Aaron Boone and Bertrand Decharme

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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

• 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

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• 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

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GCM-system of models for different Processes
Example at Météo-France
MOCAGE atmospheric chemistry
ARPEGE (GCM) ALADIN (RCM)
ISBA continental land surface
TRIP river routing
Oasis Coupler
GELATO sea ice
OPA NEMO ocean model
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• 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 Futurethe 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
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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

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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/oceansexplicit,
  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

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ISBA-TRIP coupling system

• Land surface model (ISBA) model to genrate
  runoff
• River routing using TRIP (1 or 0.5 degrees)

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• Prognostic variables
• 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
• The flood height, hf

• Evaluations
• In-situ river discharge
• Satellite-derived wetland estimates (Prigent et
  al., JGR, 2007)
• SWOT derived slope, depths, floodplain water
  depth and extent(d /dt)

(Decharme et al., 2007, JGR)
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Key scientific question for SWOT better quantify
the echange between rivers and floodplains for
improved prediction
Development Methodology

• Improve in offline mode ? validation with obs
  and/or assimilation
• Use in (fully-coupled) projection ? extrapolate
  in n,t !
• NEED Global scale data!

Key variables from SWOT
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Spatial comparison between the Flood experiment
and the Satellite-derived wetland estimates


Satellite-derived wetland estimates from Prigent
et al. (2007, JGR).
ISBA-TRIP flood-plain simulation
Difference
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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
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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)

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• Large biases in terms of the placement of the
  monsoon rains by the GCMs RCMs
• Turns out, ensemble AVG good!

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• 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!
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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
• Need multi-year records to develop robust GCM
  parameterizations (length of SWOT mission?
  Followup?)

Partly due to a lack of adequate data
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Extra..
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Some words on assimilation GCMS not really
relevant RCMs could be, but Reanalysisdont use
GCMs, but NWP at global scale (GFS, ECMWF).but
need to incorporate river routing/floodplain type
models
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Potential research and operational hydrology
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
  fully-coupled OGCM model (complete description of
  water cycle)
• II) Operational Hydrological Forecasting
• Real-time monitoring of the water resources at
  the national level (France) SAFRAN-ISBA-MODCOU
  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)

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Conclusions Perspectives

• 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

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Assesment of a 10-year application of
SIM-France Comparison of the daily riverflow
Spatial repartition of the discharge error
The SAFRAN-ISBA-MODCOU (SIM) hydrometeorological
model applied over France

• 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
Habets, Boone, Champeaux, Etchevers,
Franchistéguy, Leblois, Ledoux, Le Moigne,
Martin, Morel, Noilhan, Quintana-Segui, Rousset,
Viennot
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Potential research and operational hydrology
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
  fully-coupled OGCM model (complete description of
  water cycle)
• II) Operational Hydrological Forecasting
• Real-time monitoring of the water resources at
  the national level (France) SAFRAN-ISBA-MODCOU
  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)

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