Articles | Volume 15, issue 3
Research article
06 Feb 2015
Research article |  | 06 Feb 2015

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

T. Vlemmix, H. J. Eskes, A. J. M. Piters, M. Schaap, F. J. Sauter, H. Kelder, and P. F. Levelt

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 cm−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 cm−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.

Short summary
Ground-based remote sensing measurements of nitrogen dioxide are compared to the Lotos-Euros air quality (AQ) model. Measurements were taken in the Netherlands with a UV-Vis spectrometer which observes scattered sunlight under different elevation viewing angles. On average, a surprisingly good agreement is found. Perhaps most striking is the agreement between model and observations as a function of wind direction. This demonstrates the quality of the AQ model and underlying emission inventory.
Final-revised paper