Upload
valentine-banks
View
227
Download
4
Embed Size (px)
Citation preview
1
Applications of Remote Sensing: SeaWiFS and MODIS Ocean ColorApplications of Remote Sensing:
SeaWiFS and MODIS Ocean Color
Outline Physical principles behind the remote sensing of
ocean color parameters Satellite sensors enabling remote sensing of
ocean color–SeaWiFS, OCTS, MODIS, GLI
Instrument characteristics–Spacecraft, spatial resolution, swath width, sensor characteristics, and unique characteristics
Ocean color monitoring from existing satellite systems
Future capabilities Opportunities for the future
2
“Course” spatial resolution (i.e., >1 km) but frequent temporal resolution (i.e., every other day)–Low marine biomass/high primary production–Marine primary production poorly understood–Single satellite with wide field of view (i.e.,CZCS and SeaWiFS)»Highly variable atmospheric effects»Variable directional reflectance effects»Forming composite images is the key
–Coastal Zone Color Scanner (1979-1986)–SeaWiFS (August 1997 › …)–MODIS (February 2000 › …)
Ocean Color Time Series Remote Sensing
3
Applications Ocean Color Studies — all channels Atmospheric Studies (clouds, aerosols) — all channels Land Vegetation Index — all channels Cryosphere Studies — all channels
Objectives To determine the spatial and temporal distributions of
phytoplankton blooms, along with the magnitude and variability of primary production by marine phytoplankton on a global scale
To quantify the ocean’s role in the global carbon cycle and other biogeochemical cycles
To identify and quantify the relationships between ocean physics and large-scale patterns of productivity
Sea-viewing Wide Field of View Sensor
4
Radiative Accuracy: <5% absolute each band Relative Precision: <1% linearity Between Band <5% relative band-to-band
Precision: (over 0.5 - 0.9 full scale) Polarization: <2% sensitivity (all angles) Nadir Resolution: 1.1 km LAC, 4.5 km GAC
Orbit Type: Sun synchronous at 750 km Equator Crossing: Noon ± 20 minutes descending Saturation Recovery: <10 samples Swath Width 2,801 km LAC
(at equator) 1,502 km GAC Scan Plane Tilt +20°, 0°, -20° Digitization: 10 bits
SeaWiFS Mission Characteristics and Sensor Accuracy
5
OrbView-2 Satellite and SeaWiFS Scanning
GeometryLaunched August 1, 1997
6
Sea-viewing Wide Field-of-view Sensor (SeaWiFS)
NASA, OrbView-2– launched August 1997– descending polar orbit of
705 km, noon crossing time Sensor Characteristics
– eight spectral bands, from 412 to 865 nm
– daily global coverage– scan angle of ±58.3°; scan
swath of 2800 km– ±20° tilt to avoid sun glint– resolution of 1.13 km (with
optional 4.5 km) at nadir– solar and lunar maneuvers
for calibration– polarization sensitivity ≤
1%
7
SeaWiFS Instrument Schematic
8
Rayleigh Scattering Coefficients for the Eight SeaWiFS Channels
9
OrbView-2 Launch Sequence and Satellite with Solar Panels
Deployed
10
Simulated Pigment Absorption and Chlorophyll-a versus Total
Pigments Ca
– chlorophyll-a Cb
– chlorophyll-b Cc
– chlorophyll-c Cps
– photosynthetic carotenoids
Cpp
– photoprotectant carotenoids
Ctp – total pigment
concentration, a sum of all the other parameters
11
Simulated Pigment Absorption and Chlorophyll-a versus Total
Pigments
12
July 1998
Correlation of AVHRR Sea Surface Temperature and Chlorophyll-a
Concentration
13
Galapagos Islands El Niño/La Niña Transitions
14Ocean: Chlorophyll-a ConcentrationLand: Normalized Difference Vegetation Index
SeaWiFS Captures El Niño/La Niña Transitions in the
Equatorial Pacific
15
April 25, 1998
Coccolithophore Bloom in the Bering
Sea
16
Chlorophyll and SeaWiFS-derived NDVI September-November 1997
17
Chlorophyll and SeaWiFS-derived NDVI December 1997 - February 1998
18
Chlorophyll and SeaWiFS-derived NDVI March-May 1998
19
Chlorophyll and SeaWiFS-derived NDVI May-August 1998
20
Moderate Resolution Imaging Spectroradiometer (MODIS) on
Terra
MODIS
Terra
21
MODIS Ocean Color/Phytoplankton Bands
BandBandwidthSpectral RadianceRequired SNR
8 405 - 420 44.9 8809 438 - 448 41.9 83810 483 - 493 32.1 80211 526 - 536 27.9 75412 546 - 556 21.0 75013 662 - 672 9.5 91014 673 - 683 8.7 108715 743 - 753 10.2 58616 862 - 877 6.2 516
22
6 years of Seawifs data 6 years of Seawifs data seawifs.gsfc.nasa.govseawifs.gsfc.nasa.gov