In a novel approach to represent the coupling between the land surface and atmosphere, DHI and DMI (Danish Meteorological Institute) are exploiting OpenMI technology to link hydrological and climate models. Modelling the effects of climate change on the hydrological cycle requires a proper understanding of the water and energy exchange between the atmosphere and the land surface. This exchange is a process that can have a significant impact on the hydrological cycle under a changing climate. OpenMI provides a practical way of linking the achievements of the meteorological and hydrological modelling community.
Climate change
While there is evidence of increases in both severe droughts and heavy rains, (Huntington, 2006) and changes in the magnitude and distribution of both precipitation and evapotranspiration, there is still considerable uncertainty in quantifying the effects on hydrological systems from climate change. Traditionally, the hydrological impacts of climate change have been based on driving hydrological models with the output of regional climate models, (e.g. Graham et al., 2007). This means that the feedbacks to the atmosphere are neglected, which has an unknown impact on the predictions of climate change, particularly at the local scale. These climate models often operate at spatial and temporal scales that are much larger than the scales required to analyse the effects on the hydrological system. Furthermore the representation of the hydrology in these climate models is often very simplified and therefore not suitable for detailed hydrological analyses.
OpenMI
To develop improved methods for assessing the effects of climate change on water resources, a coupled hydrological and climate modelling system is being developed using two state-of-the-art model codes: the climate model code HIRHAM (Christensen et al. 1996) and the hydrological model code MIKE SHE (Graham and Butts, 2006). OpenMI technology is used to link these two existing model systems. This work is being carried out in the HYACINTS project supported by the Danish Strategic Research Council. OpenMI provides a standardized interface to define, describe and transfer data on a time basis between software components that run simultaneously, thus supporting systems where feedback between the modelled processes is necessary (Gregersen et al., 2007). Therefore, OpenMI is ideally suited to linking hydrological and climate models and allows linking with different spatial and temporal representations and across different platforms. This new technology will also be effective in linking the meteorological and hydrological modelling communities.
MIKE SHE
MIKE SHE is an advanced, flexible framework for hydrologic modelling (Butts et al., 2004; Graham & Butts 2006). MIKE SHE covers the major processes in the hydrological cycle and includes process models for evapotranspiration, overland flow, unsaturated flow, groundwater flow, and channel flow and their interactions. Each of these processes can be represented at different levels of spatial distribution and complexity according to the goals of the modelling study, the availability of field data and the modeller’s choices, (Butts et al. 2004).
A new energy-based evapotranspiration model has been implemented in MIKE SHE (Overgaard et al., 2007) and will be used to model the feedback processes between the land surface and atmosphere. This new evapotranspiration model was successfully evaluated against observations (see below) of energy fluxes collected during the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE). FIFE was conducted in a 15x15 km area near Manhattan, Kansas, in and around the Konza Prairie.
HIRHAM
HIRHAM is a regional atmospheric climate model (Christensen et al. 1996) based on a subset of the HIRLAM (Undén et al, 2002) and ECHAM models (Roeckner et al, 2003), combining the dynamics of the former model with the physical parameterization schemes of the latter. The original HIRHAM model was developed in collaboration between DMI, the Royal Netherlands Meteorological Institute (KNMI) and Max Planck Institute of Meteorology (MPI). HIRHAM has been widely used in regional modelling studies including the EU projects PRUDENCE and ENSEMBLES. Throughout the last two years a new and improved version of the model has been developed at DMI and at the Alfred Wegener Institute in Potsdam.
A PhD study is being carried out in connection with these activities by PhD Søren Højmark Rasmussen
This news article has been derived from a number of recent publications.
REFERENCES
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Christensen JH, Christensen OB, Lopez P, van Meijgaard E, Botzet M (1996) The HIRHAM4 Regional Atmospheric Climate Model; DMI Scientific Report 96-4. Danish Meteorological Institute. Christensen JH,
Christensen JH, Christensen OB (2007) A summary of the PRUDENCE model projections of changes in European climate by the end of this century, Climatic Change, doi: 10.1007/s10584-006-9210-7.
Graham, D.N. and M. B. Butts, Flexible, integrated watershed modelling with MIKE SHE. In Watershed Models, Eds. V.P. Singh & D.K. Frevert, pp 245-272, CRC Press. ISBN: 0849336090. (2005)
Graham LP, Hagemann S, Jaun S, Beniston M (2007) On interpreting hydrological change from regional climate models, 81 Suppl. 1, 97-122. doi: 10.1007/s10584-006-9217-0
Gregersen JB, Gijsbers PJA, Westen SJP (2007) OpenMI: Open modelling interface. Journal of Hydroinformatics, 09.3, 175-191. doi: 10.2166/hydro.2007
Huntington, T.G., 2006: Evidence for intensifi cation of the global water cycle: Review and synthesis. J. Hydrol., 319, 83−95.
Overgaard J, Butts MB, Rosbjerg D (2007) Improved scenario prediction by using coupled hydrological and atmospheric models. In: Quantification and Reduction of Predictive Uncertainty for Sustainable Water Resources Management (Eds: Boegh E, Kunstmann H, Wagner T, Hall A, Bastidas L, Franks S, Gupta H, Rosbjerg D Schaake J), IAHS Publ. 313, 242-248.
Overgaard J., M. Butts, D. Rosbjerg, J. Gregersen (2006) Coupling hydrological and meteorological models using OpenMI to investigate land-use and climate change. Proceedings of the 7th International Conference on Hydroinformatics Editted by P. Gourbesville, J. Cunge, V. Guinot, S-Y Liong., HIC 2006, Nice, France, September 2006, Vol III, 2040-2047.
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