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List of Abstracts 220using gas chromatographs with a HgO reduction detector. The observed H2 concentration showed clearvertical gradient and height-dependent seasonal cycle. The H2 concentration showed small seasonalvariation in upper altitude and mean concentration decreased with decreasing height. At lower altitudes,peak-to-peak amplitude of seasonal cycles were large and maximum and minimum concentrations appearedin July/August and November, respectively. We compared observational results from our observation andfrom NOAA/ESRL observation network with those from model simulation using a global chemical transportmodel, CHASER. The model was coupled with land process model (MATSIRO) and H2 uptake by enzymesin soil, which determined by a function of both soil moisture and soil temperature, was calculated. Themodel reproduced spatial distributions and seasonal variations of surface stations and airborne observationswell. Simulated H2 concentrations show large seasonal amplitudes on the continent surface of northern highlatitudes, with the maximum and minimum in boreal spring and autumn, respectively. The global burden ofH2 in the troposphere is 163 Tg and its overall lifetime in the troposphere is 1.86 years. Soil uptake is 63.9Tg, with the contribution of 73% of total H2 sink. The results show that not only soil moisture but also soiltemperature plays an important role in the seasonal variation of soil uptake and H2 concentration at northernhigh latitudes.P-Observations 2.104 ID:4121 10:30Constraining the budgets of hydrogen and carbon monoxide through in-situ measurements andmodelling.Aoife Grant, Dudley Shallcross, Alexander Archibald, Simon O'DohertyUniversity of BristolContact: aoife.grant@bristol.ac.ukHydrogen (H2) is the second most abundant atmospheric trace gas, it acts as an indirect greenhouse gas byremoving the hydroxyl (OH) radical and increasing the lifetimes of other greenhouse gases. Recent increasedattention in H2 is due to its possible introduction as a clean energy fuel alternative. However, its currentatmospheric budget is poorly constrained, particularly its source from primary and secondary emissions.Carbon monoxide (CO) is central in controlling the abundance and distribution of the OH radical. Thesecondary production of CO from the oxidation of volatile organic compounds (VOCs) remains the mostpoorly constrained sector of its global budget. This study investigates the primary and secondary productionof H2 and CO using a combination of in-situ measurements and modelling. High-frequency measurementsof H2 and CO at an urban location provide detailed information on urban time-series, diurnal cycles as wellas sources and sinks of both H2 and CO. These urban measurements help to improve assessments of primaryanthropogenic emissions of H2, largely from transport. Modelling of the secondary production of H2 andCO carried out using a box model simulating tropospheric conditions tracked the oxidation of a range ofVOCs to produce individual conversion factors for VOCs oxidation to H2 and CO. Global budget estimatesof the secondary production of H2 and CO were made based on these conversion factors. To maintain theoxidation balance within global chemical transport models which do not include a detailed suite of nonmethaneVOCs (NMVOC) it may be necessary to include the H2 and CO source from NMVOC oxidation.Transformation 1.1 ID:4223 INVITED 14:00Enhancing the prognostic capability of global aerosol models: Atmospheric aqueous chemistry and itsrole in secondary organic aerosol (SOA) formationBarbara Turpin 1 , Yong Bin Lim 1 , Yi Tan 1 , Mark Perri 2 , Katye Altieri 3 , Sybil Seitzinger 41 Rutgers University2 Sonoma State UniversityiCACGP-IGAC 2010 14 July, 2010