Investigating Relationships between Landscape,
Snowcover Depletion, and Regional Weather and Climate
Using an Atmospheric Model
Ethan M. Greene1, Glen E. Liston1, and Roger A. Pielke, Sr.1
The effects of landscape change have long been acknowledged as an important element of the cli-
mate system, and in recent years the climate-related effects of anthropogenic changes to the land
surface have become an important research topic. This study strives to improve our understanding of
the effects of landscape changes on winter and spring snow-related processes and on regional weath-
er and climate.
A climate version of the Regional Atmospheric Modeling System (CLIMRAMS) is used to investi-
gate the effects of landscape change on seasonal snow depletion and its corresponding effects on
atmospheric and hydrologic processes. Two simulations of the 1996 spring melt season in the Rocky
Mountains and Northern Great Plains are compared. The first simulation utilizes the present-day
vegetation distribution, and the second uses the same vegetation distribution with the exception that
all forested regions are replaced by grassland. This numerical deforestation affects 18% of the do-
main.
In the model the vegetation changes alter the leaf area index, transmissivity to incoming solar radia-
tion, roughness length, and surface albedo. Additional snow-related differences occur because the
snow lying over grass, and the snow under the forest canopy, exist in dramatically different radiative
and thermal regimes. The snowcover changes resulting from the simulated deforestation influence
the surface radiation balance, which leads to changes in surface sensible and latent energy fluxes,
evaporation/transpiration rates, melt rates, and air temperature. The landscape changes cause the air
temperature to be cooler in the winter and warmer in the summer.
Through hydrologic-transport processes, the effects of the landscape change teleconnect to unmodi-
fied regions. The surface snow-free date and runoff season were dramatically affected. The snow-
free date came nearly three weeks early in the deforested case, and the runoff season decreased by
nearly four weeks. The deforestation also modifies snowcover depletion rates, which in turn cause
variations in maximum values of runoff production. This numerical deforestation experiment sug-
gests that landscape changes can significantly alter the surface energy and moisture budgets, hydro-
logic cycle, and regional weather and climate.
1
Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado 80523-1371 USA
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