Wenhui_Wang.LowerTroposphericTemperatureClimateDataRecordUsingNOAANESDISSTARRecalibratedMSUObservations.pptx

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  • 1. 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
  • 2. Outline
    Background
    Methods for Developing TLT Product Using NOAA/NESDIS/STAR Recalibrated MSU Radiances
    Results and Discussion
    Summary and Future Works
  • 3. Background
    • Microwave Sounding Unit (MSU, 1978/11-2006/9)
    • 4. 9 instruments (NOAA TIROS-N – NOAA-14)
    • 5. 4 channels
    Channel 2- mid-troposphere (TMT)
    Channel 3 - upper-troposphere
    Channel 4 - lower-stratosphere
    • 11 scan angles: 0 – 47.35°
    • 6. Widely used in long-term atmospheric Tb trends studies
    • 7. 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
  • 8. 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
  • 9. Methods for STAR TLT Product
    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
    • 10. Can reduce inter-satellite bias by an order of magnitude compared to NOAA pre-launch calibration
  • Methods for STAR TLT Product
    Using NOAA/NESDIS/STAR Recalibrated MSU Radiances
    NOAA 10 -14 averaged σ of intersatellite biases
    SNO calibration (curve)
    SNO + Christy Bias Correction (straight line)
    Christy Bias Correction is used to removes residual WT contamination after SNO calibration
    Noises in TLT are 2 times as large as those in MSU channel 2 (TMT)
  • 11. Methods for STAR TLT Product
    Satellite Altitude & Orbital Decay Effect Correction
    • Satellite altitudes are different (morning versus noon satellites)
    • 12. Satellite altitude trends to decay over time
    • 13. Cause view zenith angle changes, effects vary with different limb positions
  • Methods for STAR TLT Product
    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)
  • 14. Methods for STAR TLT Product
    Diurnal Drift Effect Correction same as STAR TMT products (Zou and Wang 2009)Using RSS monthly averaged diurnal anomaly climatology
    Before Diurnal Correction
    NOAA 11 - NOAA 10
    Adjust the scene radiances at different observation time to the local noon time
    After Diurnal Correction
  • 15. Results
    5-day averaged MSU global mean TLT & TMT time series
    Temporal Coverage: 1978/11-2006/9
    Spatial Coverage: -82.5° – +82.5 °
  • 16. Results: Spatial Trend Patterns (1978-2006)
    TLT After Orbital Drift Effect Correction
    TMT (channel 2)
    TLT Without Orbital Decay Effect Corr.
  • 17. Comparing STAR, UAH (v5.3), RSS (v3.2) MSU TLT Products (1979 - 2003)
  • 18. 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
  • 19.
  • 20. Results
    TLT show similar trend stability as TMT (Zouand Wang, 2010)
    Christy bias correction (almost horizontal lines)
    Constant bias correction