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YHK 2006 Pan Gewex Meeting October 9-13 ESRIN It
SMOS Soil moisture
retrieval Algorithm
Y. H. Kerr1, …and the SMOS team
YHK 2006 Pan Gewex Meeting October 9-13 ESRIN It
Outline
• SMOS mission overview in a nutshell
• Soil moisture retrievals– Level 2– Level 3 – Level 4
• Results, issues and next steps
• Conclusion
YHK 2006 Pan Gewex Meeting October 9-13 ESRIN It
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 2006 Pan Gewex Meeting October 9-13 ESRIN It
• 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 2006 Pan Gewex Meeting October 9-13 ESRIN It
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 2006 Pan Gewex Meeting October 9-13 ESRIN It
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 2006 Pan Gewex Meeting October 9-13 ESRIN It
Validation of soil moisturearea 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 2006 Pan Gewex Meeting October 9-13 ESRIN It
Validation of soil moisturearea averages for Oklahoma
surface soil moisture
• Nudging / satellite data remove water effectively and produce a realistic drydown.
• Nudging the satellite results in the mostaccurate 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 2006 Pan Gewex Meeting October 9-13 ESRIN It
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 2006 Pan Gewex Meeting October 9-13 ESRIN It
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
TB(40,V) 1st February 87 (K)
TB(40,V) 1
st February 87 (K)
TB(40,H) 1
st February 87 (K)
0 7200
300
TB(40,H) 1st February 87 (K)
TB(40,H) 1
st February 87 (K)
TB(40,H) 1
st February 87 (K)
0 7200
300
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 2006 Pan Gewex Meeting October 9-13 ESRIN It
Interferometry• angular resolution
provided by distantantennas
• correlation productss(1)*s(2) → visibilityfunctions V(D/λ)
• Inverse F.T. on V → TB(θ)
Space sampling requirement : every λ/2 value at least onetime ; hence "thinning" possibilities.
1
θ
DD '
∆θ
∆θ ≈ λ / D'
2
YHK 2006 Pan Gewex Meeting October 9-13 ESRIN It
•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°, 0.875λ,
P. Waldteufel, 2003
YHK 2006 Pan Gewex Meeting October 9-13 ESRIN It
SMOSBaseline
• 18+5 elements /armconfiguration
• Mean Altitude --> 757 km +/- 500 m• 30° steer angle• 32.5° tilt angle • Elements spacing
0.875 λ• Dual or Full pol
2006 Pan Gewex Meeting October 9-13 ESRIN It
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 2006 Pan Gewex Meeting October 9-13 ESRIN It
Schedule• Current:
– Payload module is being assembled (CASA)– Antennas have been measured (TUD)– Ground segment at various stages depending levels– Delivery of PLM after testing early 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 2006 Pan Gewex Meeting October 9-13 ESRIN It
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 2006 Pan Gewex Meeting October 9-13 ESRIN It
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
2006 Pan Gewex Meeting October 9-13 ESRIN It
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 Traitementdes DonnéesSmos (L3-L4)
USERS
L0,L1,L2
L3,L4Reports
L2,L3,L4Requests
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
2006 Pan Gewex Meeting October 9-13 ESRIN It
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 2006 Pan Gewex Meeting October 9-13 ESRIN It
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 2006 Pan Gewex Meeting October 9-13 ESRIN It
Models and mixed pixels
global B T at SM O Santennas
S ynthetic antenna d irectional ga ind i
e1 e2 e3 e4 e5 e6 e7 e8 e9
G 2
G 5
type 1 em itter ⇒ C F 1
type 2 em itter ⇒ C F 2
type 3 em itter ⇒ C F 3
antenna footprin t
G 7
: 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 2006 Pan Gewex Meeting October 9-13 ESRIN It
0 5010 4020 30
Teodosio Lacava – IMAA-CNR;
Mean Soil Moisture (% volume): January 2003-2005 A
Projection: EASE Grid Global; Datum: WGS-84
YHK 2006 Pan Gewex Meeting October 9-13 ESRIN It
Teodosio Lacava – IMAA-CNR
Projection: EASE Grid Global; Datum: WGS-84
0 5010 4020 30
Mean Soil Moisture (% volume): April 2003-2005 A
YHK 2006 Pan Gewex Meeting October 9-13 ESRIN It
Pre Processing filter SMOS views co-locate auxiliary data with DGG node compute aggregated mean cover fractions compute reference values
Iterative parameters retrievalfit 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 auxiliaryFixed reference Evolving reference User parameters file
TB models libraryforward 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 Productretrieved parameters parameters variances science & quality flags
Data Analysis Report
algorithms internal datafull flags
Do full retrieval again eliminate bad views decrease free number of parameters
Level 2:Soil moistureAlgorithm
layout
YHK 2006 Pan Gewex Meeting October 9-13 ESRIN It
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 2006 Pan Gewex Meeting October 9-13 ESRIN It
The SMOSworld….And DGGs…
DFFG @ δkm
=300 km, for φ ∈ {−87,87} & λ ∈ {0,360}
Orthographic Projection
YHK 2006 Pan Gewex Meeting October 9-13 ESRIN It
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 2006 Pan Gewex Meeting October 9-13 ESRIN It
What is in a Pixel?!!!Working Area @ DGG ID #32002432 [φ = 44.42°, λ = −1.115°, 123 km x 123 km]
EEAP DFFG @ δkm
= 4 km, Zone #72
Albers Equal−Area 2oW 30’ 1oW 30’ 0o
40’
44oN
20’
40’
45oN
Working area contains all
the footprints and more
Nodes spatial sampling
Elementary surfaces (DFFG)
YHK 2006 Pan Gewex Meeting October 9-13 ESRIN It
The land use map (MétéoFrance –Ecoclimap binned into generic classes)How homogeneous ?areas with prevailing nominal and forested aggregated LC fractions
YHK 2006 Pan Gewex Meeting October 9-13 ESRIN It
In conclusion: SM retrievals can be attempted in many areas with varying
expected accuracy
YHK 2006 Pan Gewex Meeting October 9-13 ESRIN It
Algorithm validation PlanDirect simulation Lo-
op Selection x / + N data set
Data options for DQX runs 792 TBL1Surface scene
Scene 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 TL2 Mixing 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 2006 Pan Gewex Meeting October 9-13 ESRIN It
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 2006 Pan Gewex Meeting October 9-13 ESRIN It
NAFE ’05 J Walker et al.Regional Data: 1km
796
183
Elevation
Visible
YHK 2006 Pan Gewex Meeting October 9-13 ESRIN It
Issues• Water bodies• Varying features (Frozen, snow)• Perturbations (rain interception)• RFI• Unknown surfaces (urban, barren ….)• And things to discover….
YHK 2006 Pan Gewex Meeting October 9-13 ESRIN It
23 January 2003LEWIS
L band for Estimating
WaterIn
Soils
High QualityGround 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
YHK 2006 Pan Gewex Meeting October 9-13 ESRIN It
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 2006 Pan Gewex Meeting October 9-13 ESRIN It
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……….
AQUARIUSAQUARIUSSea Surface Salinity Mission
YHK 2006 Pan Gewex Meeting October 9-13 ESRIN It
Data Assimilation ProductsData Assimilation Products
Land Surface Modeled PhysicsDataData
Model IntegrationsModel Integrations
UpdateUpdate
UpdateUpdate
Global at 5 kmat model time-step
L4_5km_4DDAL4_5km_4DDAproductproduct
YHK 2006 Pan Gewex Meeting October 9-13 ESRIN It
Atmospheric Forcing(Rg, Ra, Ta, qa, U, P) Remote sensing
Soil and vegetationparameters
LAI
SVAT model
SURFACESoil moistureTemperature
VegetationOpticalthickness
InteractiveVegetation
Radiative Transfermodel
Root-zonesoilmoisture
Plant growthparametersor biomass
Radiances
OPTIMISATION
RootRoot Zone Zone soilsoil moisturemoisturePRINCIPLE OF THE ASSIMILATION OF REMOTE PRINCIPLE OF THE ASSIMILATION OF REMOTE
SENSING DATASENSING DATA
Calvet et al.
YHK 2006 Pan Gewex Meeting October 9-13 ESRIN It
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-aggregationPixel to pixel comparison
YHK 2006 Pan Gewex Meeting October 9-13 ESRIN It
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