Comparison of tropospheric NO<sub>2</sub> columns from MAX-DOAS retrievals and regional air quality model simulations

Abstract

Multi-axis differential optical absorption spectroscopy (MAX-DOAS) tropospheric NO 2 column retrievals from four European measurement stations are compared to simulations from five regional air quality models which contribute to the European regional ensemble forecasts and reanalyses of the operational Copernicus Atmosphere Monitoring Service (CAMS). Compared to other observational data usually applied for regional model evaluation, MAX-DOAS data are closer to the regional model data in terms of horizontal and vertical resolution, and multiple measurements are available during daylight, so that, for example, diurnal cycles of trace gases can be investigated.In general, there is good agreement between simulated and retrieved NO 2 column values for individual MAX-DOAS measurements with correlations between 35 % and 70 % for individual models and 45 % to 75 % for the ensemble median for tropospheric NO 2 vertical column densities (VCDs), indicating that emissions, transport and tropospheric chemistry of NO x are on average well simulated. However, large differences are found for individual pollution plumes observed by MAX-DOAS. Most of the models overestimate seasonal cycles for the majority of MAX-DOAS sites investigated. At the urban stations, weekly cycles are reproduced well, but the decrease towards the weekend is underestimated and diurnal cycles are overall not well represented. In particular, simulated morning rush hour peaks are not confirmed by MAX-DOAS retrievals, and models fail to reproduce observed changes in diurnal cycles for weekdays versus weekends. The results of this study show that future model development needs to concentrate on improving representation of diurnal cycles and associated temporal scalings.Published by Copernicus Publications on behalf of the European Geosciences Union. 2796A.-M. Blechschmidt et al.: Comparison of NO 2 columns from MAX-DOAS and regional air quality models

Evaluation of the coupled high-resolution atmospheric chemistry model system MECO(n) using in situ and MAX-DOAS NO<sub>2</sub> measurements

“…Moreover, even within the actual sensitivity volume, the sensitivity might vary as a function of distance from the telescope. Blechschmidt et al (2020) have previously demonstrated that accounting for vertical sensitivity of MAX-DOAS (via averaging kernels) does not noticeably affect the simulated VCDs, because most of the NO 2 is located within the boundary layer, and the averaging kernel profile has a similar shape as the model NO 2 vertical profiles. Hence, vertical sensitivity was not an issue where most of the NO 2 is located.…”

“…Previous studies (e.g. Blechschmidt et al, 2020, andVlemmix et al, 2015) used the optimal estimation-based profile inversion approach, which also requires an a priori estimate of the NO 2 vertical profile and can bias the model evaluation if the assumed a priori profile is similar to that simulated by the model. The averaging kernels (A k ) can be applied on the model partial column (V k ) to calculate the modified VCD (VCD corr ), using the a priori profile V a k according to Eq.…”

“…To our knowledge, regional model comparison studies with MAX-DOAS are very limited (e.g. Shaiganfar et al, 2015;Vlemmix et al, 2015;Blechschmidt et al, 2020) and mostly focus on the tropospheric VCDs. These studies have shown moderate correlations between MAX-DOAS and regional model calculated VCDs with major differences arising due to inappropriate representation of anthropogenic emissions, differences between model-simulated and actual wind vectors, the presence of clouds, and uncertainties related to the MAX-DOAS VCD retrieval.…”

Sudden changes in nitrogen dioxide emissions over Greece due to lockdown after the outbreak of COVID-19

“…In this work, we use the publicly available TROPOMI offline v1.2 and v1.3 tropospheric NO 2 data for March-April 2019 and for March-April 2020, accessed via the Copernicus Open Access Hub. The algorithm producing these data is described by van Geffen et al 2019and is based on the approach used for processing OMI/Aura NO 2 data within DOMINO (Dutch OMI NO 2 ) and the FP7 Quality Assurance for Essential Climate Variables projects (Boersma et al, 2011(Boersma et al, , 2018. Routine validation is being carried out by the Validation Data Analysis Facility, who also provide the quarterly validation report of the Copernicus Sentinel-5 Precursor Operational Data Products.…”

Variation Characteristics and Transportation of Aerosol, NO2, SO2, and HCHO in Coastal Cities of Eastern China: Dalian, Qingdao, and Shanghai

“…In urban areas, industrial and transportation emissions affect the level of pollutants, and human production activities have a certain periodicity. The traffic load on the roads on weekends and the slowdown of industrial activities produce lower pollutant emissions levels [52,53]. Previous studies have shown that there are no significant weekend effects in many major cities in China.…”