HR: 09:15h
AN: A41C-05    [Abstracts]
TI: Measurements of Nitric Acid and Fine Aerosol Sulfate Made Aboard the NASA DC-8 During INTEX-A
AU: * Scheuer, E
EM: eric.scheuer@unh.edu
AF: Institute for the Study of Earth, Oceans, and Space, Morse Hall, University of New Hampshire, Durham, NH 03824 United States
AU: Dibb, J
EM: jack.dibb@unh.edu
AF: Institute for the Study of Earth, Oceans, and Space, Morse Hall, University of New Hampshire, Durham, NH 03824 United States
AB: We present measurements of HNO$_{3}$ and fine aerosol SO$_{4}$$^{=}$ made at 1.75 minute resolution from the NASA DC-8 during INTEX-A in summer 2004. INTEX-A addressed multiple objectives, including: satellite validation, testing chemical transport models, documenting the distribution of pollutants over North America (to better constrain emissions inventories), and sampling fresh North American outflow over the western North Atlantic as part of the multinational ICARTT experiment. Our preliminary analysis contributes to the last two objectives. In all regions over North America HNO$_{3}$ and aerosol SO$_{4}$$^{=}$ mixing ratios were highest in the boundary layer. Sulfate generally decreased less rapidly with altitude than HNO$_{3}$ did, reflecting production of HNO$_{3}$ in convective outflow and occasional stratospheric influence on the mid and upper troposphere. Regionally, boundary layer (below 1 kilometer) distributions reflected known large source regions with SO$_{4}$$^{=}$ mixing ratios highest in the south eastern U.S., while maximum HNO$_{3}$ (about 5 ppbv) was observed over CA and in the south east during regional pollution events. Average boundary layer HNO$_{3}$ mixing ratios in these regions were about 1 ppbv, twice the average of the north east boundary layer. Mixing ratios of HNO$_{3}$ and SO$_{4}$$^{=}$ in the outflow over the North Atlantic were lower than we observed immediately downwind of Asia during TRACE-P. This presumably reflects precipitation scavenging of these soluble compounds, since all major outflow events sampled during INTEX-A were associated with frontal systems and extensive clouds.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0343 Planetary atmospheres (5405, 5407, 5409, 5704, 5705, 5707)
DE: 0345 Pollution--urban and regional (0305)
DE: 0365 Troposphere--composition and chemistry
DE: 0368 Troposphere--constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting