MAX-DOAS measurements of NO<sub>2</sub>, HCHO and CHOCHO at a rural site in Southern China

Abstract

Abstract. We performed MAX-DOAS measurements during the PRIDE-PRD2006 campaign in the Pearl River Delta region (PRD), China, for 4 weeks in July 2006 at a site located 60 km north of Guangzhou. The vertical distributions of NO2, HCHO, and CHOCHO were independently retrieved by an automated iteration method. The NO2 mixing ratios measured by MAX-DOAS showed reasonable agreement with the simultaneous, ground based in-situ data. The tropospheric NO2 vertical column densities (VCDs) observed by OMI on board EOS-Aura satellite were higher than with those by MAX-DOAS. The 3-D chemical transport model CMAQ overestimated the NO2 VCDs as well as the surface concentrations by about 65%. From this observation, a reduction of NOx emission strength in CMAQ seems to be necessary in order to well reproduce the NO2 observations. The average mixing ratios of HCHO and CHOCHO were 7 ppb and 0.4 ppb, respectively, higher than in other rural or semirural environments. The high ratio of 0.062 between CHOCHO and HCHO corresponds to the high VOCs reactivity and high HOx turnover rate consistent with other observations during the campaign.

Modeling of HCHO and CHOCHO at a semi-rural site in southern China during the PRIDE-PRD2006 campaign

“…Yet simultaneous ground-based measurements of HCHO and CHOCHO in this region are quite limited. During the PRIDE-PRD2006 campaign, which was dedicated to the understanding of the formation mechanism of O 3 and SOA in this heavy polluted region, we performed 1 month of continuous MAX-DOAS observations for HCHO and CHOCHO at a semirural site in the PRD (Li et al, 2013). The measured HCHO and CHOCHO concentrations as well as R GF were as high as those obtained in other urban environments.…”

“…Since the concentration retrieval has been described in detail in Li et al (2013), only a brief outline follows. During the retrieval, HCHO and CHOCHO are assumed to be well-mixed in a layer with height H .…”

The use of NO<sub>2</sub> absorption cross section temperature sensitivity to derive NO<sub>2</sub> profile temperature and stratospheric–tropospheric column partitioning from visible direct-sun DOAS measurements

“…In the past two decades, ground-based multi-axis DOAS (MAX-DOAS) techniques have been developed, measuring scattered sunlight at multiple low elevation angles (Wagner et al, 2004(Wagner et al, , 2007Heckel et al, 2005;Frieß et al, 2006;Sinreich et al, 2005;Li et al, 2008Li et al, , 2010Li et al, , 2013Irie et al, 2008Irie et al, , 2009Clémer et al, 2010). In contrast to the zenith DOAS, MAX-DOAS has significant sensitivity to tropospheric gas absorption due to increased photon path length through the lower troposphere.…”

Observations of the vertical distributions of summertime atmospheric pollutants and the corresponding ozone production in Shanghai, China

“…Combined with forward radiative transfer simulations, MAX-DOAS measurements can provide vertical distribution information about aerosol extinction and trace gas concentration in the lower troposphere (Hönninger and Platt, 2002;Bobrowski et al, 2003;Hönninger et al, 2004;Wagner et al, 2004;Wittrock et al, 2004;Platt and Stutz, 2008). In the past decade, ground-based MAX-DOAS has been widely used for atmospheric aerosol and trace gas measurements (Frieß et al, 2006;Irie et al, 2008;Li et al, 2010Li et al, , 2013. MAX-DOAS measurements are often used to validate satellite observations of atmospheric trace gases, e.g., NO 2 , SO 2 and HCHO (Irie et al, 2008;Kramer et al, 2008;Ma et al, 2013;Wang et al, 2017).…”