Geoscience Reference
In-Depth Information
Requirements from SVATS
: modern SVATS can be complex and may calculate
many variables but the motivating purpose for calculating these additional
values remains to calculate the time evolution of the limited set of area-
average requirements listed in Table 24.1.
●
Early SVATS
: originally SVATS prescribed fixed, globally-applied surface
parameters (e.g., surface roughness, albedo, emissivity, etc.) and used a sim-
ple 'bucket model' for surface energy partition, but using these in GCMs
demonstrated the sensitivity of modeled climate to changes in these
parameters.
●
Micrometeorological SVATS
: subsequent development resulted in a genera-
tion of SVATS, here called 'micrometeorological' SVATS, that were fairly
detailed one-dimensional models of the interactions of different uniform
vegetation canopies that strictly only apply at the scale of a few hundred
meters.
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Hydrological improvements in SVATS:
further development sought
improvements in SVATS' ability to describe hydrological processes,
including:
●
— improving basic parameterizations of hydrologic processes such as
infiltration, surface runoff, subsurface runoff and snow processes;
— representing the effects of subgrid spatial variability due to heteroge-
neity of soil properties, topography, vegetation and precipitation using
statistical-dynamical approaches.
'Greening' of SVATS:
recognition of potential climate change caused a major
shift in direction in SVAT development toward providing improved capabil-
ity to simulate CO
2
exchange, and this shift resulted in a substantial revision
in the preferred representation of plant stomatal behavior in SVATS (e.g.,
from the Jarvis-Stewart to the Ball-Berry parameterization).
●
Ongoing development of SVATS:
current development is concerned with
addressing more difficult aspects of surface-atmosphere interactions includ-
ing the impacts of surface-groundwater interactions on the land-atmosphere
system, and hydraulic redistribution (or hydraulic lift).
●
Future value of SVAT development:
further developments of SVATS that
add complexity will not necessarily improve their performance in climate
and weather prediction, more likely it will improve ability to interpret pre-
dicted weather and climate in terms of their impact on human welfare and
ecological status.
●
References
Ball J.T., Woodrow I.E. and Berry J.A. (1987) A model predicting stomatal conductance and
its contribution to the control of photosynthesis under different environmental
conditions. In: Biggins, I. (ed.)
, Progress in Photosynthesis Research, vol.
IV
pp.
221
-
224.
Martinus-Nijhoff Publishers, Dordrecht, The Netherlands.
