Review of the manuscript “A Lagrangian analysis of upper-tropospheric anticyclones associated with heat waves in Europe” by Philipp Zschenderlein, Stephan Pfahl, Heini Wernli, and Andreas H. Fink

Abstract. This study presents a Lagrangian analysis of upper-tropospheric anticyclones that are connected to surface heat waves in different European regions for the period 1979 to 2016. In order to elucidate the formation of these anticyclones and the role of diabatic processes, we trace air parcels backwards from the upper-tropospheric anticyclones and quantify the diabatic heating in these air parcels. Around 25 %–45 % of the air parcels are diabatically heated during the last 3 d prior to their arrival in the upper-tropospheric anticyclones, and this amount increases to 35 %–50 % for the last 7 d. The influence of diabatic heating is larger for heat-wave-related anticyclones in northern Europe and western Russia and smaller in southern Europe. Interestingly, the diabatic heating occurs in two geographically separated air streams; 3 d prior to arrival, one heating branch (remote branch) is located above the western North Atlantic, and the other heating branch (nearby branch) is located over northwestern Africa and Europe to the southwest of the target upper-tropospheric anticyclone. The diabatic heating in the remote branch is related to warm conveyor belts in North Atlantic cyclones upstream of the evolving upper-level ridge. In contrast, the nearby 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. Most European regions are influenced by both branches, whereas western Russia is predominantly affected by the nearby branch. The remote branch predominantly affects the formation of the upper-tropospheric anticyclone, and therefore of the heat wave, whereas the nearby branch is more active during its maintenance. For long-lasting heat waves, the remote 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 timescales.

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

10.5194/egusphere-egu2020-4574 ◽

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 &#8211; 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>

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

10.5194/wcd-2019-17 ◽

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 ◽

Small Scale ◽

European Regions ◽

Lagrangian Analysis ◽

Upper Level ◽

Warm Conveyor Belts

Abstract. This study presents a Lagrangian analysis of upper-tropospheric anticyclones that are connected to surface heat waves in different European regions for the period 1979 to 2016. In order to elucidate the formation of these anticyclones and the role of diabatic processes, we trace air parcels backwards from the upper-tropospheric anticyclones and quantify the diabatic heating in these air parcels. 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-related 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 warm conveyor belts in North Atlantic cyclones 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. Most European regions are influenced by both branches, whereas western Russia is predominantly affected by the eastern branch. The western branch predominantly affects the formation of the upper-tropospheric anticyclone, and therefore of the heat wave, whereas the eastern branch is more active during its maintenance. 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.

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Supplemental Material for Promoting Protection Against a Threat That Evokes Positive Affect: The Case of Heat Waves in the United Kingdom

Journal of Experimental Psychology Applied ◽

10.1037/xap0000083.supp ◽

2016 ◽

Keyword(s):

United Kingdom ◽

Positive Affect ◽

Heat Waves ◽

The United Kingdom

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Stochastic simulation of the spatio-temporal field of the average daily heat index in Southern Russia

Climate Research ◽

10.3354/cr01623 ◽

2020 ◽

Vol 82 ◽

pp. 149-160

Author(s):

N Kargapolova

Keyword(s):

Heat Waves ◽

Numerical Models ◽

Heat Index ◽

Real Field ◽

Gaussian Field ◽

The Real ◽

Southern Russia ◽

Weather Stations ◽

Spatio Temporal ◽

Temporal Field

Numerical models of the heat index time series and spatio-temporal fields can be used for a variety of purposes, from the study of the dynamics of heat waves to projections of the influence of future climate on humans. To conduct these studies one must have efficient numerical models that successfully reproduce key features of the real weather processes. In this study, 2 numerical stochastic models of the spatio-temporal non-Gaussian field of the average daily heat index (ADHI) are considered. The field is simulated on an irregular grid determined by the location of weather stations. The first model is based on the method of the inverse distribution function. The second model is constructed using the normalization method. Real data collected at weather stations located in southern Russia are used to both determine the input parameters and to verify the proposed models. It is shown that the first model reproduces the properties of the real field of the ADHI more precisely compared to the second one, but the numerical implementation of the first model is significantly more time consuming. In the future, it is intended to transform the models presented to a numerical model of the conditional spatio-temporal field of the ADHI defined on a dense spatio-temporal grid and to use the model constructed for the stochastic forecasting of the heat index.

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