EOL Seminar by Alan Fried (EOL/APOL)
Formaldehyde (CH 2O) is a ubiquitous component of both the remote atmosphere and polluted urban atmospheres. This important gas-phase intermediate is a primary emission product from hydrocarbon combustion sources as well as from oxidation of natural hydrocarbons emitted by plants and trees. As many hydrocarbon oxidation reactions proceed through CH 2O as an intermediate, CH 2O becomes important in testing present hydrocarbon oxidation mechanisms. In addition, CH 2O through its decomposition can be a major source of hydrogen radicals, species that affect ozone levels and the oxidizing capacity of the atmosphere. In the mid to upper troposphere, CH 2O formation of these radicals can be particularly dominant, as the magnitude of other hydrogen radical sources decrease with altitude.
One means of assessing our current understanding of these processes is through measurement-model comparisons. In the past, such comparisons have exhibited both large positive and negative deviations. In addition to the possibility of measurement errors, such discrepancies suggest gaps in our understanding of CH 2O production and destruction pathways, and hence in tropospheric oxidation processes. The present talk will discuss a long term effort at NCAR employing tunable diode laser absorption spectroscopy to acquire accurate and sensitive measurements of CH 2O on airborne platforms to address these issues. Measurement-model comparisons will be presented for three recent airborne campaigns and inferences regarding atmospheric processes and emission factors will be discussed.
Seminar is from 3:30 to 4:30 pm in FL2 Room 1022
on Tuesday, March 15, 2005.
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