Retrieval of tropospheric NO<sub>2</sub> columns over Berlin from high-resolution airborne observations with the spectrolite breadboard instrument

Abstract

Abstract. This paper presents the retrieval method that was developed to derive tropospheric NO 2 columns from UV/VIS spectral measurements obtained with the Spectrolite Breadboard Instrument during the AROMAPEX campaign in Berlin (April 2016). A typical DOAS retrieval approach is followed. For the calculation of air mass factors this study specifically focuses on the impact of the surface reflectance, which varies considerably from pixel to pixel over this urban region. Groundbased aerosol optical thickness measurements are used as prior information. It is shown that retrieved surface reflectance shows 5 good agreement with those derived from Landsat 8 measurements performed on the same day. Furthermore we demonstrate that tropospheric NO 2 columns retrieved for pairs of adjacent pixels are self-consistent in the sense that they do not show a substantial systematic dependence on surface reflectance, in contrast to differential slant column densities. Also some cases are identified to illustrate this on a pixel-by-pixel level. An error budget is provided to quantify the impact of various assumptions on the accuracy of the retrieval of surface reflectance and tropospheric NO 2 columns. Both in the morning and afternoon flight

Intercomparison of four airborne imaging DOAS systems for tropospheric NO<sub>2</sub> mapping – The AROMAPEX campaign

“…The corresponding surface reflectances, and viewing and sun geometries recorded by the AirMAP instrument are also provided in the plot, as well as the other RTM parameter settings. A strong dependence of the AMF on the surface reflectance can be observed, consistent with previous studies reported in Lawrence et al (2015), Meier et al (2017) and Tack et al (2017). In Fig.…”

“…The Airborne imaging DOAS instrument for Measurements of Atmospheric Pollution (AirMAP) has been developed for the purpose of airborne trace gas measurements and pollution mapping by the Institute of Environmental Physics in Bremen (IUP-Bremen). The instrument specifications and previous campaign results have been thoroughly discussed in Schönhardt et al (2015) and Meier et al (2017). AirMAP is a pushbroom UV-Vis imager with a wide FOV of around 51.7°, resulting in a swath width of approximately the same size as the flight altitude.…”

“…Although primarily designed for future application in space, SBI was adapted to an airborne instrument and performed its maiden flight during the AROMAPEX campaign. The instrument specifications are discussed in more details in de Goeij et al 2016, while the NO 2 retrieval approach and AROMAPEX campaign results are reported in Ge and Vlemmix (2016), and Vlemmix et al (2017). It was decided only shortly before the AROMAPEX campaign to add SBI to the instrumental set-up, which made it an ambitious and challenging task to get the breadboard ready.…”

“…The majority of these studies have focused on the retrieval of the NO 2 field over urban areas and/or industrial sites, i.e. Heue et al (2008), Kowalewski and Janz (2009), Popp et al (2012), General et al (2014), Lawrence et al (2015), Schönhardt et al (2015), Nowlan et al (2016), Broccardo et al (2017), Lamsal et al (2017), Meier et al (2017), Merlaud et al (2017), Tack et al (2017) and Vlemmix et al (2017).…”

Nitrogen dioxide and formaldehyde measurements from the GEOstationary Coastal and Air Pollution Events (GEO-CAPE) Airborne Simulator over Houston, Texas

“…NO 2 amounts over industrial regions and urban areas have been mapped at high spatial resolution by several recently developed airborne push-broom sensors (Heue et al, 2008;Popp et al, 2012;Schönhardt et al, 2015;Lawrence et al, 2015;Nowlan et al, 2016;Meier et al, 2017;Tack et al, 2017Tack et al, , 2018Vlemmix et al, 2017;Broccardo et al, 2018). Airborne remote-sensing CH 2 O measurements have previously been made from aircraft using limb-viewing geometry by airborne multi-axis differential optical absorption spectroscopy (AMAX-DOAS) (Baidar et al, 2013) and by the whisk-broom scanning technique (where the cross-track spatial dimension is provided by mechanical scanning) using the Airborne Compact Atmospheric Mapper (ACAM) (Liu et al, 2015b).…”