HR: 1340h
AN: A43C-0074    [Abstracts]
TI: Case study of an ozone titration event in Narragansett at the 28th of July during the NEAQS-ITCT 2004 Campaign
AU: Sebastian, O
EM: oliver.sebastian@iup.uni-heidelberg.de
AF: University of Heidelberg, Insitute of Environmental Physics, Im Neuenheimer Feld 229, Heidelberg, 69120 Germany
AU: Filsinger, F
EM: frank.filsinger@iup.uni-heidelberg.de
AF: University of Heidelberg, Insitute of Environmental Physics, Im Neuenheimer Feld 229, Heidelberg, 69120 Germany
AU: Heikes, B
EM: bheikes@gso.uri.edu
AF: University of Rhode Island, Graduate School of Oceanography, South Ferry Road, Narragansett, RI 02882 United States
AU: Kern, C
EM: christoph.kern@iup.uni-heidelberg.de
AF: University of Heidelberg, Insitute of Environmental Physics, Im Neuenheimer Feld 229, Heidelberg, 69120 Germany
AU: Merrill, J
EM: jmerrill@gso.uri.edu
AF: University of Rhode Island, Graduate School of Oceanography, South Ferry Road, Narragansett, RI 02882 United States
AU: * Sinreich, R
EM: roman.sinreich@iup.uni-heidelberg.de
AF: University of Heidelberg, Insitute of Environmental Physics, Im Neuenheimer Feld 229, Heidelberg, 69120 Germany
AU: Wagner, T
EM: thomas.wagner@iup.uni-heidelberg.de
AF: University of Heidelberg, Insitute of Environmental Physics, Im Neuenheimer Feld 229, Heidelberg, 69120 Germany
AU: Platt, U
EM: ulrich.platt@iup.uni-heidelberg.de
AF: University of Heidelberg, Insitute of Environmental Physics, Im Neuenheimer Feld 229, Heidelberg, 69120 Germany
AB: During the New England Air Quality Study - Intercontinental Transport and Chemical Transformation (NEAQS-ITCT) 2004 Campaign we performed measurements with Multiple Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) at several sites in the northeast of the USA. Ultraviolet spectra of scattered sunlight were measured continuously at five elevation angles, including the zenith. Analysis using the DOAS technique yields slant column densitites, and with radiative transfer modelling, vertical column densities of several trace gases, including NO$_{2}$. At Narragansett, RI ozonesonde profiles were observed daily. On July 28 we observed reduced light intensity in the presence of surface fog and deep clouds, and elevated NO$_{2}$ concentrations throughout the day. The ozone profile at 1830 UTC (1430 local time) showed an absence of ozone at the surface, with values increasing to approximately 65 ppbv above 300 m. A capping inversion trapped pollutants in this layer over an area extending from central Long Island to Boston, MA. Maximum 8 hour average ozone mixing ratios from monitors in Rhode Island were remarkably low, below 11 ppbv for this day. The slant column density for NO$_{2}$ was greater than 4 \cdot 10$^{16}$ molecules per cm$^{2}$ for the lowest elevation angle (3$^{\circ}$). The light intensity at mid-day was extremely low, comparable to twilight conditions. Analysis of the spectra suggests that aerosol scattering was also high near the surface. Together, these observations suggest that ozone titration took place even in mid-afternoon during this event.
DE: 0365 Troposphere--composition and chemistry
DE: 0368 Troposphere--constituent transport and chemistry
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting