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Bremen 6.12.2010

Limb tracegases : verification with scientific processors K-U- Eichmann, C. von Savigny , H. Bovensmann , A. Kokhanovsky , (presented by M. Weber). Bremen 6.12.2010. IUP & DLR limb ozone retrieval:. IUP V2.1 (L1 V6/V7):

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Bremen 6.12.2010

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  1. Limb tracegases: verification with scientific processorsK-U- Eichmann, C. von Savigny, H. Bovensmann, A. Kokhanovsky,(presented by M. Weber) Bremen 6.12.2010

  2. IUP & DLR limb ozone retrieval: IUP V2.1 (L1 V6/V7): central wavelength of the Chappuis triplet is shifted from 601 to 589 nm Tikhonov parameter linearly decreases with altitude from 9 at 72 km to 3 at 7 km instead of constant value of 6 IUP V2.2: Foward model is changed from SCIATRAN 2.2 to SCIATRAN 3.0 Spectral region: 2 nm spectral intervals centered around: 264 nm, 267.5, 273, 283, 286, 288, 290.5, and 305 (UV) as well as 525, 589, and 675 nm (Chappuis band) Surface albedo: geographical database [Matthews, 1983] IUP V2.3: Use of a latitude dependent aerosol climatology ECSTRA [Bingen, 2000] OP 5.1 (DLR operational retrieval on L1 V7 ) DOAS retrieval in Chappuis band altitude coverage: 15-40 km (IUP retrieval: 10-70 km)

  3. Differences between IUP 2.1/2.3 and OP5 • The differences between the IUP 2.1 and 2.3 are found mainly below 33 km down to the tropopause. • These are mainly due to the use of the ECSTRA aerosol climatology in IUP2.3. Another reason could be different p/T inputs, IUP uses ECWMF data.

  4. Limb Ozone Verification: OP5.01 vs. ST2.3 201001-03 200301-04 Verification of OP5 with SCIATRAN 2.3: 4 months of data in 2003 and 2010 were used. OP5 ozone is on average about 8% higher for all tangent heights. Results are similar for the years 2003 and 2010.

  5. O3: Latitude dependency (200301-04) N25-50 N50-90 -25-+25 N50-90: +10% N25-50: +6% -25/25 : +10% S25-50: +8% S50-90: +6% S50-90 S25-50

  6. 70-90 50-70 30-50 O3: Sun zenith angle dependency (200301-04) • The difference between both models is generally lower than 10% for all scenarios. • Highest differences are found in the lowest stratosphere below 20km. For higher SZAs we find differences (>10%) in the upper stratosphere.

  7. Validation results: O3 • Validation with ozone sondes (GAW-contributing ground-based networks, see D. Hubert, SCIAVALIG validation meeting 09/2010): On average the SGP 5.01 processor showed ~10% higher O3 density values than SGP 3.01. O3 profiles retrieved with SGP 5.01 are of equivalent or better quality than those retrieved with SGP 3.01. E.G. Ascension 8°S(+10%), Uccle 50°N(~0%), Belgrano 78°S (+5%) • Comparison with lidar, sonde and microwave 2002-2004 (VALID, see talk J.A.E. van Gijsel, SCIAVALIG validation meeting 09/2010): positive bias in the tropics (~12%), midlatitudes (~7%), negative bias in the polar region(~-8%).

  8. Summary O3 OP5.1 vs IUP 2.3 • The IUP ozone retrieval in V2.3 was finetuned to reduce the high bias found in the tropical regions. This leads to less ozone found in the midlatitudes and polar regions. • Comparisons with the OP5.1 shows on average 8% lower values of the IUP2.3. This differs slightly for different latitude and sun zenith angle regions between 6 and 10%. • Highest differences above 10% were found in the upper stratosphere at high SZA and near the troposphere. • Comparing these results with the validation datasets: • Tropics: OP5.1 ~10% higher -> IUP2.3 more accurate as expected • Midlatitudes: “inconsistent” validation data: OP5.1 ~7% higher -> IUP2.3 possibly nearer to validation results • Polars: “inconsistent” validation data: OP5.1 +/-6% -> low bias of IUP2.3 can be expexted

  9. Limb NO2: OP3/4 (from PM4) and OP5.1 OP5.01: comparison with IUP V3.1 (200301-04) • The OP5.1 NO2 gives basically the same results as OP4, which is as expected.

  10. NO2: Summary • Differences between two retrievals of the OP5.1 and the IUP 3.1 are generally below 10% for the height range of 21 and 38 km. • Highest differences above 20% were found for high SZAs in the upper stratosphere and lowest stratosphere.

  11. Limb BrO: all data 2003 (01—04) • On average the differences between the BrO OP5.1 and IUP3.2 are below 10% between 20 and 30 km, but the scatter is 50% and more. These results are as expected.

  12. BrO: time dependent differences 200304 201004 • Comparing data from 2003 and 2010: • The differences between both models are slightly increasing. • The scatter drastically increases.

  13. BrO: Summary of results • On average both models OP5.1 and IUP3.2 give similar results. • The differences and the scatter found are higher in 2010 than in 2003. • The differences also depend on altitude, latitude, and SZA: • Polar NH: OP5.1 -15% (01/03) -> -5% (04/03), similar in 2010 • Polar SH: OP5.1 +50% (01/03) -> +5% (04/03) • Tropics: OP5.1 -10% (30km) / +40%(20km), no change over time

  14. Limb cloud top height - Verification with MIPAS • Cloud top height between 9.0-25.0 km • Max. Difference in distance=300 km and seconds=990 sec. • SCIAMACHY - MIPAS [km]: 200902 • 3382 Diff= -0.9 (1.9) • 30 N >50 Mean=12.0 Diff=1.4 (2.0) • 542 N 15/50 Mean=12.4 Diff:-0.7 (1.7) • 2047 T Mean=14.9 Diff=-1.30 (1.7) • 762 S -15/-50 Mean=14.1 Diff=-0.0 (2.0) • SCIAMACHY - MIPAS [km]: 200906 • 3722 Diff=-1.2 (1.5) • 57 N >50 Mean=12.3 Diff=0.4 (2.0) • 1147 N 15/50 Mean=13.6 Diff=-1.0 (1.6) • 2051 T Mean=14.4 Diff=-1.4 (1.4) • 459 S -15/-50 Mean=12.6 Diff=-0.7 (1.3) • 8 S <-50 Mean=11.8 Diff=-0.8 (0.8) • The comparison with MIPAS done for CTH above 9 km gives good results. The mean height is between 12 and 15km. The mean difference is on the order of -1 km. • Below about 9 km MIPAS has very low sensitivity.

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