The 14th Conference on Hydrology

4B.7
THE ISBA SCHEME AND ITS OWN SOIL MOISTURE ASSIMILATION OPERATIONAL AT METEO-FRANCE

Eric Bazile, Toulouse, France; and D. Giard

Major changes have been introduced in the description of the soil-atmosphere-vegetation interactions in the global NWP model ARPEGE. An updated version of the so-called ISBA scheme, with a parametrization of soil water freezing, is now used to describe exchanges over land surface. Besides, a new soil moisture analysis has been introduced, based on the 2m temperature and relative humidity forecast errors through an optimal interpolation scheme. All these modifications have become operational on 1998/03/16, simultaneously in the global variable resolution NWP model (ARPEGE-25km over France) and in the Limited Area Model (ALADIN). Two experiments -with and without the parametrization soil water freezing- of one-year long assimilation (upper air and soil moisture), covering 1997, have been performed with a lower model resolution (T79, without streching). The impact of the soil water freezing will be presented. The annual cycle of soil temperature and soil moisture are preserved and no drift has been noticed. These experiments have also been used to produce a first approximation of the climatological fields (soil moisture and soil temperature) required by the operational model.

The 14th Conference on Hydrology