c.1 – updated and complete assessment of wind related risks ......2015/09/18 · c.1.2: local...

Seite 1Stefan Greiving, Hanna Schmitt 09.09.2015

Status Report

C.1 – Updated and complete assessment of wind relatedrisks in aspect of future climate change

Source: www.essen.de

Seite 209.09.2015Stefan Greiving, Hanna Schmitt

C.1: Wind Risks and Climate Change

Chapter Structure:

General Part C.1.1 – Impact of Climate Change on Storms in Central Europe

Local Parts C.1.2 – Local Wind Phenomena and Climate Change C.1.2.1: Slovenia / Ajdovscina C.1.2.2: Croatia / Split; Dalmatia C.1.2.3: Germany / North Rhine-Westphalia; Essen


C.1.1 – Impact of Climate Change on Storms in Central Europe


C.1.1: Impact of Climate Change on Storms in Central EuropeState of Research – rather vague statements: IPCC Fifth Assessment Report: “In urban areas climate

change is projected to increase risks for people, assets, economies and ecosystems, including risks from heat stress, storms and extreme precipitation {…} (very high confidence).” (p. 69)

EEA 2012: “Observations of storm location, frequency and intensity show considerable variability across Europe during the 20th century. Storm frequency shows a general increasing trend from the 1960s to 1990s, followed by a decrease to the present. Available climate change projections show no clear consensus in either the direction of movement or the intensity of storm activity.” (p. 54)


C.1.1: Impact of Climate Change on Storms in Central Europe

EEA (2012): Key observed (1961-1990) and projected climate change and impacts for the main regions in Europe

Findings for Storms (Variable = Wind Speed)

Note: Emission scenario = A1B, Climate Models are 9GCm and 11RCM ensemble, time period is until 2080s Red: adverse changeGreen: beneficial change+ Increase in variable throughout (most of the) regiono Only small changes in the variable- Decrease in variable throughout (most of the) region() Increase or decrease only in some parts of the region

Northern Europe (incl. Arctic)

North-Western Europe

Central andEastern Europe

Mediterranean Europe

Observed Projected Observed Projected Observed Projected Observed Projected

+ (+) + (+) + (+) o (-)

Source: EEA 2012: 39


C.1.1: Impact of Climate Change on Storms in Central Europe

EEA 2012: „Climate change projections for storms in the North Atlantic and Europe region show no clear consensus in either the direction of movement or the intensity of storm activity. However, a recent study involving 20 climate models projects enhanced extreme wind speeds over northern parts of central and western Europe, and a decrease in extreme wind speeds in southern Europe.” (p. 70)

Source: EEA 2012: 71

Problem:The EEA refers to trends in the annual 95th percentile of daily maximum wind speeds in the 20th century reanalysis data set (ensemble mean) during the period 1871–2008.

This method does not appropriately cover single extreme events, such as Ela. 99.9th percentile would be required.

This method does not differenciate summer and winter events but uses annual averages.


C.1.2 – Local Wind Phenomena and Climate Change

todays frequency of severe summer storms / convective storms like ELA(less then two events in 100 years)

use of ensembles of regional climate projections (based on SRES A1B or RCP 8.5)

1) direct calculation (wind speed, wind gusts)Problems: low horizontal resolution of the models, physical deficiencies (often not able to resolve convection)

summer storms (like ELA) in a changing climate

Guido Halbig 09/2015 8

near (2031-2050) or far future (2071-2100):will this events occur more frequent?

2) indirect method: weather conditions / patterns with high convective potential: frequency today and in the future (based on climate projections)

C.1.2: Local Wind Phenomena and Climate Change


C.1.2: Local Wind Phenomena and Climate ChangeProblem for Ela in Essen: Statements on a) extreme and b) summer events are

needed.

Approach: As summer storms mainly result from weather conditions

with a high convective potential (hot and humid air, high instability), the future development can be approximated by projecting macro weather situations with a high convective potential.

Question: What is the superior macro weather situation bringing a

high convective potential to Germany and how will itdevelop in the future?



Relevant factors for the investigation:

1. Identification of macro weather situations with whichthunderstorms are mostly associated,

2. Prevailing wind direction and paths of the(se) weather situation(s),

3. Macro weather situation during Ela (as a validation),4. Long-term measured trends for thunderstorm-

associated macro weather situations and5. Expert statement on the future situation and return

periods.



Investigation:1.) Identification of macro weather situations with whichthunderstorms are mostly associated

The occurrence of thunderstorms in Germany is mainlyassociated with one of the following macro weathersituations: Sz (Cyclonic Southerly), SEa (Anticyclonic South- Easterly), SWz (Cyclonic South-Westerly), TrW (Trough over Western Europe) or TB (Low over the British Isles). (cf. Wapler, James 2014: 240)



Investigation:2.) Prevailing wind direction and paths of these weather situations

In all before mentioned types of weather situations, thunderstorms move in a direction broadly from south-west to north-east (in Germany). (Cf. Wapler, James 2014: 241)

This path corresponds with the prevailing wind direction!



Investigation:3.) Macro weather situation during Ela (as a validation)

Macro weather situation during Ela:

SWz (Cyclonic South-Westerly):

extra-tropical cyclone ‘Ela’ (southwest, cyclonic; 950 hPa) moved towards anticyclone ‘Wolfgang’ (anti-cyclonal; 500 hPa). (Cf. Halbig 2015)

Source: DWD 2015



Investigation:4.) Long-term measured trends for thunderstorm-associated macro weather situations

Long-term measurements show an increase in days with the Cyclonic South-Westerly macro weather situation: (significant) increase from 1881

– 2008; from 2 to 14 days during the summer months (JJA) (cf. DWD 2009)

The strongest increases were measured from April – October (cf. PIK 2009: 34).

Source: DWD 2002:169.


C.1.2: Local Wind Phenomena and Climate ChangeInvestigation:5.) Expert statements on the future situation and returnperiods It can be assumed that triggered by global warming,

warm air masses may have a higher energy potential in the future and therefore the probability of occurrence for thunderstorms rises. (Cf. DWD 2015: 25)

Statement German Meteorological Service: „The probability of occurrence for a summer thunderstorm complex with a similar spatial extent of the hurricane wind field like Ela is probably distinctly larger than 50 years.“ (DWD 2015: 25)


Kontakt:Prof. Dr. Stefan GreivingTU Dortmund, [email protected] +49 (0)231 – 755 2213

M.Sc. Hanna SchmittTU Dortmund, [email protected] +49 (0)231 – 755 2475

Thank you for your attention

“Storms are one of the most important weather hazards in Europe”

(EEA 2012, p.55)


References DWD [Deutscher Wetterdienst] (2002): Klimastatusbericht. Fricke, W. (2002): Hängen vermehrte

Starkniederschläge am Hohenpeißenberg mit veränderten Wetterlagen zusammen? 165-172. Online-PDF:http://www.dwd.de/bvbw/generator/DWDWWW/Content/Oeffentlichkeit/KU/KU2/KU22/klimastatusbericht/einzelne__berichte/ksb2002__pdf/14__2002,templateId=raw,property=publicationFile.pdf/14_2002.pdf (17.09.2015)

DWD [Deutscher Wetterdienst] (2009): Auszug aus dem Vortrag von Harald Weingärtner, damaliger Leitder der DWD-Abteilung Basisvorhersagen. Unpublished.

DWD [Deutscher Wetterdienst] (2015): Extremes Gewitter NRW – Pfingsmontag, 9. Juni 2014. Bericht der Regionalen Wetterberatung Essen, Molé, F.; Witt, M.; Zedler, P.; Urban, C. Unpublished research document.

EEA [European Environment Agency] (2912): Climate Change – Impacts and Vulnerability in Europe. Online-PDF:www.eea.europa.eu/publications/climate-impacts-and-vulnerability-2012/at_download/file(08.09.2015)

Halbig, G. (2015): Expert interview German Meteorological Service. Weather Situation Classification for 9.6.2014 – Storm Event Ela. Unpublished.

IPCC [Intergovernmental Panel on Climate Change] (2014): Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth

Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. IPCC, Geneva, Switzerland, 151 pp. Online-PDF: http://www.ipcc.ch/pdf/assessment-report/ar5/syr/SYR_AR5_FINAL_full_wcover.pdf(14.09.2015).

Wapler, K.; James, P. (2014): Thunderstorm occurrence and characteristics in Central Europe under different synoptic conditions. Atmospheric Research 158 – 159 (2015), 231-244. doi:10.1016/j.atmosres.2014.07.011.

c.1 – updated and complete assessment of wind related risks ......2015/09/18 · c.1.2: local...

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