Hail

Assessment versions

Published (reviewed and quality assured)

• No published assessments

Rationale

Justification for indicator selection

Hailstorms are most common in mid-latitudes with high surface temperature and humidity, as these conditions promote the required instability associated with strong thunderstorms and the temperature in the upper atmosphere is sufficiently low to support ice formation. The occurrence of hail over Europe is not uniform over space and time. Most hail events occur in summer or nearby mountain areas where convective energy and trigger mechanisms for convection are highest.

Hail is responsible for significant damage. For example, three hailstorm events in Germany in July and August 2013 caused around EUR 4.2 billion of combined damages to buildings, crops, vehicles, solar panels, greenhouses and other infrastructure.

Scientific references

• No rationale references available

Indicator definition

Hail is commonly classified according to diameter of the hailstones; for example, hail >=2cm diameter.

Hailstorm intensity scale classifies hail on a scale from H0, being hard hail with diameter 5 mm causing no damage to H10, being super hailstorms with diameter >100 mm and causing extensive structural damage with risk of severe or fatal injuries to people.

Hail is here defined with the potential hail index (PHI), which quantifies the atmospheric potential for hailstorms and can be derived from atmospheric numerical models. 

Units

PHI (unitless)

Policy context and targets

Context description

In April 2013 the European Commission presented the EU Adaptation Strategy Package (http://ec.europa.eu/clima/policies/adaptation/what/documentation_en.htm). This package consists of the EU Strategy on adaptation to climate change /* COM/2013/0216 final */ and a number of supporting documents. One of the objectives of the EU Adaptation Strategy is Better informed decision-making, which should occur through Bridging the knowledge gap and Further developing Climate-ADAPT as the ‘one-stop shop’ for adaptation information in Europe. Further objectives include Promoting action by Member States and Climate-proofing EU action: promoting adaptation in key vulnerable sectors. Many EU Member States have already taken action, such as by adopting national adaptation strategies, and several have also prepared action plans on climate change adaptation.

The European Commission and the European Environment Agency have developed the European Climate Adaptation Platform (Climate-ADAPT, http://climate-adapt.eea.europa.eu/) to share knowledge on observed and projected climate change and its impacts on environmental and social systems and on human health; on relevant research; on EU, national and subnational adaptation strategies and plans; and on adaptation case studies.

In September 2016, the EC presented an indicative roadmap for the evaluation of the EU Adaptation Strategy by 2018.

In November 2013, the European Parliament and the European Council adopted the 7^th EU Environment Action Programme (7^th EAP) to 2020, ‘Living well, within the limits of our planet’. The 7^th EAP is intended to help guide EU action on environment and climate change up to and beyond 2020. It highlights that ‘Action to mitigate and adapt to climate change will increase the resilience of the Union’s economy and society, while stimulating innovation and protecting the Union’s natural resources.’ Consequently, several priority objectives of the 7^th EAP refer to climate change adaptation.

Targets

not applicable

Related policy documents

• 7th Environment Action Programme
  DECISION No 1386/2013/EU OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 20 November 2013 on a General Union Environment Action Programme to 2020 ‘Living well, within the limits of our planet’. In November 2013, the European Parliament and the European Council adopted the 7 th EU Environment Action Programme to 2020 ‘Living well, within the limits of our planet’. This programme is intended to help guide EU action on the environment and climate change up to and beyond 2020 based on the following vision: ‘In 2050, we live well, within the planet’s ecological limits. Our prosperity and healthy environment stem from an innovative, circular economy where nothing is wasted and where natural resources are managed sustainably, and biodiversity is protected, valued and restored in ways that enhance our society’s resilience. Our low-carbon growth has long been decoupled from resource use, setting the pace for a safe and sustainable global society.’
• Climate-ADAPT: Adaptation in EU policy sectors
  Overview of EU sector policies in which mainstreaming of adaptation to climate change is ongoing or explored
• Climate-ADAPT: Country profiles
  Overview of activities of EEA member countries in preparing, developing and implementing adaptation strategies
• DG CLIMA: Adaptation to climate change
  Adaptation means anticipating the adverse effects of climate change and taking appropriate action to prevent or minimise the damage they can cause, or taking advantage of opportunities that may arise. It has been shown that well planned, early adaptation action saves money and lives in the future. This web portal provides information on all adaptation activities of the European Commission.
• EU Adaptation Strategy Package
  In April 2013, the European Commission adopted an EU strategy on adaptation to climate change, which has been welcomed by the EU Member States. The strategy aims to make Europe more climate-resilient. By taking a coherent approach and providing for improved coordination, it enhances the preparedness and capacity of all governance levels to respond to the impacts of climate change.

Methodology

Methodology for indicator calculation

Hail forms within deep convective clouds with observations recorded only by ground based hail pad networks. Proxies for hail events can be also derived from satellite temperature imagery and radar reflectivity.

The occurrence of hail is related to atmospheric instability so its likelihood is related indices such as the convective instability index (CI) and the potential hail index (PHI). These indices are usually considered in combination with mesoscale factors such as wind flow, specific humidity and water vapour flux.

Methodology for gap filling

Proxies for hail events can be also derived from satellite temperature imagery and radar reflectivity. These are supplemented with eye witness and media reports which are collected by organisations such as the Tornado and Storm Research organisation (TORRO), the European Severe Storm Laboratory (ESSL) which maintains the European Severe Weather Database (ESWD), and Schweizer Hagel (an agricultural cooperative). These databases provide information about the spatial distribution and the frequency of severe convection. However, observational databases are limited in spatial or temporal extent and biased towards population centres where there are more observers.

Methodology references

No methodology references available.

Data specifications

EEA data references

• No datasets have been specified here.

External data references

• Changes in the Hail Potential Over Past and Future Decades using a Logistic Hail Model

Data sources in latest figures

Uncertainties

Methodology uncertainty

See under "Methodology"

Data sets uncertainty

The occurrence of hail over Europe is not uniform as most hail events occur in the summer over Central Europe where convective energy is greatest. Trends in hail observations are sometimes made by using damage as a proxy although damage is also a function of hail type (size, density, accompanying horizontal wind speed and kinetic energy) and vulnerability of the impacted area to damage. The uneven distribution of hail pads across Europe makes trends difficult to detect by using only in-situ based observations.

Hail occurrences are also closely related to specific lightning signals with lightning detection data available from different sources. Radar data is another important proxy for hail events with a very high temporal and spatial resolution. However, radar reflectivity for most of European regions is only available since the mid-2000 and hence limited to assess the trends.

European MSG (SEVIRI) satellite data were used to develop a catalogue of hail events in Europe based on overshooting top data (OT).

Another method is to use combined different meteorological parameters relevant for hailstorm formation using a logistic model. Applied to different reanalysis data sets, the logistic model estimates the number of days with an increased potential of hail occurrence, denoted to as potential hail index.

Rationale uncertainty

see under methodology