Berlin 2012 – scientific programme

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UP: Fachverband Umweltphysik

UP 9: Poster session

UP 9.25: Poster

Wednesday, March 28, 2012, 18:30–19:15, Poster F

Determination of Continuous Urban Trace Gas Distribution Maps such as NO₂, O₃ and SO₂ Using Tomographic LP-DOAS Measurements — •Denis Pöhler¹, Andreas Hartl², and Ulrich Platt¹ — ¹Instiute of Environmental Physics, University of Heidelberg — ²School of Energy and Environment, City University of Hong Kong

Measurements of trace gases are nowadays performed in all larger cities for urban air pollution monitoring by applying few in-situ measurement stations which can not capture variations on scales of several 10 to 100m. Tomographic LP-DOAS measurements allow deriving two and three dimensional distributions of trace gases by measuring the average concentration along many intersecting light paths and applying tomographic inversion techniques. Results of the first application of this technique in the city of Heidelberg, Germany, are presented to derive the horizontal distribution of NO₂, SO₂, O₃, HCHO and HONO over an area of 4 * 4 km² with different emission sources.
We developed an optimised tomographic retrieval for such measurements by applying the algebraic reconstruction method SIRT (Simultaneous Iterative Reconstruction Technique). The retrieved time series had a temporal resolution of up to 15 minutes and spatial resolution of about 500m. Best results are achieved for the trace gases NO₂, SO₂ and O₃. The data are used to study the distributions of emission sources in the city, diurnal cycles of the local emission concentrations, chemical transformation processes, the distribution and transport of emission plumes and the influence from wind speed and direction.