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MAX-DOAS tropospheric nitrogen dioxide column measurements compared with the Lotos-Euros air quality model

Author: Vlemmix, T. · Eskes, H.J. · Piters, A.J.M. · Schaap, M. · Sauter, F.J. · Kelder, H. · Levelt, P.F.
Type:article
Date:2015
Publisher: Copernicus GmbH
Source:Atmospheric Chemistry and Physics, 3, 15, 1313-1330
Identifier: 523193
doi: doi:10.5194/acp-15-1313-2015
Keywords: Environment · Air quality · Atmospheric pollution · Nitrogen dioxide · Urban atmosphere · Netherlands · Utrecht [Netherlands] · Environment & Sustainability · Urbanisation · Urban Mobility & Environment · CAS - Climate, Air and Sustainability · ELSS - Earth, Life and Social Sciences

Abstract

A 14-month data set of MAX-DOAS (Multi-Axis Differential Optical Absorption Spectroscopy) tropospheric NO2 column observations in De Bilt, the Netherlands, has been compared with the regional air quality model Lotos-Euros. The model was run on a 7×7 km2 grid, the same resolution as the emission inventory used. A study was performed to assess the effect of clouds on the retrieval accuracy of the MAX-DOAS observations. Good agreement was found between modeled and measured tropospheric NO2 columns, with an average difference of less than 1% of the average tropospheric column (14.5 · 1015 molec cmg-2). The comparisons show little cloud cover dependence after cloud corrections for which ceilometer data were used. Hourly differences between observations and model show a Gaussian behavior with a standard deviation (σ) of 5.5 · 1015 molec cmg-2. For daily averages of tropospheric NO2 columns, a correlation of 0.72 was found for all observations, and 0.79 for cloud free conditions. The measured and modeled tropospheric NO2 columns have an almost identical distribution over the wind direction. A significant difference between model and measurements was found for the average weekly cycle, which shows a much stronger decrease during the weekend for the observations; for the diurnal cycle, the observed range is about twice as large as the modeled range. The results of the comparison demonstrate that averaged over a long time period, the tropospheric NO2 column observations are representative for a large spatial area despite the fact that they were obtained in an urban region. This makes the MAX-DOAS technique especially suitable for validation of satellite observations and air quality models in urban regions.