weather in motion

8/7/2019 Weather in Motion

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EP-79 Weather in Motion

National Aeronautics and Space AdministrationWashington, D. C. 20546


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Thecover photographshowsaview of the earthonNovember 18,1967 from the NASA ATS-III satellitewhich was"stationary" 22,000 miles over the equatorabove South America. This folder describes n detailthe satellite,the camera,the display,the picture information,andthe beneficial use of the satellite.The camera experiment on ATS-III wasproposedandconceived by investigators at The University of Wsconsin.Santa Barbara Research Center developed the flightmodel camera. The photographic animation of "WeatherinMotion" was developed by the Walter A. Bohan Com-pany, Park Ridge, Illinois. The entire experiment anddisplay has been supported by the Earth Observationsand ATS Programs of the National Aeronautics andSpace Administration,Washington, D.C.

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NATIONAL AERONAUTICS AND SPACE ADMINISTRATIONEarth Observations Program. Washington, D.C. 20546WEATHER IN MOTION

To observe a most striking display of weather in motion on a typical day,hold the color picture between the index finger and thumb of each hand along thesides and midway down from the top of the picture. In the display, Africa is thebright orange area in the upper right, the United States is faintly visible in theupper left, the Greenland ice cap appears in the upper center, and South Americastands out prominently in the lower central area. Tilt the top of the picture slowlytowards you and then away through a small arc (about 20). Each time the topmoves toward you, cloud motions over the entire picture area are authentic and,alternatively, are reversed when the top of the picture is tilted away.

Note the spectacular spiral cloud band off the northwest coast of Africa.The cloud system is associatedwith a storm center (center of the spiral cloud bands)and the counterclockwise rotation of the clouds indicates that it is a cyclonicdisturbance. The display also presents many other weather phenomena as revealedby cloud type, distribution, pattern, andevolution.

The display is a composite of 9 individual pictures taken at approximately60 minute intervals by the NASA Multicolor Spin-Scan Cloud Camera on theApplications Technology Satellite, ATS- III. Thetotal time interval presented inthe display is about an 8-hour period. Thus, from weather satellite pictures takenat frequent intervals clouds and cloud motions can reveal useful information onweather systems on a global scale.

The weather in motion display was conceived and developed under a NASAsponsored contract by Walter A. Bohan. XOGRAPHPrinted In U.S.A.


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Weather in MotionSpace technology for the direct benefit of manin his everyday life has been part of NASA'smission ever since the agency was createdin 1958.The world's first meteorological satellite,TIROS-1, was placed in orbit April 1, 1960, andimmediately showed the importance of cloudcover photos from space to weatherforecasting. It was followed by more TIROSspacecraft as well as the more advancedNimbus satellites to continue sensorexperimentation for a National OperationalMeteorological System.Early in 1966, the first operationalmeteorological satellite was placed in orbitfor the Weather Bureau bringing mankind astep closer to the time when accurate longrange weather forecasts, based on advancedoperational satellite-computer technology, willbe routine. This goal is expected to beat ta ined in the 1970s.In late 1966, the ATS-1 spacecraft carrying acloud cover camera was launched intogeo-stationary orbit. Thus, for the first time,man had the opportunity to observe theatmosphere below on a continuous basis. Suchobservations have proven to be extremelyimportant to the study of severe storms, theirformation, and dissipation, through time lapsephotography. The cover display is but oneexample of such photography. The ATSexperimental program has demonstrated theusefulness of such techniques and serves as astepping stone to the operational deploymentof a similar system now being developed byNASA for the Environmental Science ServicesAdministration.


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The SatelliteThe ATS-III satellite was launched fromCape Kennedy,Florida on November 5, 1967 and is orbiting the earthat analtitude of 22,300 miles above the equator. At thisaltitude, the spacecraft requires precisely 24hours tocomplete on e revolutionas does th e earththus, th esatellite is stationary above a single location on theequator. The space craft has been over South Americaduring much of its lifetime.Th e entire satellite spins at 100 rpmmuch l ike agyroscopeso that it does not tumble in space. Thisrotation is extremely precise, as if the satellite were onperfect bearings. The spin axis of the satellite is verynearly parallel to the earth's ax is of rotation.More than 24,000solar cells cover th e outside of thedrum shaped spacecraft an d provide 17 5 watts ofelectrical power for the various experiments and forradio communicationwith the earth.ATS -III carried eleven experiments into orbit; theseconcern communication,navigation, and meteorology.The Multicolor Spin-Scan Cloud Cam era, discussed inthis folder, is one of the experiments.

ATS-III Spacecraft


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The CameraTh e "camera" is really a telescope which scans acrossth e earth from west to east with each rotation of thesatellite. A rectangular picture is produced by tiltingthe camera a small amount so that each new scan lineis obtained adjacent to the previous line. The completepicture is made up of 2400 scan lines which are acquiredin 24 minutes, because the rotation rate of the satelliteis 10 0 revolutions per minute.

The extremely uniform rotation of the satellite in spaceallows the "camera" to obtain high precision picturesof the earth. Although th e satellite is 22,300 miles abovethe earth, the camera can be used to measure the distancebetween land features to within a few miles.

At the focus of the camera are 3 tiny pinhole aperatureswhich allow the formationof separateblue, green,andred images. Color photos are generated at the groundstation by combining these three-color images.


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The DisplayTh e display is a composite of 9 individual pictures takenon November 18 , 1967 at approximately 60 minuteintervals by the N ASA Multicolor Spin-Scan CloudCamera on the Appl ications Technology Sa tel l i te, ATS -III. The total time interval presented in the display isabout an 8-hour period.

This ph otograph w hich provides the se nsation of three-dimensional viewing is called a panoramic parallaxstereogram. A horizontal screen is used to alternatelyplace l ines of the nine individual pictures on the f inalimage. A lenticular screen is placed over the f in al printso that paral lax al lows viewing of al ternate images, as thepicture is tilted back an d forth.


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ThePicture InformationEarth ShadowThe South Polar region has continuous daylight at thistime (November 18), but the North Polar region receivesmuch less sunlight and the extreme northern region iscontinuously shaded from the sun's rays.

Cloud FormationThunderstormswhich usually form during the daytimecan be seen formingover th e Andes Mountainsof SouthAmerica and over th e extensive A ma zo n Basin.

Cloud DecayFog along the coast of Chile, associated with cold PacificOcean water,disappears during the day. Similarly, fogan d low stratus clouds alongthe African coasts of Liberia,Ivory Coast and Ghana dissipate during the daytimebecause of intense warming of air in the tropics. Highclouds disappear over the equatorial Atlantic because ofthe descending andwarming motion of the air near theequator.


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Cloud MotionStorm clouds movewith circular motion in mid-latitudesof both hemispheres.An active storm can be seen in thenorthwest portion of the picture over New York Statean d adissipating stormcan be seen in the northeast por-tion of the picture just off the coast of Spain. Note thatthese storms rotate in opposite directions to the stormnear the southerntip of Chile and to the young stormsouth of the bulge of Braz i l . Meteorologist arelearningfrom these time seriespictures that clouds aretied tothese large scale motions of the atmosphere.

The low, cumuliform clouds which move westward inthe tropics aredriftingwith the easterly "trade winds."Some high cirrus clouds areabove the "trade wind"region and arecarried north-eastwardin "jet streams"over the coast of Wes t Africa. Large quantities of heatand moisturearecarried poleward from the tropics bythese "jet streams."

Sun GlitterThe bright area which approaches the coast of Brazil iscaused by mirror like reflectionsof the sun's image fromthe oceansurface. The size of the area can be used tomeasure the wind speed over the ocean surface.


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The BenefitsSevere Storm DetectionThe use of earth syn chronou s satell i tes gives meteorolo-gist a valuable capabili ty for pinpointingand trackingboth hurricanes and severe storms which form tornadoes.A dramatic illustration of this capabili ty is shown by thecloud structure over Kentucky and Tennessee. Thesecellular clouds are the actual blow-off anvil tops of severethunderstorms which generated many tornadoes in thosetw o States at that time. Thus, p ictures such as this givemeteorologist a valuable tool for "nowcasting" as well asforecasting.

Remote Sensing of Atmo spheric W indsThe motion of the clouds isclearly visible by tilting thepicture to obtaina time sequence of the pictures. Byusing display techniques with greater resolution it ispossible to measure cloud displacementswith suff icientprecision to infer atmos pheric winds from the displace-ments. One series of pictures, such as these, can providewinds over 1/3 of the earths surfacewhich is a fantasticincrease over the present capability of determining windsby balloon.

ATS-III photo of cloud systems over the UnitedStates

Global MeasurementsW ith four synchrono us satell i tes properly spaced aroundthe earth, it ispossible to monitor nearly all of theearth's cloud cover all of the time. Only small areas inth e polar regions are not in view of the satell i tes. Thisunique obse rving capa bility will be implemented in themid-1970's to serve as an important component of aninternational program to make detai led, global observa-tions of theatmosphere.

U. S. GOVERNMENT PRINTING OFFICE : 1970 O - 406-164