MEC - Surface and Hydrology (MESH)
How to obtain MESH
Events and Training

Modélisation Environmentale Communautaire (MEC) is a community environmental modelling system, developed by Environment Canada as a framework within which to facilitate coupling between models representing different components of the earth system. The ultimate objective of MEC is to use the coupled models to produce operational forecasts. IP3 employs a configuration of MEC specialised for coupling land-surface and hydrological models, known as MEC – Surface and Hydrology or MESH. This system is the Canadian result of an intensive global research effort to couple atmospheric and hydrological models, in orer to improve hydrological flow simulations and atmospheric predictions in both climate- and weather-prediction models.

Understanding of the linkages between hydrological and atmospheric processes, in the form of transfers of water (between surface water, snow and ice, and precipitation and atmospheric water vapour), and of energy (between the atmosphere and soil, snow and vegetation) has improved markedly over the past few decades, but until relatively recently, hydrological and atmosperic models operated in mutual isolation, and this interaction was not well represented. The linkage between land-surface and atmospheric models was eventually provided through the development of Land Surface Schemes (LSS), which have become increasingly sophisticated; the Canadian LSS, CLASS, is a particularly good example. More recently, LSS models have also been incorporated into hydrological models, to provide stand-alone Hydrology-Land-Surface Scheme (HLSS) systems. This in turn has enabled the linkage of atmospheric and hydrological models, as in MEC/MESH. When a HLSS is incorporated into an atmospheric model, the result is a fully coupled system.

However, most of these efforts have led ony to the development of research modelling tools; the use of these architectures in hydrometeorological forecasting systems has been more limited, largely because of the technical hurdles involved in testing changes to an operational NWP system. MEC is being developed to overcome this obstacle. The MEC system allows different surface models to coexist within the same modelling framework, so that the outputs which they generate from exactly the same forcings, interpolation procedures, grid, time period, time step, and output specifications may be compared easily. The model coupler may also be used to couple models running on different grids, and potentially on different time steps. An important feature of MEC is the option which it provides to read atmospheric forcings from files, instead of sourcing directly from the atmospheric model through the coupler. This makes it possible to test changes to the surface schemes offline (ie, without the complication of the atmospheric model always having to run concurrently). The land-surface scheme is thus independent of the atmospheric model, and it is therefore possible to increase the spatial resolution of the land-surface scheme without changing the resolution of the atmospheric model. It is additionally possible to run MEC in an offline mode (de-coupled from the atmosphere) to allow the land-surface to develop without atmospheric constraint.

The current versions of MEC and MESH include three land-surface schemes:

One of the primary goals with respect to the MESH modelling system is to improve the description and quantification of the importance of sub-grid variability; to achieve this, CLASS may be configured to run on a number of different HRUs or tiles within each gridcell, allowing subgrid variability in the landscape to be taken into account. MESH then permits the routing of water and transfers of energy between tiles (within a grid) and between grids. This is achieved through the two main components of MESH: a tile connector and a grid connector. The tile connector currently consists of a simple aggregation of results from the tile process algorithm. This system does not allow for transfer of water between tiles, but runoff between tiles will be accommodated by the 'fill and spill' method (where lake or pond tiles fill to a defined volume and then spill downstream), or by the transfer of blowing snow between tiles. The grid connector in MESH routes flow volumes to and from successive grids.

The two main advantages of the MESH modelling system are that

This not only means that researchers and end-users can use it and modify it freely, but also that MESH will continue to improve over the years, benefitting from improvements made to the modelling system for both research-related and operational purposes. The development of MESH ties directly into a series of existing projects and programs in Canada including the Drought Research Initiative (DRI, another CFCAS Network), the National Agri-Environmental Standards Initiative (NAESI), the International Polar Year (IPY), and IP3.

A paper describing MESH and its applications is available here: more information is available from the MESH wiki.

How to obtain MESH
Environment Canada's Hydrometeorology and Arctic Laboratory, with support from IP3, IPY, and DRI, has produced a stand-alone version of the MESH system, which is available for download here.

If you have any enquiries relating to MESH, please contact Brenda Toth, the MESH coordinator.

We have also established a MESH forum to provide a vehicle for feedback and discussion.

Events and Training
If you would like to receive details of forthcoming MESH events and training courses, please contact the IP3 Network Manager

MESH Modelling Training Course
8 September 2011; Saskatoon, SK
Environment Canada National Hydrology Research Centre

IP3 held a MESH Workshop as part of the network's wrap-up workshop: Program

MESH Modelling Training Course
1 October 2009; Edmonton, AB
Alberta Sustainable Resource Development's Computer Lab/Training Room

MESH/CLASS Training Course (part of the 'Theme 3 - Prediction' Workshop)
16-17 March 2009; Waterloo, ON
Wilfrid Laurier University