6. One paragraph description of your model (e.g. abstract from report or
   paper);

Net radiation at the land surface is partitioned into sensible, latent, ground
and snowmelt heat fluxes. Ground heat fluxes and surface temperatures are
calculated using a soil model with four layers extending to about 2 m below the
surface. Insulation of the ground by a snowpack, assumed to have a constant
density, is represented by reducing the thermal conductivity of the surface
layer when there is lying snow; the conductivities of the snowpack and the
surface soil layer are combined in series. Model vegetation cover is derived
from the Wilson and Henderson-Sellers (1985) land cover classification. A
snow-free roughness length, a snow-free albedo and a cold deep-snow albedo are
specified for each vegetation type. Surface roughness lengths and albedos are
interpolated between snow-free and deep-snow values, according to snow depth.
The albedo is decreased as a simple representation of aging when the surface
temperature exceeds -2C. After the surface temperature reaches 0C, subsequent
net energy input to the snowpack is used to melt snow, and the resulting melt
water is passed to the hydrology routine, which calculates infiltration and
run-off. A single unfrozen soil moisture store is used, but a multi-layer
hydrology scheme which represents freezing and thawing of the soil has been
developed.

50. Please provide references relevant to the model description and use.

Essery, 1998: Snow modelling in the Hadley Centre GCM,
Physics and Chemistry of the Earth, 23 (5/6), 655-660.

Essery. Boreal forests and snow in climate models.
Submitted to Hydrological Processes.

Essery (1997). Seasonal snow cover in the Hadley Centre GCM. 
Ann. Glaciol., 25, in press.

Essery (1997). Modelling fluxes over heterogeneous snow cover.
Ann. Glaciol., 25, in press.

Foster et al. (1996). Snow cover and snow mass intercomparisions of general
circulation models and remotely sensed datasets. 
J. Climate, 9, 409-426.

Foster et al. (1996). Snow mass intercomparison in the boreal forest from
general circulation models and remotely sensed datasets.
Polar Record, 32, 199-208.

Foster et al. (1995). Snow cover and snow mass estimates from remote sensing,
climatology and the United Kingdom Meteorological Office general circulation
model.
Proc. ESA/NASA Passive Microwave Workshop, St. Lary, France.

Foster et al. (1994). Intercomparison of snow cover and snow mass in North
America from general circulation models and remote sensing.
Proc. Sixth Conf. on Climate Variations, Nashville, TN, Amer. Meteor. Soc.,
207-211.

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Richard Essery                Phone : 01344 854501
                              Fax   : 01344 854898
H303                          Email : rlhessery@meto.gov.uk
Hadley Centre
Met. Office
London Road
Bracknell, Berks.
RG12 2SZ
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