The Relevance of the Location of Blocking Highs for Stratospheric Variability in a Changing Climate

Abstract Previous research shows that blocking highs (BHs) influence wintertime polar stratospheric variability through the modulation of the climatological planetary waves (PWs) depending on the BH location. BHs over the Euro-Atlantic sector tend to enhance the upward PW propagation, and those over the northwestern Pacific Ocean tend to reduce it. Future changes are examined in the response of the wave activity flux to the BH location and their relationship with wintertime stratospheric variability in transient simulations of ECHAM/Modular Earth Submodel System (MESSy) Atmospheric Chemistry (EMAC). After it is verified that EMAC can reproduce qualitatively well the geographical dependence of the BH influence on PW activity injection, it is shown that this dependence does not change in the future. However, an eastward shift of the pattern of the BH influence on PW propagation over the Pacific, a farther eastward extension of the pattern over the Atlantic Ocean, and an intensification of the wavenumber-1 component of the interaction between climatological and anomalous waves are detected. Changes in the upper-tropospheric jet and an intensification of the wavenumber-1 climatological wave due to a strengthening of the Aleutian low agree with these variations. The spatial distribution of future BHs preceding extreme polar vortex events is also affected by the slight modifications in the wave activity pattern. Hence, future BHs preceding strong vortex events tend to be more concentrated over the Pacific than in the past, where BHs interfere negatively with wavenumber-1 climatological waves. Future BHs prior to major stratospheric warmings are located in a broader area than in the past, predominantly over an extended Euro-Atlantic sector.

Download Full-text

The Major Stratospheric Sudden Warming of January 2013: Analyses and Forecasts in the GEOS-5 Data Assimilation System

Monthly Weather Review ◽

10.1175/mwr-d-14-00023.1 ◽

2015 ◽

Vol 143 (2) ◽

pp. 491-510 ◽

Cited By ~ 26

Author(s):

Lawrence Coy ◽

Steven Pawson

Keyword(s):

Data Assimilation ◽

Polar Vortex ◽

Wave Activity ◽

Time Data ◽

Weather System ◽

Stratospheric Sudden Warming ◽

The Pacific ◽

Data Assimilation System ◽

Wave Activity Flux ◽

Assimilation System

Abstract The major stratospheric sudden warming (SSW) of 6 January 2013 is examined using output from the NASA Global Modeling and Assimilation Office (GMAO) Goddard Earth Observing System version 5 (GEOS-5) near-real-time data assimilation system (DAS). GEOS-5 analyses showed that the SSW of January 2013 was a major warming by 1200 UTC 6 January, with a wave-2 vortex-splitting pattern. Upward wave activity flux from the upper troposphere (~23 December 2012) displaced the ~10-hPa polar vortex off the pole in a wave-1 pattern, enabling the poleward advection of subtropical values of Ertel potential vorticity (EPV) into a developing anticyclonic circulation region. While the polar vortex subsequently split (wave-2 pattern) the wave-2 forcing [upward Eliassen–Palm (EP) flux] was smaller than what was found in recent wave-2, SSW events, with most of the forcing located in the Pacific hemisphere. Investigation of a rapidly developing tropospheric weather system over the North Atlantic on 28–29 December 2012 showed strong transient upward wave activity flux from the storm with influences up to 10 hPa; however, the Pacific hemisphere wave forcing remained dominate at this time. Results from the GEOS-5 five-day forecasts showed that the forecasts accurately predicted the major SSW of January 2013. The overall success of the 5-day forecasts provides motivation to produce regular 10-day forecasts with GEOS-5, to better support studies of stratosphere–troposphere interaction.

Download Full-text

Radiative and dynamical contributions to past and future Arctic stratospheric temperature trends

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-1679-2014 ◽

2014 ◽

Vol 14 (3) ◽

pp. 1679-1688 ◽

Cited By ~ 16

Author(s):

P. Bohlinger ◽

B.-M. Sinnhuber ◽

R. Ruhnke ◽

O. Kirner

Keyword(s):

Atmospheric Chemistry ◽

Planetary Wave ◽

Climate Model ◽

Stratospheric Ozone ◽

Wave Activity ◽

The Arctic ◽

Radiosonde Data ◽

Data Set ◽

The Past ◽

Stratospheric Temperature

Abstract. Arctic stratospheric ozone depletion is closely linked to the occurrence of low stratospheric temperatures. There are indications that cold winters in the Arctic stratosphere have been getting colder, raising the question if and to what extent a cooling of the Arctic stratosphere may continue into the future. We use meteorological reanalyses from the European Centre for Medium Range Weather Forecasts (ECMWF) ERA-Interim and NASA's Modern-Era Retrospective-Analysis for Research and Applications (MERRA) for the past 32 yr together with calculations of the chemistry-climate model (CCM) ECHAM/MESSy Atmospheric Chemistry (EMAC) and models from the Chemistry-Climate Model Validation (CCMVal) project to infer radiative and dynamical contributions to long-term Arctic stratospheric temperature changes. For the past three decades the reanalyses show a warming trend in winter and cooling trend in spring and summer, which agree well with trends from the Radiosonde Innovation Composite Homogenization (RICH) adjusted radiosonde data set. Changes in winter and spring are caused by a corresponding change of planetary wave activity with increases in winter and decreases in spring. During winter the increase of planetary wave activity is counteracted by a residual radiatively induced cooling. Stratospheric radiatively induced cooling is detected throughout all seasons, being highly significant in spring and summer. This means that for a given dynamical situation, according to ERA-Interim the annual mean temperature of the Arctic lower stratosphere has been cooling by −0.41 ± 0.11 K decade−1 at 50 hPa over the past 32 yr. Calculations with state-of-the-art models from CCMVal and the EMAC model qualitatively reproduce the radiatively induced cooling for the past decades, but underestimate the amount of radiatively induced cooling deduced from reanalyses. There are indications that this discrepancy could be partly related to a possible underestimation of past Arctic ozone trends in the models. The models project a continued cooling of the Arctic stratosphere over the coming decades (2001–2049) that is for the annual mean about 40% less than the modeled cooling for the past, due to the reduction of ozone depleting substances and the resulting ozone recovery. This projected cooling in turn could offset between 15 and 40% of the Arctic ozone recovery.

Download Full-text

Differences in the Sub-seasonal Predictability of Extreme Stratospheric Events

10.5194/wcd-2021-84 ◽

2022 ◽

Author(s):

Rachel Wai-Ying Wu ◽

Zheng Wu ◽

Daniela I. V. Domeisen

Keyword(s):

Extreme Events ◽

Weather Prediction ◽

Polar Vortex ◽

Wave Activity ◽

Prediction System ◽

Wave Amplification ◽

Weather Forecasts ◽

Surface Weather ◽

Linear Behaviour ◽

Strong Vortex

Abstract. Extreme stratospheric events such as sudden stratospheric warming and strong vortex events associated with an anomalously weak or strong polar vortex can have downward impacts on surface weather that can last for several weeks to months. Hence, successful predictions of these stratospheric events would be beneficial for extended range weather prediction. However, the predictability limit of extreme stratospheric events is most often limited to around 2 weeks or less. The predictability also strongly differs between events, and between event types. The reasons for the observed differences in the predictability, however, are not resolved. To better understand the predictability differences between events, we expand the definitions of extreme stratospheric events to wind deceleration and acceleration events, and conduct a systematic comparison of predictability between event types in the European Centre for Medium-Range Weather Forecasts (ECMWF) prediction system for the sub-seasonal predictions. We find that wind deceleration and acceleration events follow the same predictability behaviour, that is, events of stronger magnitude are less predictable in a close to linear relationship, to the same extent for both types of events. There are however deviations from this linear behaviour for very extreme events. The difficulties of the prediction system in predicting extremely strong anomalies can be traced to a poor predictability of extreme wave activity pulses in the lower stratosphere, which impacts the prediction of deceleration events, and interestingly, also acceleration events. Improvements in the understanding of the wave amplification that is associated with extremely strong wave activity pulses and accurately representing these processes in the model is expected to enhance the predictability of stratospheric extreme events and, by extension, their impacts on surface weather and climate.

Download Full-text

Influence of the spatial distribution of gravity wave activity on the middle atmospheric dynamics

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-15755-2016 ◽

2016 ◽

Vol 16 (24) ◽

pp. 15755-15775 ◽

Cited By ~ 12

Author(s):

Petr Šácha ◽

Friederike Lilienthal ◽

Christoph Jacobi ◽

Petr Pišoft

Keyword(s):

Spatial Distribution ◽

Gravity Wave ◽

Large Scale ◽

Mechanistic Model ◽

Polar Vortex ◽

Wave Activity ◽

Northwestern Pacific ◽

Residual Circulation ◽

Teleconnection Patterns ◽

Longitudinal Variability

Abstract. Analysing GPS radio occultation density profiles, we have recently pointed out a localised area of enhanced gravity wave (GW) activity and breaking in the lower stratosphere of the east Asian–northwestern Pacific (EA/NP) region. With a mechanistic model of the middle and upper atmosphere, experiments are performed to study the possible effect of such a localised GW breaking region on large-scale circulation and transport and, more generally, a possible influence of the spatial distribution of gravity wave activity on middle atmospheric dynamics.The results indicate the important role of the spatial distribution of GW activity for polar vortex stability, formation of planetary waves and for the strength and structure of zonal-mean residual circulation. Furthermore, a possible effect of a zonally asymmetric GW breaking in the longitudinal variability of the Brewer–Dobson circulation is analysed. Finally, consequences of our results for a variety of research topics (e.g. sudden stratospheric warming, atmospheric blocking, teleconnection patterns and a compensation mechanism between resolved and unresolved drag) are discussed.

Download Full-text

MONARCHS, TRAVELLERS AND EMPIRE IN THE PACIFIC'S AGE OF REVOLUTIONS

Transactions of the Royal Historical Society ◽

10.1017/s0080440120000043 ◽

2020 ◽

Vol 30 ◽

pp. 77-96

Author(s):

Sujit Sivasundaram

Keyword(s):

Pacific Islanders ◽

Modern World ◽

Global History ◽

The Past ◽

The Pacific ◽

Cultural Terms ◽

The Pacific Ocean ◽

Definition Of ◽

The Uk ◽

A Site

AbstractThe Pacific has often been invisible in global histories written in the UK. Yet it has consistently been a site for contemplating the past and the future, even among Britons cast on its shores. In this lecture, I reconsider a critical moment of globalisation and empire, the ‘age of revolutions’ at the end of the eighteenth century and the start of the nineteenth century, by journeying with European voyagers to the Pacific Ocean. The lecture will point to what this age meant for Pacific islanders, in social, political and cultural terms. It works with a definition of the Pacific's age of revolutions as a surge of indigeneity met by a counter-revolutionary imperialism. What was involved in undertaking a European voyage changed in this era, even as one important expedition was interrupted by news from revolutionary Europe. Yet more fundamentally vocabularies and practices of monarchy were consolidated by islanders across the Pacific. This was followed by the outworkings of counter-revolutionary imperialism through agreements of alliance and alleged cessation. Such an argument allows me, for instance, to place the 1806 wreck of the Port-au-Prince within the Pacific's age of revolutions. This was an English ship used to raid French and Spanish targets in the Pacific, but which was stripped of its guns, iron, gunpowder and carronades by Tongans. To chart the trajectory from revolution and islander agency on to violence and empire is to appreciate the unsettled paths that gave rise to our modern world. This view foregrounds people who inhabited and travelled through the earth's oceanic frontiers. It is a global history from a specific place in the oceanic south, on the opposite side of the planet to Europe.

Download Full-text

Seasonal prediction of the boreal winter stratosphere

Climate Dynamics ◽

10.1007/s00382-021-05787-9 ◽

2021 ◽

Author(s):

Alice Portal ◽

Paolo Ruggieri ◽

Froila M. Palmeiro ◽

Javier García-Serrano ◽

Daniela I. V. Domeisen ◽

...

Keyword(s):

Southern Oscillation ◽

Polar Vortex ◽

Seasonal Prediction ◽

Wave Activity ◽

Boreal Winter ◽

Quasi Biennial Oscillation ◽

Stratospheric Polar Vortex ◽

Eddy Heat Flux ◽

Prediction Systems ◽

Model Database

AbstractThe predictability of the Northern Hemisphere stratosphere and its underlying dynamics are investigated in five state-of-the-art seasonal prediction systems from the Copernicus Climate Change Service (C3S) multi-model database. Special attention is devoted to the connection between the stratospheric polar vortex (SPV) and lower-stratosphere wave activity (LSWA). We find that in winter (December to February) dynamical forecasts initialised on the first of November are considerably more skilful than empirical forecasts based on October anomalies. Moreover, the coupling of the SPV with mid-latitude LSWA (i.e., meridional eddy heat flux) is generally well reproduced by the forecast systems, allowing for the identification of a robust link between the predictability of wave activity above the tropopause and the SPV skill. Our results highlight the importance of November-to-February LSWA, in particular in the Eurasian sector, for forecasts of the winter stratosphere. Finally, the role of potential sources of seasonal stratospheric predictability is considered: we find that the C3S multi-model overestimates the stratospheric response to El Niño–Southern Oscillation (ENSO) and underestimates the influence of the Quasi–Biennial Oscillation (QBO).

Download Full-text

Spatial and seasonal variability of PM<sub>2.5</sub> acidity at two Chinese megacities: insights into the formation of secondary inorganic aerosols

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-1377-2012 ◽

2012 ◽

Vol 12 (3) ◽

pp. 1377-1395 ◽

Cited By ~ 105

Author(s):

K. He ◽

Q. Zhao ◽

Y. Ma ◽

F. Duan ◽

F. Yang ◽

...

Keyword(s):

Atmospheric Chemistry ◽

Temporal Variations ◽

Early Summer ◽

Heterogeneous Reactions ◽

Rural Site ◽

Urban Site ◽

Simultaneous Increase ◽

Northwestern Pacific ◽

Inorganic Aerosols ◽

Aerosol Acidity

Abstract. Aerosol acidity is one of the most important parameters influencing atmospheric chemistry and physics. Based on continuous field observations from January 2005 to May 2006 and thermodynamic modeling, we investigated the spatial and seasonal variations in PM2.5 acidity in two megacities in China, Beijing and Chongqing. Spatially, PM2.5 was generally more acidic in Chongqing than in Beijing, but a reverse spatial pattern was found within the two cities, with more acidic PM2.5 at the urban site in Beijing whereas the rural site in Chongqing. Ionic compositions of PM2.5 revealed that it was the higher concentrations of NO3− at the urban site in Beijing and the lower concentrations of Ca2+ within the rural site in Chongqing that made their PM2.5 more acidic. Temporally, PM2.5 was more acidic in summer and fall than in winter, while in the spring of 2006, the acidity of PM2.5 was higher in Beijing but lower in Chongqing than that in 2005. These were attributed to the more efficient formation of nitrate relative to sulfate as a result of the influence of Asian desert dust in 2006 in Beijing and the greater wet deposition of ammonium compared to sulfate and nitrate in 2005 in Chongqing. Furthermore, simultaneous increase of PM2.5 acidity was observed from spring to early summer of 2005 in both cities. This synoptic-scale evolution of PM2.5 acidity was accompanied by the changes in air masses origins, which were influenced by the movements of a subtropical high over the northwestern Pacific in early summer. Finally, the correlations between [NO3−]/[SO42−] and [NH4+]/[SO42−] suggests that under conditions of high aerosol acidity, heterogeneous reactions became one of the major pathways for the formation of nitrate at both cities. These findings provided new insights in our understanding of the spatial and temporal variations in aerosol acidity in Beijing and Chongqing, as well as those reported in other cities in China.

Download Full-text

Summary of Coastal Geologic Evidence for past Great Earthquakes at the Cascadia Subduction Zone

Earthquake Spectra ◽

10.1193/1.1585800 ◽

1995 ◽

Vol 11 (1) ◽

pp. 1-18 ◽

Cited By ~ 163

Author(s):

Brian F. Atwater ◽

Alan R. Nelson ◽

John J. Clague ◽

Gary A. Carver ◽

David K. Yamaguchi ◽

...

Keyword(s):

British Columbia ◽

North America ◽

Subduction Zone ◽

Forest Soils ◽

Pacific Coast ◽

Cascadia Subduction Zone ◽

Level Change ◽

The Past ◽

The Pacific ◽

Juan De Fuca

Earthquakes in the past few thousand years have left signs of land-level change, tsunamis, and shaking along the Pacific coast at the Cascadia subduction zone. Sudden lowering of land accounts for many of the buried marsh and forest soils at estuaries between southern British Columbia and northern California. Sand layers on some of these soils imply that tsunamis were triggered by some of the events that lowered the land. Liquefaction features show that inland shaking accompanied sudden coastal subsidence at the Washington-Oregon border about 300 years ago. The combined evidence for subsidence, tsunamis, and shaking shows that earthquakes of magnitude 8 or larger have occurred on the boundary between the overriding North America plate and the downgoing Juan de Fuca and Gorda plates. Intervals between the earthquakes are poorly known because of uncertainties about the number and ages of the earthquakes. Current estimates for individual intervals at specific coastal sites range from a few centuries to about one thousand years.

Download Full-text

“The ice has gone”: Vernacular meteorology, fisheries and human–ice relationships on Sakhalin Island

Polar Record ◽

10.1017/s0032247421000127 ◽

2021 ◽

Vol 57 ◽

Author(s):

Nadezhda Mamontova

Keyword(s):

Well Being ◽

Community Based ◽

Rural People ◽

The Past ◽

Weather Observations ◽

The Pacific ◽

Management Policies ◽

Subsistence Activities ◽

Human Subsistence

Abstract This paper examines vernacular weather observations amongst rural people on Sakhalin, Russia’s largest island on the Pacific Coast, and their relationship to the ice. It is based on a weather diary (2000–2016) of one of the local inhabitants and fieldwork that the author conducted in the settlement of Trambaus in 2016. The diary as a community-based weather monitoring allows us to examine how people understand, perceive and deal with the weather both daily and in the long-term perspective. Research argues that amongst all natural phenomena, the ice is the most crucial for the local inhabitants as it determines human subsistence activities, navigation and relations with other environmental forces and beings. People perceive the ice as having an agency, engage in a dialogue with it, learn and adjust themselves to its drifting patterns. Over the past decade, the inability to predict the ice’s behaviour has become a major problem affecting people’s well-being in the settlement. The paper advocates further integrating vernacular weather observations and their relations with natural forces into research on climate change and local fisheries management policies.

Download Full-text

Rattus exulans (Pacific rat).

10.1079/cpc.46834.20210099928 ◽

2021 ◽

Author(s):

Aaron Shiels

Keyword(s):

Southeast Asia ◽

Bird Species ◽

Tropical Pacific ◽

Pacific Basin ◽

The Past ◽

The Pacific ◽

Ground Nesting ◽

The Tropical Pacific

Abstract The Pacific rat, R. exulans, is an major agricultural and environmental pest in parts of Southeast Asia and the Pacific. Thought to have spread with Polynesian colonists over the past several thousand years, it is now found through much of the Pacific basin, and is extensively distributed in the tropical Pacific. It poses a significant threat to indigenous wildlife, particularly ground-nesting birds, and has been linked to the extinction of several bird species. R. exulans may also transmit diseases to humans.

Download Full-text