YHK GEWEX May June 2007 Land Surface Flux Workshop
SMOS Soil moisture
retrieval Algorithm
Y. H. Kerr1, …
and the SMOS team
YHK GEWEX May June 2007 Land Surface Flux Workshop
Outline
• SMOS mission overview in a nutshell
• Soil moisture retrievals– Level 2
– Level 3
– Level 4
• Results, issues and next steps
• Conclusion
YHK GEWEX May June 2007 Land Surface Flux Workshop
Ocean salinity rationale• Thermohaline overturning circulation.
How can climate variations induce changes in the global ocean circulation?• Air-sea freshwater budget.
How are global precipitation, evaporation, and the cycling of water changing?• Tropical ocean and climate feedback
Science Objectives for SMOS: Salinity
Lagerloef et al., 2001
YHK GEWEX May June 2007 Land Surface Flux Workshop
• Role of Soil moisture in surface
atmosphere interactions:storage of water (surface and root
zone), water uptake by vegetation (root zone), fluxes at the interface (evaporation), influence on run-off
• Implies relevance forWeather ForecastsClimatic studiesWater resources crop managementForecast of extreme events
• Climate change predictions and rain event forecasts requires SST and SM
Science Objectives for SMOS: Soil Moisture
YHK GEWEX May June 2007 Land Surface Flux Workshop
How to access soil moisture • Ground measurements• Networks (GEWEX)• SW, SWIR, ….• THIR….• Low frequency microwaves
– Active microwaves• Vegetation, roughness• Revisit• Sensitivity
– Passive microwaves antenna issue
YHK GEWEX May June 2007 Land Surface Flux Workshop
Science Objectives for SMOS: The SMOS Mission
•Need for soil moisture and sea surface salinity fields•Only passive L band suitable•Real aperture systems currently not adequate (antenna size) ==>Synthetic antenna
Mission specificationsSoil Moisture
multi-angulardual pol
4 % vol 3 day revisit(Vegetation 7 day)better than 50 km
Sea Surface Salinitymulti acquisitions
dual pol or 1st stokesbetter than 0.1 psu10 day to monthly
Grid scale (200 km)
SMOS is the second Earth Explorer opportunity mission (1st round)An ESA/CNES/CDTI projectSelected in 1999, initiated in 2000 Phase B finished, C/D Started in January 2004 for a launch in 2008A new technique (2D interferometry) to provide global measurements from space of key variables (SSS and SM) for the first time.
Pellarin et alLe Traon et al
YHK GEWEX May June 2007 Land Surface Flux Workshop
Interferometry • angular resolution
provided by distant antennas
• correlation products s(1)*s(2) visibility functions V(D/)
• Inverse F.T. on V TB()
Space sampling requirement : every /2 value at least one time ; hence "thinning" possibilities.
1
DD '
/ D'
2
YHK GEWEX May June 2007 Land Surface Flux Workshop
•Each integration time, (2.4 s) a full scene is acquired (dual or full pol)•Average resolution 43 km, global coverage•A given point of the surface is thus seen with several angles•Maximum time (equator) between two acquisitions 3 days
Principle of operations
SMOS FOV; 755 km, 3x6, 33°, 0.875,
P. Waldteufel, 2003
YHK GEWEX May June 2007 Land Surface Flux Workshop
SMOS Baseline
• 18+5 elements /arm configuration
• Mean Altitude --> 757 km +/- 500 m• 30° steer angle• 32.5° tilt angle • Elements spacing
0.875 • Dual or Full pol
GEWEX May June 2007 Land Surface Flux Workshop
Payload Module (deployed)
Payload Module (stowed)SMOS in Rockot
CASA EADS, 2003
SMOS Instrument: MIRAS derived conceptCASA EADS (Spain)
BUS: PROTEUS Alcatel Space Industry
Launcher ROCKOTGround segment: Level 0-2 Villafranca
Level 3-4 Toulouse
Esa lead with contributions from France and Spain
YHK GEWEX May June 2007 Land Surface Flux Workshop
Schedule• Current:
– Payload module is finished and under final testing– Antennas have been measured (TUD)– Ground segment at various stages depending levels– Delivery of PLM after testing mid 2007– Level 1 Prototype operational end 2006– Level 2 Breadboards-prototypes Mid 2007– CATDS (Level 3 and 4) initiated end 2007
• Overall schedule– Launch 2008– 6 months commissioning phase– 2.5 + 2 years operation
• Cal val AO• Science use AO• Near Real Time• SMOSOps
YHK GEWEX May June 2007 Land Surface Flux Workshop
Hardware
YHK GEWEX May June 2007 Land Surface Flux Workshop
LEAF picture
YHK GEWEX May June 2007 Land Surface Flux Workshop
LSS picture
YHK GEWEX May June 2007 Land Surface Flux Workshop
Schedule• Current:
– Payload module is being assembled (CASA)– Antennas are being measured (TUD)– Ground segment at various stages depending levels– Delivery of PLM after testing end of year– Level 1 Prototype operational end 2006– Level 2 Breadboards-prototypes Mid 2007– CATDS (Level 3 and 4) initiated end 2007
• Overall schedule– Launch 2008– 6 months commissioning phase– 2.5 + 2 years operation
• Cal val AO• Science use AO• Near Real Time• SMOSOps
YHK GEWEX May June 2007 Land Surface Flux Workshop
HUT Demonstrator
Brightness temperature (K) measured by HUT-2D over densely forested forestareas surrounded by open field areas. Right: land use classification for the measuredarea. High brightness temperature areas correlate well with forest areas, and lowerbrightness temperature areas correlate well with open areas. The flight altitude is 1500meters resulting in a ground resolution of approximately 100 x 100 meters.
Juha Kainulainen, et al. 2006
YHK GEWEX May June 2007 Land Surface Flux Workshop
YHK GEWEX May June 2007 Land Surface Flux Workshop
GEWEX May June 2007 Land Surface Flux Workshop
Technical Elements
Payload Data Processing CenterOperations Data Flow – Open Loop Concept
S-bandX-band
XBASX-Band Acqusition Station
TTCETTM & TC Earth Terminal
SOCCSpacecraft Operations
Control Center
PDPCPayload Data Processing
Centre (LO-L2)ESOC
CATDSCentre Aval de Traitement des Données Smos (L3-L4)
USERS
L0,L1,L2
L3,L4Reports
L2,L3,L4
Requests
Pass Plans S/C & PL commandsTTCET commands
Pass plans
HKTM-PHKTM-R
TTCET Monitoring Data
Calibration Data & PL status
PL-HKTM, PL-TM, Pass plans & Orbit determination information
Villafranca Kiruna
IF
SC status & PLTM S/C & PL commands
HKTM
A. Hahne Estec
ESLExpert Support
Laboratory
GEWEX May June 2007 Land Surface Flux Workshop
spatial Data products available will be:
Level 1: brightness temperature at H and V polarisation
Level 2: daily soil moisture and ocean salinity (swath) maps at basic temporal and resolutions
Level 3: daily global soil moisture maps global salinity maps
Level 4: special products (root zone SM, SSS (Godae) fields, HYDROS / AQUARIUS / AMSR mix etc,
Other: Improved algorithms (level 1 and 2), and calibration, CalVAl
Services
All data products are produced (with quality statement) and distributed to registered users.
• All data products are archived for the duration of the mission plus 10 years.
• All data products are in a catalogue with a browse facility.
Data products
YHK GEWEX May June 2007 Land Surface Flux Workshop
Aim and boundary conditions• Derive Soil moisture and Vegetation optical thickness
(Water content) and …depending upon data available• Characterisation of angular signature (max up to over
100 measurements per pixels ( 10) down to a very few at the end of the swath)
• Two polarisations every 3 days• Basic resolution 43 km on average (~25 to 50 km)• Higher spatial sampling 15 km typically (nodes)• Equal area projection• Blackman apodisation Weighting function/area• Many surface types per integration area /pixel
elementary surfaces
YHK GEWEX May June 2007 Land Surface Flux Workshop
Models and mixed pixels
global BT at SMOSantennas
Synthetic antenna directional gaindiagram
e1 e2 e3 e4 e5 e6 e7 e8 e9
G2
G5
type 1 emitter CF1
type 2 emitter CF2
type 3 emitter CF3
antenna footprint
G7
: Aggregated fractions FM0 and FM
FM0 class Aggregated land cover FM class Complementarity A B C D E
FNO Vegetated soil + sand FNO
FFO Forest FFO
FWL Wetlands FWL
Open fresh water FWP
Open saline water FWS
FWO Open water
FEB Barren FEB
FTI Total Ice fraction
Ice & permanent snow FEI
Sea Ice FSI
FUL Low urban coverage
FUM Moderate urban coverage
Comple-mentary
Sum of comple-mentary fractions equals unity
FTS Strong topography
FTM Moderate topography
FRZ Frost FRZ
Non permanent dry snow
Non permanent wet snow FSN
Non permanent mixed snow
FSN
Supple-mentary
Supple-mentary fractions are super-imposed
Set of models fror each surface type
YHK GEWEX May June 2007 Land Surface Flux Workshop
YHK GEWEX May June 2007 Land Surface Flux Workshop
0 5010 4020 30
Teodosio Lacava – IMAA-CNR;
Mean Soil Moisture (% volume): January 2003-2005 A
Projection: EASE Grid Global; Datum: WGS-84
YHK GEWEX May June 2007 Land Surface Flux Workshop
Teodosio Lacava – IMAA-CNR
Projection: EASE Grid Global; Datum: WGS-84
0 5010 4020 30
Mean Soil Moisture (% volume): April 2003-2005 A
YHK GEWEX May June 2007 Land Surface Flux Workshop
Pre Processing filter SMOS views co-locate auxiliary data with DGG node compute aggregated mean cover fractions compute reference values
Iterative parameters retrieval fit the selected forward model to observations use other models for default contribution
Decision Tree select main fraction for retrieval select one model for retrieval select other models for default contributions
SMOS L1c Data products files Auxiliary files
SMOS L2 auxiliary Fixed reference Evolving reference User parameters file
TB models library forward models default models future models
Post Processing compute parameters posterior variances retrieval analysis and diagnostics compute modeled surface TB @ 42.5° generate flags
DGG node data iterator
Generate output data
User Data Product retrieved parameters parameters variances science & quality flags
Data Analysis Report
algorithms internal data full flags
Do full retrieval again eliminate bad views decrease free number of parameters
Level 2:Soil moistureAlgorithm
layout
YHK GEWEX May June 2007 Land Surface Flux Workshop
Issues: What is inside a pixel?
• Decision tree set of models– Fixed features:
• Low vegetation, forested, barren, water, permanent snow/ice, urban
– Variable features• Snow, variable water bodies/ floods, frozen ground/
vegetation
– Overlapping perturbing factors• Topography, RFI
– Issues:• Knowledge• Temporal signatures
YHK GEWEX May June 2007 Land Surface Flux Workshop
External data
YHK GEWEX May June 2007 Land Surface Flux Workshop
The SMOS world….And DGGs…
YHK GEWEX May June 2007 Land Surface Flux Workshop
Pure pixels?...
15oW 10oW 5oW 0o 5oE 10oE
42oN
45oN
48oN
51oN
54oN WA_DGG_exact
Colour code/ ● ocean, ● inland water body, ● rivers, ● All others, ● WA_DGG_nowater;
YHK GEWEX May June 2007 Land Surface Flux Workshop
The land use map (MétéoFrance –Ecoclimap binned into generic classes)
How homogeneous ?areas with prevailing nominal and forested aggregated LC fractions
YHK GEWEX May June 2007 Land Surface Flux Workshop
In conclusion: SM retrievals can be attempted in many areas with varying
expected accuracy
YHK GEWEX May June 2007 Land Surface Flux Workshop
Algorithm validation Plan
Direct simulation Lo-op
Selection x / + Ndata set
Data options for DQX runs 792 TBL1
Surface sceneScene homogeneous nominal ; suggested code 166WEF none necessary
Input parameters for simulated dataSM SL 0.0 to 0.5 step 0.1 x 6TAU TL1 0, 0.01, 0.025, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 x 12Sand, clay 0.4, 0.3Tsurf 288Tsky 3.7T0 atm, P0, WVC 288, 1013, 3ro_s, alpha, SAL, eps_pa From UPF LUTHR, NR_H, etc. from CLASS LUT for selected code
Input observation conditionsRadiometric uncertainty simulated based on L1c test scenarioX_SWATH (km) XL 0, 100, 200, 300, 350, 400, 425, 450, 475, 500, 525 x 11Incidence & rotation angles from L1c test scenarioFaraday angles from L1c test scenarioL1c flags from L1c test scenario
Additional data options for bias runs 726Radiometric uncertainty Zeronon uniform TAU Mixing 2 direct models with TAU=0 and 0.6 + 1 TBL3
non uniform SM TL2Mixing 2 direct models with 2 SM TBD around loop value, for TAU=0 to 0.6 step 0.2 + 4 TBL4
Faraday angle TL2 Double L1_TS values; TAU=0 to 0.6 step 0.2 + 2 TBL5Rotation angle TL2 2° uniform; TAU=0 to 0.6 step 0.2 + 4 TBL6SM SL 0.0 to 0.5 step 0.1 x 6X_SWATH XL 0, 100, 200, 300, 350, 400, 425, 450, 475, 500, 525 x 11
Total 1518
Need to validate the algorithm and the products:
A) Theoretical scenes, homogeneous, all over the swath, exact data acquisition, typical noise figure, exact geometry
B) Step in SM and vegetation opacity over the whole range
C) Same analysis on realistic synthetic data sets
Global and high resolution15 days at several dates (solstices and
equinox)
D) Validation on ground data sets and then real sat data during commissioning phase
The Murrumbidgee Catchment
SM retrieval performance with free TAUSM
SM retrieval performance with constrained TAU
YHK GEWEX May June 2007 Land Surface Flux Workshop
Cal Val• Initiated (2005)
• Teams selected (2005)
• Optimisation process under way
• Rely on CEOP whenever possible
• GEWEX soil moisture network
• Possibility to add sites
• Work with modellers
YHK GEWEX May June 2007 Land Surface Flux Workshop
NAFE ’05 J Walker et al.Regional Data: 1km
Legend
amsr2Value
796
183
0 20 Kilometers
Elevation
Visible
YHK GEWEX May June 2007 Land Surface Flux Workshop
LAND
THNADIR>TVNADIR by
AVG=0.3 K, STD=0.9 K
1. EMIRAD calibration: Second ‘new’ calibration
19/34
WATER
THNADIR>TVNADIR by
AVG=1.4 K, STD=1.8 K
5
YHK GEWEX May June 2007 Land Surface Flux Workshop
Issues• Water bodies
• Varying features (Frozen, snow)
• Perturbations (rain interception)
• RFI
• Unknown surfaces (urban, barren ….)
• And things to discover….
YHK GEWEX May June 2007 Land Surface Flux Workshop
AMSR DATA RFI at 6.8 (blue) and 10.7 (green)
YHK GEWEX May June 2007 Land Surface Flux Workshop
AMSR DATA RFI at 6.8 (blue) and 10.7 (green)
YHK GEWEX May June 2007 Land Surface Flux Workshop
Level 3 product• Basis : maximum possibilities: full resolution • Compatibility with other « products » • With well defined sampling on a fixed grid
– Composite over well defined periods– Typical sampling
• 1,3, 6-7, 10, 30days 1 year• 40 km, 1 °
– But updated daily in several cases– GODAE like
• And tool boxes• Common format with other missions?• From ideally level 2 but actually L1 more likely
YHK GEWEX May June 2007 Land Surface Flux Workshop
Level 4• Mainly research• Merged products (other existing missions)• Synergisms with future missions• Inter-calibration• Merge with models (run off, dis -aggregation, assimilation,
Mercator etc…)• Stress on coastal areas, , Sea ice, Ice?, flooded areas,
Catchments, flood /drought risks flags• Fire prone areas• Sky Map• Sun activity /tec• Non exhaustive list……….
AQUARIUSAQUARIUS Sea Surface Salinity Mission
YHK GEWEX May June 2007 Land Surface Flux Workshop
Atmospheric Forcing(Rg, Ra, Ta, qa, U, P) Remote sensing
Soil and vegetationparameters
LAI
SVAT model
SURFACESoil moistureTemperature
Vegetation Opticalthickness
Interactive
Vegetation
Radiative Transfermodel
Root-zone soil moisturePlant growth parametersor biomass
Radiances
OPTIMISATION
Root Zone soil moistureRoot Zone soil moisturePRINCIPLE OF THE ASSIMILATION OF REMOTE PRINCIPLE OF THE ASSIMILATION OF REMOTE
SENSING DATASENSING DATA
Calvet et al.
YHK GEWEX May June 2007 Land Surface Flux Workshop
Data Assimilation ExperimentsM. Drusch ECMWF
1. CTRL OI (Optimum Interpolation) based on screen level analyses
for the top three model soil layers.
2. OL (Open Loop) without any soil moisture analysis.
3. NUDGE (Nudging) experiment using the TMI Pathfinder soil
moisture product.Common features:
- Full atmospheric 4DVar analysis using ~ 106 observations / 6h
(reflecting the operational configuration).
- Model version CY29R1.
- T511 spectral resolution, 60 vertical levels.
- ‘Early delivery’ set up with 10-day forecasts from 00 and 12 UTC.
- Study period from 1 June to 31 July 2002.
YHK GEWEX May June 2007 Land Surface Flux Workshop
Soil moisture increments (CTRL OI)
80°S80°S
70°S 70°S
60°S60°S
50°S 50°S
40°S40°S
30°S 30°S
20°S20°S
10°S 10°S
0°0°
10°N 10°N
20°N20°N
30°N 30°N
40°N40°N
50°N 50°N
60°N60°N
70°N 70°N
80°N80°N
160°W
160°W 140°W
140°W 120°W
120°W 100°W
100°W 80°W
80°W 60°W
60°W 40°W
40°W 20°W
20°W 0°
0° 20°E
20°E 40°E
40°E 60°E
60°E 80°E
80°E 100°E
100°E 120°E
120°E 140°E
140°E 160°E
160°E
-250
-200
-150
-100
-50
-10
10
50
100
150
200
250
[mm]
Accumulated root zone soil moisture increments for June 2 to July 30, 2002.
Analysis increments are a sizeable part of the terrestrial water budget.
YHK GEWEX May June 2007 Land Surface Flux Workshop
Validation of soil moisture
area averages for Oklahoma (72 stations)
surface soil moisture
model forecast (OI)
observationsmodel forecast (OL)
• Too quick dry downs (model problem).• Too much precip in July (model problem).• Too little water added in wet conditions (analysis problem).• NO water removed in dry conditions (analysis problem).
root zone soil moisture
model forecast (OI)
observationsmodel forecast (OL)
• Precipitation errors propagate to the root zone.• Analysis constantly adds water.• The monthly trend is underestimated.
The current analysis fails to produce more accurate soil moisture estimates.
M Drusch
YHK GEWEX May June 2007 Land Surface Flux Workshop
Validation of soil moisturearea averages for Oklahoma
surface soil moisture
• Nudging / satellite data remove water effectively and produce a realistic dry down.• Nudging the satellite results in the most accurate surface soil moisture estimate.
root zone soil moisture
• The information introduced at the surface propagates to the root zone.• The monthly trend is well reproduced using the nudging scheme.
Satellite derived soil moisture improves the soil moisture analysis and results in the most accurate estimate.
M Drusch
YHK GEWEX May June 2007 Land Surface Flux Workshop
Dis-aggregation• With use of higher resolution data (O. Merlin 2005)• Topo and vegetation+ SVAT model (J. Pellenq 2003)
Measured SM (SGP ’97)
Dis aggregated SM (O Merlin 2005)
SMOS pixel 40x40 km
AVHRR Pixels TIR
1 km
Dis-aggregation
Pixel to pixel comparison
YHK GEWEX May June 2007 Land Surface Flux Workshop
Conclusion
• SMOS will be the first mission to deliver global fields of soil moisture and sea surface salinity
• It is an EXPLORER Mission ==> new concept new instrument new measurements!!
• The challenge NO data exists, NO Algorithm exists: we are breaking new grounds
• Launch date 2008 - tomorrow!• Payload and Bus well underway• Ground segment started• Campaigns underway (CoSMOS NAFE and SSS, AMMA…)• Specific scientific activities (modelling, exotic targets, wiggles etc..)• Cal Val AO initiated
– ( http//www.cesbio.ups-tlse.fr/us/indexsmos.html)• Issues: NRT, RFI• SMOS Ops
YHK GEWEX May June 2007 Land Surface Flux Workshop
Thank you …..Any questions ? http//www.cesbio.ups-tlse.fr/us/indexsmos.html
YHK GEWEX May June 2007 Land Surface Flux Workshop
23 January 2003LEWIS
L band for Estimating
Water In
Soils
High Quality Ground based radiometer
1.4 GHz, H & Vsensitivity 0.1 K
main lobe 12.5 @3db, 22° beam efficiency 0.986No « visible » back lobes
ONERA/CESBIOOperational since 23/1/2003