Model input data

The BETHY vegetation and surface modelling scheme derives its climatic input data largely from maps originally based on ground station meteorological observations. This insures a more realistic simulation of surface climate than it would be possible within a GCM. Input data all have a monthly time step and are converted to the 1° equal-area grid used here.

Monthly climatological means of precipitation, near-surface diurnal mean and amplitude are taken from the climatology of Cramer and Leemans [Cramer, pers. comm.][Leemans and Cramer, 1991], the number of wet days per month from Friend (pers. comm.) based on [Müller, 1982], and incident PAR from the International Satellite Cloud Climatology Project (ISCCP) [Pinker andLaszlo, 1992].

Other input data are the global maps of soil brightness and land-cover by [Wilson and Henderson-Sellers, 1985], from which relative abundances of up to three vegetation types out of a list of 23 are derived. The 23 vegetation types are also assigned a list of values [Knorr, 1997] specifying photosyn-thetic capacity [Beerling and Quick, 1995] and pathway, phenological type, height, and leaf area per dry mass [Schulze et al., 1994]. For reasons of compatibility with the ECHAM-4 climate model (cf. above), the total soil waterholding capacity, wx, is taken from published data [Patterson, 1990], and converted to wmax by taking 65% of that value. This allows translating adjusted fields of wmax, - after assimilation - again into saturated soil-water content, to be used in a sensitivity test with ECHAM-4.

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