scholarly journals Future changes in stratospheric quasi-stationary wave-1 in the extratropical southern hemisphere spring and summer as simulated by ACCESS-CCM

2021 ◽  
Author(s):  
Kane A. Stone ◽  
Andrew R. Klekociuk ◽  
Robyn Schofield
Keyword(s):  
Southern Hemisphere ◽  
Stationary Wave

Southern Hemisphere Stationary Wave Response to Changes of Ozone and Greenhouse Gases

2013 ◽  
Vol 26 (24) ◽  
pp. 10205-10217 ◽  
Author(s):  
Lei Wang ◽  
Paul J. Kushner ◽  
Darryn W. Waugh
Keyword(s):  
Phase Shift ◽  
Greenhouse Gases ◽  
Southern Hemisphere ◽  
Ozone Depletion ◽  
Wave Amplitude ◽  
Climate Model ◽  
Recovery Period ◽  
Stationary Wave ◽  
Early Summer ◽  
Model Simulations

Abstract The Southern Hemisphere (SH) stratospheric stationary wave amplitude increased significantly in late spring and early summer during the last two decades of the twentieth century. A suite of chemistry climate model simulations are examined to explore the underlying cause and the separate effects of anthropogenic forcing from ozone depleting substances (ODSs) and greenhouse gases (GHGs) in the past and projected SH stationary wave evolution. The model simulations produce trends in the wave amplitude similar to that observed, although somewhat weaker. In simulations with changing ODSs, this increase in amplitude is reproduced during the ozone depletion period and is reversed during the ozone recovery period. This response is related to changes in the strength and timing of the breakdown of the SH polar vortex associated with ozone depletion and recovery. GHG increases have little impact on the simulated stratospheric stationary wave amplitude but are projected to induce an eastward phase shift of the waves. This phase shift is linked to the strengthening of the subtropical jets driven by GHG forcing via sea surface warming.

scholarly journals Tropical and subtropical forcing of future southern hemisphere stationary wave changes

2021 ◽  
pp. 1-48
Author(s):  
Matthew Patterson ◽  
Tim Woollings ◽  
Thomas J. Bracegirdle
Keyword(s):  
Climate Change ◽  
Southern Hemisphere ◽  
Rossby Wave ◽  
Regional Climate ◽  
Stationary Wave ◽  
Hadley Cell ◽  
Cmip5 Models ◽  
Wave Source ◽  
Barotropic Model ◽  
Rossby Wave Source

AbstractStationary wave changes play a significant role in the regional climate change response in Southern Hemisphere (SH) winter. In particular, almost all CMIP5 models feature a substantial strengthening of the westerlies to the south of Australia and enhancement of the subtropical jet over the eastern Pacific in winter. In this study we investigate the mechanisms behind these changes, finding that the stationary wave response can largely be explained via reductions in the magnitude of the upper level Rossby wave source over the tropical / subtropical East Pacific. The Rossby wave source changes in this region are robust across the model ensemble and are strongly correlated with changes to low latitude circulation patterns, in particular, the projected southward migration of the Hadley cell and weakening of the Walker circulation. To confirm our mechanism of future changes, we employ a series of barotropic model experiments in which the barotropic model is given a background state identical to a particular CMIP5 model and an anomalous Rossby wave source is imposed. This simple approach is able to capture the primary features of the ensemble mean change, including the cyclonic anomaly south of Australia, and is also able to capture many of the inter-model differences. These findings will help to advance our understanding of the mechanisms underpinning SH extratropical circulation changes under climate change.

scholarly journals Zonal asymmetries in middle atmospheric ozone and water vapour derived from Odin satellite data 2001–2010

2011 ◽  
Vol 11 (2) ◽  
pp. 4167-4198 ◽  
Author(s):  
A. Gabriel ◽  
H. Körnich ◽  
S. Lossow ◽  
D. H. W. Peters ◽  
J. Urban ◽  
...  
Keyword(s):  
Water Vapour ◽  
Southern Hemisphere ◽  
Satellite Data ◽  
Stationary Wave ◽  
Atmospheric Ozone ◽  
Tracer Transport ◽  
Meridional Transport ◽  
Mixing Processes ◽  
Double Peak Structure ◽  
Wave Patterns

Abstract. Based on Odin satellite data 2001–2010 we investigate stationary wave patterns in middle atmospheric ozone (O3) and water vapour (H2O) as indicated by their seasonal long-term means of the zonally asymmetric components O3* = O3-[O3] and H2O* = H2O-[H2O] ([O3], [H2O]: zonal means). At mid- and polar latitudes of Northern and Southern Hemisphere, we find a pronounced wave one pattern in both constituents. In the Northern Hemisphere, the wave one patterns increase during autumn, maintain their strength during winter and decay during spring, with maximum amplitudes of about 10–20% of zonal mean values. During winter, the wave one in stratospheric O3* is characterized by a maximum over North Pacific/Aleutians and a minimum over North Atlantic/Northern Europe and by a double-peak structure with enhanced amplitude in the lower and in the upper stratosphere. The wave one in H2O* extends from lower stratosphere to upper mesosphere with a westward shift in phase with increasing height including a jump in phase at upper stratosphere altitudes. In the Southern Hemisphere, similar wave one patterns occur during southern spring when the polar vortex breaks down. Based on a simplified tracer transport approach we explain these wave patterns as a first-order result of zonal asymmetries in mean meridional transport by geostrophically balanced winds, which were derived from combined temperature profiles of Odin, and ECMWF (European Centre of Medium-Range Weather Forecasts) Reanalysis data (ERA Interim). Further influences which may contribute to the stationary wave patterns, e.g. eddy mixing processes or temperature-dependent chemistry, are discussed.

scholarly journals Quasi-Periodic Variations of the Polar Vortex in the Southern Hemisphere Stratosphere Due to Wave–Wave Interaction

2004 ◽  
Vol 61 (21) ◽  
pp. 2510-2527 ◽  
Author(s):  
Yasuko Hio ◽  
Shigeo Yoden
Keyword(s):  
Southern Hemisphere ◽  
Traveling Wave ◽  
Polar Vortex ◽  
Wave Interaction ◽  
Stationary Wave ◽  
Late Winter ◽  
Transient Wave ◽  
Reanalysis Dataset ◽  
Zonal Wavenumber ◽  
Comparable Amplitude

Abstract The winter polar vortex in the Southern Hemisphere stratosphere is characterized by prominent quasi-stationary planetary waves: zonal wavenumber 1 (wave 1) and the eastward-traveling wave (wave 2). Quasi-periodic variations of the polar vortex are investigated in terms of the wave–wave interaction between wave 1 and wave 2 with both the NCEP–NCAR reanalysis dataset from 1979 to 2002 and a spherical barotropic model. A typical case shows that the transient wave 1 generated by the wave–wave interaction has comparable amplitude to those of the stationary wave 1 and the traveling wave 2, and has a node around 60°S, where these primary waves have large amplitude. The transient wave 1 travels eastward with the same angular frequency as that of the traveling wave 2. The polar night jet also vacillates with the same frequency such that it has its minimum when the stationary wave 1 and the transient wave 1 are in phase at the polar side of the node. The vacillation is basically due to quasi-periodic variations of the wave driven by the interference between the stationary and traveling wave 1s. Similar periodic variations of the polar vortex are obtained in the model experiment here, in the circumstance that stationary wave 1 generated by surface topography has comparable amplitude to the eastward-traveling wave 2 that is generated by the barotropic instability of a forced mean zonal wind. The winter polar vortex shows large interannual variability. Similar quasi-periodic variations due to wave– wave interaction often occurred for the 24 yr in late winter when the transient wave 2 was vigorous.

Southern Hemisphere Seti Survey: Five Years of Project Meta II

1997 ◽  
Vol 161 ◽  
pp. 611-621
Author(s):  
Guillermo A. Lemarchand ◽  
Fernando R. Colomb ◽  
E. Eduardo Hurrell ◽  
Juan Carlos Olalde
Keyword(s):  
Southern Hemisphere ◽  
Scattering Theory ◽  
Galactic Plane ◽  
Narrow Band ◽  
Neutral Hydrogen ◽  
Sky Survey ◽  
Inertial Frames ◽  
Interstellar Scattering ◽  
Extraterrestrial Origin ◽  
Spectral Channels

AbstractProject META II, a full sky survey for artificial narrow-band signals, has been conducted from one of the two 30-m radiotelescopes of the Instituto Argentino de Radioastronomía (IAR). The search was performed near the 1420 Mhz line of neutral hydrogen, using a 8.4 million channels Fourier spectrometer of 0.05 Hz resolution and 400 kHz instantaneous bandwidth. The observing frequency was corrected both for motions with respect to three astronomical inertial frames, and for the effect of Earths rotation, which provides a characteristic changing signature for narrow-band signals of extraterrestrial origin. Among the 2 × 1013spectral channels analyzed, 29 extra-statistical narrow-band events were found, exceeding the average threshold of 1.7 × 10−23Wm−2. The strongest signals that survive culling for terrestrial interference lie in or near the galactic plane. A description of the project META II observing scheme and results is made as well as the possible interpretation of the results using the Cordes-Lazio-Sagan model based in interstellar scattering theory.

Alpha-Effect, Current and Kinetic Helicities for Magnetically Driven Turbulence, and Solar Dynamo

2000 ◽  
Vol 179 ◽  
pp. 387-388
Author(s):  
Gaetano Belvedere ◽  
V. V. Pipin ◽  
G. Rüdiger
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Convection Zone ◽  
Solar Surface ◽  
Momentum Transport ◽  
Angular Momentum Transport ◽  
Magnetic Buoyancy ◽  
Alpha Effect ◽  
Current Helicity

Extended AbstractRecent numerical simulations lead to the result that turbulence is much more magnetically driven than believed. In particular the role ofmagnetic buoyancyappears quite important for the generation ofα-effect and angular momentum transport (Brandenburg & Schmitt 1998). We present results obtained for a turbulence field driven by a (given) Lorentz force in a non-stratified but rotating convection zone. The main result confirms the numerical findings of Brandenburg & Schmitt that in the northern hemisphere theα-effect and the kinetic helicityℋkin= 〈u′ · rotu′〉 are positive (and negative in the northern hemisphere), this being just opposite to what occurs for the current helicityℋcurr= 〈j′ ·B′〉, which is negative in the northern hemisphere (and positive in the southern hemisphere). There has been an increasing number of papers presenting observations of current helicity at the solar surface, all showing that it isnegativein the northern hemisphere and positive in the southern hemisphere (see Rüdigeret al. 2000, also for a review).

The Hemispheric Sign Rule of Current Helicity during the Rising Phase of Cycle 23

2000 ◽  
Vol 179 ◽  
pp. 303-306
Author(s):  
S. D. Bao ◽  
G. X. Ai ◽  
H. Q. Zhang
Keyword(s):  
Solar Cycle ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Active Regions ◽  
Hemispheric Preference ◽  
Current Helicity

AbstractWe compute the signs of two different current helicity parameters (i.e., αbestandHc) for 87 active regions during the rise of cycle 23. The results indicate that 59% of the active regions in the northern hemisphere have negative αbestand 65% in the southern hemisphere have positive. This is consistent with that of the cycle 22. However, the helicity parameterHcshows a weaker opposite hemispheric preference in the new solar cycle. Possible reasons are discussed.

Measurements of the Cape Astrometric Survey of the Southern Hemisphere

1978 ◽  
Vol 48 ◽  
pp. 515-521
Author(s):  
W. Nicholson
Keyword(s):  
Southern Hemisphere ◽  
Automatic Measuring ◽  
Measuring Machine ◽  
Final Selection ◽  
Selection Of

SummaryA routine has been developed for the processing of the 5820 plates of the survey. The plates are measured on the automatic measuring machine, GALAXY, and the measures are subsequently processed by computer, to edit and then refer them to the SAO catalogue. A start has been made on measuring the plates, but the final selection of stars to be made is still a matter for discussion.

A Search for β Cephei Stars in the Southern Hemisphere - Results

1979 ◽  
Vol 46 ◽  
pp. 474-503 ◽  
Author(s):  
M. Jerzykiewicz ◽  
C. Sterken
Keyword(s):  
Southern Hemisphere ◽  
B Stars ◽  
Search Program

In 1975 we started a photometric search program of examining for variability- the bright early B stars located south of -20° declination. The main purpose we had in mind was to look for hitherto undiscovered 6 Cephei variables. Therefore, we limited our program to objects spectroscopically similar to the B Cephei stars.

RSCVn Stars in the Southern Hemisphere

1979 ◽  
Vol 46 ◽  
pp. 371-384 ◽  
Author(s):  
J.B. Hearnshaw
Keyword(s):  
Light Curve ◽  
Southern Hemisphere ◽  
Orbital Period ◽  
Binary Stars ◽  
Small Amplitude ◽  
Light Variation ◽  
Orbital Phase

RSCVn stars are fully detached binary stars which show intrinsic small amplitude (up to 0.3 amplitude peak-to-peak) light variations, as well as, in most of the known cases, eclipses. The spectra are F to G, IV to V for the hotter component and usually KOIV for the cooler. They are also characterised by abnormally strong H and K emission from the cooler star, or, occasionally, from both components. The orbital and light curve periods are in the range 1 day to 2 weeks. An interesting feature is the migration of the light variations to earlier orbital phase, as the light variation period is shorter than the orbital period by a few parts in 10+4to a few parts in 10+3.

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