Gas-Phase Chemical Characteristics of Transported Asian Emissions Observed During ITCT2k2 Over the Eastern North Pacific Ocean
Abstract
The gas-phase chemical characteristics of emission plumes transported from Asia across the Pacific Ocean observed during the Intercontinental Transport and Chemical Transformation experiment in 2002 (ITCT2k2) are described. The NOAA WP-3 conducted 13 research flights over the eastern Pacific Ocean and the western continental US at altitudes up to 8 km. Plume data were separated from the background air using 1 s measurements of carbon monoxide (CO), NOy and other gas-phase species along with back trajectory analysis. Based on these criteria, Asian transport plumes with CO mixing ratios greater than 150 ppbv were observed on six flights. Correlations between 1 s observations of CO and ozone (O3) and NOy are used to characterize the plumes. The O3/CO ratio varied among the different plumes. The NOy/CO ratios were similar in each plume and significantly lower than those derived from estimated Asian emission ratios. Observations of nitric oxide (NO), nitrogen dioxide (NO2), nitric acid (HNO3), peroxyacetyl nitrate (PAN), peroxypropionyl nitrate (PPN) and alkyl nitrates are used with the NOy measurement to further distinguish the transport plumes by their NOy partitioning. The reactive nitrogen observations along with the back trajectory analysis suggest that the NOy partitioning was largely controlled by the meteorological conditions during transport. NOy was primarily in the form of PAN in plumes that were transported in cold high latitude and high altitude regions, whereas in plumes transported in warmer lower latitude and altitude regions NOy was mainly HNO3. Additional gas phase species enhanced in these plumes include sulfuric acid, methanol, acetone, propane, and ethane. Identifying the gas phase chemical characteristics of these plumes is crucial in understanding the influence of the transport of Asian emissions on air quality in the Western U.S and on global climate change through perturbations to the tropospheric ozone budget.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2003
- Bibcode:
- 2003AGUFM.A21B..05N
- Keywords:
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- 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0365 Troposphere: composition and chemistry;
- 0368 Troposphere: constituent transport and chemistry