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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) • 9 instruments (NOAA TIROS-N – NOAA-14) • 4 channels Channel 2- mid-troposphere (TMT) Weighting Function Channel 3 - upper-troposphere (Ocean) 25 Channel 4 - lower-stratosphere NADIR • 11 scan angles: 0 – 47.35° Scan Pos 5 • Widely used in long-term atmospheric Tb trends studies 20 Scan Pos 4 Scan Pos 3• MSU Lower Tropospheric Temperature (TLT) Scan Pos 2 Height (km) 15 Scan Pos 1 – TMT Affected by stratosphere cooling effect TLT – TLT: weighted average of TMT Tb 10 at different view angles (Spencer and Christy, 1992,2003; Mears and Wentz, 2009) 5 TLT=T3+T4+T8+T9-0.75(T1+T2+T10+T11) 0 0 0.05 0.1 0.15 i=1-4, 8-10 scan positions Reduce stratosphere cooling effect
  • 4. 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
  • 5. Methods for STAR TLT Product1. 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
  • 6. Methods for STAR TLT Product1. Using NOAA/NESDIS/STAR Recalibrated MSU RadiancesNOAA 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)
  • 7. Methods for STAR TLT Product 2. Satellite Altitude & Orbital Decay Effect Correction 870 860 • Satellite altitudes are different (morning 850 versus noon satellites) 840 • Satellite altitude trends to decay over timeAltitude (km) 830 • Cause view zenith angle changes, effects vary with different limb positions 820 810 NTN N6 N7 800 N8 N9 N10 N11 N12 N14 790 1978 1983 1988 1993 1998 2003
  • 8. Methods for STAR TLT Product2. 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)
  • 9. Methods for STAR TLT Product3. 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
  • 10. Results 5-day averaged MSU global mean TLT & TMT time series Temporal Coverage: 1978/11-2006/9 Spatial Coverage: -82.5° – +82.5 °
  • 11. Results: Spatial Trend Patterns (1978-2006) TLT After Orbital Drift Effect CorrectionTLT Without Orbital Drift Effect Correction TMT (channel 2)
  • 12. Comparing STAR, UAH (v5.3), RSS (v3.2) MSU TLT Products (1979 - 2003)
  • 13. 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
  • 14. Results TLT show similar trend stability as TMT (Zou and Wang, 2010) Christy bias correction (almost horizontal lines) Constant bias correction