Download - Satellite Oceanography Modified from a Presentation at STAO 2003 By Dr. Michael J. Passow
Satellite Oceanography
Modified from a Presentation at STAO 2003By Dr. Michael J. Passow
Ocean Satellites
• Permit observations globally, especially useful where there are no ships or buoys
• Developed later than meteorological and other environmental sensing because electromagnetic radiation penetrates ocean water only to limited depths
• Improved sensors permit inferences about ocean at greater depths
"Satellite Oceanography" • Surface topography,
El Nino, and ocean winds are some of the areas investigated from space.
http://winds.jpl.nasa.gov/
Satellite Oceanography Applications
• Sea surface temperatures • Air-sea interactions• Sea Ice patterns• Monitoring ocean waves• Determining sea level variations• Analysis of ocean currents and eddies• Biological productivity• Precipitation patterns
Two basic satellite orbits
“Polar Orbiting” (POES) • Takes about 90 minutes
to make one revolution• Covers different areas
each orbit as Earth rotates
• Provides detailed images• Can produce time
sequence
Geostationary (Geosynchronous)
(GOES)• Remains over same
portion of planet by revolving with same period as Earth’s rotation
• Can provide full disk or smaller views
• Useful for weather and communication
http://www.iitap.iastate.edu/gcp/satellite/images/image7.gif
For more detailed studies, we use “polar-orbiting” satellites
• Polar-orbiting satellites are much closer to the surface (700 – 800 km) and make about 14 passes each day. They can provide good time sequence studies.
http://www.earth.nasa.gov/history/landsat/landsat4.html
Satellites can detect what’s on Earth in two ways:
• “passive” observation of energy reflected or radiated from the surface
• “active” collection of signals beamed down from the satellite and reflected back
http://topex-www.jpl.nasa.gov/
Problem 2—How do you measure from a satellite?
Sea surface temperatures (SST) and thermal properties
• Visible satellites can monitor difference between incoming solar radiation and reflected light
• Infrared satellites can monitor IR energy emitted from surfaces
• AVHRR (Advanced Very High Resolution Radiometer) measure SSTs
• Also monitored with MODIS (Moderate Resolution Imaging Spectroradiometer)
SST Images[link through DStreme Ocean]
http://www.cdc.noaa.gov/map/images/sst/sst.gif
Sea Surface Temperature Anomalies (SSTA)
• Images constructed by measuring difference between “observed” and “expected” values – anomalies
• Better approach to recognizing “what is unusual,” not just “what is”
• Especially useful for El Nino/La Nina studies—example: http://orbit-net.nesdis.noaa.gov/orad/sub/sst_anomaly_2m.html
SSTA images
http://www.osdpd.noaa.gov/PSB/EPS/SST/climo.html
• SeaWIFS has allowed us to monitor the links between physical and chemical conditions and marine biology
• Biological response to climate changes
http://seawifs.gsfc.nasa.gov/SEAWIFS.html
Sea Surface Topography
• Variations in sea surface heights caused by gravity variations (sea floor topography and geology)
• Also seasonal changes in atmospheric and ocean circulation patterns
• Radar altimeters aboard TOPEX/Poseidon and Jason satellites
• AMS “Measuring Sea Level from Space”
TOPEX-Poseidon is…
• a partnership between the U.S. and France to monitor global ocean circulation, discover the tie between the oceans and atmosphere, and improve global climate predictions. Every 10 days, the TOPEX/Poseidon satellite measures global sea level with unparalleled accuracy.
http://topex-www.jpl.nasa.gov/mission/mission.html
TOPEX has been especially useful in understanding…
• Variations in sea surface temperatures. This has been the most important instrument for observing El Nino/ La Nina changes in the Pacific Ocean, and all the effects on climate
http://topex-www.jpl.nasa.gov/elnino/elnino.html
Jason 1 is a follow-on mission to TOPEX-Poseidon• Monitors global ocean circulation, studies
ties between the oceans and atmosphere, improves global climate forecasts and predictions, and monitors events such as El Niño conditions and ocean eddies.
http://www.jpl.nasa.gov/missions/current/jason1.html
Sea Ice Extent
• Areal extent, amount, and thickness important for oceanographers and operationally
• Visible images not feasible during winter• POES microwave sensors provide
operational ice analyses• The next slide shows an example of sea
ice cover in the Northern Hemisphere
http://polar.wwb.noaa.gov/seaice/Analyses.html
Canadian Sea Ice Imagery
Ice conditions monitored by satellite and ships are available at http://ice-glaces.ec.gc.ca/App/WsvPageDsp.cfm?ID=1&Lang=eng