DOAS measurements of NO<sub>2</sub> from an ultralight aircraft during the Earth Challenge expedition

Abstract

Abstract. We report on airborne Differential Optical Absorption Spectroscopy (DOAS) measurements of NO 2 tropospheric columns above South Asia, the Arabic peninsula, North Africa, and Italy in November and December 2009. The DOAS instrument was installed on an ultralight aircraft involved in the Earth Challenge project, an expedition of seven pilots flying on four ultralight aircraft between Australia and Belgium. The instrument recorded spectra in limb geometry with a large field of view, a set-up which provides a high sensitivity to the boundary layer NO 2 while minimizing the uncertainties related to the attitude variations. We compare our measurements with OMI (Ozone Monitoring Instrument) and GOME-2 (Global Ozone Monitoring Experiment 2) tropospheric NO 2 products when the latter are available. Above Rajasthan and the Po Valley, two areas where the NO 2 field is homogeneous, data sets agree very well. Our measurements in these areas are 0.1 ± 0.1 to 3 ± 1 × 10 15 molec cm −2 and 2.6 ± 0.8 × 10 16 molec cm −2 , respectively. Flying downwind of Riyadh, our NO 2 measurements show the structure of the megacity's exhaust plume with a higher spatial resolution than OMI. Moreover, our measurements are larger (up to 40 %) than those seen by satellites. We also derived tropospheric columns when no satellite data were available if it was possible to get information on the visibility from satellite measurements of aerosol optical thickness. This experiment also provides a confirmation for the recent finding of a soil signature above desert.

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

“…Limb observations performed at different flight altitudes are particularly well suited for a reconstruction of trace gas and aerosol profiles at high vertical resolution (e.g., Heue et al, 2011;Prados-Roman et al, 2011;Merlaud et al, 2012; Atmos. Meas.…”

“…During recent decades a variety of airborne Differential Optical Absorption Spectroscopy (DOAS) measurements were reported (e.g., Wahner et al, 1990;Pfeilsticker and Platt, 1994;McElroy et al, 1999;Petritoli et al, 2002;Melamed et al, 2003;Bruns et al, 2004;Heue et al, 2005;Wang et al, 2005;Bruns et al, 2006;Wang et al, 2006;Heue et al, 2008;Dix et al, 2009;Merlaud et al, 2011;PradosRoman et al, 2011;Merlaud et al, 2012;Baidar et al, 2013), taking place at different flight altitudes and regions of the globe. The aim of these measurements ranged from studies of stratospheric chemistry to tropospheric point source emissions, but only a few of them used Imaging-DOAS (I-DOAS) techniques to acquire 2-dimensional spatially resolved trace gas distributions (e.g., Heue et al, 2008;Kowalewski and Janz, 2009;Popp et al, 2012).…”

High-resolution airborne imaging DOAS measurements of NO<sub>2</sub> above Bucharest during AROMAT

“…Airborne DOAS measurements were, for example, performed using the AMAX-DOAS (airborne multi-axis DOAS) technique facilitating the validation of satellite instruments and the retrieval of trace-gas profiles Heue et al, 2005;Baidar et al, 2013) or the measurement of shipping emissions (Berg et al, 2012). Small instruments have also been applied on ultralight aircraft (Merlaud et al, 2012).…”

A wide field-of-view imaging DOAS instrument for two-dimensional trace gas mapping from aircraft

“…Such airborne measurements are also valuable for satellite validation . Observing in flight direction, Merlaud et al (2012) apply a DOAS instrument on an ultralight aircraft and achieve high sensitivity for boundary layer NO 2 . Utilizing regular flights of an airliner, the CARIBIC project comprises DOAS measurements of several trace gases (Dix et al, 2009;Heue et al, 2011).…”