Atlas of Five-Day Normal Sea-Level Pressure Charts for the Northern Hemisphere

1958 ◽  
Vol 124 (3) ◽  
pp. 409
Author(s):  
S. Gregory ◽  
J. F. Lahey ◽  
R. A. Bryson ◽  
E. W. Wahl
Keyword(s):  
Sea Level ◽  
Northern Hemisphere ◽  
Sea Level Pressure ◽  
Level Pressure

scholarly journals Dynamical properties and extremes of Northern Hemisphere climate fields over the past 60 years

2017 ◽  
Vol 24 (4) ◽  
pp. 713-725 ◽  
Author(s):  
Davide Faranda ◽  
Gabriele Messori ◽  
M. Carmen Alvarez-Castro ◽  
Pascal Yiou
Keyword(s):  
Phase Space ◽  
Sea Level ◽  
Northern Hemisphere ◽  
Atmospheric Dynamics ◽  
Complex Nature ◽  
Human Welfare ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Dimensional Phase Space ◽  
Dynamical Properties

Abstract. Atmospheric dynamics are described by a set of partial differential equations yielding an infinite-dimensional phase space. However, the actual trajectories followed by the system appear to be constrained to a finite-dimensional phase space, i.e. a strange attractor. The dynamical properties of this attractor are difficult to determine due to the complex nature of atmospheric motions. A first step to simplify the problem is to focus on observables which affect – or are linked to phenomena which affect – human welfare and activities, such as sea-level pressure, 2 m temperature, and precipitation frequency. We make use of recent advances in dynamical systems theory to estimate two instantaneous dynamical properties of the above fields for the Northern Hemisphere: local dimension and persistence. We then use these metrics to characterize the seasonality of the different fields and their interplay. We further analyse the large-scale anomaly patterns corresponding to phase-space extremes – namely time steps at which the fields display extremes in their instantaneous dynamical properties. The analysis is based on the NCEP/NCAR reanalysis data, over the period 1948–2013. The results show that (i) despite the high dimensionality of atmospheric dynamics, the Northern Hemisphere sea-level pressure and temperature fields can on average be described by roughly 20 degrees of freedom; (ii) the precipitation field has a higher dimensionality; and (iii) the seasonal forcing modulates the variability of the dynamical indicators and affects the occurrence of phase-space extremes. We further identify a number of robust correlations between the dynamical properties of the different variables.

scholarly journals Interdependence of the growth of the Northern Hemisphere ice sheets during the last glaciation: the role of atmospheric circulation

2014 ◽  
Vol 10 (1) ◽  
pp. 345-358 ◽  
Author(s):  
P. Beghin ◽  
S. Charbit ◽  
C. Dumas ◽  
M. Kageyama ◽  
D. M. Roche ◽  
...  
Keyword(s):  
Sea Level ◽  
Atmospheric Circulation ◽  
Northern Hemisphere ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Stationary Waves ◽  
Sea Level Pressure ◽  
Feedback Mechanisms ◽  
Orographic Effect ◽  
Level Pressure

Abstract. The development of large continental-scale ice sheets over Canada and northern Europe during the last glacial cycle likely modified the track of stationary waves and influenced the location of growing ice sheets through changes in accumulation and temperature patterns. Although they are often mentioned in the literature, these feedback mechanisms are poorly constrained and have never been studied throughout an entire glacial–interglacial cycle. Using the climate model of intermediate complexity CLIMBER-2 coupled with the 3-D ice-sheet model GRISLI (GRenoble Ice Shelf and Land Ice model), we investigate the impact of stationary waves on the construction of past Northern Hemisphere ice sheets during the past glaciation. The stationary waves are not explicitly computed in the model but their effect on sea-level pressure is parameterized. We tested different parameterizations to study separately the effect of surface temperature (thermal forcing) and topography (orographic forcing) on sea-level pressure, and therefore on atmospheric circulation and ice-sheet surface mass balance. Our model results suggest that the response of ice sheets to thermal and/or orographic forcings is rather different. At the beginning of the glaciation, the orographic effect favors the growth of the Laurentide ice sheet, whereas Fennoscandia appears rather sensitive to the thermal effect. Using the ablation parameterization as a trigger to artificially modify the size of one ice sheet, the remote influence of one ice sheet on the other is also studied as a function of the stationary wave parameterizations. The sensitivity of remote ice sheets is shown to be highly sensitive to the choice of these parameterizations with a larger response when orographic effect is accounted for. Results presented in this study suggest that the various spatial distributions of ice sheets could be partly explained by the feedback mechanisms occurring between ice sheets and atmospheric circulation.

Improved Skill of Northern Hemisphere Winter Surface Temperature Predictions Based on Land–Atmosphere Fall Anomalies

2007 ◽  
Vol 20 (16) ◽  
pp. 4118-4132 ◽  
Author(s):  
Judah Cohen ◽  
Christopher Fletcher
Keyword(s):  
Snow Cover ◽  
Sea Level ◽  
Northern Hemisphere ◽  
Land Surface ◽  
Northern Eurasia ◽  
Dynamical Models ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Skill Scores ◽  
And Sea Level

Abstract A statistical forecast model, referred to as the snow-cast (sCast) model, has been developed using observed October mean snow cover and sea level pressure anomalies to predict upcoming winter land surface temperatures for the extratropical Northern Hemisphere. In operational forecasts since 1999, snow cover has been used for seven winters, and sea level pressure anomalies for three winters. Presented are skill scores for these seven real-time forecasts and also for 33 winter hindcasts (1972/73–2004/05). The model demonstrates positive skill over much of the eastern United States and northern Eurasia—regions that have eluded skillful predictions among the existing major seasonal forecast centers. Comparison with three leading dynamical forecast systems shows that the statistical model produces superior skill for the same regions. Despite the increasing complexity of the dynamical models, they continue to derive their forecast skill predominantly from tropical atmosphere–ocean coupling, in particular from ENSO. Therefore, in the Northern Hemisphere extratropics, away from the influence of ENSO, the sCast model is expected to outperform the dynamical models into the foreseeable future.

Sea-level pressure–air temperature teleconnections during northern hemisphere winter

2011 ◽  
Vol 108 (1-2) ◽  
pp. 173-189 ◽  
Author(s):  
C. D. Papadimas ◽  
A. Bartzokas ◽  
C. J. Lolis ◽  
N. Hatzianastassiou
Keyword(s):  
Sea Level ◽  
Northern Hemisphere ◽  
Air Temperature ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Hemisphere Winter ◽  
Northern Hemisphere Winter

On the Summertime Strengthening of the Northern Hemisphere Pacific Sea Level Pressure Anticyclone

2009 ◽  
Vol 22 (5) ◽  
pp. 1174-1192 ◽  
Author(s):  
Sumant Nigam ◽  
Steven C. Chan
Keyword(s):  
Sea Level ◽  
Northern Hemisphere ◽  
Asian Monsoon ◽  
Storm Track ◽  
Hadley Cell ◽  
Winter Storm ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Mascarene High ◽  
The Pacific

Abstract This study revisits the question posed by Hoskins on why the Northern Hemisphere Pacific sea level pressure (SLP) anticyclone is strongest and maximally extended in summer when the Hadley cell descent in the northern subtropics is the weakest. The paradoxical evolution is revisited because anticyclone buildup to the majestic summer structure is gradual, spread evenly over the preceding 4–6 months, and not just confined to the monsoon-onset period, which is interesting, as monsoons are posited to be the cause of the summer vigor of the anticyclone. Anticyclone buildup is moreover found focused in the extratropics, not the subtropics, where SLP seasonality is shown to be much weaker, generating a related paradox within the context of the Hadley cell’s striking seasonality. Showing this seasonality to arise from, and thus represent, remarkable descent variations in the Asian monsoon sector, but not over the central-eastern ocean basins, leads to the resolution of this paradox. Evolution of other prominent anticyclones is analyzed to critique the development mechanisms: the Azores high evolves like the Pacific one, but without a monsoon to its immediate west. The Mascarene high evolves differently, peaking in austral winter. Monsoons are not implicated in both cases. Diagnostic modeling of seasonal circulation development in the Pacific sector concludes this inquiry. Of the three forcing regions examined, the Pacific midlatitudes are found to be the most influential, accounting for over two-thirds of the winter-to-summer SLP development in the extratropics (6–8 hPa), with the bulk coming from the abatement of winter storm-track heating and transients. The Asian monsoon contribution (2–3 hPa) is dominant in the Pacific (and Atlantic) subtropics. The modeling results resonate with observational findings and attest to the demise of winter storm tracks as the principal cause of the summer vigor of the Pacific anticyclone.

scholarly journals On the Leading Patterns of Northern Hemisphere Sea Level Pressure Variability*

2015 ◽  
Vol 72 (9) ◽  
pp. 3469-3486 ◽  
Author(s):  
Brian V. Smoliak ◽  
John M. Wallace
Keyword(s):  
Time Series ◽  
Sea Level ◽  
Northern Hemisphere ◽  
Surface Air Temperature ◽  
Sea Level Pressure ◽  
Annular Mode ◽  
Level Pressure ◽  
The Pacific ◽  
Reversed Polarity ◽  
A Chain

Abstract The leading patterns of variability of the monthly mean Northern Hemisphere (NH) sea level pressure (SLP) field, as derived from empirical orthogonal teleconnection (EOT) analysis of a 93-yr (1920–2012) record of NOAA–CIRES 20th Century Reanalyses, are presented and discussed, with emphasis on wintertime patterns. The analysis yields nine or more highly reproducible wintertime hemispheric EOTs, the first six of which closely resemble EOF1 or EOF2 in their respective sectors of the hemisphere. Collectively, the first nine wintertime patterns account for 70% of the variance of NH SLP, 40% of the variance of NH surface air temperature (SAT), and 52% of the variance of the time series of NH-mean SAT poleward of 20°N. Wintertime EOT1 corresponds to the NH annular mode (NAM) and EOT2 corresponds to the SLP expression of the Pacific–North America pattern. The remaining wintertime EOT patterns are monopoles arranged like the links of a chain wrapped around the primary center of action of the annular mode. The NH summertime and Southern Hemisphere patterns are arranged in a similar manner. The continental NH wintertime patterns exhibit strong temperature anomalies of reversed polarity to their respective SLP monopoles. The interannual variability of wintertime EOTs 3–9 and summertime EOTs 2–9 is dominated by sampling fluctuations. Over the 93-yr record, the more prominent continental wintertime patterns exhibit weak trends toward falling SLP and rising SAT, particularly over Russia and Alaska. The interpretation of shorter-term trends is more ambiguous.

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