Regensburg 1998 – wissenschaftliches Programm

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SYA: Symposium Physik für die Umwelt

SYA 2: Sondersymposium “Physik für die Umwelt” – Wissenschaftliche Poster

SYA 2.48: Poster

Dienstag, 24. März 1998, 16:45–19:00, C

Field Measurements of Tropospheric OH Radicals by Long-Path Laser Absorption Spectroscopy — •Theo Brauers, Uwe Brandenburger, Martin Hausmann, and Hans-Peter Dorn — Institut für Atmosphärische Chemie (ICG-3), Forschungszentrum Jülich, D-52425 Jülich

The hydroxyl radical (OH) determines the photochemical degradation rate of atmospheric trace gases. So far only a few direct in-situ measurements of tropospheric OH exist, because the quantitative measurement is complicated by the extremely low OH concentration. We have conducted ground based in-situ measurements of tropospheric OH radicals by high resolution long-path laser absorption spectroscopy during the field measurement campaign POPCORN in North-Eastern Germany. The instrument used an optical multiple-reflection cell of 38.5 m base length through which the laser beam was passed up to 80 times. The broadband UV emission (FWHM 0.41 nm) of a frequency doubled picosecond dye laser together with a high resolution spectrograph allowed the simultaneous observation of six OH absorption lines in a spectral interval of about 0.24 nm. Along with the OH radicals the atmospheric trace gases sulfur dioxide, formaldehyde, and naphthalene were measured by this technique. We will present measured absorption spectra of ambient OH and corresponding diurnal profiles of the OH radical concentration and will discuss their dependence on photochemical parameters.