Sulfur dioxide vertical column DOAS retrievals from the Ozone Monitoring Instrument: Global observations and comparison to ground‐based and satellite data

Abstract

We present a new data set of sulfur dioxide (SO 2 ) vertical columns from observations of the Ozone Monitoring Instrument (OMI)/AURA instrument between 2004 and 2013. The retrieval algorithm used is an advanced Differential Optical Absorption Spectroscopy (DOAS) scheme combined with radiative transfer calculation. It is developed in preparation for the operational processing of SO 2 data product for the upcoming TROPOspheric Monitoring Instrument/Sentinel 5 Precursor mission. We evaluate the SO 2 column results with those inferred from other satellite retrievals such as Infrared Atmospheric Sounding Interferometer and OMI (Linear Fit and Principal Component Analysis algorithms). A general good agreement between the different data sets is found for both volcanic and anthropogenic SO 2 emission scenarios. We show that our algorithm produces SO 2 columns with low noise and is able to provide accurate estimates of SO 2 . This conclusion is supported by important validation results over the heavily polluted site of Xianghe (China). Nearly 4 years of OMI and ground-based multiaxis DOAS SO 2 columns are compared, and an excellent match is found. We also highlight the improved performance of the algorithm in capturing weak SO 2 sources by detecting shipping SO 2 emissions in long-term averaged data, an unreported measurement from space.

Sulfur dioxide retrievals from TROPOMI onboard Sentinel-5 Precursor: algorithm theoretical basis

“…Current algorithms exploit back-scattered radiance measurements in a wide spectral range using a direct fitting approach Nowlan et al, 2011), a principal component analysis (PCA) method (Li et al, 2013) or (some form of) differential optical absorption spectroscopy (DOAS; Platt and Stutz, 2008); see, e.g., Richter et al (2009), Hörmann et al (2013), or Theys et al (2015.…”

“…Figure 2 shows the full flow diagram of the SO 2 retrieval algorithm including the dependencies on auxiliary data and other L2 products. The algorithm and its application to OMI data are also described in Theys et al (2015), although there are differences in some settings. The baseline operation flow of the scheme is based on a DOAS retrieval algorithm and is identical to that implemented in the retrieval algorithm for HCHO (also developed by BIRA-IASB; see De Smedt et al, 2016).…”

“…As part of the algorithm development and during the verification exercise (Sect. 4), closed-loop retrievals have been performed (Theys et al, 2015). and application of the algorithm to real data from the GOME-2 and OMI instruments lead to threshold values and criteria as given in Table 3.…”

“…Total vertical column density (VCD) of SO 2 has been retrieved with the sensors TOMS (Krueger, 1983), GOME (Eisinger and Burrows, 1998;Thomas et al, 2005;Khokar et al, 2005), SCIAMACHY (Afe et al, 2004), OMI (Krotkov et al, 2006;Yang et al, 2007Yang et al, , 2010Li et al, 2013;Theys et al, 2015), GOME-2 Bobrowski et al, 2010;Nowlan et al, 2011;Rix et al, 2012;Hörmann et al, 2013) and OMPS . In particular, the Ozone Monitoring Instrument (OMI) has largely demonstrated the value of satellite UV-visible remote sensing (1) in monitoring volcanic plumes in near-real time (Brenot et al, 2014) and changes in volcanic degassing at the global scale , and references therein) and (2) in detecting and quantifying large anthropogenic SO 2 emissions, weak or N. Theys et al: S-5P SO 2 algorithm theoretical basis unreported emission sources worldwide (Theys et al, 2015;Fioletov et al, 2016;McLinden et al, 2016) as well as investigating their long-term changes van der A et al, 2016;He et al, 2016). An example map of OMI SO 2 columns (Theys et al, 2015) averaged over the [2005][2006][2007][2008][2009] period is shown in Fig.…”

“…In particular, the Ozone Monitoring Instrument (OMI) has largely demonstrated the value of satellite UV-visible remote sensing (1) in monitoring volcanic plumes in near-real time (Brenot et al, 2014) and changes in volcanic degassing at the global scale , and references therein) and (2) in detecting and quantifying large anthropogenic SO 2 emissions, weak or N. Theys et al: S-5P SO 2 algorithm theoretical basis unreported emission sources worldwide (Theys et al, 2015;Fioletov et al, 2016;McLinden et al, 2016) as well as investigating their long-term changes van der A et al, 2016;He et al, 2016). An example map of OMI SO 2 columns (Theys et al, 2015) averaged over the [2005][2006][2007][2008][2009] period is shown in Fig. 1, illustrating typical anthropogenic emission hotspots (China, eastern Europe, India and the Middle East) and signals from volcanic activity (e.g., from the volcanoes in DR Congo).…”