scholarly journals Hayashi spectra of the northern hemisphere mid-latitude atmospheric variability in the NCEP–NCAR and ECMWF reanalyses

2005 ◽  
Vol 25 (6) ◽  
pp. 639-652 ◽  
Author(s):  
Alessandro Dell’Aquila ◽  
Valerio Lucarini ◽  
Paolo M. Ruti ◽  
Sandro Calmanti
Keyword(s):  
Northern Hemisphere ◽  
Atmospheric Variability

scholarly journals A regime view of northern hemisphere atmospheric variability and change under global warming

2000 ◽  
Vol 27 (8) ◽  
pp. 1139-1142 ◽  
Author(s):  
A. H. Monahan ◽  
J. C. Fyfe ◽  
G. M. Flato
Keyword(s):  
Global Warming ◽  
Northern Hemisphere ◽  
Atmospheric Variability

scholarly journals Northern Hemisphere winter midlatitude atmospheric variability in CMIP5 models

2014 ◽  
Vol 41 (4) ◽  
pp. 1277-1282 ◽  
Author(s):  
Valeria Di Biagio ◽  
Sandro Calmanti ◽  
Alessandro Dell'Aquila ◽  
Paolo M. Ruti
Keyword(s):  
Northern Hemisphere ◽  
Cmip5 Models ◽  
Atmospheric Variability ◽  
Hemisphere Winter ◽  
Northern Hemisphere Winter

scholarly journals Atmospheric Modes of Variability in a Changing Climate

2006 ◽  
Vol 19 (22) ◽  
pp. 5934-5943 ◽  
Author(s):  
Jenny Brandefelt
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Spatial Patterns ◽  
Rossby Waves ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Atmospheric Variability ◽  
Modes Of Variability ◽  
Coupled Global Climate Model

Abstract The response of the atmospheric circulation to an enhanced radiative greenhouse gas forcing in a transient integration with a coupled global climate model is investigated. The spatial patterns of the leading modes of Northern Hemisphere atmospheric variability are shown to change in response to the enhanced forcing. An earlier study showed that the spatial patterns of the leading modes in the Southern Hemisphere changed in response to the enhanced forcing. These changes were associated with changes in the propagation conditions for barotropic Rossby waves. This is, however, not the case for the Northern Hemisphere, where the propagation conditions are unchanged. Other possible mechanisms for the changes in the spatial patterns of the leading modes are discussed.

scholarly journals Intrinsic and Atmospherically Forced Variability of the AMOC: Insights from a Large-Ensemble Ocean Hindcast

2018 ◽  
Vol 31 (3) ◽  
pp. 1183-1203 ◽  
Author(s):  
Stephanie Leroux ◽  
Thierry Penduff ◽  
Laurent Bessières ◽  
Jean-Marc Molines ◽  
Jean-Michel Brankart ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Large Scale ◽  
Random Phase ◽  
Stochastic Perturbation ◽  
Meridional Overturning Circulation ◽  
Intrinsic Variability ◽  
Atmospheric Variability ◽  
Intrinsic Signals ◽  
Ensemble Mean ◽  
Meridional Overturning

Abstract This study investigates the origin and features of interannual–decadal Atlantic meridional overturning circulation (AMOC) variability from several ocean simulations, including a large (50 member) ensemble of global, eddy-permitting (1/4°) ocean–sea ice hindcasts. After an initial stochastic perturbation, each member is driven by the same realistic atmospheric forcing over 1960–2015. The magnitude, spatiotemporal scales, and patterns of both the atmospherically forced and intrinsic–chaotic interannual AMOC variability are then characterized from the ensemble mean and ensemble spread, respectively. The analysis of the ensemble-mean variability shows that the AMOC fluctuations north of 40°N are largely driven by the atmospheric variability, which forces meridionally coherent fluctuations reaching decadal time scales. The amplitude of the intrinsic interannual AMOC variability never exceeds the atmospherically forced contribution in the Atlantic basin, but it reaches up to 100% of the latter around 35°S and 60% in the Northern Hemisphere midlatitudes. The intrinsic AMOC variability exhibits a large-scale meridional coherence, especially south of 25°N. An EOF analysis over the basin shows two large-scale leading modes that together explain 60% of the interannual intrinsic variability. The first mode is likely excited by intrinsic oceanic processes at the southern end of the basin and affects latitudes up to 40°N; the second mode is mostly restricted to, and excited within, the Northern Hemisphere midlatitudes. These features of the intrinsic, chaotic variability (intensity, patterns, and random phase) are barely sensitive to the atmospheric evolution, and they strongly resemble the “pure intrinsic” interannual AMOC variability that emerges in climatological simulations under repeated seasonal-cycle forcing. These results raise questions about the attribution of observed and simulated AMOC signals and about the possible impact of intrinsic signals on the atmosphere.

scholarly journals Auroral meridian scanning photometer calibration using Jupiter

2016 ◽  
Author(s):  
Brian J. Jackel ◽  
Craig Unick ◽  
Fokke Creutzberg ◽  
Greg Baker ◽  
Eric Davis ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Primary Source ◽  
Optical Field ◽  
Field Of View ◽  
Local Orientation ◽  
Atmospheric Variability ◽  
Relative Response ◽  
Cross Calibration ◽  
Photometer Calibration ◽  
Better Than

Abstract. Observations of astronomical sources provides information that can significantly enhance the utility of auroral data for scientific studies. Jupiter is used for field cross-calibration of 4 multi-spectral auroral meridian scanning photometers during 2011–15 northern hemisphere winters. Seasonal average optical field-of-view and local orientation estimates are obtained with uncertainties of 0.01° and 0.1° respectively. Estimates of absolute photometric sensitivity are repeatable to roughly 5 % from one month to the next, while the relative response between different wavelength channels is stable to better than 1 %. Astronomical field calibrations and darkroom calibration differences are on the order of 10 %. Atmospheric variability is the primary source of uncertainty; this may be reduced with data from co-located instruments such as all-sky imagers.

The ionospheric response to the 2019 and 2021 Northern Hemisphere SSWs

2021 ◽  
Author(s):  
Tarique Adnan Siddiqui ◽  
Yosuke Yamazaki ◽  
Claudia Stolle
Keyword(s):  
Northern Hemisphere ◽  
Climate Model ◽  
Lower Thermosphere ◽  
Upper Atmosphere ◽  
Atmospheric Variability ◽  
Ionospheric Response ◽  
Vertical Coupling ◽  
Highly Sensitive ◽  
Coupling Mechanisms ◽  
Made In

<p>Owing to the progress that have been made in understanding the vertical coupling mechanisms in the last decade, it is now well established that the thermosphere-ionosphere system under quiet geomagnetic conditions is highly sensitive to lower atmospheric forcing.  In this regard, the studies linking the upper atmosphere (mesosphere-lower thermosphere-ionosphere) variability and sudden stratospheric warming (SSW) events have been particularly important. The changes to atmospheric circulation due to SSW events modulate the spectrum of vertically upward propagating atmospheric waves (gravity waves, tides, and planetary waves) resulting in numerous changes in the state of the upper atmosphere. Much of our understanding about the upper atmospheric variability associated due to SSWs events have been gained by studying the 2008/2009 Northern Hemisphere (NH) SSW event, which occurred under extremely quiet geomagnetic conditions. Recently, two major NH SSW events in the winter of 2018/2019 and 2020/2021 occurred under similarly quiet geomagnetic conditions. In this work, both these SSW events have been simulated using Whole Atmosphere Community Climate Model with thermosphere and ionosphere extension (WACCM-X) and the low- and mid-latitude ionospheric response to both these SSW events will be presented.</p>

Combined solar and QBO effects on the modes of low-frequency atmospheric variability in the Northern Hemisphere

2009 ◽  
Vol 71 (13) ◽  
pp. 1471-1483 ◽  
Author(s):  
Radan Huth ◽  
Lucie Pokorná ◽  
Josef Bochníček ◽  
Pavel Hejda
Keyword(s):  
Northern Hemisphere ◽  
Low Frequency ◽  
Atmospheric Variability
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