Rd. Koster et Mj. Suarez, THE COMPONENTS OF A SVAT SCHEME AND THEIR EFFECTS ON A GCMS HYDROLOGICAL CYCLE, Advances in water resources, 17(1-2), 1994, pp. 61-78
'Bucket'-type land surface models are being replaced in some general c
irculation model (GCM) climate studies by 'SVAT' (Surface Vegetation-A
tmosphere Transfer) models, which feature an explicit treatment of veg
etation control over the surface energy balance. The evaporation calcu
lations of a typical SVAT model differ from those of a bucket model in
at least four fundamental ways: (a) the SVAT model typically allows a
greater variety of environmental stresses to limit evapotranspiration
; (b) it generally includes a canopy interception reservoir; (c) the c
ontrol of the land surface over evaporation in a SVAT model is influen
ced by the atmosphere; and (d) the land surface control in a SVAT mode
l varies on short time scales. Global fields and grid square diurnal c
ycles illustrate the hydrological cycle produced in a 20-year simulati
on with an atmospheric GCM coupled to a SVAT model. A sensitivity anal
ysis then examines the relative importance of the SVAT/bucket differen
ces in terms of their effects on the simulated hydrological cycle. The
interception reservoir exerts more control over global evaporation th
an does either the vapor pressure deficit stress or the temperature st
ress. The effect of the temperature stress is, in fact, insignificant.
The time variability of land surface control over the surface energy
balance in a SVAT model significantly increases moisture convergence o
ver land.