Satellite Oceanography Modified from a Presentation at STAO 2003 By 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 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 “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

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

Problem 2— How do you measure from a satellite? 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/

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

Biological response to climate changes 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