Transcript Slide 1
Satellite Interpretation Remote Sensing Tools RADAR SATELLITE In-Situ vs. Remote Sensing Two Types of Satellites Figure from goespoes.gsfc.nasa.gov POES • Polar Orbiting Environmental Satellite • ~ 530 miles above the earth • Animation from www.comet.ucar.edu Orbit of POES Figure from physics.uwstout.edu/wx/wxsat/types.htm POES Image Image from meted.ucar.edu/ist/poes GOES Satellite Figure from www.cira.colostate.edu/ramm/newgoes/goesover.html GOES Orbits Figure from cimms.ssec.wisc.edu/satmet/modules/sat_basics/geo_orbit.html Two GOES Satellites GOES 11 GOES 12 Figure from noaasis.noaa.gov/NOAASIS/ml/genlsatl.html Electromagnetic Radiation Radiation • The transfer of energy by electromagnetic waves • No transfer medium is required • Figure from www.geo.mtu.edu/rs/back/spectrum Wavelength Figure from www.lbl.gov/MicroWorlds/ALSTool/EMSpec Electromagnetic Spectrum Figure from www.science.uwaterloo.ca/~cchieh/cact/c120/emwave.html Sun • The sun emits its maximum amount of radiation in what part of the electromagnetic spectrum? • VISIBLE Earth • The earth emits its maximum amount of radiation in what part of the electromagnetic spectrum? • INFRARED • Image from www.goes.noaa.gov Infrared Image Photo from imagers.gsfc.nasa.gov/ems/infrared.html What Do Satellites Measure • Amount of visible radiation reflected from clouds, land/water surface • Amount of infrared radiation emitted by cloud tops, land/water surface • Instrument on satellite: radiometer Emitted Radiation • The amount of radiation emitted by an object depends on the object’s _________ • TEMPERATURE • Stefan-Boltzman Law: I = σT4 • Warmer objects emit more radiation than cooler objects Imager & Sounder Figure from ww2010.atmos.uiuc.edu GOES Imager • 5 channels • 1 visible & 4 Infrared channels • We’ll look at 3 channels and call them: Visible image Infrared image Water Vapor image Resolution • Ability to distinguish objects with clarity • • Resolution of GOES Images • Visible – 1km • Infrared – 4km • Water vapor – 8km (4km on GOES 12) • (at the satellite sub-point) Interpretation of Images Visible Image Visible Image • Based on what? • Amount of reflected sunlight • Percentage of reflected light is called the albedo • Water has a low albedo – appears dark Visible Image • • • • • Land – various shades of gray Fresh snow cover – bright, white Thick clouds – bright, white Thin clouds – not as white Cloud types: Cumulus – individual elements, textured Stratus – smooth appearance Fair Weather Cumulus Photo from asd-www.larc.nasa.gov/SCOOL/New_Clouds Squall Line on Satellite Image from www.eos.ubc.ca/courses/atsc201 Stratus Clouds www.photolib.noaa.gov Fog in California Visible Satellite Image Infrared Image Infrared Image • Based on what? • Amount of radiation emitted by land, water, cloud tops • Amount of radiation emitted depends on what? • Temperature Infrared Image (IR) • Higher clouds radiate at colder temps • Lower clouds radiate at warmer temps • Figure from www.personal.psu.edu/users/b/x/bxm209 /ir.html Infrared Image (IR) • Brightness corresponds to the temperature • White – cold high clouds • Dark – warm low clouds or land Enhanced IR • Colors added to better distinguish temperatures and therefore relative cloud heights. • Ex: Thunderstorm tops Water Vapor Image Water Vapor Image • Based on the fact that water vapor absorbs and emits IR radiation at a certain wavelength. • Satellite “sees” water vapor in the mid to upper troposphere. (Roughly between 15,000 and 39,000 ft) Weighting Function Figure from apollo.lsc.vsc.edu/classes/remote/lecture_notes/satellite/instrumentation/wv.html Enhanced Water Vapor Jet Stream Figure from apollo.lsc.vsc.edu/classes/remote/graphics/satellite_images/watervapor/jetstream_cirrus.gif