Long-Term Variation in the Tropospheric Nitrogen Dioxide Vertical Column Density over Korea and Japan from the MAX-DOAS Network, 2007–2017

Abstract

We investigated long-term observations of the tropospheric nitrogen dioxide vertical column density (NO2 TropVCD) from the Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) network in Russia and ASia (MADRAS) from 2007 to 2017 at urban (Yokosuka and Gwangju) and remote (Fukue and Cape Hedo) sites in East Asia. The monthly mean in the NO2 TropVCD from MAX-DOAS measured at ~13:30 local time, which is the Ozone Monitoring Instrument (OMI) overpass time, shows good agreement with OMI data during summer, but differences between the two datasets increase in winter. The Theil-Sen slope of the long-term trend indicate a relatively rapid and gradual reduction in NO2 at Yokosuka and two remote sites (Fukue and Cape Hedo), respectively, regardless of the season except for fall at Fukue, but significant changes in NO2 are not observed at Gwangju, Korea. In contrast, OMI satellite data reveal an increase in the NO2 TropVCD at all sites except for Yokosuka, where a decreasing trend common to MAX-DOAS is found, suggesting that the results from satellites need to be cautiously used for investigating long-term trends in less polluted or remote areas. Using backward trajectories, potential source regions are identified for the two urban sites. The spatial distribution from OMI data shows good agreement with the potential source regions at Yokosuka. The potential source regions in Gwangju are identified as the National Industrial Complex in Yeosu and Gwangyang, while the transport route is not clearly visible with OMI data because of their low sensitivity in less polluted areas. The proposed approach is suitable for identifying potential source areas that might not be recognized by satellite observations.

Surface and aloft NO2 pollution over the greater Tokyo area observed by ground-based and MAX-DOAS measurements bridged by kilometer-scale regional air quality modeling

“…In Europe, MAX-DOAS and regional air quality model simulations have been compared over Paris (Shaiganfar et al 2015) and the Netherlands (Vlemmix et al 2015), and four sites over Europe with six model ensemble experiments (Blechschmidt et al 2020). The MAX-DOAS network in Russia and Asia (MADRAS) elucidated the longterm trends in NO 2 pollution status (Kanaya et al 2014;Choi et al 2021), and these trends have been compared with model results (Kanaya et al 2014). In this study, to improve the fine-scale horizontal coverage by 4AZ-MAX-DOAS measurements (Irie et al 2021), kilometer-scale regional air quality modeling was conducted.…”

“…Given that the placement of ground-based observation is generally designed to protect human health, and most observation sites are located in densely populated areas, observation sites are sparse in rural and remote areas. To obtain a homogeneous spatial distribution of air pollutants, satellite observation can serve as a useful tool and our previous studies have reported space-borne NO 2 pollution over Asia and Japan Itahashi et al 2014Itahashi et al , 2019Choi et al 2021). Although satellite observations have the potential to contribute to understanding spatial distribution patterns, the observed concentration is the amount vertically integrated over the column from the surface through the entire troposphere or sliced layers within the troposphere.…”

Surface And Aloft NO2 Pollution Over The Greater Tokyo Area Observed By Ground-Based And MAX-DOAS Measurements Bridged By Regional Air Quality Modeling

“…Given that the placement of ground-based observation is generally designed to protect human health, and most of observation sites are located in densely populated areas, observation sites are sparse in rural and remote areas. To obtain a homogeneous spatial distribution of air pollutants, satellite observation can serve as a useful tool and our previous studies have reported space-borne NO 2 pollution over Asia and Japan Itahashi et al 2014;Itahashi et al 2019;Choi et al 2021). Although satellite observations have the potential to contribute to understanding spatial distribution patterns, the observed concentration is the amount vertically integrated over the column from the surface through the entire troposphere or sliced layers within the troposphere.…”

The greenhouse gas observation mission with Global Observing SATellite for Greenhouse gases and Water cycle (GOSAT-GW): Objectives, conceptual framework and scientific contributions

“…These calculations are markedly in uenced by atmospheric conditions (e.g., coexisting aerosol amount). Consequently, the MAX-DOAS network based in Japan(Kanaya et al, 2014;Choi et al 2021) employs an algorithm that uses O 4 measurements in the wavelength band for NO 2 (460-490 nm) to derive aerosol pro les and Aerosl Optical Depth (AOD), which are then considered as conditions for the NO 2 pro le inversions. Uncertainties associated with the MAX-DOAS-based tropospheric NO 2 VCDs have been estimated at ±17% (Kanaya et al, 2014), while the uncertainties in vertical pro les are typically larger (e.g., Tirpitz et al, 2021).…”