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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO. D16, 4496, doi:10.1029/2003JD003559, 2003

Comparisons of in situ and long path measurements of NO₂ in urban plumes

J. A. Thornton

Department of Chemistry, University of California, Berkeley, California, USA

P. J. Wooldridge

Department of Chemistry, University of California, Berkeley, California, USA

R. C. Cohen

Department of Chemistry, University of California, Berkeley, California, USA
Department of Earth and Planetary Science, University of California, Berkeley, California, USA
Energy and Environment Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA

E. J. Williams

Aeronomy Laboratory, National Oceanic and Atmospheric Administration, Boulder, Colorado, USA
Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA

D. Hereid

Aeronomy Laboratory, National Oceanic and Atmospheric Administration, Boulder, Colorado, USA
Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA

F. C. Fehsenfeld

Aeronomy Laboratory, National Oceanic and Atmospheric Administration, Boulder, Colorado, USA
Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA

J. Stutz

Department of Atmospheric Sciences, University of California, Los Angeles, California, USA

B. Alicke

Department of Atmospheric Sciences, University of California, Los Angeles, California, USA

Abstract

Measurements of NO₂ were taken at Cornelia Fort Airpark in Nashville, TN, during the 1999 Southern Oxidant Study using three different techniques: photolysis to NO followed by chemiluminescence (PCL), laser-induced fluorescence (LIF), and differential optical absorption spectroscopy (DOAS). This was an informal comparison of these techniques conducted during the 1999 Southern Oxidant Study. The PCL and LIF instruments were connected to a common manifold that sampled at the top of a 10-m-walkup tower. The DOAS instrument sampled over a 1.37-km-long light path with end points at 2 and 35 m above ground. The range of NO₂ mixing ratios measured was 0.75 ppbv to over 60 ppbv and the median value was nearly 3 ppbv. While preliminary data analysis showed overall agreement between the LIF and PCL instruments to within 1% (least squares slope = 0.99; r ² = 0.98), subsequent analysis revealed a discontinuous shift of about 12% in the PCL data, which was confirmed by comparison to the DOAS data. A leak in the PCL inlet system was the likely cause. After adjustment of the affected PCL data, a comparison of all the coincident measurements showed high correlation (r ² > 0.99) and overall agreement to within 5%. Analysis of the ratios of PCL NO₂ to LIF NO₂ showed that greater than 90% of individual data points agree to within the total combined instrumental uncertainties. However, the comparison over short time periods is more precise than the average over the campaign. We attribute this to the need for improved PCL instrument data reduction procedures. The two in situ instruments were also operated side by side a year later in Houston, TX, with similar results.

Received 3 March 2003; accepted 19 June 2003; published 20 August 2003.

Index Terms: 0345 Atmospheric Composition and Structure: Pollution—urban and regional (0305); 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry; 0368 Atmospheric Composition and Structure: Troposphere—constituent transport and chemistry; 0394 Atmospheric Composition and Structure: Instruments and techniques.

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Citation: Thornton, J. A., P. J. Wooldridge, R. C. Cohen, E. J. Williams, D. Hereid, F. C. Fehsenfeld, J. Stutz, and B. Alicke (2003), Comparisons of in situ and long path measurements of NO₂ in urban plumes, J. Geophys. Res., 108(D16), 4496, doi:10.1029/2003JD003559.

Copyright 2003 by the American Geophysical Union.