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CHEMICAL ASSIMILATION OF GOMOS NOy DATA

COST workshop, ESTEC, 11-13 March 2003. CHEMICAL ASSIMILATION OF GOMOS NOy DATA. Slimane Bekki , M. Marchand, A. Hauchecorne, J-L Bertaux IPSL (UPMC/CNRS). GOMOS MEASUREMENTS. UV-visible-Near IR spectrometer (stellar occultations)

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CHEMICAL ASSIMILATION OF GOMOS NOy DATA

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  1. COST workshop, ESTEC, 11-13 March 2003 CHEMICAL ASSIMILATION OF GOMOS NOy DATA Slimane Bekki, M. Marchand, A. Hauchecorne, J-L Bertaux IPSL (UPMC/CNRS)

  2. GOMOS MEASUREMENTS UV-visible-Near IR spectrometer (stellar occultations) -> 400 profiles/day all around the globe of : O3, NO2, NO3, H2O, aerosols and T from upper tropos./lower strat. to the mesosphere Retrieval of NO2 and NO3 adversely affected by scintillation (most acute for stars setting obliquely through the atmosphere) -> new retrieval DOAS algorithm

  3. Validation of the Self-consistency of GOMOS NO3,NO2, and O3 Data Using Chemical Data Assimilation No validation measurements for GOMOS NO3 data However, simultaneous measurements of 03 and NO2 strongly coupled chemically to NO3 -> self-consistency test NO2 O3 Night-time chemistry: NO2 + O3 -> NO3 + O2 NO3 + NO2 + M -> N2O5 + M N205 + M -> NO3 + NO2 + M NO3 N2O5 Analyzed NO3=f{O3, NO2, k(T),density} -> GOMOSNO3 GOMOSECMWF

  4. APPROACH 1/ GOMOS measurements : O3 , NO2 NO3 2/ Variational assimilation in a photochemical model 4/ Comparison 3/ Analysis : O3 , NO2 , NO3 GOMOS measurements: Star Beta Carinae (S029) °January 03: vertical star setting (little scintillation) °December 02: oblique star setting (strong scintillation) -> Test DOAS retrieval

  5. Example of case study: On 31th, January 2003 at 7h40 UT At a position of 16.23° latitude and 214.6° longitude. Time evolution of the analyzed O3 (a), analyzed NO2 (b), analyzed NO3 (b) along the trajectory.

  6. GOMOS NO3 measurements • as a function of analyzed NO3 • For all the cases (= 465) • (b) For cases when NO2 Error < 30% • (= 296) • NO3 error measurements are indicated • with vertical lines. • December (oblique star setting)  • January (vertical star setting) 

  7. GOMOS NO3 measurements • as a function of analyzed NO3 • (averaged over isentropic levels) • [735, 900, 990, 1100, 1210, 1350, 1510, • 1670, 1830, 1960 K] • For all the cases (= 465) • (b) For cases when Error of NO2 < 30% • (= 296)

  8. CONCLUSIONS Analyzed NO3=f{O3, NO2, k(T),density} -> GOMOSNO3 GOMOSECMWF ° Validation of GOMOS NO3, NO2, and O3 data: chemically consistent ° Validation of the model chemistry ° Validation of the new DOAS retrieval system (no differences between vertical and oblique star setting occultations)

  9. Example of a case study NO2 O3 NO3

  10. NO3 Slope = 0.884 NO3 GOMOS data NO3 Analysis 330 points, many superposed

  11. O3 GOMOS data O3 O3 Analysis NO2 GOMOS data NO2 NO2 Analysis

  12. NO3 GOMOS data AVERAGING OVER THETA LEVELS NO3 Analysis • no large bias in GOMOS NO3 data • GOMOS O3, NO2, NO3 data self consistent chemically. • night-time NO2 and NO3 chemistry is well understood

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