1 Applications 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 ( ) –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 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 Width2,801 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 Geometry Launched 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  C a –chlorophyll-a  C b –chlorophyll-b  C c –chlorophyll-c  C ps –photosynthetic carotenoids  C pp –photoprotectant carotenoids  C tp –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

14 Ocean: Chlorophyll-a Concentration Land: Normalized Difference Vegetation Index SeaWiFS Captures El Niño/La Niña Transitions in the Equatorial Pacific

15 April 25, 1998 Coccolithophor e Bloom in the Bering Sea

16 Chlorophyll and SeaWiFS-derived NDVI September-November 1997

17 Chlorophyll and SeaWiFS-derived NDVI December 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

22 6 years of Seawifs data seawifs.gsfc.nasa.gov