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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO. D4, 8366, doi:10.1029/2002JD002295, 2003

Measurements of OH, H2SO4, and MSA during Tropospheric Ozone Production About the Spring Equinox (TOPSE)

R. L. Mauldin III

Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado, USA


C. A. Cantrell

Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado, USA


M. A. Zondlo

Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado, USA


E. Kosciuch

Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado, USA


B. A. Ridley

Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado, USA


R. Weber

School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA


F. E. Eisele

Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado, USA


Abstract

Data from OH, H2SO4, and MSA measurements performed during Tropospheric Ozone Production About the Spring Equinox (TOPSE) are presented. Model simulations of OH results made at solar zenith angles of 60° or less showed a tendency of the model to overestimate OH concentrations. This overestimation was a factor of 1.7 at the lower latitudes (<57°N) of the study. At higher latitudes (>57°N) the model tended toward agreement and ultimately an underestimation of OH concentrations by a factor of 0.7. Comparisons of measurements and model showed the model underestimates OH concentrations at solar zenith angles greater than 70°. The results of the present study are discussed in the context of previous studies. Possible model discrepancies are discussed. Measurements of H2SO4 showed the highest concentrations at the lowest altitudes (<2000 m) and the lowest latitudes of the study. Larger H2SO4 concentrations observed at higher latitudes were accompanied at times by particle nucleation as indicated by the presence of UCN (ultra-fine condensation nuclei) with diameters of 3–4 nm. Concentrations of MSA were generally low with typical values of <2 × 105 molecule cm−3. High concentrations (>107 molecule cm−3) were found in layers and were accompanied by other compounds such as NOx and NOy indicating MSA may also have an industrial source.

Published 28 February 2003.

Index Terms: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0317 Atmospheric Composition and Structure: Chemical kinetic and photochemical properties; 0360 Atmospheric Composition and Structure: Transmission and scattering of radiation.

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Citation: Mauldin, R. L., III, C. A. Cantrell, M. A. Zondlo, E. Kosciuch, B. A. Ridley, R. Weber, and F. E. Eisele (2003), Measurements of OH, H2SO4, and MSA during Tropospheric Ozone Production About the Spring Equinox (TOPSE), J. Geophys. Res., 108(D4), 8366, doi:10.1029/2002JD002295.