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Table of Contents
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Acronyms

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Acronym

Description

C3S

Copernicus Climate Change Service

CDR

Climate Data Record

CDS

Climate Data Store

ERA5

Fifth generation ECMWF atmospheric reanalysis

ERA-Interim

ECMWF Interim reanalysis

MSLP

Mean Sea Level Pressure

SSI

Storm Severity Index

WISC

Windstorm Information Service (Copernicus)

XWS

Extreme Wind Storms Catalogue


Introduction

European winter windstorms are a major cause of losses to the insurance sector. To help the sector better understand this risk the Operational Windstorm Service for the Insurance Sector has been developed. The development of the service follows from a Proof of Concept for a Sectorial Information Service to provide information about European windstorms, which is the Windstorm Information Service (WISC), part of the Copernicus Climate Change Service (C3S). This document describes the Tier 1 indicators and how they are produced by the University of Reading. The Tier 1 indicators provide summary statistics for wind storm activity per year and per European country.

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table1
table1
Table 1: Overview of key characteristics of the Tier 1 indicator dataset.

Data Description

Dataset title

Tier 1 Indicators

Data type

Summary statistics of European windstorms.

Topic category

Natural risk zones, Atmospheric conditions

Sector

Insurance

Keyword

Number of cyclones, intensities.

Dataset language

English

Domain

Europe defined as follows:

  • West: 15°
  • East: 25°
  • South: 35°
  • North: 75°

Horizontal resolution

Statistics derived from ERA5, ~30 km.

Temporal coverage

1979-10-01/to/2021-03-31

Temporal resolution

Annual, Decadal

Vertical coverage

10-m near surface

Update frequency

No updates expected

Version

1.1

Model

ERA5

Experiment

N/A

Provider

University of Reading (UREAD)

Terms of Use

https://cds.climate.copernicus.eu/api/v2/terms/static/licence-to-use-copernicus-products.pdf

Variable Description

The Tier 1 indicators, which are provided in Excel format, include the following fields:

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table2
table2
Table 2: Overview and description of variables

Variables

Long Name

Short Name

Unit

Description

Number of windstorms (vorticity)

No. storms

Number

Based on the storm tracks. A storm is said to pass through a region if a storm's track vorticity center passes through the region. These are provided per year and per decade.

Number of windstorms (wind)

No. storms

Number

A storm is said to pass through the region if the land only 10m wind speed maximum (within 3° of the vorticity center) passes through the region. These are provided per year and per decade.

Mean maximum 10m wind speed (u10m land only) (>0.0 m s-1)

Mean Wind

m s-1

Mean maximum wind speed at 10m over land calculated for each study region directly from the reanalysis data. The threshold used here was 0.0 m s-1. These are provided per year.

Number of extreme windstorms (u10m land only) (>15.6 m s-1)

No. storms (land > 15.6 m s-1)

Number

A storm is said to pass through the region if the land only 10m wind speed maximum (within 3° of the vorticity center) is greater than 15.6 m s-1 and passes through the region. This is the same threshold used for ERA-Interim in WISC. These are provided per year and per decade.

Mean maximum wind speed (u10m land only) (>15.6 m s-1)

Mean Wind (land > 15.6 m s-1)

m s-1

Calculated for each study region directly from the reanalysis data. The threshold used here was 15.6 m s-1. Maximum averaged over all storms. These are provided per year and per decade.

Number of extreme windstorms, (u10m land only) (>20.0 m s-1)

No. storms (land > 20.0 m s-1)

Number

A storm is said to pass through the region if the land only 10m wind speed maximum (within 3° of the vorticity center) is greater than 20.0 m s-1 and passes through the region. These are provided per year and per decade.

Mean maximum wind speed (u10m land only) (>20.0 m s-1)

Mean Wind (land > 20.0 m s-1)

m s-1

Calculated for each study region directly from the reanalysis data. The threshold used here was 20.0 m s-1. Maximum averaged over all storms. These are provided per year and per decade.

Number of extreme windstorms (u10m land only) (>25.0 m s-1)

No. storms (land > 25.0 m s-1)

Number

A storm is said to pass through the region if the land only 10m wind speed maximum (within 3° of the vorticity center) is greater than 25.0 m s-1 and passes through the region. These are provided per year and per decade.

Mean maximum wind speed (u10m land only) (>25.0 m s-1)

Mean Wind (land > 25.0 m s-1)

m s-1

Calculated for each study region directly from the reanalysis data. The threshold used here was 25.0 m s-1. Maximum averaged over all storms. These are provided per year and per decade.

Mean severity of storms, per year and per decade, 20.0 m s-1 threshold.

SSI

None (Unitless SSI)

The severity of each storm was assessed using a Storm Severity Index (SSI). This metric was also calculated from the land masked wind speed of the re-analysis data. Wind threshold > 20.0 m s-1. These are provided per year and per decade.

Mean severity of storms, per year and per decade, 25.0 m s-1 threshold.

SSI

None (Unitless SSI)

The severity of each storm was assessed using a Storm Severity Index (SSI). This metric was also calculated from the land masked wind speed of the re-analysis data. Wind threshold > 25.0 m s-1. These are provided per year and per decade.

Input Data

The input data to the cyclone track and Tier 1 production is summarised in Table 3 and described below.

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table3
table3
Table 3: Overview of climate model data for input to Operational Storm Track, summarizing the model properties and available scenario simulations.

Input Data





Model name

Model centre

Scenario

Period

Resolution

ERA5

ECMWF

Reanalysis

1979-2020

~30km

Input Data 1

ERA5 Reanalysis
Data from the ECMWF ERA5 reanalysis (Hersbach et al, 2020) extracted directly from the mars archive for the period 1979-2020 at 3 hourly intervals for the seasonal period of October to March when the majority of European windstorms occur. The 850hPa relative vorticity is spectrally filtered prior to applying the tracking algorithm. Full resolution MSLP, 925hPa winds and 10m winds are also added to the cyclone tracks.

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