) centers from the late 1970s resulted in establishment of the “eastern” mode of interaction between the aquatories under consideration. The climatic changes originated in the North Atlantic basin propagated in the western half of the North Pacific via the system of atmospheric teleconnection patterns over Eurasia (“atmospheric bridge”). The establishment of the “eastern” mode became obviously one of the reasons of sharp warming of surface waters in the western and central areas of the North Pacific from the end of the 1980s, which favored the beginning of a new “salmon epoch” in its northwestern part. Along with the synchronous relationships between the Eurasian atmospheric modes and North Pacific sea surface temperature anomalies, an asynchronous response in the ocean to longitudinal shifts in position of the NAO centers, was found. The atmospheric signal associated with its southern center propagated eastward along the equatorial zone and appeared in the southwestern sector of the North Pacific 5–6 years later.

The Role of Oscillating Southern Hemisphere Westerly Winds: Global Ocean Circulation

2020 ◽  
Vol 33 (6) ◽  
pp. 2111-2130
Author(s):  
Woo Geun Cheon ◽  
Jong-Seong Kug
Keyword(s):  
Ocean Circulation ◽  
North Atlantic ◽  
North Pacific ◽  
Global Ocean ◽  
The North ◽  
Westerly Winds ◽  
The North Atlantic ◽  
Global Ocean Circulation ◽  
The Antarctic ◽  
The North Pacific

AbstractIn the framework of a sea ice–ocean general circulation model coupled to an energy balance atmospheric model, an intensity oscillation of Southern Hemisphere (SH) westerly winds affects the global ocean circulation via not only the buoyancy-driven teleconnection (BDT) mode but also the Ekman-driven teleconnection (EDT) mode. The BDT mode is activated by the SH air–sea ice–ocean interactions such as polynyas and oceanic convection. The ensuing variation in the Antarctic meridional overturning circulation (MOC) that is indicative of the Antarctic Bottom Water (AABW) formation exerts a significant influence on the abyssal circulation of the globe, particularly the Pacific. This controls the bipolar seesaw balance between deep and bottom waters at the equator. The EDT mode controlled by northward Ekman transport under the oscillating SH westerly winds generates a signal that propagates northward along the upper ocean and passes through the equator. The variation in the western boundary current (WBC) is much stronger in the North Atlantic than in the North Pacific, which appears to be associated with the relatively strong and persistent Mindanao Current (i.e., the southward flowing WBC of the North Pacific tropical gyre). The North Atlantic Deep Water (NADW) formation is controlled by salt advected northward by the North Atlantic WBC.

Satellite-Derived Tropical Cyclone Intensity in the North Pacific Ocean Using the Deviation-Angle Variance Technique

2014 ◽  
Vol 29 (3) ◽  
pp. 505-516 ◽  
Author(s):  
Elizabeth A. Ritchie ◽  
Kimberly M. Wood ◽  
Oscar G. Rodríguez-Herrera ◽  
Miguel F. Piñeros ◽  
J. Scott Tyo
Keyword(s):  
Tropical Cyclone ◽  
North Atlantic ◽  
North Pacific ◽  
Western North Pacific ◽  
North Pacific Ocean ◽  
Deviation Angle ◽  
Intensity Estimation ◽  
The North ◽  
The North Atlantic ◽  
The North Pacific

Abstract The deviation-angle variance technique (DAV-T), which was introduced in the North Atlantic basin for tropical cyclone (TC) intensity estimation, is adapted for use in the North Pacific Ocean using the “best-track center” application of the DAV. The adaptations include changes in preprocessing for different data sources [Geostationary Operational Environmental Satellite-East (GOES-E) in the Atlantic, stitched GOES-E–Geostationary Operational Environmental Satellite-West (GOES-W) in the eastern North Pacific, and the Multifunctional Transport Satellite (MTSAT) in the western North Pacific], and retraining the algorithm parameters for different basins. Over the 2007–11 period, DAV-T intensity estimation in the western North Pacific results in a root-mean-square intensity error (RMSE, as measured by the maximum sustained surface winds) of 14.3 kt (1 kt ≈ 0.51 m s−1) when compared to the Joint Typhoon Warning Center best track, utilizing all TCs to train and test the algorithm. The RMSE obtained when testing on an individual year and training with the remaining set lies between 12.9 and 15.1 kt. In the eastern North Pacific the DAV-T produces an RMSE of 13.4 kt utilizing all TCs in 2005–11 when compared with the National Hurricane Center best track. The RMSE for individual years lies between 9.4 and 16.9 kt. The complex environment in the western North Pacific led to an extension to the DAV-T that includes two different radii of computation, producing a parametric surface that relates TC axisymmetry to intensity. The overall RMSE is reduced by an average of 1.3 kt in the western North Pacific and 0.8 kt in the eastern North Pacific. These results for the North Pacific are comparable with previously reported results using the DAV for the North Atlantic basin.

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