Compounding heatwave-extreme rainfall events driven by fronts, high moisture, and atmospheric instability

Christoph Sauter; Jennifer L. Catto; Hayley J. Fowler; Seth Westra; Christopher J. White

doi:10.1029/2023jd038761

Compounding heatwave-extreme rainfall events driven by fronts, high moisture, and atmospheric instability

Christoph Sauter, Jennifer L. Catto, Hayley J. Fowler, Seth Westra, Christopher J. White

Civil And Environmental Engineering

Research output: Contribution to journal › Article › peer-review

3 Citations (Scopus)

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Abstract

Heatwaves have been shown to increase the likelihood and intensity of extreme rainfall occurring immediately afterward, potentially leading to increased flood risk. However, the exact mechanisms connecting heatwaves to extreme rainfall remain poorly understood. In this study, we use weather type data sets for Australia and Europe to identify weather patterns, including fronts, cyclones, and thunderstorm conditions, associated with heatwave terminations and following extreme rainfall events. We further analyze, using reanalysis data, how atmospheric instability and moisture availability change before and after the heatwave termination depending on whether the heatwave is followed by extreme rainfall, as well as the location of the heatwave. We find that most heatwaves terminate during thunderstorm and/or frontal conditions. Additionally, atmospheric instability and moisture availability increase several days before the heatwave termination; but only if heatwaves are followed by extreme rainfall. We also find that atmospheric instability and moisture after a heatwave are significantly higher than expected from climatology for the same time of the year, and that highest values of instability and moisture are associated with highest post-heatwave rainfall intensities. We conclude that the joint presence of high atmospheric instability, moisture, as well as frontal systems are likely to explain why rainfall is generally more extreme and likely after heatwaves, as well as why this compound hazard is mainly found in the non-arid mid and high latitudes. An improved understanding of the drivers of these compound events will help assess potential changing impacts in the future.

Original language	English
Article number	e2023JD038761
Number of pages	14
Journal	Journal of Geophysical Research: Atmospheres
Volume	128
Issue number	21
Early online date	28 Oct 2023
DOIs	https://doi.org/10.1029/2023jd038761
Publication status	Published - 16 Nov 2023

Funding

C.S. was funded by an EPSRC Doctoral Training Partnership (DTP) (Grant EP/R513349/1). J.L.C and H.J.F. were supported by NERC project STORMY‐WEATHER (Grant: NE/V004166/1). H.J.F. and C.J.W. were supported by the NERC Global Partnerships Seedcorn Fund (EMERGE; Grant: NE/W003775/1). H.J.F. was also supported by the United Kingdom NERC Changing Water Cycle programme (FUTURE‐STORMS; Grant: NE/R01079X/1), and C.J.W. was supported by the Horizon Europe Multi‐hazard and risk informed system for Enhanced local and regional Disaster risk management project (MEDiate; 10049641). This work used JASMIN, the UK’s collaborative data analysis environment ( https://jasmin.ac.uk ) for post‐processing ERA5 data. The authors would like to thank Acacia Pepler for providing the Australian weather type data set and Andrew Dowdy for providing the thunderstorm data for Europe. C.S. was funded by an EPSRC Doctoral Training Partnership (DTP) (Grant EP/R513349/1). J.L.C and H.J.F. were supported by NERC project STORMY-WEATHER (Grant: NE/V004166/1). H.J.F. and C.J.W. were supported by the NERC Global Partnerships Seedcorn Fund (EMERGE; Grant: NE/W003775/1). H.J.F. was also supported by the United Kingdom NERC Changing Water Cycle programme (FUTURE-STORMS; Grant: NE/R01079X/1), and C.J.W. was supported by the Horizon Europe Multi-hazard and risk informed system for Enhanced local and regional Disaster risk management project (MEDiate; 10049641). This work used JASMIN, the UK’s collaborative data analysis environment (https://jasmin.ac.uk) for post-processing ERA5 data. The authors would like to thank Acacia Pepler for providing the Australian weather type data set and Andrew Dowdy for providing the thunderstorm data for Europe.

Keywords

heatwave
extreme rainfall
flood risk
weather datasets
atmospheric instability

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Sauter-etal-JGRA-2023-Compounding-heatwave-extreme-rainfall-eventsFinal published version, 2.63 MBLicence: CC BY 4.0

Cite this

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title = "Compounding heatwave-extreme rainfall events driven by fronts, high moisture, and atmospheric instability",

abstract = "Heatwaves have been shown to increase the likelihood and intensity of extreme rainfall occurring immediately afterward, potentially leading to increased flood risk. However, the exact mechanisms connecting heatwaves to extreme rainfall remain poorly understood. In this study, we use weather type data sets for Australia and Europe to identify weather patterns, including fronts, cyclones, and thunderstorm conditions, associated with heatwave terminations and following extreme rainfall events. We further analyze, using reanalysis data, how atmospheric instability and moisture availability change before and after the heatwave termination depending on whether the heatwave is followed by extreme rainfall, as well as the location of the heatwave. We find that most heatwaves terminate during thunderstorm and/or frontal conditions. Additionally, atmospheric instability and moisture availability increase several days before the heatwave termination; but only if heatwaves are followed by extreme rainfall. We also find that atmospheric instability and moisture after a heatwave are significantly higher than expected from climatology for the same time of the year, and that highest values of instability and moisture are associated with highest post-heatwave rainfall intensities. We conclude that the joint presence of high atmospheric instability, moisture, as well as frontal systems are likely to explain why rainfall is generally more extreme and likely after heatwaves, as well as why this compound hazard is mainly found in the non-arid mid and high latitudes. An improved understanding of the drivers of these compound events will help assess potential changing impacts in the future.",

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AU - White, Christopher J.

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N2 - Heatwaves have been shown to increase the likelihood and intensity of extreme rainfall occurring immediately afterward, potentially leading to increased flood risk. However, the exact mechanisms connecting heatwaves to extreme rainfall remain poorly understood. In this study, we use weather type data sets for Australia and Europe to identify weather patterns, including fronts, cyclones, and thunderstorm conditions, associated with heatwave terminations and following extreme rainfall events. We further analyze, using reanalysis data, how atmospheric instability and moisture availability change before and after the heatwave termination depending on whether the heatwave is followed by extreme rainfall, as well as the location of the heatwave. We find that most heatwaves terminate during thunderstorm and/or frontal conditions. Additionally, atmospheric instability and moisture availability increase several days before the heatwave termination; but only if heatwaves are followed by extreme rainfall. We also find that atmospheric instability and moisture after a heatwave are significantly higher than expected from climatology for the same time of the year, and that highest values of instability and moisture are associated with highest post-heatwave rainfall intensities. We conclude that the joint presence of high atmospheric instability, moisture, as well as frontal systems are likely to explain why rainfall is generally more extreme and likely after heatwaves, as well as why this compound hazard is mainly found in the non-arid mid and high latitudes. An improved understanding of the drivers of these compound events will help assess potential changing impacts in the future.

AB - Heatwaves have been shown to increase the likelihood and intensity of extreme rainfall occurring immediately afterward, potentially leading to increased flood risk. However, the exact mechanisms connecting heatwaves to extreme rainfall remain poorly understood. In this study, we use weather type data sets for Australia and Europe to identify weather patterns, including fronts, cyclones, and thunderstorm conditions, associated with heatwave terminations and following extreme rainfall events. We further analyze, using reanalysis data, how atmospheric instability and moisture availability change before and after the heatwave termination depending on whether the heatwave is followed by extreme rainfall, as well as the location of the heatwave. We find that most heatwaves terminate during thunderstorm and/or frontal conditions. Additionally, atmospheric instability and moisture availability increase several days before the heatwave termination; but only if heatwaves are followed by extreme rainfall. We also find that atmospheric instability and moisture after a heatwave are significantly higher than expected from climatology for the same time of the year, and that highest values of instability and moisture are associated with highest post-heatwave rainfall intensities. We conclude that the joint presence of high atmospheric instability, moisture, as well as frontal systems are likely to explain why rainfall is generally more extreme and likely after heatwaves, as well as why this compound hazard is mainly found in the non-arid mid and high latitudes. An improved understanding of the drivers of these compound events will help assess potential changing impacts in the future.

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KW - extreme rainfall

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U2 - 10.1029/2023jd038761

DO - 10.1029/2023jd038761

M3 - Article

SN - 2169-897X

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ER -

Compounding heatwave-extreme rainfall events driven by fronts, high moisture, and atmospheric instability

Abstract

Funding

Keywords

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