Applications of Remote Sensing

Surface Temperature

Sea or lake surface temperature (SST or LST) is derived from satellites orbiting the earth. One such useful device is NOAA's (National Oceanographic and Atmospheric Administration) AVHRR or Advanced Very High Resolution Radiometer. The AVHRR operates over a very large bandwidth which ranges from visible to thermal infrared waves. Using algorithms and differences in wavelengths, surface temperature can be calculated. Surface temperature is important because it influences circulation patterns and the rates of chemical reactions, including carbon fixation rates of primary production. Without primary production, a lake's food web and biodiversity would not exist.

Productivity

As mentioned above, primary production is of vital importance in maintaining lake biodiversity. But what is primary production and how is it remote sensing used to measure it? Primary production is the basis of life and the beginning of the food web for higher organisms. Single celled chlorophyll containing plants called phytoplankton convert the sun's energy into fuel which it uses to produce more plant material. This process is known as photosynthesis. Higher organisms such as zooplankton feed on the phytoplankton and in turn are fed upon by small fishes. Remotely sensed images are used to determine productivity. What the satellite sensor "sees" indirectly when it takes pictures of a body of water is the color of the water, which can then be related to the concentration of chlorophyll. It appears green because chlorophyll absorbs the other colors of the visible light spectrum and reflects green. So, by knowing the chlorophyll concentration of a body of water, we can get an idea of it's productivity. Satellite sensors such as NASA's SeaWiFS (Sea viewing Wide Field-of-view Sensor) and MODIS (Moderate Resolution Imaging Spectroradiometer) use similar techniques mentioned previously to calculate chlorophyll content.

Suspended Materials

The biogeochemical makeup of a body of water can be greatly affected by the distribution of sediments within it. River runoff, urban/industrial discharge, and resuspended sediments can all determine the health of a body of water. Organic and inorganic suspended sediments also affect the color of a lake or ocean. Episodic events such as storms stir up sediments to give a body of water a brownish color. Resuspended sediments can carry heavy metals and other pollutants to areas that may affect the health of a population. Redistribution of sediments can cause problems in the shipping industry by changing the depth of canals and harbors. Fish productivity can be hurt when sediments cover their nesting grounds. The SeaWiFS sensor can also estimate the amount of suspended materials associated with sediment plumes, which can then be tracked and monitored remotely.

Other Uses

Remote Sensing is used in many other fields such as agriculture, forestry, cartography, hydrology, geology and meteorology. However, since the focus of this site is on Great Lakes remote sensing, these fields will not be discussed. For more information about remote sensing in geology visit the Volcano Clouds Web Site.

References

SeaWiFS Teacher's Resource, http://www.seawifs.gsfc.nasa.gov/SEAWIFS/sanctuary_1.html

EEGLE: Episodic Events - Great Lakes Experiment, http://www.glerl.noaa.gov/eegle/projects/p01/summary.html

The Conservation of Biodiversity in the Great Lakes Ecosystem, http://www.epa.gov/glnpo/ecopage/issues.html

This page was created by Mike Mikkola
Email questions about the content of this web page to : Judy Budd