Frei, A. and D. Robinson, 1998: Evaluation of snow extent and
its variability in the Atmospheric Model Intercomparison Project.
J. Geophysical Research - Atmospheres , 103, 8859-8871.
Simulations of monthly mean Northern Hemisphere snow extent
from 27 Atmospheric General Circulation Models (GCMs), run under the auspices
of the Atmospheric Model Intercomparison Project (AMIP), are compared to
observations. AMIP model runs have common values for sea surface
temperatures specified from observations for the decade 1979 through 1988.
Here, AMIP GCMs are evaluated in terms of their simulations of (1) snow
extent over Northern Hemisphere lands; and (2) synoptic conditions associated
with extremes in snow extent over particular regions. Observations of snow
extent are taken from digitized charts of remotely sensed snow extent from
visible imagery provided by the National Oceanic and Atmospheric Administration.
In general, AMIP models reproduce a seasonal cycle of snow extent similar
to the observed cycle. However, GCMs tend to underestimate fall and
winter snow extent (especially over North America), and overestimate spring
snow extent (especially over Eurasia). The majority of models display
less than half of the observed interannual variability. No temporal
correlation is found between simulated and observed snow extent, even when
only months with extremely high or low values are considered. These
poor correlations indicate that interannual fluctuations of snow extent
are not driven by sea surface temperatures. GCMs are inconsistent
in their abilities to simulate synoptic scale tropospheric circulation
patterns associated with extreme snow extent over North American regions,
although some models are able to capture many of the observed teleconnection
patterns.