[AAS07-P31] Spatiotemporal variations of NO2 over Fukuoka Japan, observed by multiple MAX-DOAS and 3-D coherent Doppler lidar
キーワード：二酸化窒素、MAX‐DOAS、TROPOMI、ドップラーライダー
To clarify spatiotemporal variations and transport processes in nitrogen dioxide (NO2) over Fukuoka, an urban area in Japan, continuous NO2 profile observations using Multi Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) with high temporal resolution of four minutes have been conducted since October 2018 at three observatories: Yakuin (33.580°N, 130.396°E), Sohara (33.580°N, 130.356°E) and Fukuoka University (33.550°N, 130.364°E).
We first performed case studies at particular days and observed enhanced NO2 contents above the city center on some days. In the case of 29 November 2018, high NO2 concentrations were observed near the ground in the morning (around 7:00–10:30 am). Higher contents of NO2 appeared gradually at higher altitudes over the urban area, and disappeared at around 13:00–14:00 pm. We investigated a three-dimensional (3-D) wind field observed using a 3-D coherent Doppler lidar installed at Fukuoka University. The NO2 variations were consistent with the wind variation: the airmass with high NO2 concentration was transported upward from near the ground over an urban area; it advected southward (landward) because of a sea breeze in the afternoon.
We also validated the tropospheric NO2 vertical column density (VCD) using the Sentinal-5P/TROPospheric Ozone Monitoring Instrument (TROPOMI) satellite with MAX-DOAS observations. Results showed that the satellite data are underestimates, as shown in earlier studies (e.g., Kanaya et al., 2014), but large variations exist from 34% to 154%. These results suggest that underestimation can be attributable not only to the shield effect by aerosols near the ground but also to inhomogeneity and transport processes of the NO2 airmass over urban areas.
We first performed case studies at particular days and observed enhanced NO2 contents above the city center on some days. In the case of 29 November 2018, high NO2 concentrations were observed near the ground in the morning (around 7:00–10:30 am). Higher contents of NO2 appeared gradually at higher altitudes over the urban area, and disappeared at around 13:00–14:00 pm. We investigated a three-dimensional (3-D) wind field observed using a 3-D coherent Doppler lidar installed at Fukuoka University. The NO2 variations were consistent with the wind variation: the airmass with high NO2 concentration was transported upward from near the ground over an urban area; it advected southward (landward) because of a sea breeze in the afternoon.
We also validated the tropospheric NO2 vertical column density (VCD) using the Sentinal-5P/TROPospheric Ozone Monitoring Instrument (TROPOMI) satellite with MAX-DOAS observations. Results showed that the satellite data are underestimates, as shown in earlier studies (e.g., Kanaya et al., 2014), but large variations exist from 34% to 154%. These results suggest that underestimation can be attributable not only to the shield effect by aerosols near the ground but also to inhomogeneity and transport processes of the NO2 airmass over urban areas.