Sensitivity of the surface hydrology to the complexity of the land- surface parameterization scheme employed

The sensitivity of the surface hydrology to the parameterization scheme incorporated in three different AGCMs is investigated. It is found that the simulations of the surface hydrology by the NCAR CCM0 and GFDL models (which incorporate the bucket type hydrological parameterization) differ markedly from the CCM1B model (which incorporates the Biosphere Atmosphere Transfer Scheme, BATS). The AGCMs which incorporate the simpler parameterizations of the land surface simulate a number of physical phenomena unrealistically. Many of these gross problems in the land surface climatology are eliminated in the CCM1B model which incorporates BATS. When present-day and doubled CO₂ scenarios are compared, it is shown that the differences between model results incorporating different surface schemes are greater than the differences between 1 × and 2 × CO₂. The implications of these results are that the surface hydrological fields from AGCMs, and their predictions of climatic change at the land surface, are likely to be unreliable. -from Authors