scholarly journals Linking air stagnation in Europe with the synoptic- to large-scale atmospheric circulation

2021 ◽  
Vol 2 (3) ◽  
pp. 675-694
Author(s):  
Jacob W. Maddison ◽  
Marta Abalos ◽  
David Barriopedro ◽  
Ricardo García-Herrera ◽  
Jose M. Garrido-Perez ◽  
...  
Keyword(s):  
Rossby Wave ◽  
Wave Breaking ◽  
Large Scale ◽  
Climate Models ◽  
Large Scale Circulation ◽  
Rossby Wave Breaking ◽  
The North ◽  
Northern Regions ◽  
Climatic Impacts ◽  
Large Scale Atmospheric Circulation

Abstract. The build-up of pollutants to harmful levels can occur when meteorological conditions favour their production or accumulation near the surface. Such conditions can arise when a region experiences air stagnation. The link between European air stagnation, air pollution and the synoptic- to large-scale circulation is investigated in this article across all seasons and the 1979–2018 period. Dynamical indices identifying atmospheric blocking, Rossby wave breaking, subtropical ridges, and the North Atlantic eddy-driven and subtropical jets are used to describe the synoptic- to large-scale circulation as predictors in statistical models of air stagnation and pollutant variability. It is found that the large-scale circulation can explain approximately 60 % of the variance in monthly air stagnation, ozone and wintertime particulate matter (PM) in five distinct regions within Europe. The variance explained by the model does not vary strongly across regions and seasons, apart from for PM when the skill is highest in winter. However, the dynamical indices most related to air stagnation do depend on region and season. The blocking and Rossby wave breaking predictors tend to be the most important for describing air stagnation and pollutant variability in northern regions, whereas ridges and the subtropical jet are more important to the south. The demonstrated correspondence between air stagnation, pollution and the large-scale circulation can be used to assess the representation of stagnation in climate models, which is key for understanding how air stagnation and its associated climatic impacts may change in the future.

scholarly journals Linking air stagnation in Europe with the large-scale atmospheric circulation

2021 ◽  
Author(s):  
Jacob W. Maddison ◽  
Marta Abalos ◽  
David Barriopedro ◽  
Ricardo García-Herrera ◽  
Jose M. Garrido-Perez ◽  
...  
Keyword(s):  
Air Quality ◽  
Rossby Wave ◽  
Wave Breaking ◽  
Large Scale ◽  
Climate Models ◽  
Large Scale Circulation ◽  
Rossby Wave Breaking ◽  
The North ◽  
Northern Regions ◽  
Large Scale Atmospheric Circulation

Abstract. The build-up of pollutants to harmful levels can occur when meteorological conditions favour their production or accumulation near the surface. Previous studies have shown that such conditions are often associated with air stagnation. Understanding the development of stagnant conditions is therefore crucial for studying poor air quality. The link between European air stagnation and the large-scale circulation is investigated in this article across all seasons and the 1979–2018 period. Dynamical based indices identifying atmospheric blocking, Rossby wave breaking, subtropical ridges, and the North Atlantic eddy-driven and subtropical jets are used to describe the large-scale circulation as predictors in a statistical model of air stagnation variability. It is found that the large-scale circulation can explain approximately 60 % of the variance in monthly air stagnation in five distinct regions within Europe. The variance explained by the model does not vary strongly across regions and seasons. However, the dynamical indices most related to air stagnation do depend on region and season. The blocking and Rossby wave breaking predictors tend to be the most important for describing air stagnation variability in northern regions whereas ridges and the subtropical jet are more important to the south. The demonstrated correspondence between air stagnation and the large-scale circulation can be used to assess the representation of stagnation in climate models, which is key for understanding how air quality and its associated health risks may change in the future.

Linking air stagnation in Europe with the large-scale atmospheric circulation

2021 ◽  
Author(s):  
Jacob Maddison ◽  
Marta Abalos ◽  
David Barriopedro ◽  
Ricardo Garcia Herrera ◽  
José Manuel Garrido Pérez ◽  
...  
Keyword(s):  
Air Quality ◽  
Health Risks ◽  
Rossby Wave ◽  
Wave Breaking ◽  
Large Scale ◽  
Climate Models ◽  
Large Scale Circulation ◽  
Rossby Wave Breaking ◽  
The North ◽  
Weak Winds

<div>Air stagnation refers to a period when a stable air mass becomes settled over a region and remains quasi-stationary for an extended amount of time. Weak winds in the lower- to mid-troposphere and the absence of precipitation during air stagnation prohibit the ventilation and washout of particles so pollutants can accumulate near the surface. This allows for such pollutants to reach levels harmful to humans, and poses severe health risks. Understanding the development of stagnant conditions is therefore crucial for studying poor air quality and its societal impact. </div><p><br>Here, the linear relationship between European air stagnation and the large-scale circulation is explored across all seasons and during the 1979--2018 period. Dynamical based indices identifying atmospheric blocking, Rossby wave breaking, subtropical ridges, and the North Atlantic eddy-driven and subtropical jets are used to describe the large-scale circulation as predictors in a statistical model of air stagnation variability. It is found that the large-scale circulation can explain approximately 60% of the variance in monthly air stagnation in five distinct regions within Europe. The variance explained by the model does not vary strongly across regions and seasons. However, the dynamical indices most related to air stagnation do depend on region and season. The blocking and Rossby wave breaking predictors tend to be the most important for describing air stagnation variability in northern regions whereas ridges and the subtropical jet are more important to the south. The demonstrated correspondence between air stagnation and the large-scale circulation can be used to assess the representation of air stagnation in climate models, which is key for understanding how air quality and its associated health risks may change in the future.</p>

scholarly journals Dynamical Evolution of North Atlantic Ridges and Poleward Jet Stream Displacements

2011 ◽  
Vol 68 (5) ◽  
pp. 954-963 ◽  
Author(s):  
Tim Woollings ◽  
Joaquim G. Pinto ◽  
João A. Santos
Keyword(s):  
Rossby Wave ◽  
North Atlantic ◽  
Wave Breaking ◽  
Large Scale ◽  
Wave Train ◽  
Jet Stream ◽  
Rossby Wave Breaking ◽  
The North ◽  
The North Atlantic ◽  
Circulation Anomalies

Abstract The development of a particular wintertime atmospheric circulation regime over the North Atlantic, comprising a northward shift of the North Atlantic eddy-driven jet stream and an associated strong and persistent ridge in the subtropics, is investigated. Several different methods of analysis are combined to describe the temporal evolution of the events and relate it to shifts in the phase of the North Atlantic Oscillation and East Atlantic pattern. First, the authors identify a close relationship between northward shifts of the eddy-driven jet, the establishment and maintenance of strong and persistent ridges in the subtropics, and the occurrence of upper-tropospheric anticyclonic Rossby wave breaking over Iberia. Clear tropospheric precursors are evident prior to the development of the regime, suggesting a preconditioning of the Atlantic jet stream and an upstream influence via a large-scale Rossby wave train from the North Pacific. Transient (2–6 days) eddy forcing plays a dual role, contributing to both the initiation and then the maintenance of the circulation anomalies. During the regime there is enhanced occurrence of anticyclonic Rossby wave breaking, which may be described as low-latitude blocking-like events over the southeastern North Atlantic. A strong ridge is already established at the time of wave-breaking onset, suggesting that the role of wave-breaking events is to amplify the circulation anomalies rather than to initiate them. Wave breaking also seems to enhance the persistence, since it is unlikely that a persistent ridge event occurs without being also accompanied by wave breaking.

scholarly journals North Atlantic Rossby Wave Breaking during the Hurricane Season: Association with Tropical and Extratropical Variability

2019 ◽  
Vol 32 (13) ◽  
pp. 3777-3801 ◽  
Author(s):  
Gan Zhang ◽  
Zhuo Wang
Keyword(s):  
Rossby Wave ◽  
North Atlantic ◽  
Wave Breaking ◽  
Large Scale ◽  
Heat Fluxes ◽  
Weather Regimes ◽  
Rossby Wave Breaking ◽  
The North ◽  
Sst Variability ◽  
Hurricane Season

Abstract This study explores the connection of Rossby wave breaking (RWB) with tropical and extratropical variability during the Atlantic hurricane season. The exploration emphasizes subtropical anticyclonic RWB events over the western North Atlantic, which strongly affect tropical cyclone (TC) activity. The first part of the study investigates the link between RWB and tropical sea surface temperature (SST) variability. Tropical SST variability affects tropical precipitation and modulates the large-scale atmospheric circulation over the subtropical Atlantic, which influences the behaviors of Rossby waves and the frequency of RWB occurrence. Meanwhile, RWB regulates surface heat fluxes and helps to sustain SST anomalies in the western North Atlantic. The second part of the study explores the connections between RWB and extratropical atmosphere variability by leveraging weather regime analysis. The weather regimes over the North Atlantic are closely associated with RWB over the eastern North Atlantic and western Europe, but show weak associations with RWB over the western North Atlantic. Instead, RWB over the western basin is closely related to the weather regimes in the North Pacific–North America sector. The finding helps clarify why the correlation between the Atlantic TC activity and the summertime North Atlantic Oscillation is tenuous. The relations between the extratropical weather regimes and tropical climate modes are also discussed. The findings suggest that both tropical and extratropical variability are important for understanding variations of RWB events and their impacts on Atlantic TC activity.

Large-Scale Atmospheric Circulation Related to Frequent Rossby Wave Breaking near Japan in Boreal Summer

2020 ◽  
Vol 33 (15) ◽  
pp. 6731-6744
Author(s):  
Kazuto Takemura ◽  
Hitoshi Mukougawa ◽  
Shuhei Maeda
Keyword(s):  
Atmospheric Circulation ◽  
Rossby Wave ◽  
Wave Breaking ◽  
Large Scale ◽  
Boreal Summer ◽  
Rossby Wave Breaking ◽  
The Pacific ◽  
Silk Road Pattern ◽  
Large Scale Atmospheric Circulation ◽  
The Silk Road

AbstractRossby wave propagation along the Asian jet during boreal summer, such as the Silk Road pattern, frequently causes wave breaking near the Asian jet exit region. This study examines the statistical relationship between interannual variability of the Rossby wave breaking frequency near Japan and large-scale atmospheric circulation during the boreal summer. The Rossby wave breaking frequency in the midlatitudes climatologically shows its maximum near Japan, and significantly increases during La Niña years. The upper-tropospheric circulation regressed onto the Rossby wave breaking frequency near Japan in August shows large-scale anomalous convergence from the tropical central to eastern Pacific and divergence around the Indian Ocean. The consequent northward anomalous divergent wind over Eurasia contributes to enhancement and northward shift of the Asian jet. The Asian jet also shows meridional meandering with a phase of anomalous anticyclonic circulation near Japan accompanied by the frequent Rossby wave breaking, which is associated with the Silk Road pattern. The frequent Rossby wave breaking is related to southwestward intrusion of anomalous low potential temperature air mass toward the subtropical western North Pacific associated with an enhanced mid-Pacific trough. West of the southwestward cold-air intrusion, enhanced cumulus convection is seen around the northern Philippines, and the Pacific–Japan pattern is significantly seen in the lower troposphere. This result is consistent with a previous study that revealed a linkage mechanism between the Rossby wave breaking near Japan and the Pacific–Japan pattern through dynamically induced ascent resulting in an intrusion of high potential vorticity associated with the Rossby wave breaking.

Method for Identifying and Clustering Rossby Wave Breaking Events in the Northern Hemisphere

2021 ◽  
pp. 17-28
Author(s):  
A. V. Gochakov ◽  
◽  
O. Yu. Antokhina ◽  
V. N. Krupchatnikov ◽  
Yu. V. Martynova ◽  
...  
Keyword(s):  
Rossby Wave ◽  
Potential Vorticity ◽  
Wave Breaking ◽  
Large Scale ◽  
Method Development ◽  
Spatial Clustering ◽  
Potential Temperature ◽  
Reanalysis Data ◽  
Rossby Wave Breaking ◽  
Dynamic Phenomena

Many large-scale dynamic phenomena in the Earth’s atmosphere are associated with the processes of propagation and breaking of Rossby waves. A new method for identifying the Rossby wave breaking (RWB) is proposed. It is based on the detection of breakings centers by analyzing the shape of the contours of potential vorticity or temperature on quasimaterial surfaces: isentropic and iserthelic (surfaces of constant Ertel potential vorticity (PV)), with further RWB center clustering to larger regions. The method is applied to the set of constant PV levels (0.3 to 9.8 PVU with a step of 0.5 PVU) at the level of potential temperature of 350 K for 12:00 UTC. The ERA-Interim reanalysis data from 1979 to 2019 are used for the method development. The type of RWB (cyclonic/anticyclonic), its area and center are determined by analyzing the vortex geometry at each PV level for every day. The RWBs obtained at this stage are designated as elementary breakings. Density-Based Spatial Clustering of Applications with Noise algorithm (DBSCAN) was applied to all elementary breakings for each month. As a result, a graphic dataset describing locations and dynamics of RWBs for every month from 1979 to 2019 is formed. The RWB frequency is also evaluated for each longitude, taking into account the duration of each RWB and the number of levels involved, as well as the anomalies of these parameters.

scholarly journals A Feature-Based Approach to Classifying Summertime Potential Vorticity Streamers Linked to Rossby Wave Breaking in the North Atlantic Basin

2020 ◽  
Vol 33 (14) ◽  
pp. 5953-5969 ◽  
Author(s):  
Philippe P. Papin ◽  
Lance F. Bosart ◽  
Ryan D. Torn
Keyword(s):  
Rossby Wave ◽  
North Atlantic ◽  
Potential Vorticity ◽  
Wave Breaking ◽  
Activity Index ◽  
Static Stability ◽  
Japan Meteorological Agency ◽  
Average Intensity ◽  
Rossby Wave Breaking ◽  
The North

AbstractThis study examines climatological potential vorticity streamer (PVS) activity associated with Rossby wave breaking (RWB), which can impact TC activity in the subtropical North Atlantic (NATL) basin via moisture and wind anomalies. PVSs are identified along the 2-PVU (1 PVU = 10−6 K kg−1 m2 s−1) contour on the 350-K isentropic surface, using a unique identification technique that combines previous methods. In total, 21 149 individual PVS instances are identified from the ERA-Interim (ERAI) climatology during June–November over 1979–2015 with a peak in July–August. The total number of PVSs identified in this study is more than previous PVS climatologies for this region, since the new technique identifies a wider range of cases. Variations in PVS size and intensity prompt the development of a new PVS activity index (PVSI), which provides an integrated measure of PVS activity that can improve comparisons with TC activity. For instance, PVSI has a stronger negative correlation with seasonal TC activity (r = −0.55) relative to PVS frequency, size, or intensity alone. PVSI in June–July is also positively correlated with PVSI in August–November (r = 0.67), suggesting predictive capability. Compared to the ERAI and Japan Meteorological Agency 55-Year Reanalysis (JRA-55) climatology, there are more PVSs in the Climate Forecast System Reanalysis (CFSR) but these have weaker average intensity overall. While no long-term trend in PVSI is observed in the ERAI or JRA-55 climatologies, a negative trend is observed in CFSR, which could be related to differences in near tropopause static stability early in the climatological period (1979–86) between the CFSR and ERAI datasets.

scholarly journals Filamentary structure in chemical tracer distributions near the subtropical jet following a wave breaking event

2013 ◽  
Vol 13 (2) ◽  
pp. 5039-5089 ◽  
Author(s):  
J. Ungermann ◽  
L. L. Pan ◽  
C. Kalicinsky ◽  
F. Olschewski ◽  
P. Knieling ◽  
...  
Keyword(s):  
Rossby Wave ◽  
Cross Sections ◽  
Wave Breaking ◽  
Climate Models ◽  
Spatial Location ◽  
Trace Gas ◽  
Filamentary Structure ◽  
Air Mass ◽  
Rossby Wave Breaking ◽  
Air Mass Types

Abstract. This paper presents a set of observations and analyses of trace gas cross-sections in the extratropical upper troposphere/lower stratosphere (UTLS). The spatially highly-resolved (≈0.5 km vertically and 12.5 km horizontally) cross-sections of ozone (O3), nitric acid (HNO3), and peroxyacetyl nitrate (PAN), retrieved from the measurements of the CRISTA-NF infrared limb sounder flown on the Russian M55-Geophysica, revealed intricate layer structures in the region of the subtropical tropopause break. The chemical structure in this region shows an intertwined stratosphere and troposphere. The observed filaments in all discussed trace gases are of a spatial scale of less than 0.8 km vertically and about 200 km horizontally across the jet-stream. Backward trajectory calculations confirm that the observed filaments are the result of a breaking Rossby wave in the preceding days. An analysis of the trace gas relationships between PAN and O3 identifies four distinct groups of air mass: polluted subtropical tropospheric air, clean tropical upper-tropospheric air, the lowermost stratospheric air, and air from the deep stratosphere. The tracer relationships further allow the identification of tropospheric, stratospheric, and the transitional air mass made of a mixture of UT and LS air. Mapping of these air mass types onto the geo-spatial location in the cross-sections reveals a highly structured extratropical transition layer (ExTL). Finally, the ratio between the measured reactive nitrogen species (HNO3 + PAN + ClONO2) and O3 is analysed to estimate the influence of tropospheric pollution on the extratropical UTLS. In combination, these diagnostics provide the first example of a multi-species two-dimensional picture of a chemically inhomogeneous UTLS region. Since Rossby wave breaking occurs frequently in the region of the tropopause break, these observed fine scale filaments are likely ubiquitous in the region. The implications of the layered structure for chemistry and radiation need to be examined, and the representation of this structure in chemistry-climate models is discussed.

scholarly journals How Rossby wave breaking modulates the water cycle in the North Atlantic trade wind region

2020 ◽  
Author(s):  
Franziska Aemisegger ◽  
Raphaela Vogel ◽  
Pascal Graf ◽  
Fabienne Dahinden ◽  
Leonie Villiger ◽  
...  
Keyword(s):  
Rossby Wave ◽  
North Atlantic ◽  
Wave Breaking ◽  
Water Cycle ◽  
Cloud Layer ◽  
Trade Wind ◽  
Rossby Wave Breaking ◽  
Atlantic Trade ◽  
The North ◽  
The Caribbean

Abstract. The interaction between low-level tropical clouds and the large-scale circulation is a key feedback element in our climate system, but our understanding of it is still fragmentary. In this paper, the role of upper-level extratropical dynamics for the development of contrasting shallow cumulus cloud patterns in the western North Atlantic trade wind region is investigated. Stable water isotopes are used as tracers for the origin of air parcels arriving in the sub-cloud layer above Barbados, measured continuously in water vapour at the Barbados Cloud Observatory during a 24-day measurement campaign (isoTrades, 25 January to 17 February 2018). This data is combined with a detailed air parcel back-trajectory analysis using hourly ERA5 reanalyses of the European Centre for Medium Range Weather Forecasts. A climatological investigation of the 10-day air parcel history for January and February in the recent decade shows that 55 % of the air parcels arriving in the sub-cloud layer have spent at least one day in the extratropics (north of 35° N) before arriving in the eastern Caribbean at about 13° N. In 2018, this share of air parcels with extratropical origin was anomalously large with 88 %. In two detailed case studies during the campaign, two flow regimes with distinct isotope signatures transporting extratropical air into the Caribbean are investigated. In both regimes, the air parcels descend from the lower part of the midlatitude jet stream towards the equator, at the eastern edge of subtropical anticyclones, in the context of Rossby wave breaking events. The zonal location of the wave breaking, and the surface anticyclone, determines the dominant transport regime. The first regime represents the typical trade wind situation with easterly winds bringing moist air from the eastern North Atlantic into the Caribbean, in a deep layer from the surface up to ∼600 hPa. The moisture source of the sub-cloud layer water vapour is located on average 2000 km upstream of Barbados. In this regime, Rossby wave breaking and the descent of air from the extratropics occurs in the eastern North Atlantic, at about 33° W. The second regime is associated with air parcels descending slantwise by on average 300 hPa (6 d)-1 directly from the northeast, i.e., at about 50° W. These originally dry airstreams experience a more rapid moistening than typical trade wind air parcels when interacting with the subtropical oceanic boundary layer, with moisture sources being located on average 1350 km upstream to the northeast of Barbados. The descent of dry air in the second regime can be steered towards the Caribbean by the interplay of a persistent upper-level cutoff low over the central North Atlantic (about 45° W) and the associated surface cyclone underneath. The zonal location of Rossby wave breaking, and consequently, the pathway of extratropical air towards the Caribbean, is shown to be relevant for the sub-cloud layer humidity and shallow cumulus cloud cover properties of the North Atlantic winter trades. Overall, this study highlights the importance of extratropical dynamical processes for the tropical water cycle and reveals that these processes lead to a substantial modulation of stable water isotope signals in the near-surface humidity.

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