A revised hydrology for the ECMWF model: Verification from field site to terrestrial water storage and impact in the Integrated Forecast System
The Tiled ECMWF Scheme for Surface Exchanges over Land (TESSEL) is used operationally in the Integrated Forecast System (IFS) for describing the evolution of soil, vegetation, and snow over the continents at diverse spatial resolutions. A revised land surface hydrology (H-TESSEL) is introduced in the ECMWF operational model to address shortcomings of the land surface scheme, specifically the lack of surface runoff and the choice of a global uniform soil texture. New infiltration and runoff schemes are introduced with a dependency on the soil texture and standard deviation of orography. A set of experiments in stand-alone mode is used to assess the improved prediction of soil moisture at the local scale against field site observations. Comparison with basin-scale water balance (BSWB) and Global Runoff Data Centre (GRDC) datasets indicates a consistently larger dynamical range of land water mass over large continental areas and an improved prediction of river runoff, while the effect on atmospheric fluxes is fairly small. Finally, the ECMWF data assimilation and prediction systems are used to verify the effect on surface and near-surface quantities in the atmospheric-coupled mode. A midlatitude error reduction is seen both in soil moisture and in 2-m temperature.
Plain English Discussion
Forecasts from the European Weather Centre now use this new model to describe how rainfall flows through the soil; how some is taken up by the roots of plants and trees and some flows into rivers. And how snowfall accumulates on the surface, reflecting sunlight; and slowly melting and infiltrating into the soil. These changes improve the accuracy of forecasts of air temperature
Balsamo, G., P. Viterbo, A. Beljaars, B. van den Hurk, M. Hirschi, A.K. Betts and K. Scipal (2009), A revised hydrology for the ECMWF model: Verification from field site to terrestrial water storage and impact in the Integrated Forecast System., J. Hydrometeorol., 10, 623–643. ECMWF Tech. Memo 563. http://www.ecmwf.int/publications/library/ecpublications/_pdf/tm/501-600/tm563.pdf http://ams.allenpress.com/perlserv/?request=get-abstract&doi=10.1175%2F2008JHM1068.1