Multiple wavelength retrieval of tropospheric aerosol optical properties from MAXDOAS measurements in Beijing

Abstract

We report on the retrieval of aerosol extinction profiles at four wavelengths from ground-based multi-axis differential absorption spectroscopy (MAXDOAS) measurements performed in Beijing, China. Measurements were made over a 10-month time period (June 2008 to April 2009) using a newly developed MAXDOAS instrument. A retrieval algorithm, based on an on-line implementation of the radiative transfer code LIDORT and the optimal estimation technique, has been designed to provide near real time information on aerosol extinction vertical profiles. The algorithm was applied to O<sub>4</sub> measurements at four wavelengths (360, 477, 577, and 630 nm). The total aerosol optical depths (AODs) calculated from the retrieved profiles exhibit higher values in spring and summer and lower values in autumn and winter. Comparison of the retrieved total AODs with values from a co-located CIMEL sunphotometer revealed a good correlation. The best results are obtained for the UV region with a correlation coefficient (<I>R</I>) of 0.91 and a slope of the linear regression fit of 1.1. At the longest wavelength, <I>R</I> drops down to 0.67 and the slope increases to 1.5. The results confirm that good quality O<sub>4</sub> slant column measurements are essential for the success of the retrievals. A method is presented to determine a correction factor to account for systematic errors. It is demonstrated that the algorithm is capable of reliably retrieving aerosol extinction profiles for a wide range of atmospheric conditions (total AODs at 360 nm ranging from about 0.1 to 3). The results open up new perspectives for the extension of the algorithm for the near real time retrieval of trace gas vertical profiles

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.…”

The Heidelberg Airborne Imaging DOAS Instrument (HAIDI) – a novel imaging DOAS device for 2-D and 3-D imaging of trace gases and aerosols

“…Tech., 7, 3459-3485, 2014 www Baidar et al, 2013;Dix et al, 2013). This is usually done in a two-stage process using inverse modeling of the atmospheric radiative transfer (e.g., Sinreich et al, 2005;Wagner et al, 2004;Frieß et al, 2006;Irie et al, 2008;Clémer et al, 2010;Wagner et al, 2011). First, the aerosol extinction profile is retrieved from the absorption of the oxygen collision complex O 4 , which has a horizontally constant atmospheric concentration (apart from pressure variations) and therefore serves as a proxy of the light path which is affected by aerosols.…”

Validation of OMI, GOME-2A and GOME-2B tropospheric NO<sub>2</sub>, SO<sub>2</sub> and HCHO products using MAX-DOAS observations from 2011 to 2014 in Wuxi, China: investigation of the effects of priori profiles and aerosols on the satellite products

“…Frieß et al, 2006Frieß et al, , 2011Frieß et al, , 2016Wittrock et al, 2006b;Irie et al, 2008Irie et al, , 2011Clémer et al, 2010;Li et al, 2010, X. Li et al, 2013Vlemmix et al, 2010Vlemmix et al, , 2011Vlemmix et al, , 2015bWagner et al, 2011;Yilmaz, 2012;Hartl and Wenig, 2013;Wang et al, 2013a, b). MAX-DOAS observations provide valuable information that can be applied for a quantification of air pollutants (e.g.…”