Geoscience Reference
In-Depth Information
Figure 9.6.
Basin averaged snow water equivalent (SWE) from March (approximately
the month of the annual maximum) from the 21 PILPS 2e land surface models (listed as
a-u) over the 1989-1998 period (from Bowling et al.,
2003
, by permission of Elsevier).
from 301 to 481 mm. For some models, subsurface runoff dominates, whereas for
others, runoff is solely from the surface. Differences in modeled snow accumula-
tion and surface-subsurface runoff partitioning contribute to large variations in the
shapes of mean hydrographs.
In a more recent effort, A. Slater et al. (
2007
) compared the performance of five
LSMs (CHASM, NOAH, CLM, VIC, and ECMWF) in their ability to simulate
hydrologic processes across the Arctic terrestrial drainage. All of the models were
forced by the same data derived from the ERA-40 atmospheric reanalysis for the
1980-2001 period. The primary conclusion is that no single model has the best or
worst performance when compared to observations - performance depends on the
variable, or variables, in question. As assessed for large Arctic-draining watersheds
such as the Lena, there is up to a 30 percent difference between the five models
in how annual precipitation is partitioned between runoff and evapotranspiration.
Capturing the correct base flow of rivers was found to be consistent problem, and
model hydrographs have a tendency to peak too early in summer, indicating that
snow melt occurs too early. The five models were found to have similar errors in
snow water equivalent while differing widely in snow quantities such as snowfall,
snow depth, and sublimation rates.
Figure 9.8
shows the annual cycle of monthly
