Abstract
Abstract. We present an improved TROPOspheric Monitoring Instrument (TROPOMI) retrieval of formaldehyde (HCHO) over China. The new retrieval optimizes the slant column density (SCD) retrieval and air mass factor (AMF) calculation for TROPOMI observations of HCHO over China. Retrieval of HCHO differential SCDs (DSCDs) is improved using the basic optical differential spectroscopy (BOAS) technique resulting in lower noise and smaller random error, while AMFs are improved with a priori HCHO profiles from a higher resolution regional chemistry transport model. Compared to the operational product, the new TROPOMI HCHO retrieval shows better agreement with ground-based Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements in Beijing. The improvements are mainly related to the AMF calculation with more precise a priori profiles in winter. Using more precise a priori profiles in general reduces HCHO vertical column densities (VCDs) by 52.37 % (± 27.09 %) in winter. Considering the aerosol effect in AMF calculation reduces the operational product by 11.46 % (± 1.48 %) and our retrieval by 17.61 % (± 1.92 %) in winter. The improved and operational HCHO are also used to investigate the spatial–temporal characteristics of HCHO over China. The result shows that both improved and operational HCHO VCDs reach maximum in summer and minimum in winter. High HCHO VCDs mainly located over populated areas, i.e., Sichuan Basin and central and eastern China, indicate a significant contribution of anthropogenic emissions. The hotspots are more obvious on the map of the improved HCHO retrieval than the operational product. The result indicates that the improved TROPOMI HCHO retrieval is more suitable for the analysis of regional- and city-scale pollution in China.
Highlights
Formaldehyde (HCHO) is an important trace gas playing a crucial role in atmospheric chemistry processes
The normalized mean bias (NMB) between satellite and MAXDOAS data is used as the benchmark in the comparison
The overestimation of the operational product at the University of Chinese Academy of Sciences (UCAS) site is opposite to a previous study which showed that the TROPOspheric Monitoring Instrument (TROPOMI) operational product underestimated HCHO vertical column densities (VCDs) in Xianghe located ∼ 50 km southeast of Beijing compared to Fourier transform infrared (FTIR) measurements (Vigouroux et al, 2020)
Summary
Formaldehyde (HCHO) is an important trace gas playing a crucial role in atmospheric chemistry processes. W. Su et al.: An improved TROPOMI tropospheric HCHO retrieval over China ted from both primary and secondary sources. Compared to its predecessor satellite instruments, TROPOMI provides HCHO observations with a much higher spatial resolution with daily global coverage. We have improved the TROPOMI HCHO retrieval over China by optimizing the slant column density (SCD) retrieval and the air mass factor (AMF) calculation. The AMF calculation is improved by using higher resolution a priori profiles from the regional Weather Research and Forecasting model (WRF-Chem) It takes the fine-scale pollution into account, and the result is expected to be more realistic for the investigation of spatiotemporal variation of HCHO over China.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
