![Page 1: Remote Sensing Reflectance and Derived Products: MODIS …...MODISA Instrument Calibration Update Goal was to mitigate some temporal artifacts observed in previous ocean color trends,](https://reader036.vdocuments.mx/reader036/viewer/2022071105/5fdfb86b5dfbad0925019b04/html5/thumbnails/1.jpg)
Remote Sensing Reflectance and Derived Products: MODIS and VIIRS
MODIS/VIIRS Science Team, 15-19 October 2018, Silver Spring, MD
Bryan FranzOcean Ecology Laboratory
NASA Goddard Space Flight Center
![Page 2: Remote Sensing Reflectance and Derived Products: MODIS …...MODISA Instrument Calibration Update Goal was to mitigate some temporal artifacts observed in previous ocean color trends,](https://reader036.vdocuments.mx/reader036/viewer/2022071105/5fdfb86b5dfbad0925019b04/html5/thumbnails/2.jpg)
Project Team
MODIS Algorithm MaintenanceRemote Sensing Reflectance, Chlorophyll, Diffuse Attenuation
Science of Terra/Aqua/SNPPAdvancingtheQualityandContinuityofMarineRemoteSensingReflectanceandDerivedOceanColorProductsfromMODIStoVIIRS
TeamMember RoleBryanFranz(PI) ProjectleadAmirIbrahim(Co-I) AtmosphericcorrectionSeanBailey(Co-I) VicariouscalibrationGerhardMeister(Co-I) InstrumentcalibrationJeremyWerdell (Co-I) Bio-opticalalgorithmsZiaAhmad(Supp) AC&radiativetransfercodeGeneEplee (Supp) Instrumentcalibration(VIIRS)Shihyan Lee(Supp) Instrumentcalibration(MODIS)ChrisProctor(Supp) InsituvalidationErdem Karakoylu (Supp) Uncertainties
andtheOceanBiologyProcessingGroup
![Page 3: Remote Sensing Reflectance and Derived Products: MODIS …...MODISA Instrument Calibration Update Goal was to mitigate some temporal artifacts observed in previous ocean color trends,](https://reader036.vdocuments.mx/reader036/viewer/2022071105/5fdfb86b5dfbad0925019b04/html5/thumbnails/3.jpg)
Contents
1. StatusofMODIS&VIIRSOceanColorProducts
2. StatusandPlansforAlgorithmAdvancement
1. Multi-bandAtmosphericCorrection
2. Rrs UncertaintyProduct
![Page 4: Remote Sensing Reflectance and Derived Products: MODIS …...MODISA Instrument Calibration Update Goal was to mitigate some temporal artifacts observed in previous ocean color trends,](https://reader036.vdocuments.mx/reader036/viewer/2022071105/5fdfb86b5dfbad0925019b04/html5/thumbnails/4.jpg)
Ocean Color Reprocessing R2018.0
Completed• Dec2017(VIIRS/SNPP),January2018(MODIS/Aqua),April2018(MODIS/Terra)
Purpose• incorporateupdatestovicariouscalibrationduetorevisedMOBYtime-series• incorporateupdatestoinstrumentcalibration• noalgorithmchanges
![Page 5: Remote Sensing Reflectance and Derived Products: MODIS …...MODISA Instrument Calibration Update Goal was to mitigate some temporal artifacts observed in previous ocean color trends,](https://reader036.vdocuments.mx/reader036/viewer/2022071105/5fdfb86b5dfbad0925019b04/html5/thumbnails/5.jpg)
Impact of MOBY Revisions on MODISA Ocean ColorGlobal Deep Water Time-Series Test (MOBY change only)
MOBYinsituradiometryisusedforvicariouscal ofvisiblebands,allmissions
MOBYreprocessedbyMOTin2016and2017• reviseddepthofsensorarms• newstraylightcorrection
Impactwasto• increaseRrs by2-10%• decreaseglobalChl by8%
RrsR
atio
Rrs(sr
-1)
ChlRatio
Chl(mgm
-3)
MOBYbiasshift+2-10%inRrs
MOBYbiasshift-8%inChl
![Page 6: Remote Sensing Reflectance and Derived Products: MODIS …...MODISA Instrument Calibration Update Goal was to mitigate some temporal artifacts observed in previous ocean color trends,](https://reader036.vdocuments.mx/reader036/viewer/2022071105/5fdfb86b5dfbad0925019b04/html5/thumbnails/6.jpg)
MODISA Instrument Calibration UpdateGoalwastomitigatesometemporalartifactsobservedinpreviousoceancolortrends,believedtobeassociatedwithcal datasmoothing/fittingdecisions.
Completeend-to-endre-analysisofon-boardcalibrationwasperformed,largelyfollowingMCSTapproach,butwithsomedifferences.• SD/SDSMscreens,SDBRF:derivedfromsimplefitofyawmaneuverdata,notgeometricmodeling
• SDSMCal:SDdegradationsinred/NIRweredeterminedbywavelengthmodeling(Leeetal.,2018)
• RVS:simpleatmosphericcorrectionaddedwhencomputingdeserttrendstotrackRVS in412,443nm
• ModulatedRSR:impactonoceandataestimatedandusedtoadjust412nmtemporalgains(Leeet.al.2017)
• RSBLUTs:useofsmoothingratherthanfittingtotheinstrumenttemporalcalibrationtrendingand
characterization(i.e.,noassumptiononfunctionalform)
Monthlyupdatetomaintaincalibrationtrendconsistencyinforwardprocessing.
![Page 7: Remote Sensing Reflectance and Derived Products: MODIS …...MODISA Instrument Calibration Update Goal was to mitigate some temporal artifacts observed in previous ocean color trends,](https://reader036.vdocuments.mx/reader036/viewer/2022071105/5fdfb86b5dfbad0925019b04/html5/thumbnails/7.jpg)
MODISA Global Deep-Water (R2018.0 vs R2014.0)
RrsR
atio
Rrs(sr
-1)
ChlRatio
Chl(mgm
-3)
instrumentcalibrationupdate
MOBYbiasshift+2-10%inRrs
MOBYbiasshift-8%inChl
Late-missiondriftinblueRrs resolved.
Largeseasonalspikesinchlorophyllremoved.
![Page 8: Remote Sensing Reflectance and Derived Products: MODIS …...MODISA Instrument Calibration Update Goal was to mitigate some temporal artifacts observed in previous ocean color trends,](https://reader036.vdocuments.mx/reader036/viewer/2022071105/5fdfb86b5dfbad0925019b04/html5/thumbnails/8.jpg)
MODISA Rrs Anomaly Trend in Global Oligotrophic Water
Inveryclear-water,openoceanregions(Chl <0.1),weexpectminimalvariabilityingreenspectralbands.
R2018showsimprovedstabilityintemporaltrendsofwater-leavingreflectanceinthegreenbandsofMODIS/Aqua.
R2014.0
R2014.0
R2018.0
R2018.0R
rs(5
47)
Rrs
(555
)
![Page 9: Remote Sensing Reflectance and Derived Products: MODIS …...MODISA Instrument Calibration Update Goal was to mitigate some temporal artifacts observed in previous ocean color trends,](https://reader036.vdocuments.mx/reader036/viewer/2022071105/5fdfb86b5dfbad0925019b04/html5/thumbnails/9.jpg)
instrumentcalibrationupdate
biasshift+3-5%inRrs
biasshift-9%inChl
RrsR
atio
Rrs(sr
-1)
ChlRatio
Chl(mgm
-3)
VIIRS/SNPP Global Deep-Water (R2018.0 vs R2014.0)
InstrumentCalibrationupdatesinclude:
• revisedtemporalcalwithadditionalsolar&lunarmeasurementssinceR2014
• lunarmeasurementscorrectedfordetectorgainvariability
• absolutecalibrationofallspectralbandsbasedonobservationsofthesunthroughthesolardiffuser
![Page 10: Remote Sensing Reflectance and Derived Products: MODIS …...MODISA Instrument Calibration Update Goal was to mitigate some temporal artifacts observed in previous ocean color trends,](https://reader036.vdocuments.mx/reader036/viewer/2022071105/5fdfb86b5dfbad0925019b04/html5/thumbnails/10.jpg)
VIIRS/SNPP R2018.0 Reprocessingimproved agreement with in situ
Rrs(412) Rrs(443) Chlorophyll
R2014.0
R2018.0
Bias
Bias=5%Bias=-0.00032 Bias=+0.00001
VIIRS/SNPP R2018.0 Reprocessingimproved agreement with in situ
Rrs(412) Rrs(443) Chlorophyll
R201
4.0
R201
8.0
Bias
Bias = 5%Bias = -0.00032 Bias = +0.00001
Bias=-0.001
![Page 11: Remote Sensing Reflectance and Derived Products: MODIS …...MODISA Instrument Calibration Update Goal was to mitigate some temporal artifacts observed in previous ocean color trends,](https://reader036.vdocuments.mx/reader036/viewer/2022071105/5fdfb86b5dfbad0925019b04/html5/thumbnails/11.jpg)
MODISA R2018.0 Reprocessingimproved agreement with in situ
R2014.0
R2018.0
Rrs(412) Rrs(443)
Bias
Chlorophyll
Bias=32%
Bias=18%
Bias=-0.00077
Bias=+0.00005 Bias=+0.00008
Bias=-0.00027
![Page 12: Remote Sensing Reflectance and Derived Products: MODIS …...MODISA Instrument Calibration Update Goal was to mitigate some temporal artifacts observed in previous ocean color trends,](https://reader036.vdocuments.mx/reader036/viewer/2022071105/5fdfb86b5dfbad0925019b04/html5/thumbnails/12.jpg)
In situ Rrs Match-up Statistics for MODISA
Product NumberMatchups
MeanBias(sr-1) MeanAbsoluteError(sr-1)
R2014.0 R2018.0 R2014.0 R2018.0Rrs(412) 3934 -0.00077 0.00005 0.00125 0.00099
Rrs(443) 4134 -0.00027 0.00008 0.00082 0.00075
Rrs(488) 3772 -0.00067 -0.00050 0.00088 0.00077
Rrs(531) 2076 -0.00063 -0.00057 0.00083 0.00079
Rrs(547) 3619 -0.00052 -0.00048 0.00078 0.00076
Rrs(555) 3534 -0.00081 -0.00075 0.00096 0.00090
Rrs(667) 3573 -0.00017 -0.00016 0.00030 0.00029
Rrs(678) 472 -0.00016 -0.00014 0.00034 0.00033
• equalorreducedmeanbiasandMAEinallbands• largenegativebiasinbluereducedtosmallpositivebias
identicalfielddatasourcesfromAERONET-OCandSeaBASS
![Page 13: Remote Sensing Reflectance and Derived Products: MODIS …...MODISA Instrument Calibration Update Goal was to mitigate some temporal artifacts observed in previous ocean color trends,](https://reader036.vdocuments.mx/reader036/viewer/2022071105/5fdfb86b5dfbad0925019b04/html5/thumbnails/13.jpg)
0.10
0.12
0.14
0.16
0.18
0.20
Chla
(mg
m−3)
0.10
0.12
0.14
0.16
0.18
0.20
Chla
(mg
m−3)
Jan
1998
Jan
2002
Jan
2006
Jan
2010
Jan
2014
−20
0
20
40
Chla
(%)
−0.04
−0.02
0.00
0.02
0.04Ch
la A
nom
aly
(mg
m−3)
−0.04
−0.02
0.00
0.02
0.04Ch
la A
nom
aly
(mg
m−3)
Jan
1998
Jan
2002
Jan
2006
Jan
2010
Jan
2014
−20
−10
0
10
20
Chla
Ano
mal
y (%
)
a.
b.
SeaWiFS MODISA VIIRS
Multivariate Enso Index (MEI)
SeaWiFS MODISA VIIRS
21-year Multi-mission Chlorophyll TimeseriesDeep-Water, +/- 40 deg latitude
• MODISAingoodagreementwithSeaWiFS andVIIRS(through~2015)
• anomalytrendsgenerallyconsistentwithexpectationsbasedonMEI
• suspectlatemissiontrendinVIIRS(didnotrecoverfrom2015/16ENSOevent)
• likelyissueisunresolvedimpactsinbluebandstochangingspectralresponseofVIIRS(TBD)
Chloroph
yll(mgm
-3)
Chloroph
yllA
nomaly(m
gm
-3)
![Page 14: Remote Sensing Reflectance and Derived Products: MODIS …...MODISA Instrument Calibration Update Goal was to mitigate some temporal artifacts observed in previous ocean color trends,](https://reader036.vdocuments.mx/reader036/viewer/2022071105/5fdfb86b5dfbad0925019b04/html5/thumbnails/14.jpg)
from Ibrahim et al., Ocean Optics XXIV, October 2018, Dubrovnik, Croatia.
Gordon and Wang, 1994
MSE MBAC
SSàMS
AC Algorithm Refinement
![Page 15: Remote Sensing Reflectance and Derived Products: MODIS …...MODISA Instrument Calibration Update Goal was to mitigate some temporal artifacts observed in previous ocean color trends,](https://reader036.vdocuments.mx/reader036/viewer/2022071105/5fdfb86b5dfbad0925019b04/html5/thumbnails/15.jpg)
TOAradiance
Lt
Rayleigh,gas,andglintcorrection
Estimate the optical depth at the longest high performance band
Estimate the aerosol spectral reflectance for a set of models
Lrgc
𝛁𝝌𝟐minimization
Averagebestmodels,calculatetransmittances
Rrs ,𝝉a,Angstrom
Multi-band Atmospheric Correction (MBAC)
![Page 16: Remote Sensing Reflectance and Derived Products: MODIS …...MODISA Instrument Calibration Update Goal was to mitigate some temporal artifacts observed in previous ocean color trends,](https://reader036.vdocuments.mx/reader036/viewer/2022071105/5fdfb86b5dfbad0925019b04/html5/thumbnails/16.jpg)
MBAC Cost Function
observed/predictedaerosolreflectance adaptivespectralweight
radiometricuncertainty
SensorWavelength(l,nm)
MODIS 748 859 869 1240 1640 2130
VIIRS 746 868 1238 1604 2258
PACE-OCI 750 860 870 1038 1250 1615 2130 2260
𝑆𝑊(𝜆)
0
1
NIRiterations(Baileyetal.,2010)increasingwatercomplexity
![Page 17: Remote Sensing Reflectance and Derived Products: MODIS …...MODISA Instrument Calibration Update Goal was to mitigate some temporal artifacts observed in previous ocean color trends,](https://reader036.vdocuments.mx/reader036/viewer/2022071105/5fdfb86b5dfbad0925019b04/html5/thumbnails/17.jpg)
Operational MBACChesapeake Bay
Pamlico Sound
Operational MBAC
• MBACchlorophyllretrievalssimilartostandardalgorithm,exceptinturbidcoastalregions.
• Differenceisduetoretrievedaerosolmodels(aerosoltype).
Application to MODISA (MBAC vs Std AC)
![Page 18: Remote Sensing Reflectance and Derived Products: MODIS …...MODISA Instrument Calibration Update Goal was to mitigate some temporal artifacts observed in previous ocean color trends,](https://reader036.vdocuments.mx/reader036/viewer/2022071105/5fdfb86b5dfbad0925019b04/html5/thumbnails/18.jpg)
MODISA In Situ Match-up Analysis (MBAC vs Std AC)
SeaBASS in-situ matchups to
water-leaving reflectance shows
reduction in error using MBAC
relative to standard algorithm, at
all spectral bands.
Artifacts ?
Highly turbid example for upper
Chesapeake Bay, MBAC shows
more meaningful (positive) Rrs
retrievals in blue channels.
![Page 19: Remote Sensing Reflectance and Derived Products: MODIS …...MODISA Instrument Calibration Update Goal was to mitigate some temporal artifacts observed in previous ocean color trends,](https://reader036.vdocuments.mx/reader036/viewer/2022071105/5fdfb86b5dfbad0925019b04/html5/thumbnails/19.jpg)
• Algorithm
• Sensor Random Noise
• Sensor Systematic Noiseuncertainty
𝐿+
RetrievalAlgorithm(InverseProblem)
uncertainty
bias
𝑅-.
observations retrievals
Development of a Per-Pixel Rrs(l) Uncertainty Product
from Ibrahim et al., Ocean Optics XXIV, October 2018, Dubrovnik, Croatia.
![Page 20: Remote Sensing Reflectance and Derived Products: MODIS …...MODISA Instrument Calibration Update Goal was to mitigate some temporal artifacts observed in previous ocean color trends,](https://reader036.vdocuments.mx/reader036/viewer/2022071105/5fdfb86b5dfbad0925019b04/html5/thumbnails/20.jpg)
Uncertainty per-pixel
TOA measurements noise
Step-by-steperrorpropagation
Error Propagation
Sensor Random Noise
• SensornoisecanbepropagatedthroughtheMSE/MBACalgorithmsusingstandarderrorpropagation.
• ResultsagreeverywellwithMCsimulations(presentedpreviously).
MC Simulation
![Page 21: Remote Sensing Reflectance and Derived Products: MODIS …...MODISA Instrument Calibration Update Goal was to mitigate some temporal artifacts observed in previous ocean color trends,](https://reader036.vdocuments.mx/reader036/viewer/2022071105/5fdfb86b5dfbad0925019b04/html5/thumbnails/21.jpg)
𝜃0123
𝜃.45 = 10° 𝜃.45 = 20°
𝜃.45 = 30° 𝜃.45 = 60°
𝜃0123
𝜃0123
𝜃0123
Simulationparameters:• 𝜃0123 = 0°: 80°,• ∆𝜑 = 0°: 180°,• 𝜃.45 = 10°, 20°, 30°, 60°• 𝜏D = 0.05: 0.35• RH = 77.5% à Not in the LUT• 𝑓 = 0: 0.95• chlor-a=0.03mg/m3
• total#cases:1037400
• average∆𝜌3 443 =0.0015
• uncertaintyincreaseswithsolar
zenithangle
• uncertaintyincreasessignificantly
forlargerfine-modefractioncases
duetothelinear-mixinglimitations
𝝀 = 𝟒𝟒𝟑𝒏𝒎
Algorithm Uncertainty
![Page 22: Remote Sensing Reflectance and Derived Products: MODIS …...MODISA Instrument Calibration Update Goal was to mitigate some temporal artifacts observed in previous ocean color trends,](https://reader036.vdocuments.mx/reader036/viewer/2022071105/5fdfb86b5dfbad0925019b04/html5/thumbnails/22.jpg)
𝜃0123
𝑅𝑒𝑑𝑢𝑐𝑡𝑖𝑜𝑛𝑖𝑛∆𝜌3𝑤𝑖𝑡ℎ𝑀𝐵𝐴𝐶
𝜃0123 𝜃0123
Simulationparameters:• classicalcovarianceanalysis• assumecorrelatedbiasof2%onbands>750nmand0.5%onVNIRbands
• assume10%correlatedcovariancebetweenbands
average uncertainty:
• Operational 2-band AC à 0.0036
• MODIS-MBAC 6-band à 0.0024
• Uncertainty is reduced by à 34%
𝝀 = 𝟒𝟒𝟑𝒏𝒎, 𝜽𝒔𝒖𝒏 = 𝟑𝟎°
𝑀𝐵𝐴𝐶 𝑆𝑡𝑎𝑛𝑑𝑎𝑟𝑑𝐴𝑙𝑔𝑜𝑟𝑖𝑡ℎ𝑚
Sensor Systematic Error
![Page 23: Remote Sensing Reflectance and Derived Products: MODIS …...MODISA Instrument Calibration Update Goal was to mitigate some temporal artifacts observed in previous ocean color trends,](https://reader036.vdocuments.mx/reader036/viewer/2022071105/5fdfb86b5dfbad0925019b04/html5/thumbnails/23.jpg)
Future DevelopmentMulti-BandAtmosphericCorrection• assess/improvespectral-relativecalibrationforNIR/SWIRregion(MODIS&VIIRS)• assess/improveperformanceofadaptiveweightingscheme• initiateglobal-scaletestingforMODIS&VIIRS
Rrs UncertaintyProduct• completethealgorithmframeworkforRrs uncertaintyproduct(combined
random/systematic/algorithmerror)• refinesystematicerrortermsforeachinstrument• assessuncertaintyestimatesrelativetomatch-upresults(closureexperiment)
InstrumentCalibration• reassessVIIRSspectralresponsechanges,impactontrendsinblue• evaluateMODIS-TerraR2018.0results