The sensitivity of the land surface to the parameter values: a reassessment

The sensitivity of a land surface scheme to the values chosen for individual parameters is assessed by linking the scheme to a Single Column Model which included surface-atmosphere feedbacks. The land surface scheme (Biosphere-Atmosphere Transfer-Scheme, BATS) is found to be most sensitive to the roughness length, the fractional vegetation cover and the rooting ratio. This contrasts with other studies which did not identify the rooting ratio as important. However, the ranking of BATS' sensitivity to model parameters is dependent on the length of simulation, the type of vegetation simulated, the method of assessment of sensitivity and the magnitude of the change in the parameter values. The identification of the rooting ratio as the most important parameter in BATS (for a tropical forest) is a problem since there are few data on how to specify it for all vegetation types in global climate model simulations. -Author