A Novel Approach to Diagnosing Southern Hemisphere Planetary Wave Activity and Its Influence on Regional Climate Variability

2015 ◽  
Vol 28 (23) ◽  
pp. 9041-9057 ◽  
Author(s):  
Damien Irving ◽  
Ian Simmonds
Keyword(s):  
Climate Variability ◽  
Sea Ice ◽  
Southern Hemisphere ◽  
Planetary Wave ◽  
Regional Climate ◽  
Meridional Flow ◽  
Wave Activity ◽  
Novel Approach ◽  
Zonal Wavenumber ◽  
The Antarctic

Abstract Southern Hemisphere mid- to upper-tropospheric planetary wave activity is characterized by the superposition of two zonally oriented, quasi-stationary waveforms: zonal wavenumber 1 (ZW1) and zonal wavenumber 3 (ZW3). Previous studies have tended to consider these waveforms in isolation and with the exception of those studies relating to sea ice, little is known about their impact on regional climate variability. A novel approach is taken to quantifying the combined influence of ZW1 and ZW3, using the strength of the hemispheric meridional flow as a proxy for zonal wave activity. The methodology adapts the wave envelope construct routinely used in the identification of synoptic-scale Rossby wave packets and improves on existing approaches by allowing for variations in both wave phase and amplitude. While ZW1 and ZW3 are both prominent features of the climatological circulation, the defining feature of highly meridional hemispheric states is an enhancement of the ZW3 component. Composites of the mean surface conditions during these highly meridional, ZW3-like anomalous states (i.e., months of strong planetary wave activity) reveal large sea ice anomalies over the Amundsen and Bellingshausen Seas during autumn and along much of the East Antarctic coastline throughout the year. Large precipitation anomalies in regions of significant topography (e.g., New Zealand, Patagonia, and coastal Antarctica) and anomalously warm temperatures over much of the Antarctic continent were also associated with strong planetary wave activity. The latter has potentially important implications for the interpretation of recent warming over West Antarctica and the Antarctic Peninsula.

Burst of Unusual Quasi-10 day Wave During the 2019 Southern Sudden Stratospheric Warming

2021 ◽  
Author(s):  
Jack Wang ◽  
Scott Palo ◽  
Jeffrey Forbes ◽  
John Marino ◽  
Tracy Moffat-Griffin
Keyword(s):  
Southern Hemisphere ◽  
Planetary Wave ◽  
Wave Activity ◽  
Stratospheric Warming ◽  
Atmospheric Conditions ◽  
Meteor Radar ◽  
Sudden Stratospheric Warming ◽  
Zonal Wavenumber ◽  
Wind Measurements ◽  
Mlt Region

<div> <p>An unusual sudden stratospheric warming (SSW) occurred in the Southern hemisphere in September 2019. Ground-based and satellite observations show the presence of a transient westward-propagating quasi-10 day planetary wave with zonal wavenumber one during the SSW. The planetary wave activity maximizes in the MLT region approximately 10 days after the SSW onset. Analysis indicates the quasi-10 day planetary wave is symmetric about the equator which is contrary to theory for such planetary waves. </p> </div><div> <p>Observations from MLS and SABER provide a unique opportunity to study the global structure and evolution of the symmetric quasi-10 day wave with observations of both geopotential height and temperature during these unusual atmospheric conditions. The space-based measurements are combined with meteor radar wind measurements from Antarctica, providing a comprehensive view of the quasi-10 day wave activity in the southern hemisphere during this SSW. We will also present the results of our mesospheric and lower thermospheric analysis along with a preliminary analysis of the ionospheric response to these wave perturbations.</p> </div>

scholarly journals Response of the Antarctic stratosphere to warm pool El Niño Events in the GEOS CCM

2011 ◽  
Vol 11 (3) ◽  
pp. 9743-9767 ◽  
Author(s):  
M. M. Hurwitz ◽  
I.-S. Song ◽  
L. D. Oman ◽  
P. A. Newman ◽  
A. M. Molod ◽  
...  
Keyword(s):  
El Niño ◽  
Planetary Wave ◽  
Lower Stratosphere ◽  
El Nino ◽  
Warm Pool ◽  
Wave Activity ◽  
Central Pacific ◽  
Quasi Biennial Oscillation ◽  
South Central ◽  
The Antarctic

Abstract. A new formulation of the Goddard Earth Observing System Chemistry-Climate Model, Version 2 (GEOS V2 CCM), with an improved general circulation model and an internally generated quasi-biennial oscillation (QBO), is used to investigate the response of the Antarctic stratosphere to (1) warm pool El Niño (WPEN) events and (2) the sensitivity of this response to the phase of the QBO. Two 50-yr time-slice simulations are forced by repeating annual cycles of sea surface temperatures and sea ice concentrations composited from observed WPEN and neutral ENSO (ENSON) events. In these simulations, greenhouse gas and ozone-depleting substance concentrations represent the present-day climate. The modelled responses to WPEN, and to the phase of the QBO during WPEN, are compared with NASA's Modern Era Retrospective-Analysis for Research and Applications (MERRA) reanalysis. WPEN events enhance poleward planetary wave activity in the central South Pacific during austral spring, leading to relative warming of the Antarctic lower stratosphere in November/December. During the easterly phase of the QBO (QBO-E), the GEOS V2 CCM reproduces the observed 3–5 K warming of the polar region at 50 hPa, in the WPEN simulation relative to ENSON. In the recent past, the response to WPEN events was sensitive to the phase of the QBO: the enhancement in planetary wave driving and the lower stratospheric warming signal were mainly associated with WPEN events coincident with QBO-E. In the GEOS V2 CCM, however, the Antarctic response to WPEN events is insensitive to the phase of the QBO: the modelled response is always easterly QBO-like. OLR, streamfunction and Rossby wave energy diagnostics are used to show that the modelled QBO does not extend far enough into the lower stratosphere and upper troposphere to modulate convection and thus planetary wave activity in the south central Pacific.

scholarly journals Stratospheric gravity waves at Southern Hemisphere orographic hotspots: 2003–2014 AIRS/Aqua observations

2016 ◽  
Vol 16 (14) ◽  
pp. 9381-9397 ◽  
Author(s):  
Lars Hoffmann ◽  
Alison W. Grimsdell ◽  
M. Joan Alexander
Keyword(s):  
Gravity Wave ◽  
Southern Hemisphere ◽  
Antarctic Peninsula ◽  
Gravity Waves ◽  
General Circulation ◽  
Wave Activity ◽  
Small Scale ◽  
Mountain Wave ◽  
Kerguelen Islands ◽  
The Antarctic

Abstract. Stratospheric gravity waves from small-scale orographic sources are currently not well-represented in general circulation models. This may be a reason why many simulations have difficulty reproducing the dynamical behavior of the Southern Hemisphere polar vortex in a realistic manner. Here we discuss a 12-year record (2003–2014) of stratospheric gravity wave activity at Southern Hemisphere orographic hotspots as observed by the Atmospheric InfraRed Sounder (AIRS) aboard the National Aeronautics and Space Administration's (NASA) Aqua satellite. We introduce a simple and effective approach, referred to as the “two-box method”, to detect gravity wave activity from infrared nadir sounder measurements and to discriminate between gravity waves from orographic and other sources. From austral mid-fall to mid-spring (April–October) the contributions of orographic sources to the observed gravity wave occurrence frequencies were found to be largest for the Andes (90 %), followed by the Antarctic Peninsula (76 %), Kerguelen Islands (73 %), Tasmania (70 %), New Zealand (67 %), Heard Island (60 %), and other hotspots (24–54 %). Mountain wave activity was found to be closely correlated with peak terrain altitudes, and with zonal winds in the lower troposphere and mid-stratosphere. We propose a simple model to predict the occurrence of mountain wave events in the AIRS observations using zonal wind thresholds at 3 and 750 hPa. The model has significant predictive skill for hotspots where gravity wave activity is primarily due to orographic sources. It typically reproduces seasonal variations of the mountain wave occurrence frequencies at the Antarctic Peninsula and Kerguelen Islands from near zero to over 60 % with mean absolute errors of 4–5 percentage points. The prediction model can be used to disentangle upper level wind effects on observed occurrence frequencies from low-level source and other influences. The data and methods presented here can help to identify interesting case studies in the vast amount of AIRS data, which could then be further explored to study the specific characteristics of stratospheric gravity waves from orographic sources and to support model validation.

scholarly journals Antarctic regional modelling of atmospheric, sea-ice and oceanic processes and validation with observations

2000 ◽  
Vol 31 ◽  
pp. 348-352 ◽  
Author(s):  
David A. Bailey ◽  
Amanda H. Lynch
Keyword(s):  
Sea Ice ◽  
Global Climate ◽  
Regional Climate ◽  
Climate System ◽  
The Arctic ◽  
Small Scale ◽  
Atmospheric Conditions ◽  
Regional Modelling ◽  
Climate System Model ◽  
The Antarctic

AbstractHigh-latitude interactions of local-scale processes in the atmosphere-ice-ocean system have effects on the local, Antarctic and global climate. Phenomena including polynyas and leads are examples of such interactions which, when combined, have a significant impact on larger scales. These small-scale features, which are typically parameterized in global models, can be explicitly simulated using high-resolution regional climate system models. As such, the study of these interactions is well suited to a regional model approach and is considered here using the Arctic Regional Climate System Model (ARCSyM). This model has been used for many simulations in the Arctic, and is now implemented for the Antarctic. Observations of such processes in the Antarctic are limited, which makes model validation difficult. However, using the best available observations for an annual cycle, we have determined a suite of model parameterization which allows us to reasonably simulate the Antarctic climate. This work considers a fine-resolution (20 km) simulation in the Cosmonaut Sea region, with the eventual goal of elucidating the mechanisms in the formation and maintenance of the sensible-heat polynya which is a regular occurrence in this area. It was found in an atmosphere-sea-ice simulation that the ocean plays an important role in regulating the sea-ice cover in this region in compensating for the cold atmospheric conditions.

scholarly journals Planetary wave activity in the Arctic and Antarctic lower stratospheres during 2007 and 2008

2009 ◽  
Vol 9 (4) ◽  
pp. 14601-14643
Author(s):  
S. P. Alexander ◽  
M. G. Shepherd
Keyword(s):  
Northern Hemisphere ◽  
Planetary Wave ◽  
Travelling Waves ◽  
Maximum Amplitude ◽  
Wave Activity ◽  
Planetary Waves ◽  
The Arctic ◽  
Stationary Waves ◽  
Wave Amplification ◽  
Zonal Wavenumber

Abstract. Temperature data from the COSMIC GPS-RO satellite constellation are used to study planetary wave activity in both polar stratospheres from September 2006 until November 2008. One major and several minor sudden stratospheric warmings (SSWs) were recorded during the boreal winters of 2006/2007 and 2007/2008. Planetary wave morphology is studied using space-time spectral analysis while individual waves are extracted using a linear least squares fitting technique. Results show the planetary wave frequency and zonal wavenumber distribution varying between hemisphere and altitude. Most of the large Northern Hemisphere wave activity is associated with the winter SSWs, while the largest amplitude waves in the Southern Hemisphere occur during spring. Planetary wave activity during the 2006/2007 and 2007/2008 Arctic SSWs is due largely to travelling waves with zonal wavenumbers |s|=1 and |s|=2 having periods of 12, 16 and 23 days and stationary waves with |s|=1 and |s|=2. The latitudinal variation of wave amplification during the two Northern Hemisphere winters is studied. Most planetary waves show different structure and behaviour during each winter. Abrupt changes in the latitude of maximum amplitude of some planetary waves is observed co-incident in time with some of the SSWs.

Classification of Regional Climate Variability in the State of California

2009 ◽  
Vol 48 (8) ◽  
pp. 1527-1541 ◽  
Author(s):  
John T. Abatzoglou ◽  
Kelly T. Redmond ◽  
Laura M. Edwards
Keyword(s):  
Climate Variability ◽  
Large Scale ◽  
Regional Climate ◽  
Principal Component ◽  
The State ◽  
Monthly Precipitation ◽  
Regional Patterns ◽  
Novel Approach ◽  
Circulation Patterns

Abstract A novel approach is presented to objectively identify regional patterns of climate variability within the state of California using principal component analysis on monthly precipitation and temperature data from a network of 195 climate stations statewide and an ancillary gridded database. The confluence of large-scale circulation patterns and the complex geography of the state result in 11 regional modes of climate variability within the state. A comparison between the station and gridded analyses reveals that finescale spatial resolution is needed to adequately capture regional modes in complex orographic and coastal settings. Objectively identified regions can be employed not only in tracking regional climate signatures, but also in improving the understanding of mechanisms behind regional climate variability and climate change. The analysis has been incorporated into an operational tool called the California Climate Tracker.

scholarly journals Structure and Mechanisms of the Southern Hemisphere Summertime Subtropical Anticyclones

2010 ◽  
Vol 23 (8) ◽  
pp. 2115-2130 ◽  
Author(s):  
Takafumi Miyasaka ◽  
Hisashi Nakamura
Keyword(s):  
Southern Hemisphere ◽  
Rossby Wave ◽  
Sensible Heat Flux ◽  
Wave Activity ◽  
Convective Heating ◽  
Surface Cooling ◽  
Near Surface ◽  
Low Level ◽  
Zonal Wavenumber ◽  
Upper Level

Abstract The three-dimensional structure and dynamics of the climatological-mean summertime subtropical anticyclones in the Southern Hemisphere (SH) are investigated. As in the Northern Hemisphere (NH), each of the surface subtropical anticyclones over the South Pacific, South Atlantic, and South Indian Oceans is accompanied by a meridional vorticity dipole aloft, exhibiting barotropic and baroclinic structures in its poleward and equatorward portions, respectively, in a manner that is dynamically consistent with the observed midtropospheric subsidence. Their dynamics are also similar to their NH counterpart. It is demonstrated through the numerical experiments presented here that each of the SH surface anticyclones observed over the relatively cool eastern oceans can be reproduced as a response to a local near-surface cooling–heating couplet. The cooling is mainly due to radiative cooling associated with low-level maritime clouds, and the heating to the east is due to sensible heat flux over the dry, heated continental surface. The low-level clouds act to maintain the coolness of the underlying ocean surface, which is also maintained by the alongshore surface southerlies. As in the NH, the presence of a local atmosphere–ocean–land feedback loop is thus suggested, in which the summertime subtropical anticyclones and continental cyclones to their east are involved. Both the model experiments conducted here and the diagnosed upward flux of Rossby wave activity suggest that, in addition to continental deep convective heating, the land–sea heating–cooling contrasts across the west coasts of the three continents can contribute to the formation of the summertime upper-level planetary wave pattern observed in the entire subtropical SH, characterized by the zonal wavenumber-3 component. Though rather subtle, there are some interhemispheric differences in the summertime subtropical anticyclones, including their smaller magnitudes in the SH and the stronger equatorward propagation of upper-level Rossby wave activity emanating from the SH surface anticyclones.

scholarly journals Response of the Antarctic stratosphere to warm pool El Niño Events in the GEOS CCM

2011 ◽  
Vol 11 (18) ◽  
pp. 9659-9669 ◽  
Author(s):  
M. M. Hurwitz ◽  
I.-S. Song ◽  
L. D. Oman ◽  
P. A. Newman ◽  
A. M. Molod ◽  
...  
Keyword(s):  
El Niño ◽  
Planetary Wave ◽  
Lower Stratosphere ◽  
El Nino ◽  
Warm Pool ◽  
Wave Activity ◽  
Central Pacific ◽  
Quasi Biennial Oscillation ◽  
South Central ◽  
The Antarctic

Abstract. The Goddard Earth Observing System Chemistry-Climate Model, Version 2 (GEOS V2 CCM) is used to investigate the response of the Antarctic stratosphere to (1) warm pool El Niño (WPEN) events and (2) the sensitivity of this response to the phase of the QBO. A new formulation of the GEOS V2 CCM includes an improved general circulation model and an internally generated quasi-biennial oscillation (QBO). Two 50-yr time-slice simulations are forced by repeating annual cycles of sea surface temperatures and sea ice concentrations composited from observed WPEN and neutral ENSO (ENSON) events. In these simulations, greenhouse gas and ozone-depleting substance concentrations represent the present-day climate. The modelled responses to WPEN, and to the phase of the QBO during WPEN, are compared with NASA's Modern Era Retrospective-Analysis for Research and Applications (MERRA) reanalysis. WPEN events enhance poleward tropospheric planetary wave activity in the central South Pacific region during austral spring, leading to relative warming of the Antarctic lower stratosphere in November/December. During the easterly phase of the QBO (QBO-E), the GEOS V2 CCM reproduces the observed 4–5 K warming of the polar region at 50 hPa, in the WPEN simulation relative to ENSON. In the recent past, the response to WPEN events was sensitive to the phase of the QBO: the enhancement in planetary wave driving and the lower stratospheric warming signal were mainly associated with WPEN events coincident with QBO-E. In the GEOS V2 CCM, however, the Antarctic response to WPEN events is insensitive to the phase of the QBO: the modelled response is always easterly QBO-like. The QBO signal does not extend far enough into the lower stratosphere and upper troposphere to modulate convection and thus planetary wave activity in the south central Pacific.

scholarly journals The Antarctic Oscillation Structure in an AOGCM with Interactive Stratospheric Ozone

2012 ◽  
Vol 2012 ◽  
pp. 1-12
Author(s):  
S. Brand ◽  
K. Dethloff ◽  
D. Handorf
Keyword(s):  
General Circulation ◽  
Planetary Wave ◽  
Middle Atmosphere ◽  
Stratospheric Ozone ◽  
Circulation Model ◽  
Wave Activity ◽  
Antarctic Oscillation ◽  
Wave Dynamics ◽  
Hemisphere Winter ◽  
The Antarctic

Based on 150-year equilibrium simulations using the atmosphere-ocean-sea ice general circulation model (AOGCM) ECHO-GiSP, the southern hemisphere winter circulation is examined focusing on tropo-stratosphere coupling and wave dynamics. The model covers the troposphere and strato-mesosphere up to 80 km height and includes an interactive stratospheric chemistry. Compared to the reference simulation without interactive chemistry, the interactive simulation shows a weaker polar vortex in the middle atmosphere and is shifted towards the negative phase of the Antarctic Oscillation (AAO) in the troposphere. Differing from the northern hemisphere winter situation, the tropospheric planetary wave activity is weakened. A detailed analysis shows, that the modelled AAO zonal mean signal behaves antisymmetrically between troposphere and strato-mesosphere. This conclusion is supported by reanalysis data and a discussion of planetary wave dynamics in terms of Eliassen-Palm fluxes. Thereby, the tropospheric planetary wave activity appears to be controlled from the middle atmosphere.

scholarly journals A SPECIES DISTRIBUTION MODEL OF THE ANTARCTIC MINKE WHALE (BALAENOPTERA BONAERENSIS)

2022 ◽  
Author(s):  
Volodymyr Tytar
Keyword(s):  
Sea Ice ◽  
Chlorophyll A ◽  
Southern Hemisphere ◽  
Species Distribution ◽  
Sea Ice Concentration ◽  
Chlorophyll A Concentration ◽  
Antarctic Minke Whale ◽  
Ice Concentration ◽  
Balaenoptera Bonaerensis ◽  
The Antarctic

The Antarctic minke whale (Balaenoptera bonaerensis) is regarded a Southern Hemisphere endemic found throughout the Southern Hemisphere, generally south of 60°S in austral summer. Here they have been routinely observed in highest densities adjacent to and inside the sea ice edge, and where they feed predominantly on krill. Detecting abundance trends regarding this species by employing visual monitoring is problematic. Partly this is because the whales are frequently sighted within sea ice where navigational safety concerns prevent ships from surveying. In this respect species-habitat models are increasingly recognized as valuable tools to predict the probability of cetacean presence, relative abundance or density throughout an area of interest and to gain insight into the ecological processes affecting these patterns. The objective of this study was to provide this background information for the above research needs and in a broader context use species distribution models (SDMs) to establish a current habitat suitability description for the species and to identify the main environmental covariates related to its distribution. We used filtered 464 occurrences to generate the SDMs. We selected eight predictor variables with reduced collinearity for constructing the models: mean annuals of the surface temperature (ºC), salinity (PSS), current velocity (m/s), sea ice concentration (fraction, %), chlorophyll-a concentration (mg/m³), primary productivity (g/m3/day), cloud cover (%), and bathymetry (m). Six modeling algorithms were test and the Bayesian additive regression trees (BART) model demonstrated the best preformance. Based on variable importance, those that best explained the environmental requirements of the species, were: sea ice concentration, chlorophyll-a concentration and topography of the sea floor (bathymetry), explaining in sum around 62% of the variance. Using the BART model, habitat preferences have been interpreted from patterns in partial dependence plots. Areas where the AMW have particularly high likelihood of occurrence are East Antarctica, NE of the Weddell Sea, areas around the northern tip of the Antarctica Peninsula, areas bordering the Scotia–Weddell Confluence. Given the association of AMWs with sea ice the pagophilic character of their biology makes them particularly vulnerable to climate change and a perfect biological indicator for tracking these changes.

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