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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 M t o-France – PowerPoint PPT presentation

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Title: Aaron Boone and Bertrand Decharme


1
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.

2
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

3
  • 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

4
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
5
  • 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
6
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

7
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

8
ISBA-TRIP coupling system
  • Land surface model (ISBA) model to genrate
    runoff
  • River routing using TRIP (1 or 0.5 degrees)

9
  • 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)
10
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
11
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
12
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
13
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)

14
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15
  • Large biases in terms of the placement of the
    monsoon rains by the GCMs RCMs
  • Turns out, ensemble AVG good!

16
  • 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!
17
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
18
Extra..
19
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
20
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)

21
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

22
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
23
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)

24
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