Chapter 5: Remote Sensing Radar Satellites Lidar Wind Profiler - - PowerPoint PPT Presentation

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
• nly 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