Advanced Sounder Capabilities- Airborne Demonstration with NAST-I W.L. Smith, D.K. Zhou, and A.M. Larar NASA Langley Research Center, Hampton, Virginia 23681 Twelfth International TOVS Study Conference (Lorne Australia, 27 Feb-5 Mar, 2002) NAST on Proteus Performance: Ceiling 65-75 kft Airspeed 300 ktas Endurance 12-22 hrs Operating Altitude: 100 to 60,000 f ER-2
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Advanced Sounder Capabilities- Airborne Demonstration with NAST-I W.L. Smith, D.K. Zhou, and A.M. Larar NASA Langley Research Center, Hampton, Virginia.
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Advanced Sounder Capabilities-Airborne Demonstration with NAST-I
W.L. Smith, D.K. Zhou, and A.M. LararNASA Langley Research Center, Hampton, Virginia 23681
Twelfth International TOVS Study Conference (Lorne Australia, 27 Feb-5 Mar, 2002)
NAST on Proteus
Performance: Ceiling 65-75 kft Airspeed 300 ktas Endurance 12-22 hrs Operating Altitude: 100 to 60,000 ft
NAST-I Observes 3-Dimensional StructureNAST-I Observes 3-Dimensional Structure With High Spatial Resolution and Radiometric AccuracyWith High Spatial Resolution and Radiometric Accuracy
Optimal Regression Retrieval Approach for Optimal Regression Retrieval Approach for NAST-I ApplicationNAST-I Application
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imismni
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imim )(
kj
S
1kkiij S
1M
τ*dB)ε-(1τdBτεBRsP
acP
sP
acP
ss R = radiance = surface emissivityBs = surface Planck radiance = transmittance
s = surface transmittance* = (s)2 / Ps = surface pressurePac = aircraft pressureS = number of sample profiles = radiance deviation from the mean M = covariance matrix of E = eigenvectors of M – EOFsC = radiance EOF amplitudesA = {Ts, , T, q, ...} parametersK and k = regression coefficients = emissivity EOF amplitudes
5
1
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iii Ck
NAST-I Spectrum and Retrieval ChannelsNAST-I Spectrum and Retrieval Channels
NAST-I SpmRTVL Chnls
Retrieval Accuracy Vs EOF NumberRetrieval Accuracy Vs EOF Number
Full Noise
1/2 Noise
2610
58
Observed Vs Calculated from RetrievalObserved Vs Calculated from Retrieval
Retrievals for Two Different EOF #sRetrievals for Two Different EOF #s
48 EOFsRadiosonde23 EOFs
Radiosonde ValidationRadiosonde Validation
Alt
itu
de
(km
)
Relative H
um
idity (%
)
Distance (75 km)
3km
Andros Is. Bahamas, Sept 12, 1998
NASTRaob
Spectral HSpectral H22O SensitivityO Sensitivity
H2O Sensitivity [dTB(,p)/dlnq(p)]
Water Vapor Retrieval Water Vapor Retrieval SensitivitySensitivity
75 km
LW-side of H2O Band
SW-side of H2O Band
ARM CART-Site Sounding Validation
CD
A
BSpace & Time
Variability
Spatial (~22km) & Temporal (~2-3hr) Temperature Variation Over Purcell
Sfc Temp (21Z)
Sfc Temp (19Z)
P
P
PROTEUS NAST-I Flight Over CART Site Loop 1 [18:06 – 19:50 UT, March 19, 2000]
PROTEUS/NAST-I Flight Over CART Site Loop 2 [19:50 – 21:24 UT, March 19, 2000]
Surface Skin Temperature (July 14, 2001)Surface Skin Temperature (July 14, 2001)
296.52º K ( = 0.54º K) NAST-I retrieved (within 0.1 Lat. and Lon.)297.45º K NOAA buoy site CHLV2 measured (i.e., the bulk SST). The cool “skin”, observed by NAST-I, relative to the sub-surface water, observed by the buoy, is expected as a result of evaporative cooling.
NPOESS Aircraft Sounding Testbed (NAST) soundings over Alaska from the ~15km flight altitude of the Proteus (March 20-21, 2001). Upper panels show flight track and cross-section. (Note the updrafts and downdrafts seen in the water vapor at 7-9 km.) Bottom panels show comparisons with North Slope CART-site radiosondes.
IR Image along track
Surface Skin Temperature Along Track
Can CAT Be Measured ?
Strong Turbulence Signatures at 300 mb
Weak Turbulence Signatures at 150 mb
No Turbulence Signatures at 500 mb
Downdrafts:Warm & Dry Updrafts:Cold & Moist
Temp
Temp
Temp
Moisture
Moisture
Moisture
NAST Near Fairbanks AK (3/21/01; 1-2 GMT)
Moisture
200 km
SummarySummary• The NAST provides high spatial resolution radiance measurements which can be used to validate the radiometric accuracy and retrieval products of advanced IR sounding systems
• High spatial resolution features of atmospheric temperature, moisture, and clouds can be retrieved from NAST radiances
• Lower tropospheric water vapor profiles depend on measurements along the shortwave side of the 6.3 m H2O band
• High spectral/spatial resolution sounders can profile above an opaque overcast cloud cover and above and below thin and/or broken clouds
• Surface skin temperature and emissivity can be retrieved simultaneously from the spectral radiance measurements and this is important for the retrieval of accurate lower tropospheric moisture profiles
• Atmospheric turbulence might be observed with very high spatial resolution advanced sounders