and Physics High spatial resolution measurements of NO2 applying Topographic Target Light scattering-Differential Optical Absorption Spectroscopy (ToTaL-DOAS)

called Target-DOAS, is a novel experimental procedure to re-trieve 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 dif-ferent 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 build-ings located along a main Avenue. We obtain temporal vari-ation 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 observa-tions 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.