Land and Ocean ColorSlide 2Measuring Vegetation (NDVI, EVI, and Ocean Color)Attenuation in the Visible WavelengthsSlide 5Daytime VisibilityNighttime VisibilityRevisiting Daytime VisibilitySlide 9Daytime Visibility RevisitiedAerosol Hygroscopic GrowthSky ImagingNDVISlide 14Advanced Very High Resolution Radiometer (AVHRR)Satellite NDVI data sourcesEVI (Enhanced Vegetation Index)History of the NDVI & Vegetation IndicesSlide 19Beltsville USA winter wheat biomassWinter wheat biomass “harvest”S NDVI vs. total dry biomassMarked contrasts between the dry and wet seasonsAverage NDVI 1981-2006Species mapping with physiological indicesSpectral Indices: NDVIGlobal Vegetation Mapping5 SeaWiFS land bandsOcean ColorTasmanian SeaSlide 31Slide 32Atmospheric Correction MethodsAtmospheric Aerosol Correction ProcedureSlide 35Slide 36Slide 37Slide 38Land and Ocean Color•Though we often take the plants and trees around us for granted, almost every aspect of our lives depends upon them. •By carefully measuring the wavelengths and intensity of visible and near-infrared light reflected by the land surface back up into space a "Vegetation Index" may be formulated to quantify the concentrations of green leaf vegetation around the globe.Normalized Difference Vegetation Index (NDVI)•Distinct colors (wavelengths) of visible and near-infrared sunlight reflected by the plants determine the density of green on a patch of land and ocean.•The pigment in plant leaves, chlorophyll, strongly absorbs visible light (from 0.4 to 0.7 μm) for use in photosynthesis. The cell structure of the leaves, on the other hand, strongly reflects near-infrared light (from 0.7 to 1.1 μm). •The more leaves a plant has or the more phytoplankton there is in the column, the more these wavelengths of light are affected, respectively.Measuring Vegetation (NDVI, EVI, and Ocean Color)Attenuation in the Visible WavelengthsGrant Petty, 2004Attenuation in the Visible WavelengthsGrant Petty, 2004Daytime VisibilityDistant Dark ObjectsAppear Brighter“Clear” DayHazy DayNighttime VisibilityDistant Bright Objectsare dimmerRevisiting Daytime VisibilityWhite Sunlight Top of AtmosphereHorizon Color and IntensityHorizon alwaysWhitened relative toSky aboveDistance to the Dark ObjectHenceforth, we shall only consider scatteringby clouds and aerosolsRevisiting Daytime VisibilityWhite Sunlight Top of AtmosphereIncreased contribution ofwhite lightObject appears lighterwith distance Longer Distance to the Dark ObjectDaytime Visibility RevisitiedDistant Dark ObjectsAppear Brighter“Clear” DayHazy DayENVI-1200 Atmospheric PhysicsAerosol Hygroscopic Growth•Deliquescence–Dry crystal to solution droplet•Hygroscopic–Water-attracting•Efflorescence–Solution droplet to crystal (requires ‘nucleation’)•Hysteresis–Particle size and phase depends on humidity history500 nmRV Ron BrownCentral PacificAOT=0.08Sea of JapanAOT=0.98 AMFNiamey, NigerAOT=2.5-3 Sky ImagingNDVINDVI = (NIR — VIS)/(NIR + VIS)Calculations of NDVI for a given pixel always result in a number that ranges from minus one (-1) to plus one (+1)--no green leaves gives a value close to zero. --zero means no vegetation --close to +1 (0.8 - 0.9) indicates the highest possible density of green leaves. NASA Earth Observatory (Illustration by Robert Simmon)NDVI•NDVI is calculated from the visible and near-infrared light reflected by vegetation. •Healthy vegetation (left) absorbs most of the visible light that hits it, and reflects a large portion of the near-infrared light. •Unhealthy or sparse vegetation (right) reflects more visible light and less near-infrared light. •Real vegetation is highly variable.Advanced Very High Resolution Radiometer (AVHRR) •NOAA has two polar-orbiting meteorological satellites in orbit at all times, with one satellite crossing the equator in the early morning and early evening and the other crossing the equator in the afternoon and late evening. Morning-satellite data are most commonly used for land studies, while data from both satellites are used for atmosphere and ocean studies.NOAA 11NOAA 11AVHRRAVHRR1980 200019901985 201020051995NOAA 7NOAA 7AVHRRAVHRRNOAA 9NOAA 9AVHRRAVHRRNOAA 14NOAA 14AVHRRAVHRRSeaWiFSSeaWiFSSPOTSPOT MODISesMODISesNOAA-16NOAA-16NPPNPPNOAA 9NOAA 9NOAA-17NOAA-17Satellite Satellite NDVI NDVI data data sourcessourcesNOAA-18NOAA-18C. TuckerEVI (Enhanced Vegetation Index)•In December 1999, NASA launched the Terra spacecraft, the flagship in the agency’s Earth Observing System (EOS) program. Aboard Terra flies a sensor called the Moderate-resolution Imaging Spectroradiometer, or MODIS, that greatly improves scientists’ ability to measure plant growth on a global scale. Briefly, MODIS provides much higher spatial resolution (up to 250-meter resolution), while also matching AVHRR’s almost-daily global cover and exceeding its spectral resolution.History of the NDVIHistory of the NDVI& Vegetation Indices& Vegetation IndicesCompton TuckerCompton TuckerNASA/UMD/CCSPONASA/UMD/CCSPOIndexFormula Details CitationSimple RatioGreen vegetation cover.Various wavelengths,depending on sensor. (e.g.NIR = 845nm, R=665nm)Pearson, 1972NormalizedDifferenceVegetation IndexGreen vegetation cover.Various wavelengths,depending on sensor. (e.g.NIR = 845nm, R=665nm)Tucker 1979EnhancedVegetation IndexC1 =6; C2=7; L=1; G=2,5Huete 1997PerpendicularVegetation IndexPerpendicular distance fromthe pixels to the soil line.Richardsonand Wiegand1977Soil AdjustedVegetation IndexL = soil adjusted factor Huete 1988Modified SoilAdjustedVegetation IndexL = (1-2a x(NIR-aR) x NDVI)Self adjusting L:f on tooptimize for soil effects.Higher dynamic range.Qi et al 1994Transformed SoilAdjustedVegetation Indexa=slope of soil lineb=intercept of soil lineBaret andGuyot 1991Soil andAtmosphericallyResistantVegetation IndexMore independent of surfacebrightnessHuete et al1997BRNIRRNIR.7615.2   ) 1 ( 08 . 0 ) ( 2 a b NIR a R b aR NIR a       R NIR R R RNIRRNIRRRRR 22)( NIRvNIRsRvRs  LLRNIRRNIR1Vegetation Indices from Susan UstinVegetation Indices from Susan UstinC. TuckerBeltsville USA winter wheat biomassBeltsville USA winter wheat biomassC. TuckerWinter wheat biomass “harvest”Winter wheat biomass “harvest”C. Tucker NDVI vs. total dry biomassNDVI vs. total dry biomassExplained 80% of biomass accumulationC. TuckerMarked contrasts between the dry and