Transcript Slide 1
Cassandra Wheeler
Univ. of Colorado Department of Atmospheric and Oceanic Sciences (ATOC) Cooperative Institute for Research in Environmental Sciences (CIRES) National Oceanic and Atmospheric Administration (NOAA) Semester Project for Katja Fredrick’s Fall 2008 Independent Study: Introduction to Remote Sensing Instrumentation (ATOC 5900) (Click on callouts at upper left of slides for presentation notes.)
Overview of ASCOS Field Campaign and Remote Sensors
Vertically Pointing Radars
Ceilometer/Lidar
Radiometers
Preliminary Results
Further Reading
(Click on title to go to section title slide.)
Goal:
Determine the persistence of low-level clouds and their impacts on the energy budget
NOAA’s Contribution:
conditions Remotely observe cloud layers and environmental
Location: Duration: Platform :
87 ˚ N 1 Aug –15 Sept 2008 Swedish Icebreaker Oden 85 ˚ N
Svalbard, Norway Greenland
0 ˚E
Ceilometer 2-Channel Microwave Radiometer S-Band Radar Ka-Band Radar Wind Profiler Scanning Radiometer Lidar
Wind Profiler Ceilometer S-Band Radar Ka-Band Radar Active 2-Channel Radiometer Microwave Radiometer Passive Ice Liquid Precip Air
Ka-Band Radar S-band Radar Wind Profiler Ceilometer Lidar Scanning Radiometer 2-Channel Radiometer
Beamwidth Frequency
0.2˚ 34.86 GHz
Spatial Resolution
45 to 90 m 2.5˚ 10˚ 0.04˚ 0.17˚ 6.5˚ 4.7˚ to 5.8˚ 2.875 GHz 449 MHz 330.4 THz 10 THz 60 Hz 23.8 and 31.6 GHz 45, 60, 105 and 420 m 30 and 100 m 15 m 15 m 4.5˚ 0.1 to 1 K
Temporal Resolution
9 s 30 s 60 min 15 s 5 min 2 s 19 s
Radar Wind Profiler Rayleigh Region Ceilometer Lidar Mie or Resonance Region Optical Region Instrument Beamwidths 0.2˚ Ka-Band Radar 2.5˚ S-Band Radar circumference/wavelength = 2 π a/ λ Rayleigh: CCN (0.1 μ m) Mie: Cloud Drop (10 – 50 μ m) Optical: Raindrop (100 – 1000 μ m) Note: 1000 μ m = 1 mm of a piece of paperboard the width 5˚ 2-Ch Radiometer 10˚ Wind Profiler The lidar is 5% and the ceilometer is 80% of the Ka-band radar
Electromagnetic Spectrum
Frequency (Hz) 10 19 10 18 10 17 10 16 10 15 10 14 10 13 10 12 10 11 10 10 10 9 10 8 FM VHF 10 7 10 6 Wavelength 400 nm 500 nm 600 nm 700 nm
Ware 2008
Signal encounters target Target scatters EM wave Signal encounters target Radar emits EM wave at specified frequency and pulse length Radar collects backscatter from target Returned signal is collected by radar for processing
t=0 t=1 t=2 Higher Frequency Shorter Wavelength Lower Altitudes t=0 t=1 t=2 Lower Frequency Longer Wavelength Higher Altitudes
Pulse Length Emitted beam expanding out into a cone shape, similar to a flashlight beam Radar Emitted EM Wave
Rayleigh Region is assumed.
Radar Equation
Received Transmitted Radar Constant Unknown Where Surface Area is Defined as Constant Unknown The Diameter can be found from the Reflectivity Equation The return power is proportional to the diameter of the target to the sixth.
Receiver P R =P E Emitted Pulse P E Receiver P R =P E / θ θ Receiver P R =0 Target www.azonano.com/Details.asp?ArticleID=1239
Melting Layer
Doppler spectrum (reflectivity, Doppler velocity, spectral width) Minimal attenuation except in heavy precip conditions Signal is dominated by large particles (Z to d 6 ) e is proportional Attenuate cloud fringes or small-particle cloud layers
Cloud particles moving away from the radar.
Cloud particles moving towards the radar.
Doppler spectrum (reflectivity, Doppler velocity, spectral width) Rain attenuation is not as severe as MMCR.
Cloud particles moving towards the radar.
Cloud particles moving away from the radar.
-5 5
Noise Turbulent Eddies
Wind Profiling. 2004.
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(
V r
4 (
V r
1 (
V r
4
V r
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V r
2 ) )
V r
3 / / 2 sin( )
EW
) 2 / sin( 2
NS
cos( )
EW w
(
V r
1
V r
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NS
) )
Example Let
:
v
1 5
m
/
s
,
v
2 10
m
/
s
,
v
3 7
m
/
Yeilding
:
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,
v
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u
8
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, 0 .
52
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o
v
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Ecklund et al., 1988
Example 1: Wind Example 2: Spectral Moment
2K
Fog Practically no rain attenuation Can detect cloud base in fog, rain, snow and haze Cloud Base
Measures lower cloud boundaries of liquid hydrometeors Backscatter provides hydrometer phase classification Optically thick cloud attenuation due to low operating frequencies Stronger signal from liquid droplets than from larger ice particles Cloud Base Haze Display image in Baltimore, MD alg.umbc.edu/usaq/archives/2008_08.html
Measures liquid water path and temperature over an atmospheric column (does not give vertical distribution) Attenuation for clouds with low liquid water amounts Liquid Water Content over Boulder, CO http://www.radiometrics.com/
Attenuation from the 2-Ch radiometer can be improved by adding higher frequency channels to retrievals, such as a scanning radiometer Measures temperature in a vertical column (does not give vertical distribution) Scanning antenna rotates 360˚ every 0.4 s 5 min time avgerage with averaging over 5 angular samples yields 4.5 ˚ angular resolution Atmospheric Temperature over Boulder, CO
ECMWF Mean Sea-Level Pressure and Ten Meter Wind Maps
26 Aug 2008 00Z
∙∙∙∙ Ceilometer - Ka-Band Radar Radiosonde - Derived
26 Aug 2008 12Z
- 2 Ch Radiometer - Wind Profiler
ECMWF Mean Sea-Level Pressure and Ten Meter Wind Maps
20 Aug 2008 00Z
∙∙∙∙ Ceilometer - Ka-Band Radar Radiosonde - Derived
20 Aug 2008 12Z
- 2 Ch Radiometer - Wind Profiler
Balsley, B. B. and K. S. Gage: Sept 1982. On the Use of Radars for Operational Wind Profiling. Bulletin American Meteorological Society. 62: 1009-1018.
Chandrasekat, V.: presented 23 October 2005. Micorphysical characterization of precipitation systems using dual-polarization radar measurements: Hydrometer Identification. Education Forum: Joint 11
th Conference on Mesoscale Processes and 32 nd
Conference on Radar Meteorology.
Ecklund, W. L., et al.: 1988. A UHF Wind Profiler for the Boundary Layer: Brief Description and Initial Results. Journal of Atmospheric and Oceanic Techonology. 5: 432-441.
Haby, Jeff. Weather Radar FAQ. Available at http://www.theweatherprediction.com/radared/radarfaq/ Hall, Steven E. Radar Meteorology: Online Remote Sensing Guide. Available at http://ww2010.atmos.uiuc.edu/(Gh)/guides/rs/rad/home.rxml
McLaughlin, Scott and Daniel Wolfe: presented 4 Feb 2002. A New ETL 449 MHz Wind Profiler for TARS.
Met Office: http://www.metoffice.gov.uk/ Moran, Kenneth P., et al: 1998. An Unattended Cloud-Profiling Radar for Use in Climate Research. Bulletin of the American Meteorological Society. 79: 443-455.
NOAA/ESRL/PSD: Nov 2007. Coastal Wind Profiler Technology Evaluation: An Integrated Ocean Observing System Project Final Report.
Rinehart, Ronald E. Radar for Meteorologists: Third Edition. Rinehart: 1997.
Sauvageot, Henri. Radar Meteorology. Artech House: 1992.
White, Allen B., et al. 1999. Extending the Dynamic Range of an S Band Radar for Cloud and Precipitation Studies. Journal of Atmospheric and Oceanic Technology. 17: 1226-1234.
Wind Profiling: The History, Principles, and Applications. Technical Note. Vaisala. December 2004.
Flynn, C.:2004. Vaisala Ceilometer (Model CT25K) Handbook.
Alvarez II, R. J. et al.: 1990. High-Spectral Resolution Lidar Measurement of Tropospheric Backscatter Ratio Using Barium Atomic Blocking Fliters. Journal of Atmospheric and Oceanic Technology. 7: 876-881.
Alvarez II, R. J. and L. M. Caldwell: 1993. Profiling Temperature, Pressure, and Aerosol Properties Using a High Spectral Resolution Lidar Employing Atomic Blocking Filters. Journal of Atmospheric and Oceanic Technology. 10: 546-556.
Barton I. J., et al.: 2003. The Miami2001 Infrared Radiometer Calibration and Intercomparison. Part II: Shipboard Results. Journal of Atmospheric and Oceanic Technology. 21: 268-283.
NOAA Ground Based Radiometers. Available at: http://www.etl.noaa.gov/technology/radiometers Ware, Radolf: presented on 22 May 2008. Colorado Tornadoes: WeatherCam, Radiosonde and Radar Observations.
Ware, Randolf: presented on 1 Aug 2008. WeatherCam Temperature, Humidity and Liquid Profiling: Introduction and Tutorial.
Westwater, Ed R. et al.:2005. Prinicples of Surface-based Micorwave and Millimeter wave Radiometric Remote Sensing of the Troposphere. Quaderni Della Societa Italiana Di Elettromagnetismo. 1: 50-90.
Westwater, Edgeworth R. et al.: 2003. Radiosonde Humidity Soundings and Microwave Radiometers during Nauru99. Journal of Atmospheric and Oceanic Technology. 20: 953-971.