Connecting Atmospheric Blocking to European Temperature Extremes in Spring

Brunner, Lukas; Hegerl, Gabriele C.; Steiner, Andrea

doi:10.1175/jcli-d-16-0518.1

Cited by 106 publications

(108 citation statements)

References 32 publications

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“…In spring and autumn, the HW/WS events develop both under advective (as also stated by Brunner et al [39] for central Europe) and radiative conditions. This sub-type of synoptic pattern is characteristic for 10.9% of days under HWs/WSs conditions.…”

Section: Frequency Of Hws/wss By Synoptic Conditions Typessupporting

confidence: 58%

“…(ii) High pressure conditions at sea level over Central and Southeastern Europe are associated very often with intense activity of Azores High during blocking circulation developed at a continental scale. Blocking conditions usually prevent cold fronts from bringing relief to the hot weather [14] and are well-known as an important factor for HWs/WSs occurrence in Europe [39]. This is the main dynamic cause for recording breaking HWs in Europe [74].…”

Section: Synoptic Conditions Generating Radiative Hws/wssmentioning

confidence: 99%

“…Blocking conditions usually prevent cold fronts from bringing relief to the hot weather [14] and are well-known as an important factor for HWs/WSs occurrence in Europe [39]. This is the main dynamic cause for recording breaking HWs in Europe [74].…”

Section: Synoptic Conditions Generating Radiative Hws/wssmentioning

confidence: 99%

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Synoptic Conditions Generating Heat Waves and Warm Spells in Romania

et al. 2017

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Abstract:Heat waves and warm spells are extreme meteorological events that generate a significant number of casualties in temperate regions, as well as outside of temperate regions. For the purpose of this paper, heat waves and warm spells were identified based on daily maximum temperatures recorded at 27 weather stations located in Romania over a 55-year period . The intensity threshold was the 90th percentile, and the length of an event was of minimum three consecutive days. We analyzed 111 heat wave and warm spell events totaling 423 days. The classification of synoptic conditions was based on daily reanalysis at three geopotential levels and on the online version of a backward trajectories model. The main findings are that there are two major types of genetic conditions. These were identified as: (i) radiative heat waves and warm spells (type A) generated by warming the air mass due to high amounts of radiation which was found dominant in warm season; and (ii) advective heat waves and warm spells (type B) generated mainly by warm air mass advection which prevails in winter and transition seasons. These major types consist of two and three sub-types, respectively. The results could become a useful tool for weather forecasters in order to better predict the occurrence of heat waves and warm spells.

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Section: Frequency Of Hws/wss By Synoptic Conditions Typessupporting

confidence: 58%

Section: Synoptic Conditions Generating Radiative Hws/wssmentioning

confidence: 99%

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Synoptic Conditions Generating Heat Waves and Warm Spells in Romania

et al. 2017

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“…Since the development of new indices was not the focus of this paper, we opted to discuss snow outside of the matrix visualization, but an SSI (Standardized Snow Index) could be a beneficial addition to the hydrologists toolbox. Other possible additions or new indices could be for atmospheric phenomena, such as, e.g., blocking (which is related to cold spells in our region; see Brunner et al, 2017). Also possible connections between different (sub)regions and the role of rivers as connector of far away regions does warrant further investigation.…”

Section: Future Workmentioning

confidence: 96%

Characterizing the spatiotemporal variability of groundwater levels of alluvial aquifers in different settings using drought indices

Haas

Birk

2017

Hydrol. Earth Syst. Sci.

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Abstract. To improve the understanding of how aquifers in different alluvial settings respond to extreme events in a changing environment, we analyze standardized time series of groundwater levels (Standardized Groundwater level Index -SGI), precipitation (Standardized Precipitation Index -SPI), and river stages of three subregions within the catchment of the river Mur (Austria). Using correlation matrices, differences and similarities between the subregions, ranging from the Alpine upstream part of the catchment to its shallow foreland basin, are identified and visualized.Generally, river stages exhibit the highest correlations with groundwater levels, frequently affecting not only the wells closest to the river, but also more distant parts of the alluvial aquifer. As a result, human impacts on the river are transferred to the aquifer, thus affecting the behavior of groundwater levels. Hence, to avoid misinterpretation of groundwater levels in this type of setting, it is important to account for the river and human impacts on it.While the river is a controlling factor in all of the subregions, an influence of precipitation is evident too. Except for deep wells found in an upstream Alpine basin, groundwater levels show the highest correlation with a precipitation accumulation period of 6 months (SPI6). The correlation in the foreland is generally higher than that in the Alpine subregions, thus corresponding to a trend from deeper wells in the Alpine parts of the catchment towards more shallow wells in the foreland.Extreme events are found to affect the aquifer in different ways. As shown with the well-known European 2003 drought and the local 2009 floods, correlations are reduced under flood conditions, but increased under drought. Thus, precipitation, groundwater levels and river stages tend to exhibit uniform behavior under drought conditions, whereas they may show irregular behavior during floods. Similarly, correlations are found to be weaker in years with little snow as compared with those with much snow. This is in agreement with typical aquifer response times over 1 month, suggesting that short events such as floods will not affect much of the aquifer, whereas a long-term event such as a drought or snow-rich winter will.Splitting the time series into periods of 12 years reveals a tendency towards higher correlations in the most recent time period from 1999 to 2010. This time period also shows the highest number of events with SPI values below −2. The SGI values behave in a similar way only in the foreland aquifer, whereas the investigated Alpine aquifers exhibit a contrasting behavior with the highest number of low SGI events in the time before 1986. This is a result of overlying trends and suggests that the groundwater levels within these subregions are more strongly influenced by direct human impacts, e.g., on the river, than by changes in precipitation. Thus, direct human impacts must not be ignored when assessing climate change impacts on alluvial aquifers situated in populated valleys.

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“…Conversely, blocking has also been connected to winter CSs (e.g., Buehler et al, 2011; Sillmann et al., 2011), mainly through the advection of cold air (e.g., Bieli et al, 2015; Sousa et al, 2018). Recently, also the blocking impacts during the transition seasons such as spring have come into focus (e.g., Brunner et al, 2017; Cassou & Cattiaux, 2016). Extreme temperatures in spring can have strong impacts on vegetation, as plants are particularly vulnerable during the early green‐up phase (e.g., Hufkens et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Dependence of Present and Future European Temperature Extremes on the Location of Atmospheric Blocking

Brunner

Schaller

Anstey

et al. 2018

Geophysical Research Letters

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103

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The impact of atmospheric blocking on European heat waves (HWs) and cold spells (CSs) is investigated for present and future conditions . A 50‐member ensemble of the second generation Canadian Earth System Model is used to quantify the role of internal variability in the response to blocking. We find that the present blocking‐extreme temperature link is well represented compared to ERA‐Interim, despite a significant underestimation of blocking frequency in most ensemble members. Our results show a strong correlation of blocking with northern European HWs in summer, spring, and fall. However, we also find a strong anticorrelation between blocking and HW occurrence in southern Europe in all seasons. Blocking increases the CS frequency particularly in southern Europe in fall, winter, and spring but reduces it in summer. For the future we find that blocking will continue to play an important role in the development of both CSs and HWs in all seasons.

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Connecting Atmospheric Blocking to European Temperature Extremes in Spring

Cited by 106 publications

References 32 publications

Synoptic Conditions Generating Heat Waves and Warm Spells in Romania

Synoptic Conditions Generating Heat Waves and Warm Spells in Romania

Characterizing the spatiotemporal variability of groundwater levels of alluvial aquifers in different settings using drought indices

Dependence of Present and Future European Temperature Extremes on the Location of Atmospheric Blocking

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