Diapositive 1 - Ohio State University

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Transcript Diapositive 1 - Ohio State University

SWOT measurements for improving
hydrological parameterizations in Regional
and Global Climate Models
Aaron Boone and Bertrand Decharme
CNRM-GAME Météo-France
SWOT Meeting, Sep.15-17, Columbus, OH.
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GCM: Global Climate Model
SWOT & GCM-RCM Continental Hydrology
Typical GCM
configuration:
• 15-30 vertical levels
• 1-5 degree horiz
resolution
*RCM higher res (n,z,t)
(sub-domain,
downscaling…)
This limits the level of
complexity: only first
order processes relevant
to the climate are
considered…
SWOT, OSU, Sept. 15-17
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SWOT & GCM-RCM Continental Hydrology
Modes of usage:
• High resolution (~50 km)  10 years
• Climate Projection (~1-5 deg)  100
years
* fixed SSTs OR fully coupled OGCMs
• Long term, paleo-climate 1000+
years…
* Regional (RCM) : downscaling.
Large scale forcing imposed (possibly
by re-analysis data)  process
studies
SWOT, OSU, Sept. 15-17
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SWOT & GCM-RCM Continental Hydrology
GCM-system of models for different
Processes: Example at Météo-France:
MOCAGE
atmospheric chemistry
ARPEGE (GCM)
ALADIN (RCM)
ISBA continental land
surface
GELATO
sea ice
OPA NEMO
ocean model
SWOT, OSU, Sept. 15-17
Oasis
Coupler
TRIP
river
routing
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SWOT & GCM-RCM Continental Hydrology
Goal of Continental hydrology in GCMs: the past
(although still the present for some GCMs):
• Obtain good estimates of the surface latent heat flux
(implies correct paritioning of incoming net radiation into
evaporation and atmospheric sensible heating)
• Implies a good estimate of the paritioning between
infiltration, runoff and soil storage
• Runoff purely a diagnostic
Present & Future…the dream:
Estimates of river discharge from climate change simulations can aslo be
used to assess the impact of climate change on water resources and the
hydrology of the major river basins. Arora and Boer, 1999, JGR
SWOT, OSU, Sept. 15-17
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SWOT & GCM-RCM Continental Hydrology
GCM representation of continental hydrology:
• Representation of wetlands, bogs
• Lake parameterizations
• Flooded zones: dynamics, interactions with lakes, rivers
• Freshwater discharge into sea/oceans
• River/Groundwater exchanges
• Precipitation spatial distribution at the surface
• Snow, ice (permafrost) representations
• Soil moisture, energy balance (evapotranspiration…)
• Runoff (Dunne and Horton) and baseflow
SWOT, OSU, Sept. 15-17
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SWOT & GCM-RCM Continental Hydrology
GCM representation of continental hydrology:
• Representation of wetlands, bogs generally not accounted for explicitly
• Lake parameterizations often prescribed Tsfc or 1D thermal transfer
• Flooded zones: dynamics, interactions with lakes, rivers few GCMs
• Freshwater discharge into sea/oceans…explicit, implicit, just a diagnostic
• River/Groundwater exchanges few GCMs
• Precipitation spatial distribution at the surface few GCMs
• Snow, ice (permafrost) representations
• Soil moisture, energy balance (evapotranspiration…)
• Runoff (Dunne and Horton) and baseflow
• Important to keep in mind: the above are primarily sub-grid
parameterizations, and there are restrictions on the complexity. Also,
resulting feedback mechanisms must be studied carefully…
SWOT, OSU, Sept. 15-17
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SWOT & GCM-RCM Continental Hydrology
ISBA-TRIP
coupling system
• Land surface model (ISBA) model to
genrate runoff
• River routing using TRIP (1 or 0.5 degrees)
SWOT, OSU, Sept. 15-17
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SWOT & GCM-RCM Continental Hydrology
Prognostic variables:
The ISBA-TRIP coupling system
•The river height, hs
•The river flow velocity, v (Manning
formula)
•The floodplain volume (calculated
using the sub-grid topography)
Other important variables:
•The flood fraction, fflood
TRIP
•The flood height, hf
ISBA
Evaluations:
•In-situ river discharge
•Satellite-derived wetland estimates
(Prigent et al., JGR, 2007)
(Decharme et al., 2007, JGR)
SWOT, OSU, Sept. 15-17
• SWOT derived slope, depths,
floodplain water depth and
extent…(d /dt)
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SWOT & GCM-RCM Continental Hydrology
The ISBA-TRIP coupling system
Key scientific question
for SWOT: better
quantify the echange
between rivers and
floodplains for improved
prediction
Development Methodology
TRIP
ISBA
Key variables from
SWOT
SWOT, OSU, Sept. 15-17
1) Improve in « offline »
mode  validation with
obs and/or assimilation
2) Use in (fully-coupled)
projection  extrapolate
in n,t !
* NEED Global scale data!
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SWOT & GCM-RCM Continental Hydrology
Spatial comparison between the Flood experiment
and the Satellite-derived wetland estimates
%
Satellite-derived wetland
estimates from Prigent et
al. (2007, JGR).
%
ISBA-TRIP floodplain simulation
SWOT, OSU, Sept. 15-17
Difference
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SWOT & GCM-RCM Continental Hydrology
2 simulations (10-years atmospheric forcing from GSWP-2 at 1° by 1°):
with (Flood) and without (CTL) the flooding scheme
• Evaporation from floodplains quite significant for some regions: possible
feedbacks with atmosphere…
GSWP-2, Dirmeyer et al., 2006
SWOT, OSU, Sept. 15-17
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SWOT & GCM-RCM Continental Hydrology
Inconvenient Truth: reliable river discharge in climate projections is still a ways off…
West African Monsoon Modelling and
Evaluation (WAMME) Project
Y. Xue, B. Lau, et al.
• 14 GCM and 4 RCM
simulations
• 2000, 2003, 2004, 2005
• Use AMMA Land surface
Model Intercomparison Project
(ALMIP) Forcing and
simulated fields to evaluate
fully coupled WAMME models
(surface component)
SWOT, OSU, Sept. 15-17
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SWOT & GCM-RCM Continental Hydrology
SWOT, OSU, Sept. 15-17
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SWOT & GCM-RCM Continental Hydrology
• Large biases in terms of the
placement of the monsoon rains
by the GCMs & RCMs
• Turns out, ensemble AVG good!
SWOT, OSU, Sept. 15-17
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SWOT & GCM-RCM Continental Hydrology
Cimate Projections:
SWOT data esp important a high lats in
the context of projected climate change:
a sample of IPCC Météo-France
results…(B2 scenario)
Significant Change in regimes for:
• Wetlands, flooded zones
• Lakes
• Discharge (potenial feedbacks with ocean
and ice….)
• Wetland Carbon, Methane emssions…
Need global scale data to develop & improve
parameterizations for useful climate
projections of hydrological impacts!
SWOT, OSU, Sept. 15-17
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SWOT & GCM-RCM Continental Hydrology
Message:
The main need for SWOT products in terms of GCM applications is to
provide multi-year data at the global scale of discharge, water height and
slope within the context of improving the hydrological parameterizations:
notably in terms of exchanges between rivers and floodplains, changes in
lakes/wetlands, and freshwater discharge into the oceans.
Critical if we are to have reliable estimates of projected changes in water storage
and river volume, and possible feedbacks with the atmosphere…
Some caveats:
• Precipitation generally not well predicted by GCMs, notably for monsoon circulations
• Not all GCMs include river/floodplain, lake, wetland models
• Ditto for carbon and methane wetland processes
Partly due to a lack of
adequate data…
• Need multi-year records to develop robust GCM parameterizations (length of SWOT
mission? Followup?)
SWOT, OSU, Sept. 15-17
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SWOT & GCM-RCM Continental Hydrology
Extra…………..
SWOT, OSU, Sept. 15-17
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SWOT & GCM-RCM Continental Hydrology
Some words on assimilation:
GCMS not really relevant
RCMs could be, but…
Reanalysis…don’t use GCMs, but NWP at
global scale (GFS, ECMWF)….but need
to incorporate river routing/floodplain type
models
SWOT, OSU, Sept. 15-17
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Potential
researchContinental
and operational
SWOT
& GCM-RCM
Hydrologyhydrology applications of
WATER-HM at Météo-France
I) Need to evaluate river routing and floodplain parameterizations for use in GCMs
and regional scale modeling:
• Used to study possible global climate change impacts on flood risk/frequency
• Long term impact on lake storage: possible aid to water resource planning (seasonal and
long term)
• Better description of lake changes at high latitudes: links with freeze thaw, greenhouse gas
release
• NEED river depth, floodplain depth/extent, river velocity: WATER-HM probably adequate!
*End Result: Better river discharge/routing, lake parameterizations to be utilized within fullycoupled OGCM model (complete description of water cycle)
II) Operational Hydrological Forecasting:
• Real-time monitoring of the water resources at the national level (France): SAFRAN-ISBAMODCOU distributed hydrological modeling system
• Ensemble streamflow forecast studies: initialized using current river heights: potential flood
risk forcasted
• NEED high spatial resolution (100m probably not fine enough?) and daily (?) observations
• Potential uses in developing countries with relatively low spatial density observational
discharge/river monitoring networks (eg. Western Africa)
SWOT, OSU, Sept. 15-17
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Conclusions & Perspectives
SWOT & GCM-RCM Continental Hydrology
•Good results in terms of river discharges.
•Reasonable agreement between the simulated flooded areas and
Satellite-derived wetland estimates.
•Must be confirmed over other large river basins using an extended
atmospheric forcing such as the global 1948-2000 dataset of Sheffield et
al. (J. Climate, 2006).
•Nevertheless, underestimation of floodplains compared to satellite data.
•Some limitations could be raised by adding an explicit representation of
lakes, marshes, and large ponds.
•Other limitations come from the lack of global and temporal observations
like:
•River and/or floodplains height
•River velocity
SWOT, OSU, Sept. 15-17
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Assesment of a 10-year application of SIM-France
SWOT & GCM-RCM Continental Hydrology
Comparison of the daily riverflow
The SAFRAN-ISBA-MODCOU (SIM)
hydrometeorological model applied over
France
Spatial repartition of the discharge error:
• Real-time monitoring of the water
resources at the national scale
• Ensemble streamflow forecast studies
Two kinds of Ensemble streamflow were
tested:
Long term : 10-day forecast, using ECMWF
EPF (50 members + ctrl)
Rousset et al., ECMWF Newsletter 2007
Short term: 2-day forecast, using PEARP
EPF (10 members + ctrl)
Thiriel et al., submitted 2007
*The SIM real-time application is used to
initialize the ensemble streamflow forecast:
could be improved using real-time WATER-HM
SWOT, OSU, Sept. 15-17
Habets, Boone, Champeaux, Etchevers, Franchistéguy,
Leblois, Ledoux, Le Moigne, Martin, Morel, Noilhan, QuintanaSegui, Rousset, Viennot
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Potential
researchContinental
and operational
SWOT
& GCM-RCM
Hydrologyhydrology applications of
WATER-HM at Météo-France
I) Need to evaluate river routing and floodplain parameterizations for use in GCMs
and regional scale modeling:
• Used to study possible global climate change impacts on flood risk/frequency
• Long term impact on lake storage: possible aid to water resource planning (seasonal and
long term)
• Better description of lake changes at high latitudes: links with freeze thaw, greenhouse gas
release
• NEED river depth, floodplain depth/extent, river velocity: WATER-HM probably adequate!
*End Result: Better river discharge/routing, lake parameterizations to be utilized within fullycoupled OGCM model (complete description of water cycle)
II) Operational Hydrological Forecasting:
• Real-time monitoring of the water resources at the national level (France): SAFRAN-ISBAMODCOU distributed hydrological modeling system
• Ensemble streamflow forecast studies: initialized using current river heights: potential flood
risk forcasted
• NEED high spatial resolution (100m probably not fine enough?) and daily (?) observations
• Potential uses in developing countries with relatively low spatial density observational
discharge/river monitoring networks (eg. Western Africa)
SWOT, OSU, Sept. 15-17
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SWOT & GCM-RCM Continental Hydrology
SWOT, OSU, Sept. 15-17