Chapter 5: Remote Sensing - TCNJ
Transcript of Chapter 5: Remote Sensing - TCNJ
Chapter 5: Remote Sensing
Satellites
Wind Profiler
Radar
Lidar
Satellites: Geostationary vs. Polar Orbiting
•What does geostationary mean?•Resolution determined by distance and wavelength
Satellites: Visible, Infrared, and Water Vapor
•Sensing devices are called radiometers
•Sensitive at different wavelengths
•Difference wavelengths reveal different information about weather
•It take practice to use satellites to infer information about clouds and weather
http://cimss.ssec.wisc.edu/satmet/modules/index.html
Satellites: Visible
ADVANTAGES
•High resolution (1 km and less)
•Intuitive interpretation (like a photo)
•Can see more than clouds when clear
•Easy to distinguish different cloud types
DISADVANTAGES
•Blind at night
•No information about temperature
Visible Satellites: what is this?
Visible Satellites: Why are the lakes clear?
Visible satellites: More than clouds
http://modis.gsfc.nasa.gov/gallery/
Satellites: Infrared
ADVANTAGES
•Direct information about temperature
•Can provide vertical profile of Temp. when clear
•Equally effective at night
DISADVANTAGES
•Lower resolution (4+ km)
•Interpretations non-intuitive
Infrared Satellites: Sensitive to temperature
Infrared Satellites: “False Color” and cloud top temp
Bright= cold=high=strong storms (maybe)
Doppler Radar
ADVANTAGES
•Direct Measurement of falling precipitation
•Strong indication of precipitation intensity
•Can detect hail and indicate likely tornados
•Doppler Effect can help determine wind patterns
•Can “see” birds, insects, dust
DISADVANTAGES
•Hard to distinguish between rain and snow
•Useless when clear (no wind info)
•Range and resolution are limited
http://www.srh.noaa.gov/srh/jetstream/doppler/doppler_intro.htm
NEXRAD 88-D radar locations
http://water.weather.gov/
NEXRAD 88-D radar locations
Beams cover about 250 mile diamter
NEXRAD 88-D radar beams:
•Radar beam covers about 1 degree angle
•The further away from the radar you are, the wider the beam spreads
•This causes decreased resolution at long distance
Radar Beam Geometry
•These are the direction that the radar beam is sent out and received
•These 16 angles are rotated through a full 360 degrees
•The entire sky volume is scanned in 5 minutes
•This output can give a 3-D dimensional view of a storm, though usually we only look at the “base” reflectivity.
•The base reflectivity represents a higher height further from the radar
Doppler Radar: Thunderstorm closeup
Doppler wind speeds
•The returned radiation is shifted in frequency by the motion of the target•This can be used to calculate drop speed along the radial path•This path is basically horizontal toward or away from the radar•Green = INBOUND; RED=OUTBOUND
Doppler Radar: Tornadic hook echo and velocity couplet
Doppler winds: only toward or away from radar
http://www.spc.noaa.gov/coolimg/cape_may.htm
Lidar measurements of ice crystals falling on Mars?
Wind Profiler sample data