SWOT River Model Inter-Comparison

CaMa-Flood Results- Mississippi River Dai Yamazaki
JAMSTEC – Japan Agency for Marine-Earth Science and Technology
7 Nov 2016 @ SWOT-ST Tele-Con

CaMa-Flood FrameworkForcing Data (External)
Catchment/Hillslope
Land Hydrology(External)

CaMa-Flood (Yamazaki et al., 2011, 2012, 2013, WRR; 2014 GRL)River/Floodplain Routine

RoutineFloodplain

River Channel(External or Neglected)

L
SfDfDrNo hillslope process &no groundwater delay
in CaMa simulationsfor SWOT MIPZTotal Runoff

1D river network (default)
Local Inertial Flow Equation- Backwater effect represented- Both channel and floodplain flows- No lake or reservoir routine

NLDAS was used for SWOT MIP

SfSrWBAc
AfAcAfSub-grid flood inundation- No depression in floodplain (no levee)- Same water elevation between
river channel and floodplains- No 2D floodplain flow

River network map + Sub-grid toporaphy

Topography (External, with some modifications)
CaMa is almost same as MGB-IPH by Rodrigo,
but it only solves river/floodplain routine.
Land hydrology and catchment/hillslope routine
should be calculated by external models.

Flow Direction (HydroSHEDS 15sec DIR)
Elevation(HydroSHEDS 15sec DEM)
+ hydrological adjustment(Yamazaki et al., 2012, JoH)

Channel Geometry (W and B from Kostas)
Above were used for SWOT MIP

CaMa-Flood characteristics 1
Quasi-2D Catchment Discretization

The top left unit-catchment in each 3x3 grid-boxes
is highlighted.

One unit-catchment is defined for one coarse-resolution grid box. (e.g. 0.25deg in the above figure)- The average size of unit-catchments is similar to that of coarse-resolution grid-box.
- The actual size of each unit-catchment varies.
Irregular-shape catchments allocated on a regular lon-lat grid system.
- The maps and output of CaMa-Flood are in a lon-lat gridded format.
- Very easy to analyze.

(Yamazaki et al., 2009 HESS; 2011 WRR)

CaMa-Flood river network @0.25 deg

CaMa-Flood characteristics 2
Quasi-2D River Network (Channel Bifurcation)

Bifurcation channels can be added by analyzing 3sec topography data (optional).
- Channel bifurcation in a delta region, quasi-2D flow in floodplains can be simulated.
# This option was not used in Mississippi simulations for SWOT-MIP(Yamazaki et al., 2014 GRL)

CaMa-Flood simulations
Hydrodynamic simulation for the Mississippi River using NLDAS runoff
Date: 01 Jan 2000 – 31 DEC 2010(+1year spin-up using year 2000 runoff)

Resolution: 0.1 deg / 0.25 deg
Time Step: Automatically adjusted following CFL
Topography: Default SWOT-MIP setting(but DEM was adjusted due to CaMa-Flood requirement)

Required wall-clock time:
1 model-year simulation takes ~2min at 0.1deg resolution~15sec at 0.25deg resolution
Using Intel Fortran + OpenMP on 3.0-GHz 8-core Intel Xeon on Apple MacPro-2013CaMa-Flood simulations results
Hydrodynamic simulation for the Mississippi River using NLDAS runoff
Relative Bias (Qsim / Qobs)

Correlation (Qsim & Qobs)

Selection of USGS gauges were same as HRR presentation by EdCaMa-Flood simulations results
Hydrodynamic simulation for the Mississippi River using NLDAS runoff

60000

Vicksburg, MS
USGS obs
CaMa-Flood 0.1deg
CaMa-Flood 0.25deg

50000
40000
30000
20000
1000002008

2009

2010

2011

CaMa-Flood simulations results
Hydrodynamic simulation for the Mississippi River using NLDAS runoff
Max Flood Depth (CaMa-Flood)

Max Flood Depth (MGP-IPH)

From Rodrigo’s SlideSome discussions on DEMs
After last tele-con, we found “HydroSHEDS 15sec DEM” was actually not conditioned.
Void Filled 3sec DEM:

Conditioned 15sec CON:

Conditioned 3sec CON:

→Though the file name is “CON”,
the 15sec DEM on the webpage was not conditioned
The elevations were similar to 3sec Void-filled DEM.
Some negative slopes were found along river networks.

Because CaMa-Flood requires conditioned DEM,
I adjusted DEMs to remove negative slopes.
(Adjusted DEM was accessed from Cedric’s Project webpage)

Other models smoothed DEMs (MGB / LISFLOOD-FP),or assumed minimum slope (Kinematic type).

Figures generated by Rodrigo, thanks.

Some Questions about MIP framework[1] How do we submit the results to Cedric?
e.g. Discharge data in an Excel file?
If a sample output data format is available, we can just follow it.

[2] Should we keep consistently on DEM modification?
Following e-mail discussions after the last phone-call, we found that:- Some models perform “DEM conditioning” internally (i.e. New DEM was not generated)- CaMa-Flood needs to generate a conditioned DEM.
(The generated new DEM was put on the project web).
Probably, we can do simulations with two DEMs (original and conditioned).

[3] Hillslope/catchment routine (before river/floodplain routine)
Given that these routines are independent from river/floodplain routine,
should we also assess the uncertainties due to these scheme?

Some additional news from Tokyo[1] We developed ”SWOT GLOBAL river assimilation” framework.
Poster at AGU (just beside Cedric’s poster)

Virtual SWOT twin experiment, using CaMa-Flood as a dynamical core.
- Assume model and topography are true (no uncertainty).
- Assume SWOT can observe CaMa-Flood’s water level with 10cm accuracy.
- Only uncertainty is in runoff forcing. (-25% bias, following [Andreadis, 2007, GRL])
We assimilated SWOT observed water level, with daily interval, using LETKF(Local Ensemble Transform Kalman Filter).
Similarity between assimilated and true runs

Amazon Mainstem Discharge
Near River Mouth

Blue: assimilation similar to true run
Red: assimilation similar to open-loop

Near Manaus

Blue: Open-loop, Black: true run, Red: Assimilation run
Green: (true – assimilation ) / (true – open-loop)

Some additional news from Tokyo[2] A new and better global DEM. Talk at AGU (Friday Morning)
We removed major errors from SRTM and AW3D DEMs.

(Stripe noise, Absolute bias, Tree bias, & Speckle noise)

We performed >2m correction for 37% of all land pixels.
In the new DEM, 58% of pixels have errors <2m.
and 90% of pixels have errors <5m (except mountainous region).

A description paper is in prep., the data will be available soon.