Satellite Oceanography
Dr. Michael J. Passow
Amer. Meteorological Society Education Resource Agent Ocean Satellites
• Permit observations globally, especially useful where 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"
• Sensors aboard satellites provide global views and allow temporal (time) studies not possible from surface vessels. • Surface topography, El Nino, and ocean winds are some of the areas being investi- gated 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
Problem 1— How do you get a satellite into orbit?
• Basically, a rocket is a chamber with an opening containing gas under pressure. A balloon can serve as a simple model. • As the gas escapes, its thrust in one direction propels the rocket in the opposite direction.
http://quest.arc.nasa.gov/space/teachers/rockets/principles.html What keeps an object in orbit?
• Satellites can only stay in orbit when the gravitational pull exactly balances the forward motion (inertia). • These ideas were first explained by Newton in the 1680s! http://quest.arc.nasa.gov/space/teachers/rockets/principles.html Two basic satellite orbits
Geostationary “Polar Orbiting” (Geosynchronous) (POES) (GOES) • Takes about 90 minutes • Remains over same to make one revolution portion of planet by • Covers different areas revolving with same each orbit as Earth period as Earth’s rotation rotates • Can provide full disk or • Provides detailed images smaller views • Can produce time • Useful for weather and sequence 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 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 Ocean Color – Biological Productivity http://seawifs.gsfc.nasa.gov/cgi/seawifs_browse.pl http://seawifs.gsfc.nasa.gov/cgi/seawifs_browse.pl
Sea-viewing Wide Field-of-View Sensor (SeaWIFS) and MODIS have measured chlorophyll in phytoplankton to enable useful inferences about productivity
• SeaWIFS has allowed us to monitor the links between physical and chemical conditions and marine biology • Short-term spatial and temporal variabilities • 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 Precipitation Patterns
• Preponderance of precipitation falls in tropical regions • Previously difficult to measure because few observation stations • TRMM (Tropical Rainfall Measuring Mission) began as experimental, now operational TRMM Precipitation Patterns
This shows average rainfall in the Tropics last month. Monthly records go back to 1998.
http://trmm.gsfc.nasa.gov/ Precipitation Anomaly Patterns
Anomaly images show regions of that are unusually higher or lower than normal.
http://trmm.gsfc.nasa.gov/images/3B43_anom_oct03.gif Hurricane and Lightning Images
TRMM images have permitted amazing new views of storms and related weather in the Tropics. http://trmm.gsfc.nasa.gov/images_dir/images.html Activities Based on TRMM Data
• Institute for Global Environmental Studies (IGES) http://www.strategies.org/TRMM.html
Classroom-oriented activities based on TRMM concerning ENERGY, CLOUDS, WIND, PRECIPITATION, AND WEATHER Canadian Satellite Imagery
Meteorological Service of Canada (Service météorologique du Canada) provides many satellite images at http://www.weatheroffice.ec.gc.ca/satellite/index_e.html
These utilize NOAA GOES and POES images. http://www.weatheroffice.ec.gc.ca/satellite/index_e.html#hrpt 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 Examples of Teacher-Training and Classroom-Ready Activities • AMS “Measuring Sea Level from Space” • DataStreme Ocean investigations – modified from the Fall 2003 pilot testing This slide show is available in the “Resources” Section of “Earth2Class”