Influence of the spatial distribution of gravity wave activity on the middle atmospheric circulation and transport

Mapping Intimacies ◽

10.5194/acp-2016-548 ◽

2016 ◽

Author(s):

Petr Šácha ◽

Friederike Lilienthal ◽

Christoph Jacobi ◽

Petr Pišoft

Keyword(s):

Spatial Distribution ◽

Gravity Wave ◽

Atmospheric Circulation ◽

Large Scale ◽

Mechanistic Model ◽

Polar Vortex ◽

Wave Activity ◽

Residual Circulation ◽

Density Profiles ◽

Longitudinal Variability

Abstract. Analyzing GPS radio occultation density profiles, we have recently pointed out a localized area of enhanced gravity wave (GW) activity and breaking in the lower stratosphere of the Eastern Asia/North-western Pacific (EA/NP) region. With a mechanistic model for the middle and upper atmosphere (MUAM), experiments are performed to study a possible effect of such a localized IGW breaking region on the large-scale circulation and transport and also more generally, possible influence of spatial distribution of gravity wave activity on the middle atmospheric circulation and transport. The results indicate an important role of the spatial distribution of GW activity for the polar vortex stability, formation of planetary waves (PW) and for the strength and structure of the zonal mean residual circulation. Also, a possible effect of a zonally asymmetric GW breaking in the longitudinal variability of Brewer–Dobson circulation is analyzed. Finally, consequences of our results for a variety of research topics (Sudden Stratospheric Warmings, atmospheric blocking, teleconnections and a compensation mechanism between resolved and unresolved drag) are discussed.

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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.

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Supplementary material to "Influence of the spatial distribution of gravity wave activity on the middle atmospheric circulation and transport"

10.5194/acp-2016-548-supplement ◽

2016 ◽

Author(s):

Petr Šácha ◽

Friederike Lilienthal ◽

Christoph Jacobi ◽

Petr Pišoft

Keyword(s):

Spatial Distribution ◽

Gravity Wave ◽

Atmospheric Circulation ◽

Wave Activity ◽

Supplementary Material

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The advective Brewer-Dobson circulation in the ERA5 reanalysis: variability and trends

10.5194/acp-2020-881 ◽

2020 ◽

Author(s):

Mohamadou Diallo ◽

Manfred Ern ◽

Felix Ploeger

Keyword(s):

Gravity Wave ◽

Large Scale ◽

Climate Model ◽

Southern Oscillation ◽

Natural Variability ◽

Radiation Budget ◽

Residual Circulation ◽

Quasi Biennial Oscillation ◽

Acceleration Rate ◽

Good Agreement

Abstract. The stratospheric Brewer-Dobson circulation (BDC) is an important element of climate as it determines the transport and distributions of key radiatively active atmospheric trace gases, which affect the Earth’s radiation budget and surface climate. Here, we evaluate the inter-annual variability and trends of the BDC in the ERA5 reanalysis and inter-compare with the ERA-Interim reanalysis for the 1979–2018 period. We also assess the modulation of the circulation by the Quasi-Biennial Oscillation (QBO) and the El Niño-Southern Oscillation (ENSO), and the forcings of the circulation by the planetary and gravity wave drag. A comparison of ERA5 and ERA-Interim reanalyses shows a very good agreement in the morphology of the BDC and in its structural modulations by the natural variability related to QBO and ENSO. Despite the good agreement in the spatial structure, there are substantial differences in the strength of the BDC and of the natural variability impacts on the BDC between the two reanalyses, particularly in the upper troposphere and lower stratosphere (UTLS), and in the upper stratosphere. Throughout most regions of the stratosphere, the variability and trends of the advective BDC are stronger in the ERA5 reanalysis due to stronger planetary and gravity wave forcings, except in the UTLS below 20 km where the tropical upwelling is about 40 % weaker due to a weaker gravity wave forcings at the equatorial flank of the subtropical jet. In the extra-tropics, the large-scale downwelling is stronger in ERA5 than in ERA-Interim linked to significant differences in planetary and gravity wave forcings. Analysis of the BDC trend shows a global acceleration of the annual mean residual circulation with an acceleration rate of about 1.5 % per decade at 70 hPa due to the long-term intensification in gravity and planetary wave breaking, consistent with observed and future climate model predicted BDC changes.

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Spatial distribution of Serengeti wildebeest in relation to resources

Canadian Journal of Zoology ◽

10.1139/z99-088 ◽

1999 ◽

Vol 77 (8) ◽

pp. 1223-1232 ◽

Cited By ~ 110

Author(s):

John F Wilmshurst ◽

John M Fryxell ◽

Brian P Farm ◽

ARE Sinclair ◽

Chris P Henschel

Keyword(s):

Spatial Distribution ◽

Energy Intake ◽

Large Scale ◽

Spatial Scales ◽

Mechanistic Model ◽

Large Herbivores ◽

Serengeti Ecosystem ◽

Dry Seasons ◽

Behavioural Factors ◽

Wet And Dry Seasons

We investigated the spatial distribution of radio-marked wildebeest (Connochaetes taurinus) in the Serengeti ecosystem in relation to the distribution of their food resources, comparing patterns in the wet and dry seasons and at local and landscape spatial scales. A mechanistic model of ruminant energy optimization predicted that wildebeest should maximize energy intake on swards 3 cm high and maintain energy balance on swards between 3 and 10 cm high. At the ecosystem scale, wildebeest preferred short and intermediate-height grass of moderate greenness during both the wet and dry seasons. This was consistent with the model prediction which suggests that large-scale movements by wildebeest are motivated, at least partially, by an energy-maximizing strategy. At the local scale, however, wildebeest showed spatial selectivity only on the basis of grass greenness, not on grass height. This differed from model expectations and may have resulted from wildebeest exploiting ephemeral green flushes of grass caused by localized rainfall in their movement radius. According to these results, the influence of other nutritional or behavioural factors on wildebeest distributions is not rejected, yet they suggest the potentially important role of an energy intake maximizing strategy on movement patterns. Our findings show that wildebeest movements are broadly similar to those of other large herbivores that migrate in response to resource gradients.

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Intra-annual variations of spectrally resolved gravity wave activity in the upper mesosphere/lower thermosphere (UMLT) region

Atmospheric Measurement Techniques ◽

10.5194/amt-13-5117-2020 ◽

2020 ◽

Vol 13 (9) ◽

pp. 5117-5128

Author(s):

René Sedlak ◽

Alexandra Zuhr ◽

Carsten Schmidt ◽

Sabine Wüst ◽

Michael Bittner ◽

...

Keyword(s):

Gravity Wave ◽

Annual Cycle ◽

Large Scale ◽

Middle Atmosphere ◽

Wave Spectrum ◽

Lower Thermosphere ◽

Wave Activity ◽

Environmental Research ◽

Research Station ◽

Period Range

Abstract. The period range between 6 and 480 min is known to represent the major part of the gravity wave spectrum driving mesospheric dynamics. We present a method using wavelet analysis to calculate gravity wave activity with a high period resolution and apply it to temperature data acquired with the OH* airglow spectrometers called GRIPS (GRound-based Infrared P-branch Spectrometer) within the framework of the NDMC (Network for the Detection of Mesospheric Change; https://ndmc.dlr.de, last access: 22 September 2020). We analyse data measured at the NDMC sites Abastumani in Georgia (ABA; 41.75∘ N, 42.82∘ E), ALOMAR (Arctic Lidar Observatory for Middle Atmosphere Research) in Norway (ALR; 69.28∘ N, 16.01∘ E), Neumayer Station III in the Antarctic (NEU; 70.67∘ S, 8.27∘ W), Observatoire de Haute-Provence in France (OHP; 43.93∘ N, 5.71∘ E), Oberpfaffenhofen in Germany (OPN; 48.09∘ N, 11.28∘ E), Sonnblick in Austria (SBO; 47.05∘ N, 12.95∘ E), Tel Aviv in Israel (TAV; 32.11∘ N, 34.80∘ E), and the Environmental Research Station Schneefernerhaus on top of Zugspitze mountain in Germany (UFS; 47.42∘ N, 10.98∘ E). All eight instruments are identical in construction and deliver consistent and comparable data sets. For periods shorter than 60 min, gravity wave activity is found to be relatively low and hardly shows any seasonal variability on the timescale of months. We find a semi-annual cycle with maxima during winter and summer for gravity waves with periods longer than 60 min, which gradually develops into an annual cycle with a winter maximum for longer periods. The transition from a semi-annual pattern to a primarily annual pattern starts around a gravity wave period of 200 min. Although there are indications of enhanced gravity wave sources above mountainous terrain, the overall pattern of gravity wave activity does not differ significantly for the abovementioned observation sites. Thus, large-scale mechanisms such as stratospheric wind filtering seem to dominate the evolution of mesospheric gravity wave activity.

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The advective Brewer-Dobson circulation in the ERA5 reanalysis: climatology, variability, and trends

10.5194/egusphere-egu21-11920 ◽

2021 ◽

Author(s):

Mohamadou Diallo ◽

Manfred Ern ◽

Felix Ploeger

Keyword(s):

Gravity Wave ◽

Large Scale ◽

Climate Model ◽

Southern Oscillation ◽

Natural Variability ◽

Radiation Budget ◽

Residual Circulation ◽

Quasi Biennial Oscillation ◽

Acceleration Rate ◽

Good Agreement

The stratospheric Brewer-Dobson circulation (BDC) is an important element of climate as it determines the transport and distributions of key radiatively active atmospheric trace gases, which affect the Earth&#8217;s radiation budget and surface climate. Here, we evaluate the inter-annual variability and trends of the BDC in the ERA5 reanalysis and inter-compare with the ERA-Interim reanalysis for the 1979&#8211;2018 period. We also assess the modulation of the circulation by the Quasi-Biennial Oscillation (QBO) and the El Ni&#241;o-Southern Oscillation (ENSO), and the forcings of the circulation by the planetary and gravity wave drag. A comparison of ERA5 and ERA-Interim reanalyses shows a very good agreement in the morphology of the BDC and in its structural modulations by the natural variability related to QBO and ENSO. Despite the good agreement in the spatial structure, there are substantial differences in the strength of the BDC and of the natural variability impacts on the BDC between the two reanalyses, particularly in the upper troposphere and lower stratosphere (UTLS), and in the upper stratosphere. Throughout most regions of the stratosphere, the variability and trends of the advective BDC are stronger in the ERA5 reanalysis due to stronger planetary and gravity wave forcings, except in the UTLS below 20 km where the tropical upwelling is about 40 % weaker due to a weaker gravity wave forcings at the equatorial flank of the subtropical jet. In the extra-tropics, the large-scale downwelling is stronger in ERA5 than in ERA-Interim linked to significant differences in planetary and gravity wave forcings. Analysis of the BDC trend shows a global acceleration of the annual mean residual circulation with an acceleration rate of about 1.5 % per decade at 70 hPa due to the long-term intensification in gravity and planetary wave breaking, consistent with observed and future climate model predicted BDC changes.

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Enhanced internal gravity wave activity and breaking over the northeastern Pacific–eastern Asian region

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-13097-2015 ◽

2015 ◽

Vol 15 (22) ◽

pp. 13097-13112 ◽

Cited By ~ 19

Author(s):

P. Šácha ◽

A. Kuchař ◽

C. Jacobi ◽

P. Pišoft

Keyword(s):

Gravity Wave ◽

Coastal Region ◽

Internal Gravity Wave ◽

Wave Activity ◽

Satellite Mission ◽

Density Profiles ◽

Cycle Amplitude ◽

Northeastern Pacific ◽

Middle Atmospheric Dynamics ◽

The Mean

Abstract. We have found a stratospheric area of anomalously low annual cycle amplitude and specific dynamics in the stratosphere over the northeastern Pacific–eastern Asia coastal region. Using GPS radio occultation density profiles from the Formosat Satellite Mission 3/Constellation Observing System for Meteorology, Ionosphere, and Climate (FORMOSAT-3/COSMIC), we have discovered an internal gravity wave (IGW) activity and breaking hotspot in this region. Conditions supporting orographic wave sourcing and propagation were found. Other possible sources of wave activity in this region are listed. The reasons why this particular IGW activity hotspot was not discovered before as well as why the specific dynamics of this region have not been pointed out are discussed together with the weaknesses of using the mean potential energy as a wave activity proxy. Possible consequences of the specific dynamics in this region on the middle atmospheric dynamics and transport are outlined.

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Arctic Oscillation impact on thermal regime in the Eastern part of the Baltic region

Solar-Terrestrial Physics ◽

10.12737/19881 ◽

2016 ◽

Vol 2 (1) ◽

pp. 89-96

Author(s):

Индре Гечайте ◽

Indre Gecaite ◽

Александр Погорельцев ◽

Aleksandr Pogoreltsev ◽

Александр Угрюмов ◽

...

Keyword(s):

Atmospheric Circulation ◽

Geomagnetic Activity ◽

Large Scale ◽

Arctic Oscillation ◽

Polar Vortex ◽

Baltic Region ◽

Stratospheric Polar Vortex ◽

Weather Forecasts ◽

Tropospheric Circulation ◽

The Baltic

The paper presents statistical estimations of Arctic Oscillation (AO) impact on air temperature regime in the eastern part of the Baltic region. The region is characterized by high inter-annual and inter-seasonal variability. It is important to note that in the region of global warming extremely low winter temperatures can be observed on the European territory of Russia. AO is one of the large-scale global patterns of atmospheric circulation closely associated with weather variability in northern Europe. AО anomalies occur in the upper atmosphere (stratosphere) and only then are transferred to tropospheric lower layers. The anomalies can persist over a long period of time (up to two months); so they can serve as precursors in long-range weather forecasts. In turn, changes in stratospheric polar vortex and sudden stratospheric warmings can be related to geomagnetic activity. Perhaps geomagnetic activity influences the meridional temperature gradient and then changes the structure of the stratospheric zonal wind. These changes have an effect on the tropospheric circulation. The stratosphere–troposphere coupling takes place during winter months. Therefore, the paper deals with extremely cold winter anomalies in the eastern part of the Baltic Sea region. At the same time, we examine atmospheric circulation peculiarities associated with AO phase change. We analyze data for 1951–2014.

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Satellite observations of middle atmosphere gravity wave activity and dissipation during recent stratospheric warmings

10.5194/acp-2016-276 ◽

2016 ◽

Cited By ~ 1

Author(s):

Manfred Ern ◽

Quang Thai Trinh ◽

Martin Kaufmann ◽

Isabell Krisch ◽

Peter Preusse ◽

...

Keyword(s):

Gravity Wave ◽

Gravity Waves ◽

Middle Atmosphere ◽

Polar Vortex ◽

Wave Activity ◽

Planetary Waves ◽

Absolute Gravity ◽

Mountain Waves ◽

Meridional Shape ◽

Zonal Average

Abstract. Sudden stratospheric warmings (SSWs) are circulation anomalies in the polar region during winter. They mostly occur in the Northern Hemisphere and affect also surface weather and climate. Both planetary waves and gravity waves contribute to the onset and evolution of SSWs. While the role of planetary waves for SSW evolution has been recognized, the effect of gravity waves is still not fully understood, and has not been comprehensively analyzed based on global observations. In particular, information on the gravity wave driving of the background winds during SSWs is still missing. We investigate the boreal winters 2001/2002 until 2013/2014. Absolute gravity wave momentum fluxes and gravity wave dissipation (potential drag) are estimated from temperature observations of the satellite instruments HIRDLS and SABER. In agreement with previous work, we find that sometimes gravity wave activity is enhanced before the central date of major SSWs, particularly during vortex-split events. Often, SSWs are associated with polar-night jet oscillation (PJO) events. For these events, we find that gravity wave activity is strongly suppressed when winds reverse from eastward to westward (usually after the central date of a major SSW). In addition, gravity wave potential drag at the bottom of the newly forming eastward directed jet is remarkably weak, while considerable potential drag at the top of the jet likely contributes to the downward propagation of both the jet and the new elevated stratopause. During PJO events, we also find some indication for poleward propagation of gravity waves. Another striking finding is that obviously localized gravity wave sources, likely mountain waves and jet-generated gravity waves, play an important role during the evolution of SSWs and potentially contribute to the triggering of SSWs by preconditioning the shape of the polar vortex. The distribution of these hot spots is highly variable and strongly depends on the zonal and meridional shape of the background wind field, indicating that a pure zonal average view sometimes is a too strong simplification for the strongly perturbed conditions during the evolution of SSWs.

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Rossby wave activity associated with Euro-Atlantic weather regimes in the PRIMAVERA historical runs.

10.5194/egusphere-egu21-9605 ◽

2021 ◽

Author(s):

Paolo Ghinassi ◽

Federico Fabiano ◽

Susanna Corti

Keyword(s):

Spatial Distribution ◽

High Resolution ◽

Rossby Wave ◽

Large Scale ◽

Wave Activity ◽

Large Scale Circulation ◽

Temporal Behaviour ◽

Weather Regime ◽

Weather Regimes ◽

Isentropic Coordinates

In this study we aim to assess how the upper tropospheric Rossby wave activity is represented in the PRIMAVERA models. The low and high resolution historical coupled simulations will be compared with ERA5 reanalysis (spanning the 1979-2014 period) to enlighten model deficiencies in representing the spatial distribution and temporal evolution of Rossby wave activity and to emphasize the benefits of increased resolution. Our analysis focuses on the wintertime large scale circulation over the Euro-Atlantic sector. A diagnostic based on Local Wave Activity (LWA) in isentropic coordinates is used to identify Rossby waves and to quantify their amplitude. LWA is partitioned into its stationary and transient components, to distinguish the contribution from planetary versus synoptic scale waves (i.e. wave packets). This diagnostic is then combined with another one to identify persistent and recurrent large scale circulation patterns, the so called weather regimes. Weather regimes in the Euro-Atlantic sector are identified with the usual approach of EOF decomposition and k-mean clustering applied to daily anomalies of Montgomery streamfunction, in order to have a consistent framework with LWA (which is defined in isentropic coordinates). A composite of transient LWA is realised for each weather regime to obtain the spatial distribution of Rossby wave activity associated with each weather regime.Results show a marked intermodel variability in the ability of reproducing the correct (i.e. the one observed in reanalysis data) LWA distribution. Many of the models in fact fails to reproduce the localized (in space) maxima of LWA associated with each weather regime and to distribute LWA over a larger region compared to reanalysis. High resolution helps to correct this bias in the majority of the models, in particular in those where the low-resolution LWA distribution was already close to reanalysis. Finally, the temporal behaviour of the spatially averaged LWA in the examined period is discussed.

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