Simulations of the Sea Surface Temperature (SST) (left) and the air temperature at 2m over the North Atlantic by the global ultra-


Impact on the European transport system


Intense rainfall can cause direct significant and long lasting impacts on transport operations, due to flooding, while indirectly impacting transport safety and bringing damage to transport infrastructure. Submerged roads and railway tracks become unusable, towns become inaccessible, movement of people and goods becomes disrupted, and floods could even lead to human casualties.

High water in the Elve River. Pixabay

Knowledge about projected future changes in extreme rainfall events, and the projected changes in factors contributing to the occurrence of floods is needed. Such knowledge, combined with the sector's understanding of its vulnerability to these events, will allow transport organizations to develop strategies to minimize the potential risks brought about by changes in the characteristics of flood events in the future.

Impacts on the European transport system

  • Railways

    Heavy rain can lead to delays and line closures, due to flooding of the track or lineside equipment, or to flood-related debris on tracks; track damage (e.g. ballast washout); embankment scour and washout; bridge scour; flooding of depots; landslips; embankment landslides; overwhelmed railway drainage in cuttings.

    Damage to a Railway track. Wikimedia Commons.
  • Roads

    Roads can suffer structural damage from water and debris, such as road edges erosion, subsidence and heave; embankments and culverts damage; landslips.

    Flooding in Cockermouth, UK. University of Salford Press.
  • Inland waterways

    Operations can be disrupted due to river flooding and debris accumulation. In anomalously strong currents, it can become difficult or impossible to manoeuvre large vessels safely. Additionally, debris accumulation can reduce the under-keel clearance of the vessels.

    Danube flooding. Imaresz.
  • Ports and airports

    Flooding at ports and airports limits their operability. Floods may also have indirect impacts: even if ports and airports can operate, access by road and/or rail can be limited by flooding external to the airport or port.

    Passengers stranded in Gatwick airport during the floods of December 25th 2003. Chris Healey.

Example: 2002 European floods

During the period 11th-14th August 2002, exceptionally heavy rain affected central Europe, which caused local flash floods. The rainfall was especially extreme in South Western Germany, Western and North Eastern of the Czech Republic. Several days later, the large rivers fed from these areas, including the Elbe, Vltava and Danube, flooded many cities and towns, including Prague and Dresden, with water levels reaching record heights.

Prague Floods 2002 (Hochwasser in Prag, Tschechische republik) - Karlín, Troja. placesofinterest.

Prague's historic centre was seriously damaged and the flow of the River Vltava reached 5300 m3/s, 20% more than the flood of 1845. About 40000 people were evacuated from their homes. The subway also suffered serious damage.

In Bratislava, Budapest and Vienna, the River Danube reached its highest level in decades. However, these cities did not suffer such major damage.

Future projections

  • According to the current generation of climate models, precipitation is projected to increase throughout this century in Northern Europe, and decrease in Southern Europe.
  • The projected increase in heavy precipitation is related to the fact that warmer air can hold more water vapour, which in turn means there is more water available in the atmosphere to fall as rain.
  • A marked increase in heavy precipitation events is also projected, which could lead to an increase in river flood risk, and without adaptive measures will bring greater flood damages (Kovats et al. 2014).

Contribution from PRIMAVERA

  • The PRIMAVERA project is developing a new generation of advanced high-resolution global climate models, capable of simulating regional climate with greater fidelity.
  • The increased temporal (sub-daily) and spatial resolution (typically around 25km) of the PRIMAVERA models will allow a better representation of physical processes leading to heavy convective precipitation, and of features related to flooding, such as storms, storm tracks, and blocking structures which often deflect the storms on their paths.
  • Although convective storms are not explicitly resolved by the PRIMAVERA models, the increased temporal resolution will also allow some aspects of intense precipitation to be explored

Atmospheric blockings



Instead of the usual westerly flow, with the passing of low and high pressure systems with their associated cold and warm fronts, atmospheric blockings appear at mid-latitudes as large, quasi-stationary high pressure systems (anticyclones).

What is an atmospheric blocking?

Atmospheric blockings are stable configurations of the mid-latitude atmospheric circulation that yield persistent and anomalous weather in large regions for a time period from weeks to months.

Atmospheric blocking. deepfryedmind

On the left side of the high pressure, warm air is advected from lower latitudes, and anomalously high persistent temperatures are registered. On the right side, the opposite situation occurs, and anomalously cold conditions happen. These situations can lead to heat waves or cold spells waves depending on the season of the year.

Consequences of Atmospheric blockings

  • Persistent dry conditions do happen below the high pressure area, and also anomalously weak winds.
  • Depending on the topography and the position of the blocking, heavy rain and flooding can take place too, if the unstable persistent throughs at the sides of the blocking high pressure area have enough moisture sources (e.g., a warm water mass as the Mediterranean sea).

Atmospheric blocking patterns classification

The most typical atmospheric blocking patterns in the Euro-Atlantic sector are classified in two types: ‘omega’ block and ‘diffluent’ or ‘dipole’ block.

1. Omega block. Met Office
2. Diffluent block. Met Office
  • 1 An example of an ‘omega’ block, named after the uppercase greek letter Ω. This map would yield warm weather to ireland and cold to the Benelux. UK could suffer lack of rainfall.
  • 2 An example of a ‘diffluent’ or ‘dipole’ block. This map would yield rainy weather to France and drought to UK. This kind of blockings can be more persistent than the ‘omega’ blocks.
Explanation of Atmospheric blocking types. Met Office.

Atmospheric blockings have a huge impact on the energy sector

  • Less precipitation than average in central and northern Europe, leading to decreased hydropower generation.
  • Significant winter cold spells that affect vast areas over Europe, which increase energy demand for heating.
  • Summer heatwaves over Northern Europe, which lead to increased energy demand for cooling Summer.
  • Disruption of typical wind patterns and ‘wind drought’ events which decrease wind power generation.
  • Persistent clear skies in regions affected by high pressures, which increased solar PV generation.

Example: May 2005 Atmospheric blocking

Many of the most relevant heat waves and cold spells registered during the last decades in Europe are related to atmospheric blockings. Here we show an example of a strong blocking over Europe and its consequences.

Added value of high resolution

Atmospheric blocking. deepfryedmind

Several studies have showed that higher resolution improves the representation of the blocking in climate models. For example, Anstey et al., (2013) showed how the models with higher vertical and horizontal resolution represented more accurately the observed blocking statistics than coarser resolution models.

Contribution from PRIMAVERA

  • The PRIMAVERA project is developing a new generation of advanced high-resolution global climate models, capable of simulating and predicting regional climate with unprecedented fidelity.
  • The increase in model resolutions of the PRIMAVERA models (typically around 25km) will allow to study physical processes involved in atmospheric blockings and their future evolution with an unprecedented level of detail and accuracy.

Anstey, J. A., P. Davini, L. J. Gray, T. J. Woollings, N. Butchart, C. Cagnazzo, B. Christiansen, S. C. Hardiman, S. M. Osprey, and S. Yang (2013), Multi-model analysis of Northern Hemisphere winter blocking: Model biases and the role of resolution, J. Geophys. Res. Atmos., 118, 3956–3971, doi:10.1002/jgrd.50231

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