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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO. D8, 8000, doi:10.1029/2002JD002790, 2003

Trace gas and radical diurnal behavior in the marine boundary layer during INDOEX 1999

J. Burkert

Institute of Environmental Physics, University of Bremen, Bremen, Germany


M. D. Andrés-Hernández

Institute of Environmental Physics, University of Bremen, Bremen, Germany


L. Reichert

Institute of Environmental Physics, University of Bremen, Bremen, Germany


J. Meyer-Arnek

Institute of Environmental Physics, University of Bremen, Bremen, Germany


B. Doddridge

Department of Meteorology, University of Maryland, College Park, Maryland, USA


R. R. Dickerson

Department of Meteorology, University of Maryland, College Park, Maryland, USA


J. Mühle

Air Chemistry Division, Max Planck Institute for Chemistry, Mainz, Germany


A. Zahn

Air Chemistry Division, Max Planck Institute for Chemistry, Mainz, Germany


T. Carsey

Atlantic Oceanographic and Meteorological Laboratories, National Oceanic and Atmospheric Administration, Miami, Florida, USA


J. P. Burrows

Institute of Environmental Physics, University of Bremen, Bremen, Germany


Abstract

Selected trace gas mixing ratios (i.e., peroxy radicals (RO*2 = HO2 + ΣRO2), nonmethane hydrocarbons (NMHCs), O3, CO, HCHO, and NO) and photolysis rate coefficients of j(NO2) and j(O(1D)) were measured in the marine boundary layer (MBL) over the Indian Ocean. The measurements were performed during February, March, and April 1999 as a part of the Indian Ocean Experiment (INDOEX) on board the research vessel R/V Ronald H. Brown. During the campaign, air parcels having different origins and consequently variable compositions were encountered, but all air masses, including those heavily polluted with NMHCs and aerosols, were in the regime of rapid photochemical ozone destruction. The influence of aerosols on the photolysis frequencies was investigated by comparison of measurements and results from the radiative transfer model PHOTOST: the high optical depth (up to 0.6) and low single scattering albedo of the aerosol reduces the UV flux at the surface substantially downwind of India and Arabia causing, for instance, a reduction in j(O(1D)) by up to 40%. The diurnal behavior of the trace gases and parameters in the MBL has been investigated by using a time-dependent zero-dimensional chemical model. Significant differences between the diurnal behavior of RO*2 derived from the model and observed in measurements were identified. The measured HCHO concentrations differed from the model results and are best explained by some missing chemistry involving low amounts of Cl. Other possible processes describing these two effects are presented and discussed.

Published 17 April 2003.

Index Terms: 0322 Atmospheric Composition and Structure: Constituent sources and sinks; 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry; 3307 Meteorology and Atmospheric Dynamics: Boundary layer processes; 3339 Meteorology and Atmospheric Dynamics: Ocean/atmosphere interactions (0312, 4504).

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Citation: Burkert, J., M. D. Andrés-Hernández, L. Reichert, J. Meyer-Arnek, B. Doddridge, R. R. Dickerson, J. Mühle, A. Zahn, T. Carsey, and J. P. Burrows (2003), Trace gas and radical diurnal behavior in the marine boundary layer during INDOEX 1999, J. Geophys. Res., 108(D8), 8000, doi:10.1029/2002JD002790.