Atmospheric and surface processes

Surface and near-surface aspects of the weather forecasts are often given great attention since they affect many people in a very direct way. The research area will continue the development of processes, data assimilation and methods to improve the NWP system and, in the long run, the weather forecasts. 

Besides the general citizen’s interest in forecasts we also have special interest groups related to road conditions, agricultural farming, forestry, rescue services, constructing sector and many more. We know that success in surface and near-surface aspects of our forecasts require a great performance of many components of our NWP system. A good representation of the processes through parameterizations is crucial. Data assimilation can help to compensate for discrepancies in parameterizations, but not all the way. We see a general trend among NWP institutes towards multi-layer descriptions of soil, snow and vegetation components. The motivation for this is partly because more precise parameterizations simply perform better themselves, and now we have reached this level, but also because we need a better representation of the surface to support observation operators for satellite radiances in our data assimilation systems.

The development in big data related to e.g. satellite and crowdsource observations is huge. To utilise these observations we need short term research and development efforts related to the algorithms for atmosphere and surface data assimilation and, on the longer term, we need continuous activities related to coupled atmosphere-surface data assimilation systems which includes development of observation operators. There are also potentials beyond classical NWP surface processes and areas in e.g. hydrological, hydrodynamic and urban areas. An example is river discharge and water levels in rivers and lakes which have not been much considered by the NWP community until now.


The main objective is to identify and improve components of the ACCORD NWP system, especially the atmospheric physics packages and SURFEX, which strengthen our ability to simulate the physical evolution processes. In the atmosphere this concerns e.g. radiation, hydrometeors and turbulence. At the surface this concerns parameterizations related to different tiles (land, urban, sea, lakes), observations (e.g. crowdsource and satellite) and surface data assimilation algorithms (e.g. EKF, EnKF). Also processes related to the atmosphere-surface interface are considered. 

The atmospheric physical processes are parameterized in a number of model packages related to radiation, microphysics, shallow convection and turbulence. Although they are separate in some aspects they are also tightly connected and any single package cannot be easily replaced by another version without affecting the performance as a whole. Thus, development of these packages themselves is a very sensitive and tedious process.

International collaboration

The European NWP context, represented by the new ACCORD consortia, the MetCoOp/UWC operational environment and ECMWF, will remain our most important research and development platforms. Beyond that, more or less short- or long-term collaboration constellations can appear and contribute hugely to research and development. That NWP now strives beyond classical NWP areas also opens wider doors to collaboration with SMHI R&D groups in climate, satellite, chemistry and dispersion modelling, urban and hydrology teams. Thus, activities related to coupling between traditionally separated model systems should increase such as atmosphere and dispersion modelling (aerosols and chemistry), atmospheric chemistry and air-pollution models, atmosphere and ocean and NWP system and hydrology.