HR: 08:00h
AN: A31E-01 INVITED     [Abstracts]
TI: Some Observations About the Daytime Photochemistry Measured During INTEX-A
AU: * Brune, W
EM: brune@ems.psu.edu
AF: Pennsylvania State University, 503 Walker Building, University Park, PA 16802 United States
AU: Ren, X
A31E-01 AF: Pennsylvania State University, 503 Walker Building, University Park, PA 16802 United States
AU: Lesher, R
A31E-01 AF: Pennsylvania State University, 503 Walker Building, University Park, PA 16802 United States
AU: Mao, J
A31E-01 AF: Pennsylvania State University, 503 Walker Building, University Park, PA 16802 United States
AU: Long, R
A31E-01 AF: Pennsylvania State University, 503 Walker Building, University Park, PA 16802 United States
AU: Crawford, J
A31E-01 AF: NASA Langley Research Center, Mail Stop 483, Hampton, VA 23681-2199 United States
AU: Chen, G
A31E-01 AF: NASA Langley Research Center, Mail Stop 483, Hampton, VA 23681-2199 United States
AU: Olson, J
A31E-01 AF: NASA Langley Research Center, Mail Stop 483, Hampton, VA 23681-2199 United States
AB: Oxidation chemistry cleanses the atmosphere of chemical emissions from Earth's surface, establishes the global ozone balance, and influences climate change. It is dominated by the hydroxyl radical, OH, but involves the hydroperoxyl radical, HO₂, together called HO_x. Measurements of OH and HO₂ were made with our Airborne Tropospheric Hydrogen Oxides Sensor (ATHOS) as part of a much larger measurement suit from the NASA DC-8 aircraft during INTEX-A in summer 2004. This mission, which was conducted mainly over North America and the western Atlantic Ocean, was an excellent test of oxidation chemistry in pollution plumes throughout the troposphere. For most of the troposphere, observed OH and HO₂ were less than expected from model calculations. On average OH was over-predicted by a factor of 1.7 and HO₂ by a factor of 1.3. This observed-to-modeled comparison is similar to that for TRACE-P, another mid-latitude study, but is different from that for PEM-TB, a tropical study, for which observed and modeled HO₂ generally agreed to within a factor of 1.3. However, above 8 km during INTEX-A, the observed-to-modeled HO₂ ratio increased from about 1 at 8 km to about 3 at 11 km, a feature not seen in the previous field studies. Interesting insight into the cause of these discrepancies between observations and models comes from examining HO_x behavior in different air masses.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0365 Troposphere: composition and chemistry
DE: 0368 Troposphere: constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005