Carl Berkowitz
Pacific Northwest National Laboratory
P.O. Box 999
Richlandd, WA 99352
509-372-6183
fax 509-372-7178
carl.berkowitz@pnl.gov

R. A. Zaveri
Pacific Northwest National Laboratory

C. W. Spicer
Battelle Columbus Laboratory

Recent laboratory and modeling studies suggest that heterogeneous reactions of NO_x and O₃ on tropospheric aerosols may significantly affect oxidant chemistry at night. However, there are limited or no field observations to clearly establish their significance in urban atmospheres. Large uncertainties in our knowledge of heterogeneous chemistry at night directly affect the model performance both at night and the following day. The objective of this project is to improve our understanding of the heterogeneous reactions occurring in polluted atmospheres at night, and by doing so, to reduce the associated uncertainty in atmospheric chemistry models.

The Nighttime Aerosol/Oxidant Plume Experiment (NAOPEX) will use tetroons and aircraft to make a series of Lagrangian measurements of aerosols and trace gases within a polluted nighttime residual layer that is decoupled from the surface. This sampling strategy will minimize the effects of fresh emissions, mixing and dry deposition, with the resulting observations directly amenable to analysis using a detailed gas/aerosol Lagrangian model. A second data set from the Texas 2000 Air Quality Study will provide continuous observations from the top of a 1000-foot skyscraper. Under clear skies and during light winds, these observations will also be chemically decoupled from the surface, and therefore amenable to similar analysis. The knowledge gained from these studies will be incorporated into a 3-dimensional chemical transport model to assess the importance of heterogeneous chemistry relative to other sources and sinks for ozone and its precursors.

Some further information, on the Texas 2000 Air Quality Study (PDF) and NAOPEX (PDF) plans, can be found in the sets of viewgraphs from presentations at the Atmospheric Sciences Program Annual Meeting held in February 2001. An update to NAOPEX plans was provided at the Atmospheric Sciences Program Annual Meeting held in March 2002.