Berlin 2014 – wissenschaftliches Programm
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UP: Fachverband Umweltphysik
UP 11: Postersession
UP 11.6: Poster
Mittwoch, 19. März 2014, 17:00–18:30, MAG Poster
Long-term changes of tropospheric NO2 over megacities derived from multiple satellite instruments — •Andreas Hilboll, Andreas Richter, and John P. Burrows — Institut für Umweltphysik, Universität Bremen, Bremen, Deutschland
Nitrogen oxides (NOx = NO+NO2) in the troposphere have been retrieved from satellite-based measurements by the GOME, SCIAMACHY, OMI, and GOME-2 instruments since the mid 1990s, using the DOAS technique. These instruments differ in spatial resolution, local time of measurement, viewing geometry, and other details.
In this study, we present two ways to account for instrumental differences in trend analyses of the tropospheric NO2 columns derived from these measurements, while preserving the individual instruments’ spatial resolutions. The first method explicitly accounts for the instruments’ difference in ground pixel size (40×320 km2 vs. 30×60 km2 for GOME and SCIAMACHY), based on spatial averaging of the measured earthshine spectra and extraction of a spatial pattern of the resolution effect. The second method is an empirical correction, which summarizes all instrumental differences by including instrument-dependent offsets in a fitted trend function.
Both approaches show consistent trends of tropospheric NO2 for a selection of areas on both regional and city scales. Measured tropospheric NO2 columns have been increasing by a factor 3 over east-central China. On a megacity level, individual trends can be as large as +27.2±3.9% yr−1 and +20.7±1.9% yr−1 in Dhaka and Baghdad, while Los Angeles shows a strong decrease of -6.00±0.72% yr−1.