JULES Snow Module Development Richard Essery, Martin Best ...

JULES Snow Module Development
Richard Essery, Martin Best, Cecile Menard
Andy Wiltshire, Chawn Harlow, Dan Bewley

MOSES Snow Model
• Single model layer combined with top soil layer
• Combined surface energy balance for snow
and snow-free fractions
• Fixed density
• No storage of liquid water
• No refreezing of liquid water
• No partitioning of snowfall between canopy
interception and throughfall

JULES: point or gridbox model?
Vertical model development:
• Multi-layer snow model (Martin)
• Microwave emission modelling (Chawn)
• Exposed vegetation over snow (Cecile, Andy)
Horizontal model development:
• Partial snow cover (Andy)
• Snow redistribution (Cecile)
• Generalized tiles

Multi-layer Snow Module for JULES
800
600
400
200
0
A S O N D J F M A M J J

Snow and Vegetation
CAN_MODEL = 1-3:
All snow held in canopy
→ low albedo, high roughness, T * ≤0°C
→ high energy for sublimation and melt
CAN_MODEL = 4:
Snow partitioned and LW coupling
between canopy and ground
No SW transmission (dense canopy)

Snow and Vegetation

Snow and Vegetation

Snow and Vegetation
T 1
f v
H v
r a
H
Canopy
T v
r v
T a
r S
H S
T s
Snow
Ground

Partial Snowcover
1
0.8
0.6
f
0.4
0.2
0
0 50 100 150 200
SWE (mm)

Energy Balance of Partial Snowcover
0.8
0.6
Measured
Tiled surface
Composite surface
Albedo
0.4
0.2
0
140 150 160 170 180
Day (1999)

Blowing Snow: Horizontal Interaction Between Tiles
q s
o
q s
s
q t
s
q t
o q t
s
l o
l s
300
Open
Shrubs
Shrubs
SWE (mm)
200
100
Snowfall
Open
0
0 0.5 1 1.5 2
Shrub height (m)