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[email protected] HTAP, Geneva, Switzerland
March 20-22nd 2013
Discussion of Needs for Impact Assessment
Theme 4
Focus on O3 deposition for ecosystem risk assessment
Lisa Emberson
Stockholm Environment Institute (SEI), University of York
[email protected] HTAP, Geneva, Switzerland
March 20-22nd 2013
Process Flux (Tg yr-1)
Strat trop exchange 520 ± 200
Chem prod 5060 ± 570
Chem loss 4560 ± 720
Net chem term 500 ± 550
Deposition 1010 ± 220
Why is O3 deposition important ?
…for CTM mass balance
Vieno et al. (2010)
Model simulations that ‘turn-off’ deposition (red line)
estimate higher surface O3 concentrations
[email protected] HTAP, Geneva, Switzerland
March 20-22nd 2013
Process Flux (Tg yr-1)
Strat trop exchange 520 ± 200
Chem prod 5060 ± 570
Chem loss 4560 ± 720
Net chem term 500 ± 550
Deposition 1010 ± 220
Why is O3 deposition important ?
…for climate
Why is O3 deposition important ?
Stomatal
Ozone Flux
Human health Ecosystems
Flux-R
relationships
Derived from experimental
fumigation studies using the
DO3SE stomatal algorithm
…for ecosystem (and human health)
impact assessment
[email protected] HTAP, Geneva, Switzerland
March 20-22nd 2013
Why is O3 deposition important ?
[email protected] HTAP, Geneva, Switzerland
March 20-22nd 2013
But there are substantial uncertainties in the modelling of O3
deposition within global CTMs…
….most models will use 1 of 2 schemes
1. The Wesley Scheme (1989) most global CTMs?
2. The Pleim scheme (2001) CMAQ family of CTMs?
…but schemes may have been modified in CTMS???
3. The DO3SE model (2001) – a third scheme developed to estimate
deposition AND ecosystem effects….incorporated in EMEP
How can the flux based method be applied ?
....and only one of these scheme, the DO3SE model, relates stomatal
deposition directly to ecosystem effects....and this is currently based on
empirical data rather than plant processes
Why is O3 deposition important ?
[email protected] HTAP, Geneva, Switzerland
March 20-22nd 2013
Key aspects/uncertainties:
• Model formulations for
o Stomatal conductance (gsto,)
o Cuticular deposition,
o In-canopy chemical titration of O3,
o Effects of soil moisture stress on gsto and hence O3 deposition)
• Model parameterisation for different vegetation types / PFTs / biomes
o Leaf Area Index (LAI)
o Growing season
o Physiological response to environmental condition (flight, fT, fD, fSW)
• Availability of observational dataset to evaluate O3 deposition modelling
o Deposition velocity (Vg)
o O3 concentration [O3]
o H2O of CO2 flux (as proxy for gsto)
Which means that land cover (and associated dry deposition
parameterisation) is very important to determine O3 deposition as air parcels
travel over large distances
Ocean deposition
What influences O deposition?
What are the main differences in O3 dry deposition
schemes?
Wesely (1989) Pleim et al (2001) DO3SE (2003)
Surface
resistance terms
Stomatal, plant cuticle, in
canopy (buoyancy,
density, upper & lower
canopies) ground surface
Stomatal, plant cuticle, in
canopy, (empirical),
ground surface, LAI
Stomatal, plant cuticle, in
canopy, (empirical), ground
surface, LAI
Stomatal
resistance
Solar radiation, surface
air temperature
Species type, growing
season, photosynthetically
active radiation, surface air
temperature, vapour
pressure deficit, soil
moisture content
Species type, growing season,
photosynthetically active
radiation, surface air
temperature, vapour pressure
deficit, soil moisture content
Landcover
parameterisation
North America (?)
7 vegetation types and 5
seasonal categories (e.g.
Agricultural land -
Midsummer with lush
vegetation)
North America
25 vegetation types
European (& some Asian)
10 deposition cover types plus
>15 O3 sensitive target species
for effects estimates (with
climate region
parameterisations)
What can be done within HTAP ?
-to improve estimates of O3 dry deposition and estimates
stomatal O3 flux for ecosystem effects
1.Literature review of O3 dry deposition methods identify those most commonly used
within global scale CTMs
2. Identification of the key differences in these dry deposition schemes
3. Identification of the key differences in the parameterization (for different land
cover types)
4.Off-line assessment of the implications of differences in O3 dry deposition
schemes…comparison with observations from site-specific flux data and HTAP
model output
What can be done within HTAP ?
-to improve estimates of O3 dry deposition and estimates
stomatal O3 flux for ecosystem effects
1.On-line assessment of the effect O3 dry deposition schemes on hemispheric
transport of O3; regional O3 concentrations and regional O3 induced human health
and ecosystem damage.
Global modeling could show spatial fields of :
i. stomtal O3 flux;
ii. total O3 deposition;
iii.surface (canopy height) O3 concentration
𝑅𝑖 1+ 200 𝐺 + 0.1 −1 2 400 𝑇𝑠 40−𝑇𝑠 −1
𝑟𝑠𝑡𝑚𝑖𝑛
𝐹𝑙𝑖𝑔 ℎ𝑡 × 𝑓𝑇 ×𝑓𝐷 × 𝑓𝑆𝑊
𝑔𝑚𝑎𝑥 .𝑓𝑝ℎ𝑒𝑛 .𝐹𝑙𝑖𝑔 ℎ𝑡 .𝑚𝑎𝑥 𝑓𝑚𝑖𝑛 , 𝑓𝑇 .𝑓𝐷𝑓𝑆𝑊 −1
Wesley
Pleim
DO3SE
What can be done within HTAP ?
-to improve estimates of O3 dry deposition and estimate
stomatal O3 flux for ecosystem effects
2. HTAP modeling experiments
i. investigate S-R relationship for stomatal O3 flux and compare with
concentrations;
ii. alter key climate relevant characteristics:
o simulate an extended drought period,
o elevated CO2 effects on gsto, ????
o changes in surface ToC and RH% etc…)
on resulting stomatal O3 flux to indicate how ecosystem risk might change
under future climates…..but might need modification of gsto algorithms
iii.Investigate the role of landcover on O3 deposition and stomatal O3 flux
Global scale
Region1
Region2
Region4
Region3
Data output from models for off-line
analysis….covering key forest, crop & grassland
regions and lose to observation sites
What can be done within HTAP ?
Understand
HTAP
Science
Impacts
Policy
Design of HTAP
modelling experiments
Model tweaks
Policy
Model outp
ut
Common understanding
of key issues _ ICP
Vegetation
Terry’s workshops
Needs to be done in time to inform
the experimental design
• Effect of HTAP on N deposition in more pristine Northerly latitude ecosystems where as
little 5 kgN/ha/year may cause damage
• Effect of N & S on acidification…time development of damage to understand rates of
change of acidity and role of HTAP
• Effect of aerosols on radiation (total and diffuse fraction)….effect on photosynthesis and
hence ecosystems
• Effect of pollutants (N, O3, aerosol) on NPP and C sequestration….feedbacks to climate
Impacts
Patrick Büker et al. – Collaboration with the Task Force on Hemispheric
Transport of Air Pollution
Assessing HTAP effects on Ecosystems: Ozone and Aerosols
Lisa Emberson Stockholm Environment Institute,
Environment Department
University of York, UK
HTAP, Pasadena, California
Feb 1-4th 2012
Understand
HTAP
Science
Impacts Policy Design of HTAP
modelling experiments
Do we need to rethink a little the way we design these
experiments……to ensure they are policy relevant….?????
The HTAP Process ???
Understand
HTAP
Science
Impacts
Policy
Design of HTAP
modelling
experiments
Policy Impacts
Understand
HTAP
Science
Impacts Policy Design of HTAP
modelling experiments
Do we need to rethink a little the way we design these
experiments……to ensure they are policy relevant….?????
The HTAP Process ???
Understand
HTAP
Science
Impacts
Policy
Design of HTAP
modelling
experiments
Tweak models
Policy Impacts
Model outp
ut
e.g. ozone & ecosystem effects….
Conclusions from 2010 Assessment
Showed fairly substantial effect of HTAP on crop yields…causing
between 5 to 35 % of the O3 induced crop yield loss.
BUT…. By necessity, assessment used Concentration based indices....
....for 2015 we have the possibility to perform stomatal ozone flux
based ecosystem assessments in line with adopted LRTAP methods
What do we mean by flux/dry deposition?
Stomatal
flux/uptake/deposition Non-stomatal
flux/uptake/deposition
External plant
surfaces
Soil
Species,
cultivar,
Phenology,
Environmental
variables (e.g.
irradiance,
temperature,
VPD, Soil water
status, CO2
concentration)
What do we mean by flux/dry deposition?
Stomatal
flux/uptake/deposition Non-stomatal
flux/uptake/deposition
External plant
surfaces
Soil
Species,
cultivar,
Phenology,
Environmental
variables (e.g.
irradiance,
temperature,
VPD, Soil water
status, CO2
concentration)
Why is it important to use stomatal ozone flux rather than
concentration (W126, AOT40, M7 etc…) based metrics?
AOT40
2000
FLUX
2000
AOT40
2020
FLUX
2020
Simpson et al. (2007)
Flux is not so sensitive to
changes in peak O3
concentrations
Assuming gmax and rb = 50 s/m
AFst 6 in relation to O3 concentration
0
5
10
15
20
25
0 10 20 30 40 50 60
O3 (ppb)
Fs
t (n
mo
l O
3 m
-2 P
LA
s-1
)
AOT40
Wheat (450)
Potato (750)
AOT40 – only able to incorporate effect of rising global
background concentration above 40ppb
Why flux is less sensitive to O3 peaks And better for HTAP damage estimates ???
AFstY – able to differentiate species sensitivity to rising
background concentration
16 22
Detoxification threshold
Does stomatal ozone flux provide better estimates of O3
damage? ….Collation of evidence for effects important
AOT40 O3 flux
Mills et al., 2010
What tools exist to estimate flux and response ?
DO3SE: Ozone dry deposition and stomatal O3
flux model
FO3 = Vg * [O3]
Göteborg University
17 November 2011
Stomatal
Ozone Flux
Human health Ecosystems
Flux-R
relationships
Derived from experimental
fumigation studies using the
DO3SE stomatal algorithm
O3 dry deposition is an important component of making accurate O3
mass balance calculations ...
….with implications for human health.
Vieno et al. (2010)
Is this dry deposition term also important for accurate
estimates of the O3 budget ?
How can the flux based method be applied ?
The good news is that most dry deposition modules, embedded within
Ozone Chemical Transport Models (CTMs), include an estimate of
stomatal ozone flux
Variation in the length of crop growing seasons in the UK
Perhaps need to consider the early and late crops that might be more
susceptible to HTAP
Watson, (1947) Forests and grasslands
Extending to higher
elevations
Which means that land cover (and associated dry deposition
parameterisation) is very important to determine O3 deposition as air parcels
travel over large distances
Ocean deposition
How can the flux based method be applied ?
The bad news is that these CTMs embedded dry deposition schemes use
different methods....
....and only one of these scheme, the DO3SE model, relates stomatal
deposition directly to ecosystem effects....
What are the main differences in O3 dry deposition
schemes?
Wesely (1989) Pleim et al (2001) DO3SE (2003)
Surface
resistance terms
Stomatal, plant cuticle, in
canopy (buoyancy,
density, upper & lower
canopies) ground surface
Stomatal, plant cuticle, in
canopy, (empirical),
ground surface, LAI
Stomatal, plant cuticle, in
canopy, (empirical), ground
surface, LAI
Stomatal
resistance
Solar radiation, surface
air temperature
Species type, growing
season, photosynthetically
active radiation, surface air
temperature, vapour
pressure deficit, soil
moisture content
Species type, growing season,
photosynthetically active
radiation, surface air
temperature, vapour pressure
deficit, soil moisture content
Landcover
parameterisation
North America (?)
7 vegetation types and 5
seasonal categories (e.g.
Agricultural land -
Midsummer with lush
vegetation)
North America
25 vegetation types
European (& some Asian)
10 deposition cover types plus
>15 O3 sensitive target species
for effects estimates (with
climate region
parameterisations)
What can be done within HTAP ?
-to improve estimates of O3 dry deposition and estimate
stomatal O3 flux for ecosystem effects
1.Literature review of O3 dry deposition methods identify those most commonly used
within global scale CTMs
2. Identification of the key differences in these dry deposition schemes
3. Identification of the key differences in the parameterization (for different land
cover types)
4.Off-line assessment of the implications of differences in O3 dry deposition
schemes…comparison with observations from site-specific flux data
What can be done within HTAP ?
-to improve estimates of O3 dry deposition and estimate
stomatal O3 flux for ecosystem effects
1.On-line assessment of the effect O3 dry deposition schemes on hemispheric
transport of O3; regional O3 concentrations and regional O3 induced ecosystem
damage.
Global modeling could show spatial fields of
i. stomtal O3 flux;
ii. total O3 deposition;
iii.Effect on atmospheric O3 concentration
2.HTAP modeling experiments
i. investigate S-R relationship for stomatal O3 flux;
ii. alter key climate relevant characteristics (i.e. simulate an extended drought
period, elevated CO2 effects on stomatal conductance, changes in surface
ToC and RH% etc…) on resulting stomatal O3 flux to indicate how ecosystem
risk might change under future climates.
iii.Investigate the role of landcover on O3 deposition and stomatal O3 flux
Sitch et al. 2008
O3 can indirectly affect climate change through reductions in GPP leading
to alterations C sequestration...leading to more CO2 in the atmosphere
What can be done within HTAP ?
-what ecosystem effects do we want to consider?
Crops, Forests, Grasslands, Biodiversity and C sequestration…..
…..but at the same time N deposition to the oceans and terrestrial
biosphere can increase biological production drawing down CO2
Understand
HTAP
Science
Impacts
Policy
Design of HTAP
modelling experiments
Model tweaks
Policy
Model outp
ut
Common understanding
of key issues
Terry’s workshops
Needs to be done in time to inform
the experimental design
• Effect of HTAP on N deposition in more pristine Northerly latitude ecosystems
where as little 5 kgN/ha/year may cause damage
• Effect of N & S on acidification…time development of damage to understand
rates of change of acidity and role of HTAP
• Effect of aerosols on radiation (total and diffuse fraction)….effect on
photosynthesis and hence ecosystems
• Effect of pollutants (N, O3, aerosol) on NPP and C sequestration….feedbacks to
climate
Impacts
Holloway et al. 2011
…and finally a word of warning….how to communicate to the
public….
