Transcript The Impact of Aerosols and Climate on Biogenic VOC Emissions

Coupling of the Common Land
Model (CLM) to RegCM in a
Simulation over East Asia
Allison Steiner, Bill Chameides, Bob Dickinson
Georgia Institute of Technology
Atlanta, GA, USA
Jeremy Pal, Filippo Giorgi
ICTP, Trieste, Italy
ICTP Workshop on the Theory and Use of Regional Climate Models
3 June 2003
Outline of Talk

Part I: Coupling of CLM to RegCM
Model simulation over East Asia
Comparison to BATS simulation

Part II: Application of Coupled Model
Aerosol simulation
Land surface feedbacks
Common Land Model (CLM)
New land surface
package for climate models

CLM
developed as part of
NCAR Community System
Model (CCSM)
- Community effort model
-Offline model validation (Dai et
al., 2003)
-Coupled to the CCM3 (Zeng et
al., 2002, Bonan et al., 2002)
BATS currently
implemented in RegCM
(Dickinson et al., 1993)

ATMOSPHERE
Dynamics,
Radiation
energy
momentum
mass (trace gases)
LAND
SURFACE
MODEL
BATS/CLM comparison
BATS
CLM
One canopy layer
Simple stomatal
conductance model
No photosynthesis
One canopy layer
Sunlit/shaded leaves
Stomatal resistancephotosynthesis model
One snow layer
3 soil layers
Soil T: Force-restore
Soil moisture:
Diffusive/gravitational
TOPMODEL runoff
Up to five snow layers
10 uneven soil layers
Soil T and moisture:
Solved numerically
Includes liquid H2O/ice
Part I: Simulation Specifics
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Domain: East Asia
60km resolution
Two month spinup
One year simulation
(Aug 94 - Aug 95)
Two runs: one
BATS, one CLM
Similar land cover
characteristics
Kuo, SUBEX precip
schemes
Precipitation
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East Asian Monsoon:
dry winters, wet
summers
Winter, Spring: Both
models overpredict
CLM slightly less
precip annually and in
summer
Use of CLM does not
strongly affect
precipitation
Temperature

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Surface temperatures
underestimated for
both simulations
CLM tends to improve
winter cold bias by ~1
degree
CLM slightly amplifies
diurnal cycle
Surface Energy Balance

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CLM absorbs more
radiation due to
lower albedos
CLM simulates
more sensible heat
flux and less latent
heat flux
Surface Water Balance
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CLM has less
precipitation
CLM simulates more
runoff than BATS
CLM simulates less
evapotranspiration
Annually, less water
entering the soil in
CLM
Evapotranspiration
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CLM has less
ground
evaporation
BATS/CLM
canopy
evaporation
similar
CLM has more
transpiration
Soil Moisture

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CLM increases
surface soil water
(first 10cm)
But decreases root
zone soil water (first
~1-2 m)
Related to changes
in
evapotranspiration
components
Snow and Albedo Feedbacks

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CLM has less snow at
surface
CLM has warmer air
temperatures, indicating
less snowfall
Snow parameterizations
are quite different (e.g.,
melt and layer structure)
Snow and albedo
feedbacks are likely
contributing to
temperature differences
Summary of Part I
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CLM simulates seasonal cycle in East Asia
CLM slightly improves winter cold bias
Surface hydrology simulated differently
between BATS and CLM
CLM simulates much less snow than BATS
over East Asia
Part II: Aerosol-Surface Feedbacks
AEROSOL
CANOPY
Leaf Temperature
Stomatal resistance
Photosynthetic rate
ATMOSPHERE
Radiation
Air temperature
Relative humidity
Cloud
Precipitation
SURFACE FLUXES
SOIL
Soil moisture
Evapotranspiration
Sensible heat flux
Inclusion of Aerosols
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For East Asia, simulated offline aerosol fields
–
–
–
–
–
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Sulfate
Black Carbon
Organic Carbon
Ammonium
Nitrate
5 Day Simulation
2-6 July 1995
Direct Effect
Two runs
Control run (bkg
aerosols) and
aerosol run
Optical depth for aerosol simulation
Change in Absorbed
Photosynthetically Active Radiation
(APAR) (no aerosol-aerosol)
Sunlit APAR
Shaded APAR
Aerosol-Induced Change in
Photosynthesis
Sunlit Photosynthetic Rate
Shaded Photosynthetic Rate
Sunlit Leaf Photosynthesis
Dependent on Leaf Temperature
-1
12
-2
A (mmol CO2 m s )
14
10
8
6
4
2
0
-5
5
15
25
35
Leaf Temperature (oC)
45
Photosynthesis-Stomatal
Resistance Relationship

Represents the balance
between water loss and CO2
uptake
1
A
 m h p b
rs
A =
rs =
m,b
cs =
h =
cs
photosynthesis
stomatal resistance
empirical constants
surface CO2
vapor pressure
deficit term
s
1
A
 m hb
rs
cs
(Collatz et al., 1991)
Changes in the Surface Energy
Fluxes
Transpiration Flux
Sensible Heat Flux
Summary of Part II
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Under certain conditions, aerosols can
increase photosynthesis in sunlit leaves
Can alter surface energy balance
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–
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Increase transpiration
Reduce sensible heat
Implications for atmospheric boundary layer
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Temperature
Relative humidity
Cloud cover
Precipitation
Future Work
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Include in new RegCM version?
Validate snow over East Asia
Investigate tile capability of CLM
More investigation on aerosol-land surface
feedbacks
Acknowledgements
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NASA Earth System Science Fellowship
Filippo Giorgi, Jeremy Pal and PWC group