TC Science Objectives for CALIPSO · CALIPSO 1064 Calibration Issues 532 nm attenuated backscatter...
Transcript of TC Science Objectives for CALIPSO · CALIPSO 1064 Calibration Issues 532 nm attenuated backscatter...
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TC4 Science Objectives for CALIPSO
Chip TrepteNASA Langley Research
Center
with contributions from:
M. Vaughan, M. Pitts, Y. Hu, J. Mace, M. McGill, D. Hlavka, B. Hart, and D. Winker
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Laser Nd: YAG, 2x110 mJ Wavelength 532 nm, 1064 nm Repetition rate 20.16 Hz Receiver telescope 1.0 m diameter Polarization 532
Wavelength 645 nm Spectral bandwidth 50 nm IFOV / Swath 125 m / 61 km
Wavelength 8.65, 10.6,12.05 µ µ
CALIOP
Imaging Infrared Radiometer (IIR)
WideField Camera (WFC)
Payload Specifications
Wide Field Camera
Imaging InfraredRadiometerLidar
Transmitter
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Clearair Profiles
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532parallel calibration
scale factor = 3.3872 x 10
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Thermal Effect?
532parallel channel calibrated by normalization of highaltitude returns (3034 km) to molecular density
Stratospheric Aerosol?
Calibration coefficients during a 2week period, derived from 3034 km signal averaged 6000 km alongtrack
RMS variability of calibration coefficients slightly larger than expected from signal noise alone
(RMS ~ 1%)
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Validation Intercomparisons: CloudsAugust 12, 2006
532 nm Calibrated Attenuated BackscatterCoincidence
Coincidence
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Validation Intercomparisons: Aerosols
August 10, 2006
Coincidence
532 nm Attenuated Backscatter (km1 sr1)
1064 nm Attenuated Backscatter (km1 sr1)
Coincidence
CALIPSOHSRL
CALIPSOHSRL
CALIPSO
LaRC HSRL
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Aerosol Subtypes
CloudAerosol Mask
Cloud Phase
CALIPSO Data Products
Level 1: 532 nm total atten. backscatter
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Information from Depolarization
532 nm total attenuated backscatter
532 nm volume depolarization
Arctic cloudsidentification of water,
and both random and oriented ice crystals
Sahara dust with embedded water clouds
Liquid cloud
Ice cloud
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CALIPSO Scenes over Panama Region
July 25
Aug 8
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CALIPSO Geographical Cloud Occurrence
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CALIPSO Zonal Cloud OccurrenceJuly 2006 DayNight Cloud Fraction September 2006 DayNight Cloud Fraction
January 2007 DayNight Cloud FractionNovember 2006 DayNight Cloud Fraction
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Verification of CloudSat/CALIPSO Joint Cloud Products
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CALIPSO 1064 Calibration Issues532 nm attenuated backscatter profiles calibrated against molecular backscatter profiles
532 nm channel calibration is transferred to 1064 channel at the top of high altitude clouds where assumed backscatter color ratio (1064/532) = 1.
CPL observations, however, indicate that at times a shift of color ratios to lower values (mode near 0.8).
0.5 0.6 0.7 0.8 0.9 1.0LayerIntegrated Attenuated Total Color Ratio
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
Frequency
CPL TX2002 12 December 2002, High Clouds
0 10 20 30 40 50 60 70 80Mean Attenuated Scattering Ratio
0.4
0.5
0.6
0.7
0.8
0.9
1.0
LayerIntegrated Attenuated Total Color Ratio
CPL TX2002 12 December 2002, High Clouds
Courtesy of CPL Team
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Color Ratio Frequency Distribution
July 2007
Departure from unity suggests erroneous application of color ratio assumption
Courtesy of Y. Hu
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CALIPSO Validation Issues for TC4
Clouds examine detection sensitivity of thin cirrus validate backscatter and extinction profiles verify multiple scattering correction and lidar ratio validate cirrus extinction profiles and examine IWC relationships validate cirrus habit and emissivity examine microphysical interpretation of backscatter color ratio verify cloud feature mask
Aerosols verify aerosol lidar ratio and extinction profiles verify aerosol typing algorithmMuch can be achieved through vicarious
comparisons using combined aircraft observations
Direct comparisons are not essential