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Aquarius Workshop, Woods Hole, MA, USA11-12 May 2006
&
Observing regional salinity signals of major rivers: Exploring Aquarius and SMOS resolution limits
Derek Burrage, Joel Wesson, Jerry Miller, William Teague (NRL, USA), Carlos Martinez (UR, Uruguay) and Malcolm Heron (JCU,
Australia).
SMOS Workshop, Lyngby, Denmark15-18 May 2006
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• Objectives and Motivation
• Airborne Observations
• Resolution Scales
• Land Correction
• Open Issues
Observing regional salinity signals of major rivers
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• Develop enhanced SSS products for the marginal seas and coastal transition zone.
• Validate enhanced SSS products by under-flying SMOS with NRL’s STARRS radiometer system.
• Assess and demonstrate benefits of enhanced products on coastal ocean data assimilation systems.
Objectives
SMOS Salinity Retrieval, Processing andPerformance in Coastal Regions and Marginal Seas
NRL ESA SMOS project AO-3229
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NRL NCOM SSS Simulation ¼ Deg Grid
Yangtze R.Miss. R. Amazon &
Orinoco R.
Rio de laPlataBurdekin R.
NASA Aquarius ESA SMOS
Observing regional salinity signals of major rivers: Exploring Aquarius and SMOS resolution limits
Simulated Global Coverage ofSMOS 300 km Standard Product
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Scan6 km
FlightDirection
Ocean (Ts, S)
System of 6 beam L-band, 6 channel C- and 2 channelIR-band radiometers for measuring SSS, SSR and SST
Piper Navajo STARRS
Salinity, Temperature and Roughness Remote Scanner
Pixel ~1km
STARRS
Salinity-driven Advection in Littoral Deep Areas (SALIDA) J. Wesson, D. Burrage, J. Miller
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Sea Surface Salinity (SSS) in Marginal Seas
Intra-Americas Sea (IAS)/Gulf of Mexico (GoM)
GDEM3 (MODAS) SSS Climatology
Can we map it from space at regional scales?
IASGoM
15 SSS psu 37
Caribbean
10deg
• Well studied strategically and ecologically important area • Subject to Strong Seasonal Discharge Variations• Various External Forcings – eg. River Discharge, Wind, Tide• Bounded by Complex Topographies
Mississippi R.
Orinoco R.
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Nominal SMOS, Aquarius + STARRSL-band Radiometer Specifications
Instrument: SMOS Aquarius STARRS
Type Interferometer Real-Aperture Interferometer
No. Beams Multi-synthetic 3 6
Pixel Size 32-100 km 85,100,125 km 1km
1-sec NEDT* 2.8-5.5 K 0.2 K 0.5 K
SSS Precision# 5.6-11 psu 0.4 psu 1.0 psu
Repeat (Sub) Cycle
1 Month
(3 Days)
1 Week Daily (4hr flight)
Inc. Angles 30 deg cone 29, 38, 46 deg +/- 7,22,37 deg
Look Dirn 32 deg for’d tilt Downward Downward
Footprint 700 km Hex Transect 5 km Swath
*After adjusting for dwell time assuming Gaussian error distribution# Assuming Salinity Sensitivity of 2 psu / K
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SMOS Std vs Enhanced Regional Product
SMOSStd
Coastal Data Gap
50 km
CoastEnh.
Intra-Americas Sea15 37SSS psu
SSS psu 3715
300 km300 km
107 day period (~1/8 part of full cycle)
Observing Gulf of Mexico SSS in near Real-time
ESOV 59 day repeat orbit:
112 day period (wide swath => full coverage) ESOV 59 day repeat orbit:
GoM SMOS Coverage – Wide Swath
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• Spatial Resolution 200-300 km 50-100 km 1 km
• Temporal Resolution 30 days 3-7 days 0.5 days
• Domain Global Regional Local
• Coastal Data Gap 300-400 km 50 km 1 km
• Salinity Error (psu) 0.1 0.5-2.0* 1.0
PARAMETERS:
Aq/SMOS Std. A.
Regional Enh.B.
PRODUCTS:Resolution
STARRSC.
* Compensated by higher signal to noise ratios near the coast
SSS ProductSpecifications
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STARRS Mississippi River Plume Salinity
7 May2004
8 May 2004
3-4 May2004
Mississippi River Plume CharacteristicsLargest US River Discharge 14000 m3s-1
Salinity Contrast ~ 30 psuStrong Seasonal Discharge CycleOffshore extent ~ 100 km @ 30 psuAlongshelf Influence ~ 1100 km
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230 240 250 260 270 280 290 300 310 32080
85
90
95
100
105
110
115
120
125
SEPS South American Target SSS(SMOS End-End Performance Simulator)
Coarse Array 1 x 1 deg,Fine Array ½ x ½ deg
50 100 150 200 250 300 350 400
60
80
100
120
140
160
180
200
220
240
160 180 200 220 240 260 280 300 320 340
100
110
120
130
140
150
160
170
180
190
Rio de laPlata
Rio de laPlata Plume
Rio de laPlata
AmazonRiver
Brazil Current/Malvinas CurrentConfluence
Rio de la Plata plume NCOMSSS field superimposedon the SEPS SSS TargetArray.
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50 100 150 200 250 300 350 400
60
80
100
120
140
160
180
200
220
240
South America SEPS Target Run Amr01a,b
Characteristics of the Amazon River PlumeLargest World River Discharge 170000 m3s-1
(Orinoco River is 4th. Largest with 31000 m3s-1)Salinity Contrast ~ 10 psuStrong Seasonal Discharge CycleOffshore extent ~ 200 km @ 34 psuAlongshelf Influence ~ 3500 km
Amazon R.
Orinoco R.
16Amazon SEPS3.1 TB Run amr01b
Original DifferenceMeasured
Th
Tv
Simulated SMOS single-snapshot viewof Amazon River Delta
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50 100 150 200 250 300 350 400
60
80
100
120
140
160
180
200
220
240
South America SEPS Target Run Rdp01a,b
Characteristics of the Rio de la Plata PlumeLarge River Discharge ~ 25,000 m3s-1
Salinity Contrast ~ 10 psuWeakly Seasonal Discharge CycleStrong influence of Earth Rotation and WindsOffshore extent ~ 200 km @ 33 psuAlongshelf Influence ~ 1200 km
Rio de la Plata
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STARRS Plata Plume Winter 2003 Observations
Mar del Plata
Florianopolis
Patos Lagoon Outflow Plume (STARRS)
Rio Grande
Plata Plume
D=1100 kmdS=10 psu
Rio de laPlata
Casa 212
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Rio de la Plata SEPS 3.1Target TB Rdp01bSimulation and Analysis of a Single Snapshot
Fine Array
Coarse Array
Original Measured Measured-Original
Rio de laPlata
Rio de laPlata
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Herbert-BurdekinRiver System
SLFMR SSS Map24 Mar., 2000
2520151050146 147 148
20.0
19.5
19.0
18.5
18.0
17.5
17.0 200 m
200 m
Tully River
Herbert River
Burdekin River
Towns- ville
Great Barrier Reef
La
titu
de
[°S
]
Longitude [°E]
Characteristics of the Burdekin PlumeMean/Max Annual Discharge ~ 322/~3,000 m3s-1
Peaks to 25000 m3s-1, Salinity Contrast ~ 10 psuEvent-based Tropical Monsoon Flood CycleModerate Rotation Tide and Wind InfluenceOffshore extent ~ 25/50 km @ 30/34 psuAlongshelf Influence ~ 600 kmConfined within Great Barrier Reef Lagoon
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Length Scale & Salinity Anom.
L
[km]
dS
[psu]
Aq. Std.
A.
ESAStd.
B.
Cst Enh.
C.
Source
Yellow Sea 900 2 Y Y M MODAS (Barron et al.)
Gulf of Mexico 1100 2 Y Y M IAS (Ko et al.)
Gulf Stream 150 5 M N Y Le Vine & Koblinsky’99
GS WC Ring 100 2 N N M Le Vine et al (2000)
Alaska CC 150 3 N N Y Royer (1981)
Amazon/Orinoco
200 10 Y Y Y Hellweger&Gordon;
Yangtze 200 4 N N M | Geyer et al.
Plata Plume 200 10 N N Y Martinez et al (2005)
Miss.Plume 100 30 N N Y STARRS Burrage et al
Burdekin Plume 50 10 N N N SLFMR Burrage/Heron
Resolution: A150 km / 0.1 psu B300 km / 0.2 psu C50 km / 1.0 psu
Ocean Feature Salinity Resolution
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LandMain
Beams
Idealized Aquarius Beam #2 Coastal Crossing
Side LobeFOV #2
SeaTbSea
TbLand
300KFOV #1
FOV #3
FOV #2
100K
Coast
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Idealized Aquarius Beam 2 Antenna PatternE-plane (solid line) and H-plane cuts for the co-pol pattern of the middle beam at vertical polarization.
Source: “Aquarius Antenna Patterns”David le Vine (personal communication)
30 dBPeakGain
Mixed Pixel Target TemperatureIdealized Antenna Gain Pattern
Tb [K]
-50 -180 180 -3 3 50
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Gain[dB]
Azimuth [deg] – not to scale
-13
Sky
Land
Sea Sky
3
100
300
Coa
st
150 -150
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Idealized Aquarius Beam Crossing Coast
-400 -300 -200 -100 0 100 200 300 40010
-3
10-2
10-1
100
101
102
103
104
105
Distance from Coast [km]
Sea
Tb
[K]
Sea Tb Error given Land Tb error 5 10 15 [K]
Mainlobe Sidelobe Sidelobe
1.0 K
0.1 K
Errors after Correcting for Land in Field of View
Sea Land
Uncorrected
Corrected
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SMOS Sampling PatternNIR ReferenceRadiometerFOV
FOV
OpenSea
Land
Pixels(~50 km) AF-FOV
(~300 km)
Alias-freeField of View(AF-FOV)
FOVAliases
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STARRS Mixed-Pixel SurveyNIR ReferenceRadiometerFOV
Sea
Land
Alias-freeField of View(AF-FOV)
Coast
MIRASPixels
MixedPixel
STARRSFlightLines ~50
km
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• Account for Land Temperatures entering FOV
Use measured SMOS overland Tb’s for current or prior overpass?
Alternatively, use land Tb’s derived from models orThermal IR measurements and IR emissivity?
Extrapolate these toward coast.Use detailed coastal outline for region of interest
• SSS Freshwater signal typically increases toward coast=> Can trade-off radiometric resolution
for better spatial resolution in the coastal transition zone
Land Alias and Mixed Pixel CorrectionsOptimizing resolution in the coastal transition zone
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What are the practical limits and options to approach the coast?
How should OS Mixed pixel processing be performed?
How can we optimize spatial and radiometric resolution near coasts?
Do we need a ‘coastal transition zone ’ (L3) data product?
What possible modifications to L2 OS would facilitate this?
Are new data products or algorithms/modules/apodization requiredfor inclusion in the SMOS and Aquarius processing chain?
What mission and auxiliary data are needed for this chain?
How can we best validate coastal transition products?
Open Issues for SMOS/Aq. Science Team
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Regional/Coastal Data Processing:
• SMOS Level 1c
• SMOS Level 2 OS Ocean Product (with 200-300 km land overlap)
… and Depending upon Mixed Pixel Algorithms:
• SMOS Level 1b
• SMOS Level 2 (Soil Moisture Product)
Product Requirements
SMOS Salinity Retrieval, Processing and Performance in Coastal Regions and Marginal Seas
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What are the practical limits and options to approach the coast?
How should OS Mixed pixel processing be performed?
How can we optimize spatial and radiometric resolution near coasts?
Do we need a ‘coastal transition zone ’ (L3) data product?
What possible modifications to L2 OS would facilitate this?
Are new data products or algorithms/modules/apodization requiredfor inclusion in the SMOS and Aquarius processing chain?
What mission and auxiliary data are needed for this chain?
How can we best validate coastal transition products?
Open Issues for SMOS/Aq. Science Team