Abstract
Abstract. Topographic Target Light scattering – Differential Optical Absorption Spectroscopy (ToTaL-DOAS), also called Target-DOAS, is a novel experimental procedure to retrieve trace gas concentrations present in the low atmosphere. Scattered sunlight (diffuse or specular) reflected from natural or artificial targets located at different distances are analyzed to retrieve the spatial distribution of the concentration of different trace gases like NO2, SO2 and others. We report high spatial resolution measurements of NO2 mixing ratios in the city of Montevideo (Uruguay) observing three buildings as targets with a Mini-DOAS instrument. Our instrument was 146 m, 196 m, and 280 m apart from three different buildings located along a main Avenue. We obtain temporal variation of NO2 mixing ratios between 30 ppb and 65 ppb from measurements of November 2007 and mixing ratios up to 50 ppb from measurements of August and September 2008. Our measurements demonstrate that ToTaL-DOAS observations can be made over relative short distances. In polluted air masses, the retrieved absorption signal was found to be sufficiently strong to allow measurements over distances in the range of several tens of meters.
Highlights
Monitoring dispersion of trace gases in the troposphere near the earth surface is a challenge, in when mobile emission sources are involved and the area of interest has complicated topographic structures
We report high spatial resolution measurements of NO2 mixing ratios in the city of Montevideo (Uruguay) observing three buildings as targets with a Mini-DOAS instrument
The purpose of the present work is to explore the spatial resolution of ToTaL-DOAS using targets at short distances
Summary
Monitoring dispersion of trace gases in the troposphere near the earth surface is a challenge, in when mobile emission sources are involved and the area of interest has complicated topographic structures. The second condition, i.e. the spatial resolution, is fulfilled by some very well established optical techniques like LIDAR (e.g. Collis, 1996; Klett, 1981; Fernald, 1984) and Tomographic-DOAS (see e.g., Veitel et al, 2002; Laepple et al, 2004; Pundt et al, 2005; Hartl et al, 2006; Hashmonay et al, 1999). Their application is associated with high expenses and staff requirements
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