A Comparison of Four Snow Models Using Observations
from an Alpine Site
Richard Essery1, Eric Martin2, Herv Douville3,
Alberto Fernndez4, and Eric Brun2
Snow can greatly increase the albedo of a surface, reduce its roughness, insulate the underlying
ground from the atmosphere, and store or release large amounts of water. Models of snowpack pro-
cesses are thus needed for a wide range of applications, from forecasting floods and avalanches to
simulating long-term changes in climate, and many different models have been developed. To inves-
tigate the performance of snow models, the International Commission on Snow and Ice working
group on Snow and Climate is planning a snow model intercomparison project (SnowMIP). A
detailed comparison will be made between a wide range of snow models using data from several
sites with different climates and characteristics. The results and discussion presented here are taken
from a pilot study with more modest aims; results from four models with differing complexities are
compared with observations made during two contrasting winters at a site in the French Alps.
The following are models compared:
UKMO -- A simple model used in the Hadley Centre climate model and the UK Meteorolog-
ical Office forecast model;
ISBA -- A physically based model developed for use in the Mto-France ARPEGE GCM;
INM -- Another physically based model, developed at the Instituto Nacional de Meteo-
rologa for hydrological forecasting;
CROCUS -- A sophisticated snow model developed at the Centre d'tudes de la Neige for
avalanche forecasting.
Hourly measurements of air temperature, humidity, windspeed, precipitation, shortwave radiation,
and longwave radiation were used to drive the models. Model results are compared with observa-
tions of snow depth, water equivalent, surface temperature, albedo, and runoff.
The models all perform reasonably well in simulating the duration of snow cover for both winters
studied, but they differ in their predictions of peak accumulation. Differences in how the models
represent storage of liquid water in snow and exchanges of energy with the atmosphere lead to
significant differences.
A paper discussing the results of this comparison and making recommendations for SnowMIP has
been submitted to Climate Dynamics.
1
Hadley Centre, UK Meteorological Office, UK
2
Centre d'Etudes de la Neige, Mto-France, France
3
Centre National de Recherches Meteorologiques, Mto-France, France
4
Instituto Nacional de Meteorologa, Spain
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