Title: Aaron Boone and Bertrand Decharme
1SWOT 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.
2GCM 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
4GCM-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
6GCM 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
7GCM 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
8ISBA-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)
10Key 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
11Spatial 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
122 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
13Inconvenient 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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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!
17Message 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
18Extra..
19Some 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
20Potential 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)
21Conclusions 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
22Assesment 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
23Potential 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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