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Transcript of Wenhui_Wang.LowerTroposphericTemperatureClimateDataRecordUsingNOAANESDISSTARRecalibratedMSUObservations.pdf...
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Lower-Tropospheric Temperature (TLT) Climate Data Record Using NOAA/NESDIS/STAR
Recalibrated MSU Observations
Wenhui Wang1 & Cheng-Zhi Zou2
1IMSG at NOAA/NESDIS/STAR
2NOAA/NESDIS/Center for Satellite Applications and Research
IGARSS
Vancouver, Canada
July 25-29, 2011
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• Background
• Methods for Developing TLT Product Using NOAA/NESDIS/STAR Recalibrated MSU Radiances
• Results and Discussion
• Summary and Future Works
Outline
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Background • Microwave Sounding Unit (MSU, 1978/11-2006/9)
• 9 instruments (NOAA TIROS-N – NOAA-14) • 4 channels
Channel 2- mid-troposphere (TMT) Channel 3 - upper-troposphere Channel 4 - lower-stratosphere
• 11 scan angles: 0 – 47.35° • Widely used in long-term atmospheric Tb trends studies
• MSU Lower Tropospheric Temperature (TLT) – TMT Affected by stratosphere cooling effect
– TLT: weighted average of TMT Tb
at different view angles (Spencer and Christy, 1992,2003; Mears and Wentz, 2009)
TLT=T3+T4+T8+T9-0.75(T1+T2+T10+T11) i=1-4, 8-10 scan positions
Reduce stratosphere cooling effect
0
5
10
15
20
25
0 0.05 0.1 0.15
He
igh
t (k
m)
Weighting Function (Ocean)
NADIR
Scan Pos 5
Scan Pos 4
Scan Pos 3
Scan Pos 2
Scan Pos 1
TLT
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Background
• Two MSU TLT products available Using NOAA pre-launch calibrated observations
– University of Alabama group (UAH) – Remote Sensing Systems group (RSS)
• Major Issues need to addressed – Calibration Errors (Warm Target Contamination) – Orbital Decay Effect – Diurnal Drift Effect
• TLT trends have important policy making implications
• Purpose of this study – Generate STAR TLT product using NOAA/NESDIS/STAR recalibrated MSU
radiances
– Comparing STAR TLT with other two research groups
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1. Using NOAA/NESDIS/STAR Recalibrated MSU Radiances (v1.2) (Zou et al. 2006, 2009, 2010)
– Simultaneous Nadir Overpass (SNO) Method to generate consistent climate data records (CDR)
http://www.star.nesdis.noaa.gov/smcd/emb/mscat/mscatmain.htm
– Remove Warm Target (WT) Contamination at root level – Can reduce inter-satellite bias by an order of magnitude
compared to NOAA pre-launch calibration
Methods for STAR TLT Product
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SNO calibration (curve)
SNO + Christy Bias Correction (straight line)
Christy Bias Correction is used to removes residual WT contamination after SNO calibration
Methods for STAR TLT Product
NOAA 10 -14 averaged σ of intersatellite biases
Noises in TLT are 2 times as large as those in MSU
channel 2 (TMT)
1. Using NOAA/NESDIS/STAR Recalibrated MSU Radiances
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2. Satellite Altitude & Orbital Decay Effect Correction
Methods for STAR TLT Product
790
800
810
820
830
840
850
860
870
1978 1983 1988 1993 1998 2003
Alt
itu
de
(km
)
NTN N6 N7
N8 N9 N10
N11 N12 N14
• Satellite altitudes are different (morning
versus noon satellites)
• Satellite altitude trends to decay over time
• Cause view zenith angle changes, effects
vary with different limb positions
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2. Satellite Altitude & Orbital Decay Effect Correction
Simulated altitude effect climatology – Community Radiative Transfer Model (CRTM)
– NASA MERRA reanalysis
– All observations adjusted to 850 km altitude
Rate of Tb change with satellite altitude (K/km)
Methods for STAR TLT Product
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3. Diurnal Drift Effect Correction same as STAR TMT products (Zou and Wang 2009)
Using RSS monthly averaged diurnal anomaly climatology
Before Diurnal Correction
After Diurnal Correction
NOAA 11 - NOAA 10
Methods for STAR TLT Product
Adjust the scene radiances at different
observation time to the local noon time
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Results
5-day averaged MSU global mean TLT & TMT time series Temporal Coverage: 1978/11-2006/9
Spatial Coverage: -82.5° – +82.5 °
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TLT Without Orbital Drift Effect Correction
TLT After Orbital Drift Effect Correction
Results: Spatial Trend Patterns (1978-2006)
TMT (channel 2)
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Comparing STAR, UAH (v5.3), RSS (v3.2) MSU TLT Products (1979 - 2003)
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Summary and Future Works • Generated MSU TLT product using NOAA/NESDIS/STAR recalibrated
channel 2 radiances
• STAR TLT shows a global warming trend of 0.145 K/dec (1978-2006),
• STAR TLT has the smallest warming trends compared to UAH and RSS TLT products – Larger differences exist during 1979 – 1986
• Next Step – Generate TLT product using recalibrated Advanced Microwave
Sounding Unit A (AMSU-A) observations (1998 – present) – Generate MSU/AMSU-A TLT merged Product
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TLT show similar trend stability as TMT (Zou and Wang, 2010)
Christy bias correction (almost horizontal lines)
Constant bias correction
Results