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SW Diurnal Errors in ERB monthly means: some studies from CERES and GERB LMD/IPSL

SW Diurnal Errors in ERB monthly means: some studies from CERES and GERB LMD/IPSL M. Viollier and A. Ben Rehouma Ecole Polytechnique, Palaiseau, France. Comparison between the SW monthly means over two regions. Reg # 1 the whole area (45°S-45°N/60°W-60°E) Reg # 2 ( 35°-10°S/10°W-10°E)

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SW Diurnal Errors in ERB monthly means: some studies from CERES and GERB LMD/IPSL

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  1. SW Diurnal Errors in ERBmonthly means: some studies from CERES and GERB LMD/IPSL M. Viollier and A. Ben RehoumaEcole Polytechnique, Palaiseau, France GERB STM, Exeter, Oct. 2006

  2. Comparison between the SW monthly means over two regions Reg#1the whole area (45°S-45°N/60°W-60°E)Reg#2 (35°-10°S/10°W-10°E) with systematic diurnal cycle sharp diurnal errors SW standard deviationMonth: August GERB STM, Exeter, Oct. 2006

  3. SW Mean overReg#1 ScannersNonscannerISCCP-FD Negative trend See also, Wong et al(2006) Zhang et al(2004), for the tropicalmean Monthly Anomalydefined / all available years GERB STM, Exeter, Oct. 2006

  4. Regional Anomaly (Reg#2 – Reg#1) Slope Wm-2/decade±staking autocorrelation intoaccount, according to Weatherhead et al JGR (1998) Nonscanner ISCCP-FD +1.5 ± 3.0 +3.0 ± 0.8 More on our Friday presentation GERB STM, Exeter, Oct. 2006

  5. Scanner Serie (Reg#2 – Reg#1) with Terra with Averageof Terra and Aqua +5.0 ±1.5 +1.1 ± 2.0 GERB STM, Exeter, Oct. 2006

  6. Diurnal corrections for CERES-Terra,several approaches • SRBAVG geo products ( about 2 years, 2000/032004/05) • Combination (or average) of Terra and Aqua (ES4, about 4 years, 2002/07 2005/12) • Examination of GERB ARG Ed1 products 5 months: 2006, 04 to 08) GERB STM, Exeter, Oct. 2006

  7. Diurnal error, January 2003 Computed from differences betweenCERES SRBAVG GEO – NON GEO 1 x 1° Computed from differences between (Aqua+Terra) and Terra alone 2.5 x 2.5 ° GERB STM, Exeter, Oct. 2006

  8. Diurnal error, October 2003 GERB STM, Exeter, Oct. 2006

  9. SW Diurnal Errors, reg 2 (up) , reg 1 (down) REG2 REG1 GERB STM, Exeter, Oct. 2006

  10. Comparisons between contemporary T-(TA) and nonGeo-Geo / 2003 Agreement at least for these areas and their differences; the variations are higher for SRBAVG

  11. Same for Albedo , 2003 GERB STM, Exeter, Oct. 2006

  12. GERB, 2006 July, 17-18 LW fluxSW flux GERB STM, Exeter, Oct. 2006

  13. Diurnal Cycle – August 2006 X 100 Area: 2.5x2.5° GERB STM, Exeter, Oct. 2006

  14. April 2006 May 2006 Aug 2006 July 2006 Albedo Diurnal Cycle – hourly means- off Angola Area: 2.5x2.5° GERB STM, Exeter, Oct. 2006

  15. April 2006 May 2006 Aug 2006 July 2006 Albedo Diurnal Cycle – hourly means- Sahara Area: 2.5x2.5° GERB STM, Exeter, Oct. 2006

  16. SW Monthly Means Computations with GERB • Average the fluxes (2.5°x2.5°) and fill the 24x31 day-hour table • Use ‘ERBE-type’ code, with Terra flux estimates (ES9- Ed1 - CV ) to compute monthly means • Repeat using the GERB observed diurnal albedo variation shape in place of the ERBE modeled albedo GERB STM, Exeter, Oct. 2006

  17. GERB April 2006 GERB2006 GERB STM, Exeter, Oct. 2006

  18. SRBAVG, TA and GERB April SRBAVG2003 TA2003 GERB2006 SRBAVG2002 GERB STM, Exeter, Oct. 2006

  19. SRBAVG, TA and GERB August SRBAVG2003 TA2003 GERB2006 SRBAVG 2001 GERB STM, Exeter, Oct. 2006

  20. Summary of Diurnal Errors Wm-2 Caution: Not the same years for each case GERB STM, Exeter, Oct. 2006

  21. We have looked for inter-regional differences in the evolution of the SW reflected flux (Reg1, Reg2) Reg 2 (South East Atlantic): diurnal errors are critical when using ES4-Terra (morning observation) Significant agreement between 3 independent evaluations of the relative diurnal errors (SRBAVG, Aqua, GERB); waiting for overlapping periods This is shown only for the studied regions and for their differences The 1985-2005 SW positive change (relatively to the average Reg1) observed with Terra seems slightly greater than the diurnal error Conclusion GERB STM, Exeter, Oct. 2006

  22. Indo-French Megha-Tropiquessatellite project - 2009 ScaRaB Saphir : microwave sounder for water vapour sounding : 6 channels in the WV absoption band at 183.31 GHz. (cross track, 10 km) MADRAS: microwave imager for precipitation : channels at 18, 23, 37, 89 and 157 GHz, H and V polarisations. (conical swath, <10 km to 40 km)

  23. The threeinstrumentsof Megha-Tropiques • ScaRaB: wide band instrument for inferring longwave and shortwage outgoing fluxes at the top of the atmosphere (cross track scanning, 40 km resolution at nadir) • Saphir : microwave sounder for water vapour sounding : 6 channels in the WV absoption band at 183.31 GHz. (cross track, 10 km) • MADRAS: microwave imager for precipitation : channels at 18, 23, 37, 89 and 157 GHz, H and V polarisations. (conical swath, <10 km to 40 km) GERB STM, Exeter, Oct. 2006

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