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.)
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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.)
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Goal: Determine the persistence of low-level clouds and their impacts on
the energy budget
NOAA’s Contribution: Remotely observe cloud layers and environmental
conditions
Location: 87˚N
Duration: 1 Aug –15 Sept 2008
Platform : Swedish Icebreaker Oden
85 ˚N
Svalbard,
Norway
Greenland
0 ˚E
Ceilometer
2-Channel
Microwave
Radiometer
Lidar
Scanning
Radiometer
S-Band
Radar
Ka-Band
Radar
Wind
Profiler
Wind
Profiler
Ceilometer
S-Band
Radar
Ka-Band
Radar
2-Channel
Radiometer
Microwave
Radiometer
Ice
Liquid
Precip
Active
Passive
Air
Beamwidth
Frequency
Spatial
Resolution
Temporal
Resolution
Ka-Band
Radar
0.2˚
34.86 GHz
45 to 90 m
9s
S-band
Radar
2.5˚
2.875 GHz
45, 60, 105
and 420 m
30 s
Wind
Profiler
10˚
449 MHz
30 and
100 m
60 min
Ceilometer
0.04˚
330.4 THz
15 m
15 s
Lidar
0.17˚
10 THz
15 m
5 min
Scanning
Radiometer
6.5˚
60 Hz
4.5˚
2s
2-Channel
Radiometer
4.7˚ to 5.8˚
23.8 and
31.6 GHz
0.1 to 1 K
19 s
Wind Profiler
Ceilometer
Lidar
Radar
Instrument Beamwidths
σsphere/πa2
0.2˚
Ka-Band
Radar
Rayleigh
Region
Mie or
Resonance
Region
Optical
Region
circumference/wavelength = 2πa/λ
Rayleigh: CCN (0.1 μm)
Mie: Cloud Drop (10 – 50 μm)
Optical: Raindrop (100 – 1000 μm)
Note: 1000 μm = 1 mm  the width
of a piece of paperboard
2.5˚
S-Band
Radar
5˚ 2-Ch
Radiometer
10˚ Wind Profiler
The lidar is 5% and the ceilometer
is 80% of the Ka-band radar
Wavelength
400 nm
500 nm
600 nm
700 nm
1000 m
Long-waves
AM
108
100 m
109
Wind Profiler
1011 1010
10 m
Ka-Band Radar
10 cm
S-band Radar
1 m Radio, TV
Micorwave
1012
1 cm
1 mm
Far IR
1013
1000 μm
Thremal IR
1014
100 μm
10 μm
Visible
Near IR
Ceilometer
Lidar
Infra-red
1016 1015
1 μm
1000 μm
Ultraviolet
X-rays
400 MHz
1000 MHz
VHF
(7-13)
FM
100 MHz
VHF
(2-6) 50 MHz
HF
3 MHz
UHF
Frequency (Hz)
1019 1018 1017
100 nm
10 nm
1 nm
0.1 nm
0.1 Ǻ Gamma-rays
1Ǻ
Electromagnetic
Spectrum
107 106
Ware 2008
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Signal
encounters
target
Radar emits EM wave
at specified frequency
and pulse length
Target Signal encounters target
scatters
EM wave
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
Emitted EM Wave
Radar
Rayleigh Region is assumed.
Radar Equation
Received
Transmitted
Unknown
Radar
Constant
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
PR=0
Receiver
PR=PE/θ
Receiver
PR=PE
Emitted
Pulse PE
www.azonano.com/Details.asp?ArticleID=1239
θ
Target
Melting
Layer
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Doppler spectrum (reflectivity, Doppler velocity, spectral
width)
Minimal attenuation except in heavy precip conditions
Signal is dominated by large particles (Ze is proportional
to d6)
Attenuate cloud fringes or small-particle cloud layers
Cloud particles
moving away
from the radar.
Cloud particles
moving towards
the radar.
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Doppler spectrum (reflectivity, Doppler velocity,
spectral width)
Rain attenuation is not as severe as MMCR.
Height Above
Ground (km)
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Cloud particles
moving towards
the radar.
Cloud particles
moving away
from the radar.
-5
5
Height Above
Ground (km)
Noise
Turbulent
Eddies
Wind Profiling. 2004.
u  (Vr 4  Vr 3 ) / 2 sin( EW )
v  (Vr1  Vr 2 ) / 2 sin( NS )
w  (Vr 4  Vr 3 ) / 2 cos( EW )
w  (Vr1  Vr 2 ) / 2 cos( NS )
Exam ple
Let : v1  5m / s, v 2  10m / s,
v3  7 m / s, v 4  8m / s,   15o
Yeilding : u  0.52m / s
v  9.66m / s, w  7.76m / s
Ecklund et al., 1988
Example 1: Wind
Example 2: Spectral Moment
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Practically no rain attenuation
Can detect cloud base in fog,
rain, snow and haze
Altitude (m)
2K
Fog
Cloud Base
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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
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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/
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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
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ECMWF Mean Sea-Level Pressure
and Ten Meter Wind Maps
26 Aug 2008 00Z
Radiosonde
∙∙∙∙ Ceilometer
- Ka-Band Radar
- Derived
26 Aug 2008 12Z
- 2 Ch Radiometer
- Wind Profiler
ECMWF Mean Sea-Level Pressure
and Ten Meter Wind Maps
20 Aug 2008 00Z
Radiosonde
∙∙∙∙ Ceilometer
- Ka-Band Radar
- Derived
20 Aug 2008 12Z
- 2 Ch Radiometer
- Wind Profiler
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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 11th
Conference on Mesoscale Processes and 32nd 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.
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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 SBand 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.
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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.
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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.
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