How bad is the rain? Applying the extreme rain multiplier globally and for climate monitoring activities

Abstract A typical question posed following an extreme precipitation event is: How does this compare to past events? This question is being asked more frequently and is of importance to climate monitoring services, such as the Copernicus Climate Change Service (C3S). Currently, the statistics extens...

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Main Authors: David A. Lavers, Gabriele Villarini, Hannah L. Cloke, Adrian Simmons, Nigel Roberts, Anna Lombardi, Samantha N. Burgess, Florian Pappenberger
Format: Article
Language:English
Published: Wiley 2025-03-01
Series:Meteorological Applications
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Online Access:https://doi.org/10.1002/met.70031
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author David A. Lavers
Gabriele Villarini
Hannah L. Cloke
Adrian Simmons
Nigel Roberts
Anna Lombardi
Samantha N. Burgess
Florian Pappenberger
author_facet David A. Lavers
Gabriele Villarini
Hannah L. Cloke
Adrian Simmons
Nigel Roberts
Anna Lombardi
Samantha N. Burgess
Florian Pappenberger
author_sort David A. Lavers
collection DOAJ
description Abstract A typical question posed following an extreme precipitation event is: How does this compare to past events? This question is being asked more frequently and is of importance to climate monitoring services, such as the Copernicus Climate Change Service (C3S). Currently, the statistics extensively used for this purpose are not generally understandable to the wider public, or they are not tailored towards presenting extremes. To mitigate this situation, this article uses a modified version of the Extreme Rain Multiplier (ERM), which was developed for tropical cyclones, and applies it to precipitation events globally. For daily precipitation considered herein, the ERM is calculated by dividing the daily precipitation accumulation during an event by the mean historical annual maxima of daily precipitation (RX1day), which is computed over 1991–2020. Using the European Centre for Medium‐Range Weather Forecasts ERA5 reanalysis, the calculation of the ERM is illustrated for six extreme events around the world; these included convective systems, atmospheric rivers and tropical cyclones. A maximum ERM of 4 was found during Storm Daniel, in Greece, and in Tropical Cyclone Jasper in Australia, implying that four times the mean RX1day precipitation occurred. The ERM will be useful in C3S reporting activities because it can objectively identify extreme precipitation events. Furthermore, after extracting the number of precipitation events per year at each grid point that had an ERM exceeding 1, a trend analysis was undertaken to ascertain if the frequency of extreme events had changed with time. Results showed that the most widespread increasing trends in the ERM were in the tropics, but these trends are thought to be questionable in ERA5. There were few clear trends in other regions. In conclusion, the ERM can communicate the level of extreme precipitation in a clear manner and can be used in climate monitoring activities.
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spelling doaj-art-03f9f419fc274d63bd5cdf16c82909092025-08-20T02:24:49ZengWileyMeteorological Applications1350-48271469-80802025-03-01322n/an/a10.1002/met.70031How bad is the rain? Applying the extreme rain multiplier globally and for climate monitoring activitiesDavid A. Lavers0Gabriele Villarini1Hannah L. Cloke2Adrian Simmons3Nigel Roberts4Anna Lombardi5Samantha N. Burgess6Florian Pappenberger7European Centre for Medium‐Range Weather Forecasts (ECMWF) Reading UKDepartment of Civil and Environmental Engineering Princeton University Princeton New Jersey USADepartment of Geography and Environmental Science University of Reading Reading UKEuropean Centre for Medium‐Range Weather Forecasts (ECMWF) Reading UKEuropean Centre for Medium‐Range Weather Forecasts (ECMWF) Reading UKEuropean Centre for Medium‐Range Weather Forecasts (ECMWF) Reading UKEuropean Centre for Medium‐Range Weather Forecasts (ECMWF) Reading UKEuropean Centre for Medium‐Range Weather Forecasts (ECMWF) Reading UKAbstract A typical question posed following an extreme precipitation event is: How does this compare to past events? This question is being asked more frequently and is of importance to climate monitoring services, such as the Copernicus Climate Change Service (C3S). Currently, the statistics extensively used for this purpose are not generally understandable to the wider public, or they are not tailored towards presenting extremes. To mitigate this situation, this article uses a modified version of the Extreme Rain Multiplier (ERM), which was developed for tropical cyclones, and applies it to precipitation events globally. For daily precipitation considered herein, the ERM is calculated by dividing the daily precipitation accumulation during an event by the mean historical annual maxima of daily precipitation (RX1day), which is computed over 1991–2020. Using the European Centre for Medium‐Range Weather Forecasts ERA5 reanalysis, the calculation of the ERM is illustrated for six extreme events around the world; these included convective systems, atmospheric rivers and tropical cyclones. A maximum ERM of 4 was found during Storm Daniel, in Greece, and in Tropical Cyclone Jasper in Australia, implying that four times the mean RX1day precipitation occurred. The ERM will be useful in C3S reporting activities because it can objectively identify extreme precipitation events. Furthermore, after extracting the number of precipitation events per year at each grid point that had an ERM exceeding 1, a trend analysis was undertaken to ascertain if the frequency of extreme events had changed with time. Results showed that the most widespread increasing trends in the ERM were in the tropics, but these trends are thought to be questionable in ERA5. There were few clear trends in other regions. In conclusion, the ERM can communicate the level of extreme precipitation in a clear manner and can be used in climate monitoring activities.https://doi.org/10.1002/met.70031communicationERA5 precipitationextreme eventsextreme rain multiplier
spellingShingle David A. Lavers
Gabriele Villarini
Hannah L. Cloke
Adrian Simmons
Nigel Roberts
Anna Lombardi
Samantha N. Burgess
Florian Pappenberger
How bad is the rain? Applying the extreme rain multiplier globally and for climate monitoring activities
Meteorological Applications
communication
ERA5 precipitation
extreme events
extreme rain multiplier
title How bad is the rain? Applying the extreme rain multiplier globally and for climate monitoring activities
title_full How bad is the rain? Applying the extreme rain multiplier globally and for climate monitoring activities
title_fullStr How bad is the rain? Applying the extreme rain multiplier globally and for climate monitoring activities
title_full_unstemmed How bad is the rain? Applying the extreme rain multiplier globally and for climate monitoring activities
title_short How bad is the rain? Applying the extreme rain multiplier globally and for climate monitoring activities
title_sort how bad is the rain applying the extreme rain multiplier globally and for climate monitoring activities
topic communication
ERA5 precipitation
extreme events
extreme rain multiplier
url https://doi.org/10.1002/met.70031
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