skip to primary navigation skip to content
 

Preparing for Extreme and Rare Events in coastaL regions (PEARL)

Preparing for Extreme and Rare Events in coastaL regions (PEARL)

Project overview

Coastal communities are among the most vulnerable to extreme flooding events. Surface runoff from heavy rainfall, high river levels and storm/tidal surges from the sea all pose significant flood risks, and can often occur in combination, with potentially devastating consequences. This is further compounded by the expected sea level rise over the next few decades due to human-induced climate change.

PEARL logo

Accordingly, the EU(FP7)-funded project PEARL has been set up to bring together world-leading technological and socio-economical expertise in order to develop more sustainable risk management solutions for coastal communities.


Specifically, PEARL aims to:

  • develop a holistic flood risk approach for coastal communities
  • improve forecasting, prediction and early warning capabilities
  • follow a transdisciplinary approach integrating social, environmental and technical research and innovation
  • gather case studies and demonstrations of best practices across Europe, Asia and the Caribbean

Our role

The work being undertaken at the University of Cambridge contributes towards PEARL's Work Package 2 (WP2): 'Understanding formation of hazards under extreme events'.

Specifically, our researchers are developing a state-of-the-art multi-scale numerical atmospheric model, ATHAM-Fluidity, towards simulating extreme hydro-meteorological events in coastal regions. ATHAM-Fluidity combines the dynamical core of the Fluidity model, developed at Imperial College London, which uses dynamic mesh adaption to concentrate grid resolution in regions where it is most needed (Fig 1), with the Active Tracer High-resolution Atmospheric Model (ATHAM), which contains physical parameterisations for a wide range of cloud-relevant applications (Fig 2).

Potential temperature snapshot from a cold density current simulation using ATHAM-Fluidity.

Fig 1: Potential temperature snapshot from a cold density current simulation using ATHAM-Fluidity. The right panel shows how the adaptive mesh concentrates grid resolution in regions where it is most needed (image taken from Savre et al., 2016)

An example of an ATHAM simulation

Fig 2: An example of an ATHAM simulation (total condensate mixing ratio during a storm cell development) with 50 m resolution

As a result, the model is able to directly resolve the important turbulent motions that lead to the formation of heavy-precipitation clouds, whilst parameterising the smaller (subgrid) motions - a technique known as large-eddy simulation (LES). In addition, the adaptive mesh allows for more accurate representation of, e.g., topographic features and their subsequent forcing on the atmosphere, or narrow features such as squall lines (Fig 3). This represents a major breakthrough in the atmospheric LES community.

Simulation of a squall line with ATHAM-Fluidity (plot shows liquid water content)

Fig 3. Simulation of a squall line with ATHAM-Fluidity (plot shows liquid water content)

Photo from the January 2015 storm that affected Rethymno

Fig 4: Photo from the January 2015 storm that affected Rethymno

As part of the project's integrated modelling framework, the simulations performed using ATHAM-Fluidity will also provide input data (surface wind and pressure fields) for a storm surge and wave model. The larger (synoptic) scale weather patterns in ATHAM-Fluidity are forced through appropriate boundary conditions, which are provided by regional climate model simulations performed at the Max Planck Institute for Meteorology, Germany. The modelling framework also integrates river and pipe network models, thus enabling interactions between all the major sources of flooding.

In order to test the newly developed model within this integrated framework, two case studies of extreme hydro-meteorological events will be simulated; one centred on the coastal area of Greve in eastern Denmark, and the other on Rethymno on the Greek island of Crete. Both these places have been historically prone to flooding (see Fig 4 for a photo of a recent storm in Rethymno) and will therefore benefit from a better flood risk management system, a key aim in the wider context of the project.


Publications

  • Savre J, Percival J, Pain C, Herzog M. 2016. Two-dimensional evaluation of ATHAM-Fluidity, a nonhydrostatic atmospheric model using mixed continuous/discontinuous finite-elements and anisotropic grid optimization. Monthly Weather Review. Accepted for publication. doi:10.1175/MWR-D-15-0398.1