unit i. ocean color- table of contents · color from space (and the only long-term satellite...

Project Oceanography 1999 Spring Series Ocean Color1

Ocean Color

Unit I. Ocean Color- Table of Contents

This material is background information for teachers. This should be readand discussed before presentation. Student Information Sheets: This isbackground material for students. They should be copied and given tostudents before the video presentation. Activities should be done as afollow-up after the program. Questions should be discussed after the show.

Table of Contents 1History and Other Background 3

Lesson 1- Energy and Color 5

Why is Ocean Color Important? 5What is Ocean Color? 7Ocean Color and Global Warming 7How is Ocean Color Measured? 8Water-Leaving Radiance 9Activities

Internet Ocean Productivity 11Make a Greenhouse 12

Student Information Sheet 13

Lesson 2- Ocean Color From Space 15

Ocean Color Viewed from Space: What Does the Satellite See? 15 Data Processing from Level 0 to Level 3 18 True and False Color Images 20 Ground Truth 21 Activities

Analyzing the Satellite Image! 22Questions 24Student Information Sheet 27

Lesson 3 What is Ocean Color Data? Energy and Temperature 29 Ocean Color: Electromagnetic Spectrum 29 Electromagnetic Energy 30 Space and Ocean Observatories in Different Regions of the EM Spectrum 31 Diagram: Comparison of Ocean Color Instruments 33Sea Surface Temperature 34


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Instruments Used for Ocean Color Sensing 35Diagram: Comparison of Wavelength &Bandwidth Ocean Color Instruments 38

Student Information Sheet 39Vocabulary 40References 43

The staff at Project Oceanography would like to thank the followingpeople for their assistance in preparing this packet:

Executive Producer: Paula Coble, Ph.D.

Graphics: Chad EdmistenLori Huthmacher

Writers: Lori HuthmacherFrank Muller-Karger

Edited by: Paula Coble, Ph.D.Juli Rasure

Packet Distribution: Tracy Christner

Source Information Sites: NASA andathena@net


Ocean Color

History and Other Background Information

The first observations of oceancolor from space (and the onlylong-term satellite observations todate) were carried out by theCoastal Zone Color Scanner(CZCS), a radiometer with visibleand infrared spectral channelsthat operated on NASA's Nimbus-7 research satellite from 1978 to1986. Despite being designed asa proof-of-concept mission with anominal one-year lifetime, CZCSgathered a rich harvest of newdata which have permitted anunprecedented view of the world'soceans. The CZCS global datasets lay the scientific foundationfor a new generation of satelliteocean color measurements in the1990s.

The past ten years havewitnessed a revolution in the wayoceanographers view thebiological, chemical and physicalinteractions in the world's oceans.Satellite measurements of oceancolor have played a key role,permitting a quantum leap in ourunderstanding of oceanographicprocesses from regional to globalscales. The measurement ofocean color from space hasrevealed, for the first time, the

global-scale variability in thedistribution and concentration ofphytoplankton. As a result of thisnew capability, determinations ofocean productivity, visualization ofsurface currents, and the rate atwhich the oceans sequesteratmospheric carbon dioxide are allnow within our reach. Suchobservations are also critical tomajor new initiatives aimed atestablishing the role of the oceansin the biogeochemical cycles ofelements which influence bothclimate and the distribution of lifeon Earth.

Since phytoplankton pigmentsabsorb energy primarily in the redand blue regions of the spectrumand reflect green light, there is arelationship between the spectrumof sunlight backscattered by upperocean layers and the distributionof phytoplankton pigments inthese layers. Satellitemeasurements of ocean radianceat selected wavelengths can thusbe used to estimate near-surfacephytoplankton concentrations andthe extent of primary productivity.

In addition to sustaining themarine food chain, phytoplankton


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strongly influence oceanchemistry. During photosynthesis,they remove carbon dioxidedissolved in seawater to producesugars and other simple organicmolecules, and release oxygen asa by-product. Phytoplankton alsorequire inorganic nutrients (forexample, nitrogen, phosphorus,silicon) as well as trace elements(for example, iron) to synthesizecomplex molecules, such asproteins. Ocean productivity thusplays a key role in the globalbiogeochemical cycles of carbon,oxygen, and other elementscritical to both marine andterrestrial life. The risingatmospheric concentration ofcarbon dioxide, which mayproduce a global warming (the"greenhouse effect"), underscores

the additional importance of thecarbon cycle to the Earth'sclimate. The magnitude andvariability of primary productionare poorly known on a globalscale, largely because of the highspatial and temporal variability ofmarine phytoplanktonconcentrations. Oceanographicvessels move too slowly to mapdynamic, large-scale variations inproductivity; global coverage byship-borne instruments isimpossible. Only satelliteobservations can provide therapid, global coverage required forstudies of ocean productivityworldwide.

Excerpted from:http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/OCDST/ocdst_history_and_other_background_info.html


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Ocean Color Lesson I: Energy and ColorKeywords: algorithm, photosynthetic organisms, chlorophyll, particulate matter, ocean color data,MODIS, global carbon cycle, backscatter, electromagnetic spectrum, water-leaving radiance

Why is Ocean Color Important?The major reason scientistsmeasure ocean color is to studyphytoplankton, the microscopicocean plants which form the baseof the oceanic food web.Phytoplankton use sunlight andcarbon dioxide to produce organiccarbon. This process, calledphotosynthesis, is possiblebecause plants containchlorophyll, a green-coloredcompound which traps the energyfrom sunlight. Chlorophyll is alsoresponsible for giving most marineand land plants a green color.

Because different types ofphytoplankton have differentconcentrations of chlorophyll,measuring the color of an area ofthe ocean allows us to estimatethe amount and general type ofphytoplankton in that area.

Looking at ocean color also tellsus about the health and chemistryof the ocean. In addition to lightand carbon dioxide, phytoplanktonalso require nutrients such asnitrogen and phosphorus. Thedistribution of

plants in the ocean also tells uswhere nutrient levels are high, andshows where pollutants poison theocean and prevent plant growth.Other conditions can also affectphytoplankton growth, such assubtle changes in the climate dueto seasons and variations insalinity in coastal areas. Sincephytoplankton depend uponspecific conditions for growth, theyfrequently become the firstindicator of a change in theirenvironment. Comparing imagestaken at different periods tells usabout changes that occur overtime. Because phytoplankton driftwith the water, patterns in oceancolor can also be used to studyocean currents.

Why are phytoplankton soimportant? These small plants arethe beginning of the food chain formost of the planet. Asphytoplankton grow and multiply,small fish and other animals eatthem as food. Larger animals theneat these smaller ones. The oceanfishing industry finds good fishingspots by looking at ocean colorimages to locate areas rich in

Project Oceanography Spring Series 1999 - Ocean Color6

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phytoplankton. Ocean color istherefore a valuable research tool

for the study of ocean biology,chemistry, and physics.


Ocean ColorOcean Color

What is Ocean Color?The "color" of the ocean isdetermined by the interactions ofincident light with substancespresent in the water. We seecolor when light is reflected byobjects around us. White light ismade up of a spectrum orcombination of colors, as in arainbow. When light hits thesurface of an object, thesedifferent colors can be absorbed,transmitted through thesubstance, scattered, or reflectedin differing intensities. The colorwe see depends on which colorsare reflected. For example, abook that appears red to usabsorbs more of the green andblue parts of the white lightshining on it, and reflects the redparts of the white light. The lightwhich is scattered or transmittedby most objects is usually notapparent to our eyes.

The substances in seawaterwhich most affect the colorreflected are the phytoplankton,

inorganic particles, dissolvedorganic chemicals, and the wateritself. Phytoplankton containchlorophyll, which absorbs light atblue and red wavelengths andreflects green wavelengths.Particles can reflect and absorblight, which reduces the clarity(light transmission) of the water.Dissolved organic matter stronglyabsorbs blue light, and itspresence can interfere withmeasurements of chlorophyll.

When we look at the ocean orobserve it from space, we see thatthe ocean is blue because waterabsorbs red and reflects blue light.Using instruments that are moresensitive than the human eye, wecan measure a wide array of blueshades, which reveal the presenceof varying amounts ofphytoplankton, sediments, anddissolved organic chemicals.Excerpted from:http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/OCDST/seawifs_raq.html#Q1

Ocean Color and Global Warming

Besides acting as the first link inthe food chain, phytoplankton area critical part of ocean chemistry.

The carbon dioxide in theatmosphere is in balance withcarbon dioxide in the ocean.



During photosynthesisphytoplankton remove carbondioxide from sea water, andrelease oxygen as a by-product.This allows the oceans to absorbadditional carbon dioxide from theatmosphere. If fewerphytoplankton existed,atmospheric carbon dioxide wouldincrease.

Phytoplankton also affect carbondioxide levels when they die andsink to the ocean floor. The carbonin the phytoplankton is sooncovered by other material sinkingto the ocean bottom. In this way,the oceans may store excessglobal carbon, which otherwisewould accumulate in theatmosphere as carbon dioxide.

Carbon dioxide acts as a"greenhouse" gas in the

atmosphere, and therefore maycontribute to global warming.Sources of carbon dioxide in theEarth's atmosphere includedecomposition of organic matter(such as trees), the carbon dioxidethat animals and people exhale,volcanic activity, and humanactivities such as the burning offossil fuels and wood.

No one yet knows how muchcarbon the oceans and land canabsorb. Nor do we know how theEarth's environment will adjust toincreasing amounts of carbondioxide in the atmosphere.Studying the distribution andchanges in global phytoplanktonusing ocean color and other toolswill help scientists find answers tothese questions. Excerpted from:http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/OCDST/seawifs_raq.html#Q1

How is Ocean Color Measured?

The color of ocean water and itsconstituents (phytoplankton,particles, and dissolved organicmatter) can be measured in avariety of ways, and manysensitive instruments have beendesigned for this purpose.Instruments which measure thelight absorbed, transmitted, andscattered can be placed in thewater, either lowered on a cable

from a ship or moored in place ona buoy and left to collect data forlong periods of time. Absorptionand scatter measurements canalso be made on discrete watersamples, by either placing thesample in the sample chamber ofthe spectophotometer or by havingthe seawater flow continuouslythrough the instrument while theship is underway. Still other



instruments which measurereflectance, called radiometers,are used above the sea surface,either from the deck of the ship,or from an airplane or satellite.This last type measures a

property known as water-leavingradiance – the amount and color(spectral distribution) of light re-entering the atmosphere from theocean surface.

Water-Leaving RadianceThe radiance received atspacecraft altitudes is actuallycontrolled more strongly by theatmosphere than by the ocean.Solar irradiance (the fullspectrum of light emitted by thesun) is scattered and absorbedby the gases in the atmosphere,including water vapor (molecular[Rayleigh] scattering), fromparticles suspended in the air(aerosol scattering), and ozone(selective absorption). It is thisscattered light which isresponsible for the blue color ofthe sky. Sea surface reflections(sun and sky glitter) alsodecrease the amount of sunlightwhich enters the ocean. Themathematical equations used tocorrect the water-leavingradiances for these interactionsin the atmosphere are called"atmospheric correctionalgorithms."

After light enters the ocean, itinteracts with the phytoplankton,dissolved organic matter,particles, and water molecules.

Some of it is eventually scatteredback up through the surface. Thislight is called the water-leavingradiance, and it can be detectedfrom space. Generally, much lessthan 10% of the total light detectedby a satellite sensor will be water-leaving radiance. Because such alarge part of the radiance signalthe satellite detects comes fromthe atmosphere, the atmosphericcorrection factors are extremelyimportant for generating accurateocean color data. In fact, theatmospheric effect is so large thatif we were able to look at theocean from the height of thesatellite, it would appear to us tobe blue even if the actual color ofthe ocean were black. Scientistsare continuing to research howbest to design the atmosphericcorrection algorithms.

Because there is a strongrelationship between the color ofmost of the open ocean and thephytoplankton chlorophyllconcentration, it is possible todevelop a water-leaving radiance



equation (algorithm) forcalculating phytoplanktonbiomass in the ocean from

satellite data. Excerpted from:http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/OCDST/seawifs_raq.html#Q1



Activities

Activity I. Internet Ocean ProductivityOcean color sensors measure the amount of plant biomass by measuringthe color due to the presence of chlorophyll. The concentration ofphytoplankton chlorophyll and other pigments is related to phytoplanktongrowth rate, also called productivity. Thus, ocean color gives us an indirectmeasure of ocean productivity. In this activity, you can use images anddata available on the internet to draw some conclusions about where andwhy productivity is high or low.

1.Print out a blank map from internet(http://seawifs.gsfc.nasa.gov/SEAWIFS/LIVING_OCEAN/LIVING_OCEAN.html) andoutline the ocean regions with higher productivity.2. Consider the colors in the legend from green to red to be areas high inproductivity. Color these areas red on your map using a colored pencil, penor crayon.3. Color the less productive areas on your map in blue.4. Compare/contrast productivity near the coastal areas with that in themid-ocean regions.5. Compare the productivity of ocean water near the equator with that inthe northern and southern latitudes in these areas:• the mid-Atlantic• the mid-Pacific• eastern coastline of North and South America• western coastline of North and South America• western coastline of Asia

Discussion Questions:1. In the region of the equatorial Pacific, where is the ocean most

productive?2. In the region of the equatorial Atlantic, where is the ocean most

productive?3. Compare/contrast the productivity in the oceans in the northern and

southern hemispheres.4. Can you think of any factors that cause the differences?

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5. Predict at least three factors that affect the productivity of the oceans.

Activity II: Make a Greenhouse

Materials:

Two cardboard shoe boxes Clear plastic wrap Two regular "weather type" thermometers Desk light with 75 watt or larger bulb.

Procedure:

Place some paper towels loosely in the bottom of each shoe box, then laythe thermometer on the towels. Cover the open top of one box with plasticwrap, taped to the side of the box; leave the other box with the top off(open). Place the boxes side by side, and move the desk light so it shinesevenly into both boxes. Record the temperature in each box every minutefor 10 minutes. Plot the temperatures on a graph with time as the "x"(horizontal) axis and temperature as the "y,' (vertical) axis.

Analysis:

Discuss the differences you see in the observed temperatures in the twoboxes, and why this is happening.

Variation:Try replacing the paper towels in each box with black paper. Repeat theexperiment. What differences do you note? Adapted from:

http://seawifs.gsfc.nasa.gov/SEAWIFS/LIVING_OCEAN/LIVING_OCEAN.html


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Student Information Sheet Lesson 1

Why is Ocean Color Important?The major reason scientists measure ocean color is to study phytoplankton,the microscopic ocean plants which form the base of the oceanic food web.Phytoplankton use sunlight and carbon dioxide to produce organic carbon.This process, called photosynthesis, is possible because plants containchlorophyll, a green-colored compound which traps the energy fromsunlight. Chlorophyll is also responsible for giving most marine and landplants a green color. Because different types of phytoplankton havedifferent concentrations of chlorophyll, measuring the color of an area ofthe ocean allows us to estimate the amount and general type ofphytoplankton in that area.

Looking at ocean color also tells us about the health and chemistry of theocean. In addition to light and carbon dioxide, phytoplankton also requirenutrients such as nitrogen and phosphorus. The distribution ofplants in the ocean also tells us where nutrient levels are high, and showwhere pollutants poison the ocean and prevent plant growth.

Ocean color is therefore a valuable research tool for the study of oceanbiology, chemistry, and physics.

How is Ocean Color Measured?

The color of ocean water and its constituents (phytoplankton, particles,and dissolved organic matter) can be measured in a variety of ways, andmany sensitive instruments have been designed for this purpose.Instruments which measure the light absorbed, transmitted, and scatteredcan be placed in the water, either lowered on a cable from a ship ormoored in place on a buoy and left to collect data for long periods of time.Still other instruments which measure reflectance, called radiometers, areused above the sea surface, either from the deck of the ship, or from anairplane or satellite. This last type measures a property known as water-


Ocean Color

leaving radiance – the amount and color (spectral distribution) of light re-entering the atmosphere from the ocean surface.

What is Ocean Color

The "color" of the ocean is determined by the interactions of incident lightwith substances present in the water. We see color when light is reflectedby objects around us. White light is made up of a spectrum or combinationof colors, as in a rainbow. When light hits the surface of an object, thesedifferent colors can be absorbed, transmitted through the substance,scattered, or reflected in differing intensities. The color we see depends onwhich colors are reflected. For example, a book that appears red to usabsorbs more of the green and blue parts of the white light shining on it,and reflects the red parts of the white light. The light which is scattered ortransmitted by most objects is usually not apparent to our eyes.


Ocean Color

Ocean Color Lesson II: Data Processing andImagery

Ocean color observations madefrom an Earth orbit allow anoceanographic viewpoint that isimpossible from ship or shore -- aglobal picture of biological activity

in the world's oceans. In thislesson we will discuss how thedata collected by the satellitesensor are processed to obtainuseful products for researchers.

Ocean Color Viewed from Space: What Does the SatelliteSee?

The satellite radiometer “sees”light entering the sensor. In thecase of ocean colormeasurements, the satellite isviewing some portion of theearth’s surface and measuringthe amount and color(wavelength) of sunlightreflected from the earth’ssurface. As ocean color intensityis related to the amount of eachof the constituents in seawater,data from the satellite sensormay therefore be used tocalculate the concentrations ofparticulate and dissolvedmaterials in surface ocean

waters. The sensor has thecapability of makingmeasurements at several visibleand infra-red (IR) wavelengths,corresponding to different bandsof electromagnetic energy. Theseare called the spectral bands ofthe sensor. The earliest oceancolor sensor had 6 bands,SeaWiFS (Sea-viewing WideField-of-view Sensor) has 8bands, or channels. Futuresensors are planned with manymore spectral bands, which willallow scientists to determine moreseawater constituents and to doso more accurately.

What data do the satellite collect?Data received from an oceancolor satellite like the Sea-viewing Wide Field-of view

Sensor (SeaWiFS), a global oceancolor mission launched in August1997, is stored and transmitted in


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several forms. Global AreaCoverage (GAC) data arestored in the satellite'scomputers and transmitted toreceiving stations on earthduring the period the satellite isin the dark. (Remember thatpassive data can only becollected during daylightbecause sunlight is required formeasurements.) Local AreaCoverage (LAC) data aretransmitted in real-time (as soonas it is collected) to otherreceiving stations on land whereit is stored in land-basedcomputers. Scientists whoroutinely work with theSeaWiFS data have real-timeHigh Resolution PictureTransmission (HRPT) receivers

to collect this LAC data and use itin their research.

One other difference betweenGAC and LAC data is that they areat different resolutions. Each datapoint is taken in a particular areaof the ocean. This area is called apixel. LAC data pixels cover anarea which is 1 km by 1 km insize. GAC data pixels are larger,and cover an area of 4 km by 4km. Actual pixel sizes differslightly, because the earth’ssurface is curved, and becausethe satellite is sometimes lookingdown at the earth at an angle. Wesay that LAC data have higherresolution than GAC data.However, GAC data have lowercomputer storage requirements.


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Data Processing from Level 0 to Level 3

At the time when LAC and GACdata are transmitted and stored oncomputer, they consist of a stringof numbers. Each numberrepresents a single reading of oneof the sensors onboard thesatellite. For example, onenumber corresponds to theamount of red light reflected froma single pixel. The raw data areclassified as Level 0. Fullyprocessed scenes available foryou to view on the NASA websitesare Level 3 data.

The raw, or unprocessed, Level 0data include total radiances forocean, land, clouds, and icemeasured by the satellite. It alsoincludes actual SeaWiFS spectralresponses, saturation responses,telemetry data, global positioningdata and other data.

Data processing is complicated,but it is greatly facilitated by theuse of SEADAS, a softwarepackage developed by NASAscientists for processing andviewing ocean color data. All thedata for a Level 0 scene arestored as a single file. Eachscene consists of many pixels,which define a rectangular area of

the ocean. A typical scene maybe thousands of pixels on a side.

Using SEADAS, Level 0 data areconverted to Level 1 data bytransforming the string of numbersinto a data table, or matrix. Thedata matrix has columnscorresponding to each pixel in ascene and rows which correspondto a scan line. There are 8 ofthese data matrices for eachscene--one for each color band ofSeaWiFS. Each number, orelement, in the matrix representsa raw radiance value. Other datasuch as latitude and longitude foreach pixel, date, time, and all theother information required tocalibrate and process the data, arestored separately for each scanline.

The table on page 17 is a verysmall part of an actual Level 1data file. The raw radiance valuesonly vary between 817-822 in thisportion of the scene. Level 1 datacan be plotted on a map usingSEADAS. Each radiance value inthe matrix can be displayed as ashade of gray corresponding tothe magnitude of the number. Highnumbers are light, low numbers


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dark, and intermediate numbersare some shade between thesetwo. One map can be made foreach color of light measured, thatis for each radiance channel. Thevalues on the map correspond tothe intensity of radiance measuredfor each individual pixel.

On page 17 is an actual Level 1image taken over the southern tipof Florida. The brightest areas areclouds. Can you find Florida andthe Bahamas in this scene? Level1 data still largely consist of lightscattered by atmosphericcomponents, and this must beremoved to study ocean color.Level 2 processing applies theatmospheric correction algorithms,and also applies other algorithmsto convert the Level 1 data toconcentrations of substances ofinterest, for example chlorophyllconcentration. Algorithmdevelopment is still an active areaof research, since many of the

correction factors are not wellknown, and can vary due toenvironmentalfactors.

Level 2 images often contain blackareas, where all the radiance wasremoved from pixels afteratmospheric corrections. Theseare areas where clouds, ice orland were present. The area andshape of individual pixels in Level1 and Level 2 data may also bedistorted because of the angle atwhich the satellite views theearth's curved surface. Level 3data processing by SEADASremoves the distortions and alsocombines multiple scenes in agiven area to reduce the cloudcover. This is called "binning" thedata, and is similar to taking theaverage of several numbers.Scenes can be binned over timeintervals, or over intervals ofspace. Spatial binning is used tocombine incomplete scenes of aparticular area of interest.

True Color and False Color Images

Since white light is a combinationof different colors, we can addSeaWiFS data collected in singlebands to get a true color image ofthe ocean. There are 3 bluebands, 2 green bands, and a redband. One of each color of Level

1 data can be added in SEADASto get a true color image.

One other way to enhance imagesfor easier interpretation is to makefalse color images. This is similarto grayscale images, except that


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several colors are used to scalethe data. How do we assigncolors to the data? Fortemperature, it might seem logicalto let blue represent cold (lowtemperatures), green intermediate,and red hot (high temperatures),but any scheme could be used.Usually color is chosen to makethe image easy to interpret. Ascale or legend by the figuredefines the meaning of the colors.Depending on the circumstances,the colors may look real; that is,

they may look like we imagine thescene appears to the eye. Falsecolor results when some schemeother than natural color is used fordisplaying images.

The term "false color" does notmean that the data are wrong orthat the picture is deceiving you. Itonly means, don't be deceived;this figure is not a colorphotograph. You should look atthe scale or legend to interpret it.

Ground Truth Measurements and Instruments

While the advent of ocean colorsatellites has revolutionized theway ocean scientists study theocean, it has not totallyeliminated the need to study theocean from ships. In fact, themeasurement of ocean colorparameters in and just abovethe water is now moreimportant than ever to be surethat data from the satellite areinterpreted correctly. Datacollected in the field to verifyand calibrate data from satelliteocean color sensors is called"ground truth." Without groundtruth data,

scientists could not develop thealgorithms they use to calculatesuch parameters as chlorophyllconcentration.

A variety of instruments have beendeveloped to collect the requiredground truth data. The basicmeasurements needed areabsorption and scatter of the mainsubstances responsible for oceancolor, namely phytoplankton,detritus particles, and dissolvedorganic substances; water-leavingradiance; and incident solarirradiance (the amount ofsunlight striking the sea surface).These properties change with


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seasons, with depth in thewater column, and from onearea of the ocean to another.So, scientists must make theirmeasurements at differenttimes and places. They are

constantly trying to verify thatchlorophyll concentrationscalculated from satellite sensorsaccurately represent chlorophyllconcentrations in the ocean.


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Activity III. Analyzing the Satellite Image

Use the world wide web (www) to find a false color image of the entireocean.Sites: http://seawifs.gsfc.nasa.gov/SEAWIFS.html

http://ltpwww.gsfc.nasa.gov/MODIS/MODIS.htmlhttp://observe.ivv.nasa.gov/nasa/education/reference/main.html

False Color Images of Ocean Color

Since phytoplankton are just tiny microscopic plants they need the samethings to grow that the plants in your house or outside need. Your favoritehouseplant needs water, sunlight, carbon dioxide and nutrients (thesecome from the soil it grows in) in order to grow through the process ofphotosynthesis. In some parts of the ocean there are a lot of these thingsthat plants need to grow and other places which lack one or more of theseimportant ingredients. Now for the fun stuff: remember what you readabout using satellites to study the phytoplankton concentrations in theocean? Now you are going to use one of these REAL satellite images toconduct your own investigation!1. Analyzing the satellite image...

Take a look at the image above. It shows the entire world and theconcentrations of phytoplankton in the world's oceans. Next take a look atthe color scale beside the image; this tells you what the colors on the mapmean. The purple color indicates very low amounts of phytoplankton, thegreen indicates medium amounts and the red indicates very high amounts


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or concentrations of phytoplankton. Now scroll down below the imagesand see if you can answer the questions. Adapted from: http://k12science.stevens-tech.edu/curriculum/oceans/seawifs.html


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Excerpted from: http://k12science.stevens-tech.edu/curriculum/oceans/seawifs.html

Questions1. There are areas of the ocean with relatively large concentrations ofnutrients that animals and plants use as food substances. In these areasyou see a lot of phytoplankton, especially in the spring. Why do someareas have greater amounts of phytoplankton? Where would be the bestplace for deep-sea fishing?

2. If a zooplankton, a very small animal type of plankton, eats aphytoplankton, generally speaking, what happens to the carbon that wasin the phytoplankton? What happes to the carbon in the zooplanktonwhen it dies?

3. What is an example of the lowest level of the "food chain" on land?

4. Scientists use two types of satellites to study the environment. Ageostationary satellite remains above the same spot on the Earth'sequator from an altitude of about 22,500 miles and can "see" an entirehemisphere all the time. A polar-orbiting satellite travels in a circular orbit,passing above the North and South Poles while the Earth rotates beneathit. This type of satellite can "see" details as small as a mile or less. Whichof these satellites probably would be better for our ocean colorinstrument? Would one prove better than the other to track hurricanesand other large weather systems?

5. How do the atmosphere and the ocean interact?

6. How could global warming affect sea level? Why is global warmingimportant?

7. Where do plankton grow?


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ANSWERS:

1. When wind-driven surface currents carry water away from continents,an upwelling of deep ocean water occurs. These cold waters have highconcentrations of nutrients, leading to phytoplankton growth and creatinga highly productive fishing area. Ocean plants live within 200 meters fromthe surface where there is sunlight.

2. Most zooplankton migrate to the surface at night to feed onphytoplankton and then sink to greater depths during the day. Thephytoplankton carbon they eat is connected to carbon dioxideincorporated into their bodies, are excreted as fecal pellets which sink tothe ocean floor. When zooplankton die, they carry carbon with them asthey sink to the bottom of the ocean.

3. Plants and bacteria are at the bottom of the food chain. Animals thateat grass, such as sheep, belong to higher food web levels.

4. A polar-orbiting satellite potentially can "see" everywhere in the world inabout two days, and its orbit is low enough so that it can detect smallerdetails than a geostationary satellite. It will pass over a certain area oncedaily at the same time of day, which is important for instruments that usesun illumination for measurements of ocean color or land vegetation. Ageostationary orbit can view almost an entire hemisphere at the sametime, is able to track hurricanes and weather systems by makingmeasurements every half hour or so, and also is used for meteorologicalpurposes.

5. Differences in the heating and cooling rates of land and ocean affect aircirculation. Land and water temperatures rise and fall at different ratesbecause land absorbs and loses heat faster than water does. During theday, hot air rises and is replaced by cooler air. This small-scale circulationis called a sea breeze, and usually starts three or four hours after sunrise,reaching its peak by early afternoon. At night, the land is cooler than thewater because the land has given up its heat to the atmosphere. The coolair flows over the warmer water and rises as it is warmed. This circulation


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is called a land breeze, and usually starts to form in the late evening. Itreaches its peak intensity near sunrise.

6. Global warming may cause sea levels to rise by several mechanisms.Temperature increases may cause some of the ice in the polar regions tomelt, which would raise sea levels. Higher water temperatures also maycause the oceans to expand. This expansion would cause a sea-levelrise. Scientists are studying how global warming would affect sea levels,because a substantial rise in the sea level may flood coastal cities andother low-lying areas.

6. Plankton (microscopic drifting plants and animals) live near the oceansurface where there is sunlight. Satellites will see changes in the colorof water that indicates growth of ocean plants. Adapted from:

http://seawifs.gsfc.nasa.gov/SEAWIFS/LIVING_OCEAN/LIVING_OCEAN.html


Ocean Color

Student Information Sheet Lesson 2

Ocean Color Viewed from Space: What Does the SatelliteSee?

The satellite radiometer “sees” light entering the sensor. In the case ofocean color measurements, the satellite is viewing some portion of theearth’s surface and measuring the amount and color (wavelength) ofsunlight reflected from the earth’s surface. As ocean color is related to theamount of each of the constituents in seawater, data from the satellitesensor may therefore be used to calculate the concentrations of particulateand dissolved materials in surface ocean waters. The sensor has thecapability of making measurements at several visible and infra-red (IR)wavelengths, corresponding to different bands of electromagnetic energy.

True Color and False Color Images

Since white light is a combination of different colors, we can add SeaWiFSdata collected in single bands to get a true color image of the ocean. Thereare 3 blue bands, 2 green bands, and a red band. One of each color ofLevel 1 data can be added in SEADAS to get a true color image.One other way to enhance images for easier interpretation is to make falsecolor images. This is similar to grayscale images, except that severalcolors are used to scale the data.

Data Processing from Level 0 to Level 3

At the time when LAC and GAC data are transmitted and stored oncomputer, they consist of a string of numbers. Each number represents asingle reading of one of the sensors onboard the satellite. For example,one number corresponds to the amount of light in channel 1 in a singlepixel. The raw data are classified as Level 0. Fully processed scenesavailable for you to view on the NASA websites are Level 3 data.


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Ground Truth Measurements and Instruments

While the advent of ocean color satellites has revolutionized the way oceanscientists study the ocean, it has not totally eliminated the need to study theocean from ships. In fact, the measurement of ocean color parameters inand just above the water is now more important than ever to be sure thatdata from the satellite are interpreted correctly. Datacollected in the field to verify and calibrate data from satellite ocean colorsensors is called "ground truth." Without ground truth data,scientists could not develop the algorithms they use to calculate suchparameters as chlorophyll concentration.


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Lesson III: Ocean Color: Energy,Temperature, and the Big Picture

In this lesson we will discussthe Electromagnetic spectrum,

electromagnetic energy and seasurface temperature.

Electromagnetic SpectrumThe electromagnetic (EM)spectrum is the term thatscientists use to refer to alltypes of radiation. Radiation isenergy that travels andspreads out as it goes. Visiblelight that comes from a lamp inyour house and radio wavesthat come from a radio stationare two types ofelectromagnetic radiation.Other examples of EMradiation are microwaves,infrared and ultraviolet light, X-rays and gamma-rays. Therainbow of colors that we seein visible light represents only a

very small portion of theelectromagnetic spectrum.

The EM spectrum is thecontinuum of energy that rangesfrom meters to nanometers inwavelength and travels at thespeed of light. On one end of thespectrum are radio waves withwavelengths billions of timeslonger than those of visible light.On the other end of the spectrumare gamma rays. These havewavelengths millions of timessmaller than those of visible light.


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All matter (except at absolutezero temperature) radiates EMenergy with peak intensityshifting toward shorterwavelength with increasingtemperature. The amount ofenergy ( R ) radiated by ablack body per unit time perunit area is proportional totemperatures ( T ) to the fourth

power: R= σ t4 This is the Stefan-Boltzman Law and the constant σhas a value of σ = 5.67 x 10-8 w xm-2 x °K-4. Where w=watts,m=meters and °K = temperaturesin degrees Kelvin.

Electromagnetic EnergyAdapted from: Frank Mueller

Electromagnetic (EM) energy is energy that moves at the velocity oflight in a harmonic wave pattern (waves that occur at equal intervals oftime). EM energy can only be detected as it interacts with matter. EMwaves can be described in terms of velocity, wavelength, andfrequency.

EM waves travel at the velocity (speed) of light, c:

c= 299,793 km s-1c= 3x10^8 m s-1


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Wavelength (λ) is the distance from any point on one cycle or wave tothe same position on the next cycle or wave.Units: µµm=micrometers or microns=10-6 meters (VIS,IR)

nm= nanometers= 10-9 meters (VIS)

Frequency (ν) is the number of wave crests passing a given point in aspecified period of time. It is imeasurend in units called hertz (cycles persecond). The speed of light and wavelenth can with media, frequencydoes not.

http://imagine.gsfc.nasa.gov/docs/science/know_l2/emspectrum.html

Space, Earth and Ocean Observatories in DifferentRegions of the EM Spectrum

Excerpted from:http://imagine.gsfc.nasa.gov/docs/science/know_l2/emspectrum.html

Radio observatories

At present, there is one radioobservatory in space. There areplans, however, for one more inthe next year. Radio waves canmake it through the Earth'satmosphere without significant


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obstacles (In fact radiotelescopes can observe evenon cloudy days!). However, theavailability of a space radioobservatory complementsradio telescopes on the Earthin some important ways. Radioastronomers can combine datafrom two telescopes that arevery far apart and createimages which have the sameresolution as if they had asingle telescope as big as thedistance between the twotelescopes! That means radiotelescope arrays can seeincredibly small details.

Microwave observatories

The sky is a source ofmicrowaves in every direction,most often called themicrowave background. Thisbackground is believed to bethe remnant from the "BigBang" scientists believe beganour Universe. It is believed thata very long time ago all ofspace was scrunched togetherin a very small, hot ball. Theball exploded outward andbecame our Universe as itexpanded and cooled. Overthe course of the past severalbillion years (the actual age ofthe Universe is still a matter ofdebate, but is believed to be

somewhere between ten andtwenty billion years), it has cooledall the way to just three degreesabove zero. It is this "threedegrees" that we measure as themicrowave background.(Remember that temperature,energy and EM wavelength arerelated).

Infrared observatories

Currently in orbit is the biggestinfrared observatory currently inorbit is the Infrared SpaceObservatory (ISO), launched inNovember 1995 by the EuropeanSpace Agency. It has been placedin an elliptical orbit with a 24 hourperiod which keeps it in view ofthe ground stations at all times, anecessary arrangement since ISOtransmits observations as it makesthem rather than storinginformation for later playback. ISOis able to observe from 2.5 to 240microns.

Visible spectrum observatories

The only visual observatory inorbit at the moment is the HubbleSpace Telescope (HST). Likeradio observatories in space, thereare visible observatories alreadyon the ground. However, Hubblehas several special advantagesover them.


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HST's biggest advantage isthat because it is above theEarth's atmosphere, it does notsuffer distorted vision from theair. If the air were all the sametemperature and there were nowind (or the wind wereperfectly constant), telescopeswould have a perfect viewthrough the air. Alas, this is nothow our atmosphere works.There are small temperaturedifferences, wind speedchanges, pressure differences,and so on. This causes lightpassing through air to suffertiny wobbles. It gets bent alittle, much like light gets bentby a pair of glasses. But unlikeglasses, two light beamscoming from the samedirection do not get bent inquite the same way. You'veprobably seen this before --looking along the top of theroad on a hot day, everythingseems to shimmer over theblack road surface. This blursthe image telescopes see,limiting their ability to resolveobjects. On a good night in anobservatory on a highmountain, the amount ofdistortion caused by theatmosphere can be very small.But the Space Telescope has

NO distortion from the atmosphereand its perfect view gives it manymany times better resolution thaneven the best ground-basedtelescopes on the best nights.

Ultraviolet observatories

Right now there are no dedicatedultraviolet observatories in orbit.The Hubble Space Telescope canperform a great deal of observingat ultraviolet wavelengths, but ithas a very fairly small field of view.Water vapor in the atmospherecompletely absorbs incoming UV,so Earth-based UV observatoriesare not feasible.

X-ray observatories

There are several X-rayobservatories currently operatingin space with more to be launchedin the next few years.

The Rossi X-ray Timing Explorer(RXTE) was launched onDecember 30, 1995. RXTE is ableto make very precise timingmeasurements of X-ray objects,particularly those which showpatterns in their X-ray emissionsover very short time periods, suchas certain neutron star systemsand pulsars

Table 1.3 Electromagnetic spectral regions


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Region Wavelength Remarks

Gamma Ray < 0.03 nm Incoming radiation is completely absorbed by the upperatmosphere and is not available for remote sensing.

X-Ray 0.03 to 3.0 nm Completely absorbed by atmosphere. Not employed inremote sensing.

Ultraviolet 0.03 to 0.4µµm Incoming wavelengths less than 0.3 µµm are completelyabsorbed by ozone in upper atmosphere.

PhotographicUV Band

0.3 to 0.4 µµm Transmitted through atmosphere. Detectable with filmand photo detectors, but atmospheric scattering is

severe.

Visible 0.4 to 0.7 µµm Imaged with film and photo detectors. Included reflectedenergy peak of earth at 0.5µµm.

Infrared 0.7 to 100 µµm Interaction with matter varies with wavelength.Atmospheric transmission windows are separated by

absorption bands.

Reflected IRband

0.7 to 3.0 µµm Reflected solar radiation that contains no informationabout thermal properties of materials. The band from 0.7

to 0.9 µµm is detectable with film and is called aphotographic IR band.

Thermal IRband

3 to 5 µµm, 8-14µµm

Principle atmospheric windows in the thermal region.Images at these wavelengths are acquired by optical -mechanical scanners and special vidicon systems but

not by film.

Microwave 0.1 to 30 cm Longer wavelengths can penetrate clouds, fog and rain.Images may be acquired in the active or passive mode.

Radar 0.1 to 30 cm Active form of microwave remote sensing. Radar imagesare acquired at wavelength bands.

Radio >30 cm Longest wavelength portion of electromagneticspectrum. Some classified radars with very long

wavelength operate in this region.


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Sea Surface Temperature

Excerpted from: http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/OCDST/seawifs_raq.html#Q1

Sea surface temperature (SST)measures the infrared radiationemitted by the ocean surface. It issimply a measure of the intensityof this radiation and relies less onin situ verification. However,atmospheric correction andcomparison to in-situ sensors forcalibration is still quite important.Because oceanic currents andwater masses can varyconsiderably in temperature, SSTdata is particularly useful inobserving currents and circulationin the oceans. The data are quitesensitive to atmospheric effects,and are also obscured by clouds.

SST data are most commonlyobtained from polar-orbitingsatellites operated by the NationalOceanic and AtmosphericAdministration. There is no directrelationship to convert sea surfacetemperature to sea surfacetopography, or vice versa.Although a change in sea surfacetemperature will cause a changein sea surface topography, andthis can be computed

approximately via an equation,one can’t compute the totaltopography from the temperature.If this were possible, no one wouldbe interested in satellite altimetry.

SST directly influences and isinfluenced by atmosphericprocesses, such as wind,temperature, precipitation andcloud formation. In short, there is adynamic interrelationship betweenthe ocean and the atmosphere,which in turn impacts the ocean'scarbon and heat reservoirs.Storms or cold upwelling currentsmay bring up deeper, nutrient-richwaters, which serve as "fertilizer"to enhance biological productivity.

SST algorithms are used todetermine sea surfacetemperature, generate mappedSST fields, study spatial andtemporal variation anddevelopment of simple models tostudy specific scientific problems,such as the El Niño phenomenonand global warming.


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Instruments Used for Ocean Color SensingAdapted from: http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/OCDST/seawifs_raq.html#Q1

Coastal Zone Color Scanner (CZCS) CZCS was an experimental ocean color instrument launched aboardNASA's NIMBUS-7 satellite. It shared satellite resources and power withmany other sensors, and therefore collected data only sporadically.Additionally, fewer scenes were collected as the instrument aged. The dataare used to study the regional and seasonal variation in primaryproductivity, environmental change, oceanic features and even outbreaksof infectious disease. Data and more information are available from the Goddard DAAC'socean color web site: Ocean Color Data and Resources.

Modular Optoelectronic Scanner (MOS) MOS is a sensor developed by the German Aerospace ResearchEstablishment (DLR) Institute for Space Sensor Technology. The specificgoals of MOS include improved compared to CZCS) corrections foratmospheric, sea surface, and turbidity effects. MOS data will also becorrelated with SeaWiFS data. Two MOS instruments have been launched, one aboard the IndianRemote Sensing Satellite (IRS) P3, and the other in the Russian Prirodamodule, a component of the Mir space station. The IRS MOS has an extrachannel, used to enhance determination of surface roughness. Datacollection is limited to ground stations, and therefore does not provideglobal coverage.

Ocean Color and Temperature Scanner (OCTS) OCTS was an instrument aboard Japan's Advanced Earth ObservingSatellite (ADEOS). It collected chlorophyll and sea-surface temperaturedata. High resolution and low resolution data were transmitted separately.Global coverage was achieved by OCTS every three days, which providedinformation on rapidly changing phenomena. ADEOS was lost on June 30,1997.

Sea-viewing Wide Field-of-view Sensor (SeaWiFS) SeaWiFS is an ongoing ocean color mission operated by OrbitalSciences Corporation (OSC) for NASA. SeaWiFS data is being used to


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help clarify the magnitude and variability of chlorophyll and primaryproduction by marine phytoplankton. In particular, the data will helpdetermine the distribution and timing of 'spring blooms' -- the rapid increasein phytoplankton populations stimulated by increasing light availability andhigher nutrient concentrations characteristic of the spring season.

Moderate Resolution Imaging Spectroradiometer (MODIS) MODIS is an instrument that will orbit aboard the Earth ObservingSystem (EOS) AM and PM series of satellites, resulting in 15 years ofcontinuous ocean color data. It will also sense sea-surface temperature.Hardware and algorithm improvements will result in data that are moreaccurate than either CZCS or SeaWiFS.


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Comparison of Wavelength & Bandwidth for SpaceborneOcean Color Instruments

Adapted from: http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/OCDST/instruments.html

Comparison of Ocean Color Instruments

Instrument Satellite Dates of OperationSpatial Resolution Swath Width

CZCS Nimbus-7 10/24/78- 6/22/86 825 m 1556 km

SeaWiFS SeaStar 5/97 1100 m 2800 km

MODIS EOS AM-1 6/98 1000 m 2330 km

MOS IRS P3 3/18/96 520 m 200 km

Low Resolution KOMPSAT scheduled 1999 1000 m 800 km Camera


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Student Information Sheet- Lesson 3

Sea Surface TemperatureExcerpted from: http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/OCDST/seawifs_raq.html#Q1

Sea surface temperature (SST) measures the infrared radiation emitted bythe ocean surface. It is simply a measure of the intensity of this radiationand relies less on in situ verification. However, atmospheric correction andcomparison to in situ sensors for calibration is still quite important. Becauseoceanic currents and water masses can vary considerably in temperature,SST data is particularly useful in observing currents and circulation in theoceans. The data is quite sensitive to atmospheric effects and is alsoobscured by clouds. SST data is most commonly obtained from polar-orbiting satellites operated by the National Oceanic and AtmosphericAdministration. There is no direct relationship to convert sea surfacetemperature to sea surface topography, or vice versa. Although a changein sea surface temperature will cause a change in sea surface topography,and this can be computed approximately via an equation, one can’tcompute the total topography from the temperature. If this were possible,no one would be interested in satellite altimetry.

Electromagnetic SpectrumThe rainbow of colors that we see in visible light represents only a verysmall portion of the electromagnetic spectrum. EM spectrum is thecontinuum of energy that ranges from meters to nanometers in wavelengthand travels at the speed of light. On one end of the spectrum are radiowaves with wavelengths billions of times longer than those of visible light.On the other end of the spectrum are gamma rays. These havewavelengths millions of times smaller than those of visible light. All matter(except at absolute zero temperature) radiates EM energy with peakintensity shifting toward shorter wavelength with increasing temperature.


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Vocabulary

Airborne Visible and InfraRed Imaging Spectrometer (AVIRIS)- Experimentalairborne along track multispectral scanner under development at JPL to acquire 224images in the spectral region from 0.4 to 2.4 µm.

Atmosphere- layer of gases that surrounds some planets.

Atmospheric Correction- image processing procedure that compensates for effects ofselectivity scattered light in multispectral images.

AVHRR- Advanced Very High Resolution Radiometer, a multispectral imaging systemcarried by the TIROS/NOAA series of meteorological satellites.

Electromagnetic Radiation- Energy propagated in the form of and advancinginteraction between electric and magnetic fields. All electromagnetic radiation moves atthe speed of light.

Electromagnetic Spectrum- Continuous sequence of electromagnetic energyarranged according to wavelength or frequency.

False Colour Image- a colour image where parts of the non-visible EM spectrum areexpressed as one or more of the red, green and blue components, so that coloursproduced by the Earth’s surface do not correspond to normal visual experience. Alsocalled a false-colour composite (FCC). The most commonly seen false colour imagesdisplay the very near infrared as red, red as green and green as blue.

Frequency- (v) the number of wave oscillations per unit time or the number ofwavelengths that pass a point per unit time.

HIRS- High Resolution Infrared Spectrometer, carried by NOAA satellites.

Incident Energy- Electromagenetic energy inpinging on a surface.

Multispectral scanner- scanner system that simultaneously acquires images of thesame scene at a different wavelength.

Non-selective scattering- the scattering of EM energy by particles in the atmospherewhich are much larger than the wavelengths of the energy, which causes allwavelengths to be scattered equally.


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Passive Remote Sensing- Remote sensing of energy naturally reflected or radiatedfrom the terrain.

Photodetector- Device for measuring energy in the visible-light band.

Photographic IR- Short-wavelength portion (0.7 to 0.9 µm) of the IR band that isdetectable by IR color, film or IR black and white film.

Radar Scattering Coefficient- a measure of the back-scattered energy from a targetwith a large area. Expressed as the average radar cross section per unit area indecibels (dB). It is the fundamental measure of the radar properties of a surface.

Radar Scatterometer- A non-imaging device that records radar energy backscatteredfrom terrain as a function of depression angle.

Rayleigh Criterion- In radar, the relationship between surface roughness, depressionangle, and wavelength that determines whether a surface will respond in a rough orsmooth fashion to the radar pulse.

Rayleigh Scattering- Selective scattering of light in the atmosphere by particles thatare small compared with the wavelength of light.

RBV- Return-Beam-Vidicon

Reflected IR- EM energy of wavelengths from 0.7 to 3µm that consists primarily ofreflected solar radiation.

Remote Sensing- collection and interpretation of information about an object withoutbeing in physical contact with the object.

Scan Line- Narrow strip on the ground that is swept by IFOV of a detector in a scanningsystem.

Scanner- an imaging system in which the IFOV of one or more detectors is sweptacross the terrain.

Scattering- multiple reflections of electromagnetic waves by particles or surfaces.

Scattering Coefficient Curves- Display of scatterometer data in which relativebackscatter is shown as a function of incidence angle.

Scatterometer- Non-imaging radar device that quantitatively records backscatter ofterrain as a function of incidence angle.


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Spectrometer- Device for measuring intensity of radiation absorbed or reflected bymaterial as a function of wavelength.

Spectroradiometer- A device which measures the enegry reflected or radiated bymaterials in narrow EM wavebands.

Spectrum- continuous sequence of EM energy arranged according to wavelength orfrequency.

Surface Phenomena- Interaction between EM radiation and the surface of a material.

Visible Radiation- Energy at wavelengths from 0.4 to 0.7 mm that is detectable by thehuman eye.

Volume Scattering- in radar, interaction between electromagnetic radiation and theinterior of a material.

Wavelength- distance between sucessive wavecrests or other equivalant.


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References and AcknowledgementsFrank E. Muller-Karger, Ph.D.

http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/OCDST/seawifs_raq.html#Q1:Page Author: James Acker -- [email protected] Curator: Daniel Ziskin -- [email protected] official: Paul Chan, GDAAC Manager -- [email protected]

http://ltpwww.gsfc.nasa.gov/MODIS/MODIS.htmlAuthor: David Herring ([email protected])Curator: Kevin Ward ([email protected])

http://seawifs.gsfc.nasa.gov/SEAWIFS.htmlCreator: Gene Carl Feldman ([email protected])


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Frank E. Muller-Karger, Biological Oceanography

Assistant Professor, Ph.D., University of Maryland, 1988

My research on primary production in the sea takes advantage of the new technologiesbased on satellite remote sensing, archiving of large data sets, networking, and high-speed computing. This research helps in the location and monitoring of large-scalephenomena, of phenomena important in climate control and climate change and in theinterpretation of numerical models of the ocean. In my lab we pursue an intensiveanalysis of data from various satellites, the space shuttle, ships, buoys, and otherplatforms. This process has helped my students to develop international collaborativeprograms to collect ground data as well as to disseminate satellite data. The focus ofmy present work is to determine if satellites that measure ocean color and sea surfacetemperature can be used to assess the importance of continental margins, includingareas of upwelling and river discharge in the global carbon budget. Within this context, Iwork closely with NASA scientists and colleagues at other institutions to help developreliable algorithms for measurement of phytoplankton and other materials in sea waterfrom space. Of specific interest have been the plumes of the larger rivers of the world,as these provide a cause for the abundance of materials present in addition tophytoplankton. The academic program built around this research is forming with thescientists that will use the data from the satellites coming on line during the decade ofthe 1990s and beyond.

unit i. ocean color- table of contents · color from space (and the only long-term satellite...

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