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Junhua Liu and Jennifer Logan Harvard University Aura Science Team meeting Sep 14-17, 2009

The impacts of dynamics on tropical tropospheric CO inferred from Aura satellite data and GEOS-Chem model. Junhua Liu and Jennifer Logan Harvard University Aura Science Team meeting Sep 14-17, 2009. Acknowledgements: Thanks to Nathaniel Livesey and Jonathan Jiang of JPL. TES, MLS teams.

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Junhua Liu and Jennifer Logan Harvard University Aura Science Team meeting Sep 14-17, 2009

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  1. The impacts of dynamics on tropical tropospheric CO inferred from Aura satellite data and GEOS-Chem model • Junhua Liu and Jennifer Logan • Harvard University • Aura Science Team meeting • Sep 14-17, 2009 Acknowledgements: Thanks to Nathaniel Livesey and Jonathan Jiang of JPL. TES, MLS teams.

  2. Outline • Introduction • Satellite data (TES/MLS) and the GEOS-Chem Model • Driven by two versions of meteorological fields: GEOS 4 & 5 • Evaluation of model performance • TES CO in the LT • MLS CO in the UT • Diagnostics of model transport • Vertical convective and advective mass fluxes • Horizontal winds • Comparison between GEOS 4 and GEOS 5 meteorological fields • MLS data as a test of vertical transport at the start of the wet season in South America • Summary

  3. CO measurements from Aura (TES and MLS) • TES (Tropospheric Emission Spectrometer) • TES V003 • MLS (Microwave Limb Sounder) • MLS V2.2 level 2 data

  4. TES, MLS - GEOS-Chem comparisons • GEOS-Chem Simulations • v08-02-01, 4o × 5o horizontal resolution • Driven by GEOS-4 or GEOS-5 meteorological fields - diff. convection parameterization • 2-year simulation from Jan. 2005 to Dec. 2006 • Uniform prior for TES • Model profiles are sampled along the TES/MLS orbit track at the observation time, and then vertically smoothed with the TES or MLS averaging kernels. • Focus on 2005 in this talk, but show some results for 2006

  5. Temporal and spatial patterns of GFED2 emissions 2005 2006 GFED2 Aug Latitude Sep Jul Aug Longitude • South America: • Biomass burning starts one month later. • Drier in 2005 (La Nina), CO emissions in 2005 are twice the amount in 2006. • South Africa: • Relatively stable seasonality with smaller interannual variation Courtesy of Inna Megretskaia

  6. CO comparison with TES in the LT in GEOS4 TES GEOS-Chem w/ TESak DIFF (GEOS – TES) 2005 GEOS-4 681hPa Aug Sep Oct Nov Dec • South America: TES and model CO highest in Sep. and Oct., but largest underestimate also in Sep. and Oct. • Underestimate of CO in South Africa - lower fire emissions • Too much CO export in easterlies in LT to the convection region - N. of equator

  7. CO comparison with MLS in UT: 215 hPa MLS 2005 GEOS-4 MLS 2006 GEOS-4 Aug Sep Oct Nov Dec Factor of two bias in MLS at 215 hPa [Livesey et al., 2007]. • South America: CO maximum lags ~1 month in the model compared to MLS data in 2005 and 2006 • East Pacific: Model CO has a large overestimate in Aug. 2005 • Indonesia: overestimate in Oct. and Nov. 2006

  8. GEOS-4: Vertical mass flux and CO, Aug.-Dec. 2005 688 hPa 430 hPa 226 hPa Aug: Amazon: barely any convection, horizontal transport dominates in LT. Large amount of CO exported to the East equatorial Pacific. Oct & Nov ITCZ shifts south, strongest convection contributing to maximum CO in Nov. in the UT. Aug Sep Oct Nov Dec Contours: upward air mass flux (convection + advection, Pa/s: [0.05, 0.12, 0.25] for 688 hPa & 430 hPa, [0.03, 0.06, 0.12] for level 226 hPa) Color: CO (ppbv). • Fires mainly in Aug/Sep, but little vertical transport • In South America, CO max. in Sep at 688hPa, in Oct. at 430hPa, in Nov. at 215hPa

  9. Vertical profiles of upward mass flux S America (18S-2S, 70W-40W) Conv. + adv. Convection • South America: • Largest increase in vertical upward transport in Oct. (green) • Upward mass flux reaches a higher altitude in Nov., contributing to CO max. in model • most outflow of deep convection is below 200 hPa • Above 200 hPa, slow vertical ascent air

  10. Convection in GEOS-4 compared to other models (Folkins et al. 2006) Fueglistaler et al. 2009 • Compared to other models, GEOS-4 convectiondecays at a lower altitude – the top height of convective outflow is lower. • 215 hPa - slow vertical ascent air above region of convective outflow in the TTL causes the 1-month lag of CO maximum in UT in the model.

  11. CO in the UT in GEOS-4 and GEOS-5 2005: 215 hPa MLS GEOS-4 GEOS-5 Aug Sep Oct Nov Dec • South America: CO at 215 hPa is lower in GEOS-5 than in GEOS-4 • GEOS-5 maximum occurs ~1-2 months late, later than GEOS-4 • East Pacific: GEOS-5 has a better CO simulation

  12. Seasonality and interannual variation of CO - S. America From LT to UT, the lag in GEOS-5 is always greater than that in GEOS-4 MLS TES UT GEOS4_MLSak GEOS4_TESak GEOS4 GEOS4 GEOS5_TESak GEOS5_MLSak GEOS 5 GEOS 5 MLS/2 GEOS 4: 1 month lag GEOS 5: 1-3 month lag GEOS 4: No lag GEOS 5: 1 month lag (2006) Optical bench warm-up to improve CO signal LT

  13. Vertical transport in GEOS-4 & GEOS-5 (South America) GEOS-4 226 hPa GEOS-5 Top: Vertical profile of upward transport of air in GEOS4 and GEOS5 in 2005 Right: Spatial map of upward transport with CO mixing ratio in 2005 in UT. Similar pattern in 2006. The lag of CO maximum in GEOS-5 is greater in part because the convection decays at a lower altitude, and in part because the convection moves southward later than in GEOS-4

  14. Relationship between convection and CO South America (18-2S, 70W-40W) Sep,2005 GEOS4 GEOS5 COGEOS5/COGEOS4 GEOS4 GEOS5 convectionGEOS5/convectionGEOS4 • CO source region (S. America): convection is the dominant mechanism for CO vertical redistribution. In GEOS-4, stronger convection transports more CO into UT, causing higher CO above ~650 hPa.

  15. Seasonality and interannual variation of CO – East Pacific MLS MLS GEOS4_MLSak GEOS4_MLSak GEOS4 GEOS4 GEOS5_MLSak GEOS5_MLSak GEOS 5 GEOS 5 MLS/2 Vertical mass flux (Pa/s) The vertical profiles of upward transport: GEOS-4: Gradually decrease with height GEOS-5: Sharp decrease around 600 hPa

  16. Conclusion • Over S. America, deep convection in GEOS-4 decays at too low altitude, causing the lag of the CO maximum compared to MLS observations in the UT. • The lag in GEOS-5 is greater in part because the convection decays at an even lower altitude, and in part because the convection moves southward later than in GEOS-4. • The overestimate of CO in east equatorial Pacific north of the equator results from stronger local convection, and stronger easterly winds in GEOS-4 in the lower altitude. • The overestimate disappears in GEOS-5, caused by a sharp decrease of convection near 600 hPa. Is this mechanism realistic? Comparison of GEOS met. fields with NCEP or ECMWF data would be useful.

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