3-Way Comparison between AIRS, ECMWF and GPS Temperatures in Upper - PowerPoint PPT Presentation

Comparison of AIRS-ECMWF-GPS Temperature Profiles 3-Way Comparison between AIRS, ECMWF and GPS Temperatures in Upper Troposphere and Stratosphere Tom Yunck, Eric Fetzer, Anthony Mannucci, Chi Ao, Bill Irion, Brian Wilson and Gerald Manipon Jet Propulsion Laboratory California Institute of Technology AIRS Science Meeting Pasadena, CA 29 March 2007 1 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles 2 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles Some Key Points • Adjustments to data are generally subjective and can be large compared to the actual trend. • Reported trends vary considerably between groups using the same data owing to differing adjustment methods. • Most models predict greater warming in the troposphere; most observations show greater warming at the surface. The likely cause is errors in the tropospheric observations . • Recent adjustments have brought satellite observations into closer agreement with models. • “Satellite observations tend to be bias-corrected to the model.” ( Healy & Thépault , 2006) [ECMWF] 3 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles One Approach 4 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles GPS-GPS Comparison Stats from COSMIC No cloud or Std. Dev. weather ~1 K sensitivity at 30 km Bias No corrections <0.05 K or calibrations required Performance traceable to an ±1 K absolute SI (single standard instr.) Ben Ho (UCAR), Jan 07 5 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles TLS Comparison with GPS Sensors Launched 6 yrs Apart Ben Ho (UCAR), Jan 07 N18 TLS est. from COSMIC v. N18 AMSU TLS est. from CHAMP 6 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles Modeled GPSRO Temperature Sigma Modeled GPS Temperature Sigma 7 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles Controlled Three-Way Comparison: • AIRS-ECMWF-GPS temperatures • Common set of 3-way match-ups • For all of 2003 (Champ, SAC-C) First comparisons: ECMWF 30°-60° North “Sweet Spot” (“Mid North”) Match-up criteria: <200 km, <2 hrs apart 8 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles Pairwise RMS deviations A Puzzle Match-ups: 766 AIRS Quality: 0, 1 9 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles Derived AIRS & ECMWF RMS deviations 10 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles Derived AIRS & ECMWF RMS deviations “Expected” AIRS-ECMWF RMS deviation 11 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles Derived AIRS & ECMWF RMS deviations “Expected” AIRS-ECMWF RMS deviation Actual AIRS-ECMWF RMS deviation Var(X-Y) = Var(X) + Var(Y) – 2Cov(X,Y) 12 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles Derived AIRS & ECMWF RMS deviations AIRS-ECMWF “Covariation” Match-ups: 766 AIRS Quality: 0, 1 13 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles Derived AIRS & ECMWF RMS deviations AIRS-ECMWF Corr. Coeff. Match-ups: 766 AIRS Quality: 0, 1 14 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles How else can we examine this question? Compare regional performance variations, where a particular technique is known to vary in a particular way I – The Tropics 15 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles ECMWF-GPS RMS Deviations, 2003 Smoothing of Sharp Tropopause 16 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles ECMWF-GPS RMS Deviations and Means, 2003 Match-ups: 2203 AIRS Quality: 0,1 17 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles Regional Performance Variations – II Vertical Bias Patterns Mid North Far North Far South 18 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles ECMWF-GPS Means, All GPS, 2003 19 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles ECMWF & AIRS Means vs GPS, All 2003 20 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles Conclusion IF our GPSRO error model is accurate, then: 3-way comparisons show significant correlation between AIRS and ECMWF temperature errors. Caveat: We should adopt actual AIRS smoothing functions to ensure we are comparing like quantities. Next: Repeat the analysis with AIRS V5 and COSMIC data and true AIRS smoothing functions . 21 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles Backups 22 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles RMS Deviations & Covariation, All 2003 Match-ups: 766 Match-ups: 1388 Quality: 0, 1 Quality: 0, 1 23 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles RMS Deviations & Covariation, All 2003 Match-ups: 500 Match-ups: 888 Quality: 0, 1 Quality: 0, 1 24 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles RMS Deviations & Covariation, All 2003 AIRS Quality 0,1 AIRS Quality 2 Match-ups: 1731 Match-ups: 1388 Quality: 2 Quality: 0, 1 25 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles Simple Analysis Measurement error = bias (b) + zero mean random error (e): M e = b + e Measurement difference M 1 - M 2 is therefore: M 1,2 = b 1 - b 2 + e 1 - e 2 = b 1,2 + e 1 - e 2 The mean (expected) squared (MS) difference is therefore: MS 1,2 = b 1,2 2 + σ 1 2 + σ 2 2 (assuming e 1 and e 2 uncorrelated) 26 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles Or: MS 1,2 - b 1,2 2 = σ 1 2 + σ 2 2 (i.e., Var = MS - square of the mean) For the three-way comparison we have: (1) MS 1,2 - b 1,2 2 = σ 1 2 + σ 2 2 (2) MS 2,3 - b 2,3 2 = σ 2 2 + σ 3 2 (3) MS 1,3 - b 1,3 2 = σ 1 2 + σ 3 2 27 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles What this means: Measurement difference M 1 - M 2 is: M 1,2 = b 1,2 + e 1 - e 2 The mean squared (MS) difference is: MS 1,2 = b 1,2 2 + σ 1 2 + σ 2 2 - 2E[e 1 e 2 ] (assuming e 1 and e 2 uncorrelated) 28 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles Revised Analysis For the three-way comparison we now have: (1) MS E,A - b E,A 2 = σ E 2 + σ A 2 - 2 γ E,A 2 (2) MS A,G - b A,G 2 - σ G 2 = σ A 2 (3) MS E,G - b E,G 2 - σ G 2 = σ E 2 29 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles Examples of AIRS-ECMWF Temperature Error Similarity 20 K 10 K 20 K 10 K 30 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles Working Hypothesis 1. AIRS “first guess” temperatures, trained on ECMWF model , closely reproduce location-dependent ECMWF bias characteristics. 2. Where temperature gradients are small, AIRS retrieval information is weak and departures from the first guess are small. 3. This leads to significant correlation in location-dependent biases. 4. Where temperature gradients are steep (near the tropopause), AIRS retrievals are allowed to depart more from the a priori, reducing the AIRS-ECMWF correlation. 31 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles Simple Sigma Solutions, Mid North Match-ups: 766 AIRS Quality: 0, 1 32 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles ECMWF-GPS Means, 3-Way Matchups, 2003 33 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles Smoothing of Sharp Tropopause GPS-GPS Comparison Stats (COSMIC) 25 Match-ups: 2203 AIRS Quality: 0,1 20 Altitude (km) 15 10 5 -1 0 1 Temperature (K) 34 29 March 2007 AIRS Science Meeting, Pasadena

Comparison of AIRS-ECMWF-GPS Temperature Profiles Typical 3-Way Matchup For consistent comparisons GPS & AIRS were smoothed to 2 km vertical resolution 35 29 March 2007 AIRS Science Meeting, Pasadena