cloud and land surface...
TRANSCRIPT
Max-Planck-Institut für Meteorologie
Cloud and land surface interactions
Cathy Hohenegger1 and Christoph Schär2
1 Max Planck Institute for Meteorology, Hamburg, Germany 2 ETH Zurich, Zurich, Switzerland
Max-Planck-Institut für Meteorologie
Deforestation in Amazon: § Increases precipitation? 6
§ Decreases precipitation ? most
§ No effect on precipitation? 1
Max-Planck-Institut für Meteorologie
12
15
0 4 8 12 16 20 24Local Time (h)
9
6
3
12
15
0 4 8 12 16 20 24Local Time (h)
9
6
3
GCM: Parameterized convectionObservations
Prec
ipita
tion
(mm
day-1
)
LAND OCEAN
Max-Planck-Institut für Meteorologie
Convection, sunny summer day, Europe
Max-Planck-Institut für Meteorologie
Forest Deforested area
Convection, Amazon
(NASA Earth Observatory)
Max-Planck-Institut für Meteorologie
(Qian 2008)
Precipitation, maritime continent
Max-Planck-Institut für Meteorologie
Vegetation, precipitation, dry and wet seasons, Sahel
NDVI March NDVI September
Precipitation March Precipitation September
(NASA Earth Observatory)
Max-Planck-Institut für Meteorologie
Precipitation over wet/dry surfaces
Time [h]
Pre
cipi
tatio
n [m
m h
-1]
Moist Dry
0.4
0.3
0.2
0.1
0.6 10 14 18 22
(Thomas Frederikse)
Max-Planck-Institut für Meteorologie
(Malte Rieck)
HOM
HET
Precipitation over homogeneous/heterogeneous surfaces
Time [h]
Pre
cipi
tatio
n [m
m h
-1]
HET HOM
Max-Planck-Institut für Meteorologie
(Stockli et al.)
Summer heat wave 2003
Max-Planck-Institut für Meteorologie
§ Location of clouds and precipitation § Timing of clouds and precipitation § Precipitation amounts
Generates typical spatial and temporal patterns
§ the mean climate over a region § climate extremes § climate variability
Role of land surface for climate change
Land surface influences
Max-Planck-Institut für Meteorologie
1. When and where is the land surface important for clouds and precipitation?
2. How does the land surface affect clouds and precipitation?
3. What are the possible effects of the land surface on clouds, precipitation and the overall climate?
Goals
Max-Planck-Institut für Meteorologie
1. Basic concepts and processes
2. Feedbacks
1. Static heterogeneity
2. Homogeneous surface conditions
3. Dynamic heterogeneity
3. Extremes
Outline
When is land surface important?
How does LS and RR couple?
Climatic effects?
Max-Planck-Institut für Meteorologie
What makes the land surface special…
Human influence
Spatial variability
Temporal variability
Memory
Strong coupling to climate
On average: 1-2 months
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What makes it difficult….
Synoptic variability
Mathematical description
Scales
Tree=sun+water-fire…
Max-Planck-Institut für Meteorologie
Important relations Basic concepts and processes
Max-Planck-Institut für Meteorologie
Important relations Basic concepts and processes
ETpot = ρqsat(Ts)− q
raPotential evapotranspiration
Penman-Monteith combination formula ETpot =Γ
L(RN −G) + (1− Γ)ρ
qsat(T )− q
ra
Γ =∂qsat
∂T∂qsat
∂T + cpL
SWnet + LWnet = SH + L · ET +G
∂S
∂t= P − ET −R
Surface energy budget
Water balance equation
Evapotranspiration ET = ρqsat(Ts)− q
ra + rs
Evapotranspiration depends both on energy, atmospheric conditions, and land surface conditions!
Max-Planck-Institut für Meteorologie
Control on ET Basic concepts and processes
(Hartmann 1994)
Max-Planck-Institut für Meteorologie
Control on ET Basic concepts and processes
(Teuling 2009)
Rather surface controlled Energy controlled
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Control on ET Basic concepts and processes
(Budyko 1955) Rn/(L*P)
Max-Planck-Institut für Meteorologie
Budyko method Basic concepts and processes
Eva
pora
tive
fract
ion
Soil moisture content Θ Θwilt Θcrit
Dry Transitional Wet
Soil moisture limited Energy limited
Max-Planck-Institut für Meteorologie
Budyko method Basic concepts and processes
(Koster et al. 2009)