Interaction between Atlantic cyclones and Eurasian atmospheric blocking drives warm extremes in the high Arctic

2021 ◽  
Author(s):  
Sonja Murto ◽  
Rodrigo Caballero ◽  
Gunilla Svensson ◽  
Lukas Papritz
Keyword(s):  
Diabatic Heating ◽  
High Arctic ◽  
Conveyor Belt ◽  
Back Trajectory ◽  
Atmospheric Blocking ◽  
Ural Mountains ◽  
Compact Region ◽  
Westerly Flow ◽  
Upper Level ◽  
Maximum Heating

<p>Atmospheric blocking can influence Arctic weather by diverting the mean westerly flow polewards, bringing warm, moist air to high latitudes. Recent studies have shown that diabatic heating processes in the ascending warm conveyor belt branch of extratropical cyclones are relevant to blocking dynamics. This leads to the question of the extent to which diabatic heating associated with mid-latitude cyclones may influence high-latitude blocking and drive Arctic warm events. In this study we investigate the dynamics behind 50 extreme warm events of wintertime high Arctic surface temperature anomalies. We find that 30 of these events are associated with “Ural” blocking, featuring negative upper-level PV anomalies over central Siberia north of the Ural Mountains. Lagrangian back-trajectory calculations show that almost 70% of the air parcels making up these negative PV anomalies experience lifting and diabatic heating (average 14,7 K) in the 9-days prior to blocking. Further, 43,4 % of the heated trajectories undergo maximum heating and lifting in a compact region of the midlatitude North Atlantic, temporally taking place between 6 and 2.5 days before arriving in the blocking region. These trajectories mainly reside in the subtropics before being advected into the lifting region. We also find anomalously high cyclonic activity (on average 3,9 cyclones within a 3,5-day window around the time of maximum lifting) within a sector northwest of the main lifting domain. This study highlights the importance of the interaction between mid-latitude cyclones and Eurasian blocking as driver for Arctic warm extremes.</p>

scholarly journals Interaction between Atlantic cyclones and Eurasian atmospheric blocking drives wintertime warm extremes in the high Arctic

2022 ◽  
Vol 3 (1) ◽  
pp. 21-44
Author(s):  
Sonja Murto ◽  
Rodrigo Caballero ◽  
Gunilla Svensson ◽  
Lukas Papritz
Keyword(s):  
North Atlantic ◽  
High Latitude ◽  
Diabatic Heating ◽  
High Arctic ◽  
Back Trajectory ◽  
Time Of Arrival ◽  
Atmospheric Blocking ◽  
Ural Mountains ◽  
Back Trajectories ◽  
Maximum Heating

Abstract. Atmospheric blocking can influence Arctic weather by diverting the mean westerly flow and steering cyclones polewards, bringing warm, moist air to high latitudes. Recent studies have shown that diabatic heating processes in the ascending warm conveyor belt branch of extratropical cyclones are relevant to blocking dynamics. This leads to the question of the extent to which diabatic heating associated with mid-latitude cyclones may influence high-latitude blocking and drive Arctic warm events. In this study we investigate the dynamics behind 50 extreme warm events of wintertime high-Arctic temperature anomalies during 1979–2016. Classifying the warm events based on blocking occurrence within three selected sectors, we find that 30 of these events are associated with a block over the Urals, featuring negative upper-level potential vorticity (PV) anomalies over central Siberia north of the Ural Mountains. Lagrangian back-trajectory calculations show that almost 60 % of the air parcels making up these negative PV anomalies experience lifting and diabatic heating (median 11 K) in the 6 d prior to the block. Further, almost 70 % of the heated trajectories undergo maximum heating in a compact region of the mid-latitude North Atlantic, temporally taking place between 6 and 1 d before arriving in the blocking region. We also find anomalously high cyclone activity (on average five cyclones within this 5 d heating window) within a sector northwest of the main heating domain. In addition, 10 of the 50 warm events are associated with blocking over Scandinavia. Around 60 % of the 6 d back trajectories started from these blocks experience diabatic heating, of which 60 % undergo maximum heating over the North Atlantic but generally closer to the time of arrival in the block and further upstream relative to heated trajectories associated with Ural blocking. This study suggests that, in addition to the ability of blocks to guide cyclones northwards, Atlantic cyclones play a significant role in the dynamics of high-latitude blocking by providing low-PV air via moist-diabatic processes. This emphasizes the importance of the mutual interactions between mid-latitude cyclones and Eurasian blocking for wintertime Arctic warm extremes.

scholarly journals Interaction between Atlantic cyclones and Eurasian atmospheric blocking drives warm extremes in the high Arctic

2021 ◽  
Author(s):  
Sonja Murto ◽  
Rodrigo Caballero ◽  
Gunilla Svensson ◽  
Lukas Papritz
Keyword(s):  
North Atlantic ◽  
High Latitude ◽  
Diabatic Heating ◽  
High Arctic ◽  
Back Trajectory ◽  
Time Of Arrival ◽  
Atmospheric Blocking ◽  
Ural Mountains ◽  
Maximum Heating ◽  
Midlatitude Cyclones

Abstract. Atmospheric blocking can influence Arctic weather by diverting the mean westerly flow polewards, bringing warm, moist air to high latitudes. Recent studies have shown that diabatic heating processes in the ascending warm conveyor belt branch of extratropical cyclones are relevant to blocking dynamics. This leads to the question of the extent to which diabatic heating associated with midlatitude cyclones may influence high-latitude blocking and drive Arctic warm events. In this study we investigate the dynamics behind 50 extreme warm events of wintertime high Arctic temperature anomalies. Classifying the warm events based on blocking occurrence within three selected sectors, we find that 30 of these events are associated with a block over the Urals, featuring negative upper-level PV anomalies over central Siberia north of the Ural Mountains. Lagrangian back-trajectory calculations show that almost 60 % of the air parcels making up these negative PV anomalies experience lifting and diabatic heating (median 11 K) in the six days prior to the block. Further, almost 70 % of the heated trajectories undergo maximum heating in a compact region of the midlatitude North Atlantic, temporally taking place between six and one days before arriving in the blocking region. We also find anomalously high cyclone activity (on average five cyclones within this five-day heating window) within a sector northwest of the main heating domain. In addition, 10 of the 50 warm events are associated with blocking over Scandinavia; the contribution of diabatic heating to these blocks is again around 60 % for six-day back-trajectories, of which 60 % undergo maximum heating over the North Atlantic but generally closer to the time of arrival in the block and further upstream relative to heated trajectories associated with Ural blocking. This study highlights the role of diabatic heating in high-latitude blocking dynamics and the importance of the interaction between midlatitude cyclones and Eurasian blocking as driver for Arctic warm extremes.

scholarly journals The sensitivity of atmospheric blocking to changes in upstream latent heating – numerical experiments

2020 ◽  
Author(s):  
Daniel Steinfeld ◽  
Maxi Boettcher ◽  
Richard Forbes ◽  
Stephan Pfahl
Keyword(s):  
Causal Relationship ◽  
Climate Models ◽  
Weather Prediction ◽  
Conveyor Belt ◽  
Cloud Formation ◽  
Latent Heating ◽  
Atmospheric Blocking ◽  
Tropospheric Circulation ◽  
Upper Level ◽  
Microphysical Processes

Abstract. Recent climatological studies based on trajectory calculations have pointed to an important role of latent heating during cloud formation for the dynamics of anticyclonic circulation anomalies such as atmospheric blocking. However, the causal relationship between latent heating and blocking formation has not yet been fully elucidated. To explicitly study this causal relationship, we perform sensitivity simulations of five selected blocking events with a global weather prediction model in which we artificially eliminate latent heating in clouds upstream of the blocking anticyclones. This elimination has substantial effects on the upper-tropospheric circulation in all case studies, but there is also significant case-to-case variability: some blocking systems do not develop at all without upstream latent heating, while for others the amplitude of the blocking anticyclones is merely reduced. This strong influence of latent heating on the jet stream is due to the injection of air masses with low potential vorticity (PV) into the upper troposphere in strongly ascending warm conveyor belt airstreams, and the interaction of the associated divergent outflow with the upper-level PV structure. The important influence of diabatic heating demonstrated with these experiments suggests that an accurate parameterization of microphysical processes in weather prediction and climate models is crucial for adequately representing blocking dynamics.

scholarly journals The sensitivity of atmospheric blocking to upstream latent heating – numerical experiments

2020 ◽  
Vol 1 (2) ◽  
pp. 405-426
Author(s):  
Daniel Steinfeld ◽  
Maxi Boettcher ◽  
Richard Forbes ◽  
Stephan Pfahl
Keyword(s):  
Climate Models ◽  
Weather Prediction ◽  
Conveyor Belt ◽  
Cloud Formation ◽  
Latent Heating ◽  
Atmospheric Blocking ◽  
Air Masses ◽  
Tropospheric Circulation ◽  
Significant Case ◽  
Upper Level

Abstract. Recent studies have pointed to an important role of latent heating during cloud formation for the dynamics of anticyclonic circulation anomalies such as atmospheric blocking. However, the effect of latent heating on blocking formation and maintenance has not yet been fully elucidated. To explicitly study this cause-and-effect relationship, we perform sensitivity simulations of five selected blocking events with the Integrated Forecast System (IFS) global weather prediction model in which we artificially eliminate latent heating in clouds upstream of the blocking anticyclones. This elimination has substantial effects on the upper-tropospheric circulation in all case studies, but there is also significant case-to-case variability: some blocking systems do not develop at all without upstream latent heating, while for others the amplitude, size, and lifetime of the blocking anticyclones are merely reduced. This strong influence of latent heating on the midlatitude flow is due to the injection of air masses with low potential vorticity (PV) into the upper troposphere in strongly ascending “warm conveyor belt” airstreams and the interaction of the associated divergent outflow with the upper-level PV structure. The important influence of diabatic heating demonstrated with these experiments suggests that the accurate representation of moist processes in ascending airstreams in weather prediction and climate models is crucial for blocking dynamics.

scholarly journals A Lagrangian analysis of upper-tropospheric anticyclones associated with heat waves in Europe

2020 ◽  
Author(s):  
Philipp Zschenderlein ◽  
Stephan Pfahl ◽  
Heini Wernli ◽  
Andreas H. Fink
Keyword(s):  
Heat Wave ◽  
North Atlantic ◽  
Diabatic Heating ◽  
Heat Waves ◽  
Convective Available Potential Energy ◽  
Conveyor Belt ◽  
Small Scale ◽  
Lagrangian Analysis ◽  
Upper Level ◽  
Western Side

<p>Heat waves impose large impacts on various sectors. Meteorologically, these events are co-located to upper-tropospheric anticyclones. In order to elucidate the formation of these anticyclones and the role of diabatic processes, we trace air masses backwards from the upper-tropospheric anticyclones and quantify the diabatic heating in these air parcels. We analyse anticyclones that are connected to summer heat waves at the surface during the period 1979 – 2016 in different European regions. Around 25-45% of the air parcels are diabatically heated during the last three days prior to their arrival in the upper-tropospheric anticyclones and this amount increases to 35-50% for the last seven days. The influence of diabatic heating is larger for heat wave anticyclones in northern Europe and western Russia and smaller in southern Europe. Interestingly, the diabatic heating occurs in two geographically separated air streams. Three days prior to arrival, one heating branch (western branch) is located above the western North Atlantic and the other heating branch (eastern branch) is located to the southwest of the target upper-tropospheric anticyclone. The diabatic heating in the western branch is related to the warm conveyor belt of a North Atlantic cyclone upstream of the evolving upper-level ridge. In contrast, the eastern branch is diabatically heated by convection, as indicated by elevated mixed-layer convective available potential energy along the western side of the matured upper-level ridge. Central Europe is influenced by both branches, whereas western Russia is predominantly affected by the eastern branch. The formation of the upper-tropospheric anticyclone, and therefore of the heat wave, is highly depended on the western branch, whereas its maintenance is more affected by the eastern branch. For long-lasting heat waves, the western branch regenerates. The results from this study show that the dynamical processes leading to heat waves may be sensitive to small-scale microphysical and convective processes, whose accurate representation in models is thus supposed to be crucial for heat wave predictions on weather and climate time scales.</p>

scholarly journals Influential Role of Moisture Supply from the Kuroshio/Kuroshio Extension in the Rapid Development of an Extratropical Cyclone

2015 ◽  
Vol 143 (10) ◽  
pp. 4126-4144 ◽  
Author(s):  
Hidetaka Hirata ◽  
Ryuichi Kawamura ◽  
Masaya Kato ◽  
Taro Shinoda
Keyword(s):  
Diabatic Heating ◽  
Rapid Development ◽  
Kuroshio Extension ◽  
Lower Troposphere ◽  
Active Role ◽  
Conveyor Belt ◽  
Synoptic Scale ◽  
Warm Front ◽  
The Kuroshio

Abstract This study focused on an explosive cyclone migrating along the southern periphery of the Kuroshio/Kuroshio Extension in the middle of January 2013 and examined how those warm currents played an active role in the rapid development of the cyclone using a high-resolution coupled atmosphere–ocean regional model. The evolutions of surface fronts of the simulated cyclone resemble the Shapiro–Keyser model. At the time of the maximum deepening rate, strong mesoscale diabatic heating areas appear over the bent-back front and the warm front east of the cyclone center. Diabatic heating over the bent-back front and the eastern warm front is mainly induced by the condensation of moisture imported by the cold conveyor belt (CCB) and the warm conveyor belt (WCB), respectively. The dry air parcels transported by the CCB can receive large amounts of moisture from the warm currents, whereas the very humid air parcels transported by the WCB can hardly be modified by those currents. The well-organized nature of the CCB plays a key role not only in enhancing surface evaporation from the warm currents but also in importing the evaporated vapor into the bent-back front. The imported vapor converges at the bent-back front, leading to latent heat release. The latent heating facilitates the cyclone’s development through the production of positive potential vorticity in the lower troposphere. Its deepening can, in turn, reinforce the CCB. In the presence of a favorable synoptic-scale environment, such a positive feedback process can lead to the rapid intensification of a cyclone over warm currents.

scholarly journals Eurasian Cooling Linked with Arctic Warming: Insights from PV Dynamics

2020 ◽  
Vol 33 (7) ◽  
pp. 2627-2644
Author(s):  
Yongkun Xie ◽  
Guoxiong Wu ◽  
Yimin Liu ◽  
Jianping Huang
Keyword(s):  
Vertical Structure ◽  
Diabatic Heating ◽  
Linear Trend ◽  
Three Dimensional ◽  
Lower Troposphere ◽  
The Arctic ◽  
Arctic Warming ◽  
Circulation Change ◽  
General Dynamics ◽  
Upper Level

AbstractThe three-dimensional connections between Eurasian cooling and Arctic warming since 1979 were investigated using potential vorticity (PV) dynamics. We found that Eurasian cooling can be regulated by Arctic warming through PV adaptation and PV advection. Here, PV adaptation refers to the adaptation of PV to forcing and coherent dynamic–thermodynamic adaptation to PV change. In a PV perspective, first, the anticyclonic circulation change over the Arctic is produced by a negative PV change through PV adaptation, in which the change means the linear trend from 1979 to 2017. The negative PV change is directly regulated by Arctic warming because the vertical structure of Arctic warming is stronger at lower levels, which generates a negative PV change through the diabatic heating effect. Second, the circulation change produces a change in horizontal PV advection due to the existence of climatological PV gradients. Thus, as a balanced result, both the circulation change and PV change extend to the midlatitudes through horizontal PV advection and PV adaptation. Eventually, Eurasian cooling at the surface and in the lower troposphere is dominated by PV changes at the surface through PV adaptation. Meanwhile, enhanced Eurasian cooling in the middle troposphere is dominated by top-down influences of upper-level PV change through PV adaptation. Nevertheless, the upper-level PV changes are still contributed to by horizontal PV advection associated with Arctic warming. Overall, the general dynamics connecting Eurasian cooling with Arctic warming are demonstrated in a PV view.

The sensitivity of atmospheric blocking to changes in upstream latent heating

2020 ◽  
Author(s):  
Stephan Pfahl ◽  
Daniel Steinfeld ◽  
Maxi Boettcher ◽  
Richard Forbes
Keyword(s):  
Causal Relationship ◽  
Climate Models ◽  
Direct Injection ◽  
Weather Prediction ◽  
Conveyor Belt ◽  
Cloud Formation ◽  
Latent Heating ◽  
Tropospheric Circulation ◽  
Upper Level ◽  
Microphysical Processes

<p>Recent climatological studies based on trajectory calculations have pointed to an important role of latent heating during cloud formation for the dynamics of blocking anti-cyclones. However, the causal relationship between latent heating and blocking formation has not yet been fully elucidated. To explicitly study this causal relationship, we perform sensitivity simulations of selected blocking events with a global weather prediction model in which we artificially eliminate latent heating in clouds upstream of the blocking anti-cyclones. This elimination has substantial effects on the upper-tropospheric circulation in all case studies, but there is also significant case-to-case variability: some blocking systems do not develop at all without upstream latent heating, while for others the amplitude of the blocking anticyclones is merely reduced. This strong influence of latent heating on the upper-level circulation is due to a combination of two effects: the direct injection of air masses with low potential vorticity (PV) into the upper troposphere in strongly ascending “warm conveyor belt” airstreams, and the indirect effect owing to the interaction of the associated divergent outflow with the upper-level PV structure. The important influence of diabatic heating demonstrated with these experiments suggests that an accurate parameterization of microphysical processes in weather prediction and climate models is crucial for adequately representing blocking dynamics.</p>

Eurasian cooling linked with Arctic warming: Insights from PV dynamics

2020 ◽  
Author(s):  
Yongkun Xie ◽  
Guoxiong Wu ◽  
Yimin Liu
Keyword(s):  
Vertical Structure ◽  
Diabatic Heating ◽  
Linear Trend ◽  
Three Dimensional ◽  
Lower Troposphere ◽  
The Arctic ◽  
Arctic Warming ◽  
Circulation Change ◽  
General Dynamics ◽  
Upper Level

<p>The three-dimensional connections between Eurasian cooling and Arctic warming since 1979 were investigated using potential vorticity (PV) dynamics. We found that Eurasian cooling can be regulated by Arctic warming through PV adaptation and PV advection. Here, PV adaptation refers to the adaptation of PV to forcing and coherent dynamic/thermodynamic adaptation to PV change. In a PV perspective, first, the anticyclonic circulation change over the Arctic is produced by a negative PV change through PV adaptation, in which the change means the linear trend from 1979~2017. The negative PV change is directly regulated by Arctic warming because the vertical structure of Arctic warming is stronger at lower levels, which generates a negative PV change through the diabatic heating effect. Second, the circulation change produces a change in horizontal PV advection due to the existence of climatological PV gradients. Thus, as a balanced result, both the circulation change and PV change extend to mid-latitude through horizontal PV advection and PV adaptation. Eventually, Eurasian cooling at the surface and in the lower troposphere is dominated by PV changes at the surface through PV adaptation. Meanwhile, enhanced Eurasian cooling in the middle troposphere is dominated by top-down influences of upper-level PV change through PV adaptation. Nevertheless, the upper-level PV changes are still contributed by horizontal PV advection associated with Arctic warming. Overall, the general dynamics connecting Eurasian cooling with Arctic warming is demonstrated in a PV view.</p>

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