Remote Sensing Measurements at a Rural Site in China: Implications for Satellite NO₂ and HCHO Measurement Uncertainty and Emissions From Fires

Abstract

Nitrogen dioxide (NO2) and formaldehyde (HCHO) play vital roles in atmospheric photochemical processes. Their tropospheric vertical column density (TVCD) distributions have been monitored by satellite instruments. Evaluation of these observations is essential for applying these observations to study photochemistry. Assessing satellite products using observations at rural sites, where local emissions are minimal, is particularly useful due in part to the spatial homogeneity of trace gases. In this study, we evaluate OMI and TROPOMI NO2 and HCHO TVCDs using multi‐axis differential optical absorption spectroscopy (MAX‐DOAS) measurements at a rural site in the east coast of the Shandong province, China in spring 2018 during the Ozone Photochemistry and Export from China Experiment (OPECE) measurement campaign. On days not affected by local burning, we found generally good agreement of NO2 data after using consistent a priori profiles in satellite and MAX‐DOAS retrievals and accounting for low biases in scattering weights in one of the OMI products. In comparison, satellite HCHO products exhibited weaker correlations with MAX‐DOAS data, in contrast to satellite NO2 products. However, TROPOMI HCHO products showed significantly better agreement with MAX‐DOAS measurements compared to OMI data. Furthermore, case studies of the vertical profiles measured by MAX‐DOAS on burning days revealed large enhancements of nitrous acid (HONO), NO2, and HCHO in the upper boundary layer, accompanied with considerable variability, particularly in HONO enhancements.

Observation-Based Diagnostics of Reactive Nitrogen Recycling through HONO Heterogenous Production: Divergent Implications for Ozone Production and Emission Control

“…However, the ratios did not show significant differences (Figure (d), (e)). We also analyzed data from an agricultural burning event near the site on 31 March 2018 , and compared the ratios in BB and clean airmasses (Supporting Information Figure S10). While HONO was significantly enhanced during the burning event, the median ratios still showed little difference from those of clean airmasses, except for a slightly higher averaged HONO/NO 2 ratio than that of the clean airmasses.…”

“…The OPECE campaign was carried out at the Yellow River Delta Ecology Research Station of the Coastal Wetland in Dongying, Shandong, China. The rural coastal site (37.76°N, 118.98°E) is located in the Yellow River Delta region near the Shandong Yellow River Delta National Nature Reserve . The closest urban area, Dongying, is located approximately 50 km southwest of the site.…”

“…The rural coastal site (37.76°N, 118.98°E) is located in the Yellow River Delta region near the Shandong Yellow River Delta National Nature Reserve. 62 The closest urban area, Dongying, is located approximately 50 km southwest of the site. From 23 March to 22 April of 2018, surface concentrations of HONO were measured by a Long Path Absorption Photometer (LOPAP).…”

“…We also investigate the implications of the different HONO heterogeneous production mechanisms for O 3 control strategy. 62 The closest urban area, Dongying, is located approximately 50 km southwest of the site. From 23 March to 22 April of 2018, surface concentrations of HONO were measured by a Long Path Absorption Photometer (LOPAP).…”