Call number:
AWI A4-23-95497
Description / Table of Contents:
Extreme weather and climate events are one of the greatest dangers for present-day society. Therefore, it is important to provide reliable statements on what changes in extreme events can be expected along with future global climate change. However, the projected overall response to future climate change is generally a result of a complex interplay between individual physical mechanisms originated within the different climate subsystems. Hence, a profound understanding of these individual contributions is required in order to provide meaningful assessments of future changes in extreme events. One aspect of climate change is the recently observed phenomenon of Arctic Amplification and the related dramatic Arctic sea ice decline, which is expected to continue over the next decades. The question to what extent Arctic sea ice loss is able to affect atmospheric dynamics and extreme events over mid-latitudes has received a lot of attention over recent years and still remains a highly debated topic. In this respect, the objective of ...
Type of Medium:
Dissertations
Pages:
xi, 126 Seiten
,
Diagramme
URL:
https://doi.org/10.25932/publishup-60488
URN:
urn:nbn:de:kobv:517-opus4-604883
DOI:
10.25932/publishup-60488
Language:
English
Note:
Dissertation, Universität Potsdam, 2023
,
CONTENTS
1 SCIENTIFIC BACKGROUND AND RESEARCH QUESTIONS
1.1 Extreme events and attribution
1.2 Arctic climate change and mid-latitude linkages
1.3 Research questions
2 FOUNDATIONS
2.1 Atmospheric basics
2.1.1 Governing equations
2.1.2 Zonal wind and temperature profiles
2.1.3 Atmospheric waves and instabilities
2.1.4 Large-scale variability patterns and blocking
2.2 Atmospheric circulation regimes
2.2.1 Dynamical concepts
2.2.2 Regime computation
2.2.3 Regime number
2.3 Arctic climate change
2.3.1 Recent trends in Arctic sea ice and temperatures
2.3.2 Surface fluxes and energy balance in Arctic regions
2.3.3 Polar amplification mechanisms
2.3.4 Arctic-mid-latitude linkages
2.4 Weather and climate extremes
2.4.1 Recent trends
2.4.2 Dynamical driver of temperature extremes
3 DATA AND METHODS
3.1 ERA5 reanalysis
3.2 Model experiments
3.2.1 The atmospheric general circulation model ECHAM6
3.2.2 Polar Amplification Intercomparison Project data
3.3 Methods
3.3.1 Statistical significance
3.3.2 Extreme definition
4 RESULTS AND DISCUSSION
4.1 Mean circulation in ERA5 and ECHAM6 experiments
4.1.1 Climatological mean states in ERA5 and the reference simulation
4.1.2 Climatological responses in ECHAM6 sensitivity experiments
4.2 Circulation regimes and sea ice-induced frequency changes
4.2.1 Regime structures in ERA5 and ECHAM6 experiments
4.2.2 Regime frequency changes in ERA
4.2.3 Regime frequency changes in ECHAM6 experiments
4.3 Changes in Northern Hemispheric temperature extremes induced by sea ice loss
4.3.1 Extreme occurrence frequency changes
4.3.2 Temperature return level changes
4.4 Links between circulation regimes and extremes over Europe
4.4.1 Winter temperature extremes
4.4.2 Summer heat extremes
4.4.3 Winter wind extremes
4.5 Decomposition of sea ice-induced frequency changes in European winter extremes
4.5.1 Midwinter cold extremes along a SCAN storyline
4.5.2 January warm extremes along a ATl- storyline
4.5.3 February warm extremes along a NAO+ storyline
4.5.4 Comparison with futSST
4.5.5 January wind extremes along a ATL- storyline
4.6 Circulation Analogue-based approach for summer season
4.6.1 ERA5 event definitions
4.6.2 Reference flows and analogues in ERA5
4.6.3 Circulation analogues in ECHAM6 experiments
4.6.4 Decomposition of sea ice-induced changes in European heat extremes
5 CONCLUSION
5.1 Summary
5.2 Final discussion and outlook
Appendix A METHODS
A.1 Principal Component Analysis
A.2 𝑘-Means clustering
A.2.1 Algorithm
A.2.2 Computation of circulation regimes
A.3 Taylor diagram
A.4 Regression model for describing ERA5 regime frequency changes
A.4.1 General setup
A.4.2 Multinomial Logistic Regression
A.4.3 Linear predictor
A.5 Definition and calculation of return levels
A.5.1 Block maxima approach and Generalized Extreme Value distribution
A.5.2 Return level estimation
A.6 Framework for conditional extreme event attribution
Appendix B ADDITIONAL FIGURES
B.1 Circulation regimes and sea ice-induced frequency changes
B.2 Changes in Northern Hemispheric temperature extremes induced by sea ice loss
B.3 Links between circulation regimes and extremes over Europe
B.3.1 Conditioned vs. unconditioned ERA5 and wind extreme probabilities
B.3.2 Wind and synoptic-scale activity anomalies
B.4 Decomposition of sea ice-induced frequency changes in European winter extremes
B.5 Circulation Analogue-based approach for summer season
B.6 Miscellaneous
B.6.1 Recent Arctic sea ice trends
B.6.2 futSST forcing field
B.6.3 Fluxes over sea ice and ocean surfaces in ECHAM6
BIBLIOGRAPHY
Location:
AWI Reading room
Branch Library:
AWI Library
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