Interpreting MLS Observations of the Variabilities of Tropical Upper Tropospheric O 3 and CO Chenxia Cai, Qinbin Li, Nathaniel Livesey and Jonathan Jiang (with thanks to MLS Team) Jet Propulsion Laboratory California Institute of Technology Pasadena, California 3 rd GEOS-Chem Users’ Meeting

Background - Derived tropospheric ozone columns from previous satellite observations (e.g. TOMS, GOME) have been examined to understand the distribution of (tropical) tropospheric O 3. The drawback of column (tropospheric ozone) data is its lack of vertical information. - Aura Microwave Limb Sounder (MLS) provides global coverage of observations of concentrations for O 3 and CO in the upper troposphere. Objectives - To characterize the seasonal variations of O 3 and CO in the tropical upper troposphere through interpreting MLS observations and SHADOZ data using the GEOS-Chem model. - To quantify the relative source contributions to tropical upper tropospheric O 3 and CO. - To investigate inter-hemispheric transport in the tropical upper troposphere.

Data & Model Study period: 2005 Datasets - MLS 147 hPa O 3 and CO. Concentrations were averaged monthly onto 4 o latitude by 8 o longitude grid. - MOPITT 150 hPa CO. Concentrations were averaged monthly onto 4 o latitude by 8 o longitude grid. - SHADOZ ozonesonde data. - GEOS-Chem full chemistry simulation (v7.4.10)

Compare MLS with LIDAR O3 (INTEX-B) and in situ CO (WB-57 ARGUS) Product Low alt. limit Vertical resolution Single profile precision Comments Ozone215 hPa~2.5km20 – 40 ppbv Carbon monoxide215 hPa~4 km15 – 40 ppbv~2x high bias at 215 hPa = 147 hPa = 215 hPa  = 316 hPa (not recommended)  = 100 hPa = 147 hPa = 215 hPa Open symbols indicate where LIDAR value is based on extrapolation

GEOS-Chem Simulation Standard full-chemistry simulations [v ] - NASA GMAO GEOS-4 met. fields (2x2.5, 30 levels). - EDGAR fossil fuel emissions; GEIA biogenic emissions. - Monthly biomass burning emissions [Duncan et al., 2003]. (GFED emissions will also be used in sensitivity simulations to be conducted) - 6 Tg N/yr global annual lightning NO x emissions; lightning flash rates rescaled regionally to LIS/OTD observations. Sensitivity simulations [v ] - To be conducted.

Spatial Distributions of 147 hPa CO Consistent spatial and temporal distributions among the three data sets. MLSMOPITTGEOS-Chem Jan Apr Jul Oct

Spatial Distributions of 147 hPa O 3 MLSGEOS-CHEM Jan Apr Jul Oct

Data from

Natal (5ºS,35ºW) Monthly vertical profiles Modeled data, emission, lightning and OLR data are all regrided to 4 o latitude by 8 o longitude grid Seasonal cycle of ozone shows good agreement among ozonesonde, MLS and GEOS-Chem. 147 hPa Tropopause

10-day Back Trajectories Air masses at 147~300 hPa during Oct. and Nov. are from South America. Red: 147hpa Blue:300hpa Red: 147hpa Blue:300hpa Oct Nov

Nairobi (1ºS,40ºE) Monthly vertical profiles Strong CO loading at 147 hPa in winter and fall are mainly outflow of convectively lifted African biomass burning emissions. Tropopause 147hPa

La Reunion (21ºS,55ºE) Monthly vertical profiles Excellent agreement for O 3 at 147 hPa among the three datasets. High O 3 concentrations in November likely have a large influence from the stratosphere. 147 hPa Tropopause

Kuala Lumpur (3ºN,102ºE) Monthly vertical profiles Enhancement of O 3 during the first half of the year correlates well with CO concentrations – strong influence from convectively lifted SEA biomass burning emissions. Tropopause 147hPa

Conclusions MLS and GEOS-Chem O 3 at 147 hPa in the tropics shows excellent consistency with SHADOZ ozonesonde data. Seasonal patterns of 147 hPa CO from MLS, MOPITT and GEOS-Chem are in good agreement. Seasonal patterns of tropical upper tropospheric O 3 and CO vary significantly at different locations due to different source contributions. (Future work) sensitivity studies with GEOS-Chem simulations to be conducted to quantify the relative contributions from various source regions/types (biomass burning, lightning, long-range transport, etc.).

Thank you!