Satellite Oceanography

Presented at STAO 2003Dr. Michael J. Passow

White Plains Middle School,White Plains, NY,

Science Teachers Association of New York State (STANYS), and

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

“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

Ocean Color – Biological Productivityhttp://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

http://seawifs.gsfc.nasa.gov/cgi/seawifs_browse.pl

• 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

http://trmm.gsfc.nasa.gov/

This shows average rainfall in the Tropics last month. Monthly records go back to 1998.

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”

michael@earth2class.org