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MLS observations during INTEX-B: Validation and context

Validation and context of MLS upper tropospheric products during INTEX-B. Includes comparisons with DC-8 ozone data and in situ CO measurements.

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MLS observations during INTEX-B: Validation and context

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  1. MLS observations during INTEX-B:Validation and context Nathaniel Livesey and the MLS team With thanks to: DACOM, DIAL, FASTOZ, and SAGA teams

  2. MLS upper tropospheric products • The MLS upper tropospheric products are significantly improved in v2.2 • CO, O3 (and HNO3) far less sensitive to contamination from cloud signatures • The useful range of HNO3 extends lower into the upper troposphere • The ~500 pptv precision on individual points necessitates averaging • Factor of ~2 high bias in MLS 215 hPa CO compared to expectations remains MLS and INTEX-B

  3. March 2005 weekly average at 215 hPa • Version 2.2 data produced for ~90 days to date • Only a few days during INTEX period have been processed to v2.2 so far • Maps above are average for 10–17 March 2005 at 215 hPa MLS and INTEX-B

  4. Comparing MLS and DC-8 ozone (25 April) • Top panel is raw DIAL data for 25 April flight leg along MLS track • 2nd panel is least-squares fit of DIAL to MLS horizontal / pressure grid • This involves some extrapolation of DIAL at 146 and especially 100 hPa • 3rd panel is coincident MLS v2.2 O3 data • Note, MLS v2.2 O3 data not suitable for scientific use at and below 316 hPa • Thus there is limited vertical overlap • Precision on individual MLS v2.2 O3 data points is ~10–20 ppbv MLS and INTEX-B

  5.  = 146 hPa  = 215 hPa = 316 hPa (not recommended) Comparing MLS and DC-8 ozone (cont.) • Plot compares MLS v2.2 O3 (y-axis) and fitted DIAL / FASTOZ (x-axis) for all the INTEX-B flights • Open symbols indicate where DC-8 value is based on extrapolation • Error bars show MLS single-profile precision • Correlation coefficient 0.94 • Open points and 316 hPa MLS data excluded in calculation of correlation coefficient MLS and INTEX-B

  6.  = 100 hPa  = 146 hPa  = 215 hPa Comparing MLS and in situ carbon monoxide • Comparing MLS upper trop. data to in situ observations is complicated by: • Noise on individual MLS measurements • Relating high resolution in situ observations to ‘box average’ measurements from MLS • ~200 x 7 x 3 km (L x W x H) • Horizontal ‘error bar’ used here is related to variability seen by aircraft • Plots shows MLS vs. ARGUS CO measured during Costa-Rica AVE • Apart from 215 hPa (squares) there is reasonable agreement MLS and INTEX-B

  7.  = 215 hPa Comparing MLS and DC-8 DACOM CO • Most MLS / DC-8 coincidences are at 215 hPa • CO data here are known to be biased factor of ~2 high • DACOM (from both INTEX-B and Polar AVE) confirms this • The noise on individual MLS data points precludes more quantitative conclusions • The normalized 2 test for the linear fit is 0.4 MLS and INTEX-B

  8.  = 215 hPa Comparing MLS and DC-8 SAGA HNO3 • HNO3 in the upper troposphere is a new MLS product in v2.2 • Precision on individual MLS HNO3 measurements in the upper troposphere is ~700 pptv • Agreement is fairly encouraging given the MLS precision • Here, the normalized 2 for the fit is 0.2 • It’s only 1.07 (significant at 30%) for the one-to-one line MLS and INTEX-B

  9. 215 hPa 23–29 April 2006 MLS average (v1.5) MLS and INTEX-B

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