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Status of ACVE-3/pre-validation recommendationss 21.6.2007 SCIAVALIG, Bremen

Detailed overview of crucial and important issues addressed, updates in version 3.01, and resolved Level 0-2 issues in the processing of SMR data. Includes explanations for discrepancies, bug fixes, and ongoing investigations for further improvements.

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Status of ACVE-3/pre-validation recommendationss 21.6.2007 SCIAVALIG, Bremen

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  1. Status of ACVE-3/pre-validation recommendationss21.6.2007 SCIAVALIG, Bremen

  2. Status of ACVE-3/pre-validation recommendationsprepared byG. Lichtenberg, A. von Bargen, H. Bovensmann, SQWGT. Fehr, ESA

  3. Contents • Issues considered crucial before re-processing • Level 0-1 issues • Level 1b-2 issues • Issues important but not crucial • Other updates in 3.01 • Summary

  4. Level 0-1 issues - Crucial • Origin of differences between ASM spectra L1b/L0 (R11) • Two ASM spectra were provided: • ‘A1’ was specially prepared by J. Frerick on user request and does not contain all calibration improvements of version 6. It is not updated. • ‘A0’ is daily updated and contains all calibrations except the radiometric correction. • Erroneous results when using A0 spectra was caused by inconsistent data used in the test: The A0 spectrum was applied on Earth shine spectra that were differently calibrated. • Conclusion: Processing of SMR data is correct, using a consistent set of data leads to the expected result. • Deviation of leakage correction (R12): • Reason was faulty implementation in IPF 6.02. Bug is fixed in IPF 6.03.

  5. Level 1b-2 issues - Crucial (I) • Implemented (v.3.01)/Answered recommendations : • AAI and cloud data will be provided for all records by setting all records where no calculation is done to the value of the shortest integration time. Previously, those parameters were set to zero (R3,19). • Cloud quality flag is corrected. It was filled with wrong values. The meaning of the value will be documented (R4). • Reference height O3: Shift to higher altitudes will increase noise, details in TN (R6). • Apparent inconsistency of VMR: It is not possible to calculate the VMR using pressure p of the product, since p is only an ad hoc profile (tabulated value from climatology). (R7) • Offset NO2 SCD: This is fixed in version 3.01 except for the beginning of 2003 (R10): Based on a limited data set from early 2003 an offset was introduced in the processing. An analysis of a larger dataset showed that the offset is specific for the begin of 2003 and not present in other data, thus it will be removed for version 3.01. The deviation of early 2003 is under investigation.

  6. Level 1b-2 issues – Crucial (II) • (p,T) inter-change in measurement grid structure in Limb profile MDS fixed (R13) .

  7. Level 1b-2 issues - Crucial (III) • The following issues are under investigation: • Peaks in O3 Column differences (R1). • No systematic dependence on cloud parameters found, re-investigated on a larger data set after re-processing. • Remaining altitude shift in O3 profiles (R5). • It is expected that the new sensor – platform alignment parameters used in version 6.03 L0-1b processing will improve the situation. • Different behaviour profile difference year 2003 (R8) • will be re-investigated by SQWG after re-processing (better pointing). • Different behaviour profile difference near the Arctic (R9). • will be re-investigated by SQWG after re-processing (better pointing).

  8. Issues important, but not crucial • CTH and Impact on VCDs (R14, R15) • CTH algorithm improved, ISCCP no longer in user, re-investigated on large data set after reprocessing • CTH retrieval error of 250 m (R16): • Error estimate based on verification/validation will be put into disclaimer for version 3.0/3.01. Changes for version >3.01 to be decided by ESA. • Further validation of CTH necessary! • Reflectance Correction Factor for CTH (R 17) • No correction factor used as reflectance calibration sinve level 1 v6 is ok • Cause of the difference between OL and scientific retrieval of COT (R18). • Reason was a difference in input data for SACURA, not a difference of algorithms. • TN for a-priori profile extraction from Limb MDS available (R20, 21, 28) • Error bars on NO2 Limb profile retrievals are corrected, a scaling factor was erroneously applied (R22). • SciaL1C tool ported in addition to Solaris and Linux to HP-UX and DEC-Alpha environments. Further changes in product/tools under consideration by ESA (R26,27)

  9. Issues important, but not crucial • O3 VCDs vs. scientific retrievals (R24) • Investigated during verification w.r.t. SDOAS • re-investigated on large data set after reprocessing • NO2 SCDs vs. scientific retrievals (R25) • Investigated during verification w.r.t. SDOAS • re-investigated on large data set after reprocessing

  10. Other changes in L1b-2 3.01 • Integration of new SACURA version (2.1), will be used down to 5% cloud coverage. • User recommendation of switch to 4 Limb profiles implemented. • O3 SCD after molecular ring correction is now provided

  11. Summary • All crucial L0-1 issues are solved • Most crucial L1b-2 issues are solved. • Verification of OL v. 3.01 is nearly finished. • A document with more detailed answers to all recommendations from ACVE-3 is in preparation.

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