Atmospheric Blocking and Weather Extremes over the Euro-Atlantic Sector – A Review

Kautz, Lisa‐Ann; Martius, Olivia; Pfahl, Stephan; Pinto, Joaquim G.; Ramos, Alexandre M.; Sousa, Pedro M.; Woollings, Tim

doi:10.5194/wcd-2021-56

Cited by 54 publications

(26 citation statements)

References 212 publications

(274 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Another important weather system in the extratropics are atmospheric blocks, because they can be linked to extreme weather like cold spells (e.g., Sillmann et al, 2011;Bieli et al, 2015), heat waves (Quandt et al, 2019), and heavy precipitation events (e.g., Martius et al, 2013;Kautz et al, 2022). However, so far, the confidence in projected changes in atmospheric blocking is low as different physical mechanisms determine the whole blocking life cycle (Woollings et al, 2018).…”

mentioning

confidence: 99%

Warm conveyor belts in present-day and future climate simulations. Part I: Climatology and impacts

Joos

Sprenger

Binder

et al. 2022

Preprint

View full text Add to dashboard Cite

Abstract. This study investigates how warm conveyor belts (WCB) will change in a future climate. WCBs are strongly ascending airstreams in extratropical cyclones which are responsible for most of their precipitation. In conjunction with the strong cloud formation, latent heat is released which has an impact on the potential vorticity distribution and therefore on the atmospheric circulation in the mid- and upper-troposphere. Because of these and other impacts of WCBs, it is of great importance to investigate their changes in a warmer climate. To this aim, future climate simulations (RCP8.5 scenario; 2091–2100) are performed with the Community Earth System Model version 1 (CESM1) and compared to a present-day climate (1991–2000). WCB trajectories are calculated based on the six-hourly 3D wind fields. WCBs are represented reasonably well in terms of location and occurrence frequency compared to WCBs in the ERA-Interim data set. In a future climate, WCB inflow regions in the North Pacific are systematically shifted northward in winter, which is in agreement with the northward shift of the storm track in this region. In the North Atlantic, increased frequencies are discernible in the southwest and a decrease to the south of Iceland. Finally, in the Southern Hemisphere, WCB frequencies increase in the South Atlantic, whereas they decrease near Madagascar. Part of these changes are consistent with corresponding changes in the occurrence frequencies of extratropical cyclones, i.e., the driving weather systems of WCBs. Changes are also found in the WCB characteristics, e.g., in specific humidity of the WCB inflow, the WCB-related precipitation, the cross-isentropic ascent and the isentropic level reached by the WCB outflow. This has implications for WCB impacts in a future climate. For instance, the strong increase in inflow moisture leads to: (i) a strong increase in WCB-related precipitation, especially in the upper percentiles, thus extreme precipitation related to WCBs might increase; (ii) a strong increase in diabatic heating in the mid-troposphere; and (iii) a higher outflow level which favours WCBs to more strongly interact with the upper-level Rossby waveguide. In summary, by investigating a distinct weather system, the WCB, and how it changes in its occurrence frequency and characteristics in a future climate, this study provides new insights into the dynamics and impacts of climate change in the mid-latitudes.

show abstract

mentioning

confidence: 99%

Warm conveyor belts in present-day and future climate simulations. Part I: Climatology and impacts

Joos

Sprenger

Binder

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

“…Such situation occurred for instance during the first stages of the large central European flooding of early June 2013 (Klemen et al, 2016). If a blocking situation occurs, for instance Omega blocking, the persistence of precipitation is enhanced and can lead to recurrent events (Kautz et al, 2021) at the eastern flank of the ECO or CAT . The second summer precipitation mode (Fig.…”

Section: Synoptic Weather Typesmentioning

confidence: 99%

Scale-dependency of extreme precipitation processes in regional climate simulations of the greater Alpine region

Caldas-Álvarez

Feldmann

Lucio-Eceiza

et al. 2022

Preprint

Self Cite

View full text Add to dashboard Cite

Abstract. Heavy Precipitation Events (HPEs) are a challenging atmospheric phenomenon with a high impact on human lives and infrastructures. The achievement of high-resolution simulations for Convection Permitting Modelling (CPM) has brought relevant advancements in the representation of HPEs in climate simulations compared to coarser resolution Regional Climate Models (RCM). However, further insight is needed on the scale-dependency of mesoscale precipitation processes. In this study, we aim at evaluating reanalysis-driven climate simulations of the greater Alpine area in recent climate conditions and assessing the scale-dependency of thermodynamical processes influencing extreme precipitation. We evaluate COSMO-CLM simulations of the period 1971–2015, at resolutions of 25 km (RCM) and 3 km (CPM) downscaled from ERA-40 and ERA-interim. We validate our simulations against high-resolution observations (EOBS, HYRAS, MSWEP, and UWYO). In the methodology, we present a revisited version of the Precipitation Severity Index (PSI) useful for extremes detection. Furthermore, we obtain the main modes of precipitation variance and synoptic Weather Types (WTs) associated with extreme precipitation using Principal Component Analysis (PCA). PCA is also used to derive composites of model variables associated with the thermodynamical processes of heavy precipitation. The results indicate a good detection capability of the PSI for precipitation extremes. We identified four WTs as precursors of extreme precipitation in winter, associated with stationary fronts or a zonal flow regimes. In summer, 5 WTs bring heavy precipitation, associated with upper-level elongated troughs over western Europe, sometimes evolving into cut-off lows, or by winter-like situations of strong zonal circulation. The model evaluation showed that CPM (3 km) represents higher precipitation intensities, better rank correlation, better hit rates for extremes detection, and an improved representation of heavy precipitation amount and structure for selected HPEs compared to RCM (25 km). CPM overestimates grid point precipitation rates especially over elevated terrain fostered by the scale-dependency of convective dynamic processes such as stronger updrafts and more triggering of convective cells. However, at low altitudes, precipitation differences due to resolution are explained through the scale-dependency of thermodynamic variables, where the largest impact is caused by differences in surface moisture up to 1 g kg-1. These differences show a predominant north-south gradient where locations north of the Alps show larger (lower) surface moisture and precipitation in CPM (RCM) and locations south of the Alps show larger (lower) humidity and precipitation in RCM (CPM). The humidity differences are caused by an uneven partition of latent and sensible heat fluxes between RCM and CPM. RCM simulates larger emissions of latent heat flux over the Sea (25 W m-2 more), and CPM emits larger latent heat over land (15 W m-2 more). In turn, RCM emits larger surface sensible heat fluxes over land (30 W m-2 more), showing a warmer surface (0.5 to 1 °C) than CPM. These results provide evidence that CPM is a powerful tool for obtaining accurate high-resolution climate information also pointing at the different scale-dependency of dynamic and thermodynamical precipitation processes at high and low terrain.

show abstract

“…Pfahl and Wernli, 2012, who showed this relationship for the Northern hemisphere) or extended ridges (Sousa et al, 2018). Such anticyclonic circulation anomalies lead to the build-up of warm temperature extremes in summer due to the associated subsidence and adiabatic warming, the clear-sky conditions that lead to surface heating by solar radiation, low wind speeds and warm-air advection (Meehl and Tebaldi, 2004;Pfahl, 2014;Bieli et al, 2015;Zschenderlein et al, 2019;Kautz et al, 2021). Moreover, soil moistureatmosphere feedbacks enhance the heating of lower tropospheric air in the planetary boundary layer due to the increase of sensible heat fluxes and decrease of latent heat fluxes associated with reduced soil moisture content during (prolonged) drought and heatwave conditions (Fischer et al, 2007;Seneviratne et al, 2010;Stéfanon et al, 2014;Miralles et al, 2019).…”

mentioning

confidence: 93%

European heatwaves in present and future climate simulations: A Lagrangian analysis

Schielicke

2022

Preprint

Self Cite

View full text Add to dashboard Cite

Abstract. Heatwaves are prolonged periods of anomalously high temperatures that can have devastating impacts on the environment, society and economy. In the recent history, heatwaves have become more intense and more numerous over most continental areas and it is expected that this trend will continue due to the ongoing global temperature rise. This general intensification may be modified by changes also in the underlying thermodynamical and dynamical processes. In order to study potential changes in heatwave characteristics and dynamics, we compare Lagrangian backward trajectories of air streams associated with historic (1991–2000) and future (2091–2100) heatwaves in six different European regions. We use a percentile-based method (Heat Wave Magnitude Index daily) to identify heatwaves in a large ensemble of climate simulations (Community Earth System Model – Large Ensemble (CESM-LE) with 35 members). In general, we find that air parcels associated with heatwaves are located to the east or inside the respective regions three days prior to the events. For future heatwaves, the model projects a north-/northeastward shift of the origin of the air masses in most study regions. Compared to climatological values, air streams associated with heatwaves show a larger temperature increase along their trajectory, which is connected to stronger descent and/or stronger diabatic heating when the air parcels enter the boundary layer. We find stronger descent associated with adiabatic warming in the northern, more continental regions and increased diabatic heating in all regions (except of the British Isles) in the simulated future climate. The enhanced diabatic heating is even more pronounced for heatwaves over continental regions. Diabatic temperature changes of near-surface air are driven by sensible heat fluxes, which are stronger over dry soils. The amplified diabatic heating associated with future heatwaves may thus be explained by an additional drying of the land surface.

show abstract

Atmospheric Blocking and Weather Extremes over the Euro-Atlantic Sector – A Review

Cited by 54 publications

References 212 publications

Warm conveyor belts in present-day and future climate simulations. Part I: Climatology and impacts

Warm conveyor belts in present-day and future climate simulations. Part I: Climatology and impacts

Scale-dependency of extreme precipitation processes in regional climate simulations of the greater Alpine region

European heatwaves in present and future climate simulations: A Lagrangian analysis

Contact Info

Product

Resources

About