Development of a combined empirical index for a 5-day forecast of heavy precipitation over the Bernese Alps

The Bernese Alps are a region that is very prone for the initiation of thunderstorms. In fact, the flow and convergence of air and water vapor from the Swiss Plateau to the Swiss Alps is frequently favouring the formation of isolated rainfall events, which then may cause loss and damage in settlemen...

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Main Authors: Liliane Nguyen, Mario Rohrer, Manfred Schwarb, Markus Stoffel
Format: Article
Language:English
Published: Elsevier 2020-02-01
Series:Environment International
Online Access:http://www.sciencedirect.com/science/article/pii/S0160412019316307
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author Liliane Nguyen
Mario Rohrer
Manfred Schwarb
Markus Stoffel
author_facet Liliane Nguyen
Mario Rohrer
Manfred Schwarb
Markus Stoffel
author_sort Liliane Nguyen
collection DOAJ
description The Bernese Alps are a region that is very prone for the initiation of thunderstorms. In fact, the flow and convergence of air and water vapor from the Swiss Plateau to the Swiss Alps is frequently favouring the formation of isolated rainfall events, which then may cause loss and damage in settlements. Due to the complex topography of the Bernese Alps, the forecasting and nowcasting of heavy convective precipitation remain challenging. A critical need therefore exists for the development of new forecasting tools so as to improve the predictability of convective precipitation events, also with the aim to alert first responders and to subsequently reduce damage. This study aims at developing an empirical index for the forecasting of heavy precipitation events in the Bernese Alps by using two reanalysis datasets, ECMWF’s ERA-Interim and NASA’s MERRA-2; in addition, the ICON-EU model is employed here to test and verify the index for the 2018 summer period. Our approach is based on the calculation of several convective indices as well as on the assessment of their relative forecast skills using a dichotomous scheme. The Heavy Precipitation Index (HPI) is then defined by combining the best performing combination of convective indices. HPI is aimed at forecasting heavy precipitation events over the Bernese Alps. We show that the combination of several indices, including DCI or KI, have a better capability to forecast heavy precipitation in the Bernese Alps than has the commonly used CAPE. Therefore, HPI should be seen as a pre-alert index when it comes to assist first responders in situations of crisis and in the process of decision making. Keywords: Heavy precipitation, Convective indices, CAPE, Heavy Precipitation Index, Bernese Alps, Reanalysis
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spelling doaj.art-5a58f4614c9c489cad390d95c64ca0ba2022-12-22T01:02:23ZengElsevierEnvironment International0160-41202020-02-01135Development of a combined empirical index for a 5-day forecast of heavy precipitation over the Bernese AlpsLiliane Nguyen0Mario Rohrer1Manfred Schwarb2Markus Stoffel3C-CIA - Climate Change Impacts and Risks in the Anthropocene, Institute for Environmental Sciences (ISE), University of Geneva, CH-1205 Geneva, Switzerland; Corresponding author at: Nonlinearity and Climate, Institute for Environmental Sciences (ISE), University of Geneva, Boulevard Carl Vogt 66, 1205 Geneva, Switzerland.C-CIA - Climate Change Impacts and Risks in the Anthropocene, Institute for Environmental Sciences (ISE), University of Geneva, CH-1205 Geneva, Switzerland; Meteodat GmbH, Technoparkstrasse 1, CH-8005 Zurich, SwitzerlandMeteodat GmbH, Technoparkstrasse 1, CH-8005 Zurich, SwitzerlandC-CIA - Climate Change Impacts and Risks in the Anthropocene, Institute for Environmental Sciences (ISE), University of Geneva, CH-1205 Geneva, Switzerland; Department F.A. Forel for Environmental and Aquatic Sciences, University of Geneva, CH-1205 Geneva, Switzerland; Department of Earth Sciences, University of Geneva, CH-1205 Geneva, SwitzerlandThe Bernese Alps are a region that is very prone for the initiation of thunderstorms. In fact, the flow and convergence of air and water vapor from the Swiss Plateau to the Swiss Alps is frequently favouring the formation of isolated rainfall events, which then may cause loss and damage in settlements. Due to the complex topography of the Bernese Alps, the forecasting and nowcasting of heavy convective precipitation remain challenging. A critical need therefore exists for the development of new forecasting tools so as to improve the predictability of convective precipitation events, also with the aim to alert first responders and to subsequently reduce damage. This study aims at developing an empirical index for the forecasting of heavy precipitation events in the Bernese Alps by using two reanalysis datasets, ECMWF’s ERA-Interim and NASA’s MERRA-2; in addition, the ICON-EU model is employed here to test and verify the index for the 2018 summer period. Our approach is based on the calculation of several convective indices as well as on the assessment of their relative forecast skills using a dichotomous scheme. The Heavy Precipitation Index (HPI) is then defined by combining the best performing combination of convective indices. HPI is aimed at forecasting heavy precipitation events over the Bernese Alps. We show that the combination of several indices, including DCI or KI, have a better capability to forecast heavy precipitation in the Bernese Alps than has the commonly used CAPE. Therefore, HPI should be seen as a pre-alert index when it comes to assist first responders in situations of crisis and in the process of decision making. Keywords: Heavy precipitation, Convective indices, CAPE, Heavy Precipitation Index, Bernese Alps, Reanalysishttp://www.sciencedirect.com/science/article/pii/S0160412019316307
spellingShingle Liliane Nguyen
Mario Rohrer
Manfred Schwarb
Markus Stoffel
Development of a combined empirical index for a 5-day forecast of heavy precipitation over the Bernese Alps
Environment International
title Development of a combined empirical index for a 5-day forecast of heavy precipitation over the Bernese Alps
title_full Development of a combined empirical index for a 5-day forecast of heavy precipitation over the Bernese Alps
title_fullStr Development of a combined empirical index for a 5-day forecast of heavy precipitation over the Bernese Alps
title_full_unstemmed Development of a combined empirical index for a 5-day forecast of heavy precipitation over the Bernese Alps
title_short Development of a combined empirical index for a 5-day forecast of heavy precipitation over the Bernese Alps
title_sort development of a combined empirical index for a 5 day forecast of heavy precipitation over the bernese alps
url http://www.sciencedirect.com/science/article/pii/S0160412019316307
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