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Volume 16, issue 14
Atmos. Chem. Phys., 16, 9457–9487, 2016
https://doi.org/10.5194/acp-16-9457-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Ten years of Ozone Monitoring Instrument (OMI) observations...

Atmos. Chem. Phys., 16, 9457–9487, 2016
https://doi.org/10.5194/acp-16-9457-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 29 Jul 2016

Research article | 29 Jul 2016

Multi-satellite sensor study on precipitation-induced emission pulses of NOx from soils in semi-arid ecosystems

Jan Zörner1, Marloes Penning de Vries1, Steffen Beirle1, Holger Sihler1,3, Patrick R. Veres2,a, Jonathan Williams2, and Thomas Wagner1 Jan Zörner et al.
  • 1Satellite Remote Sensing Group, Max Planck Institute for Chemistry, Mainz, Germany
  • 2Atmospheric Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany
  • 3Institute of Environmental Physics, University of Heidelberg, Heidelberg, Germany
  • anow at: NOAA Earth System Research Laboratory, Boulder, CO, USA

Abstract. We present a top-down approach to infer and quantify rain-induced emission pulses of NOx ( ≡  NO + NO2), stemming from biotic emissions of NO from soils, from satellite-borne measurements of NO2. This is achieved by synchronizing time series at single grid pixels according to the first day of rain after a dry spell of prescribed duration. The full track of the temporal evolution several weeks before and after a rain pulse is retained with daily resolution. These are needed for a sophisticated background correction, which accounts for seasonal variations in the time series and allows for improved quantification of rain-induced soil emissions. The method is applied globally and provides constraints on pulsed soil emissions of NOx in regions where the NOx budget is seasonally dominated by soil emissions.

We find strong peaks of enhanced NO2 vertical column densities (VCDs) induced by the first intense precipitation after prolonged droughts in many semi-arid regions of the world, in particular in the Sahel. Detailed investigations show that the rain-induced NO2 pulse detected by the OMI (Ozone Monitoring Instrument), GOME-2 and SCIAMACHY satellite instruments could not be explained by other sources, such as biomass burning or lightning, or by retrieval artefacts (e.g. due to clouds).

For the Sahel region, absolute enhancements of the NO2 VCDs on the first day of rain based on OMI measurements 2007–2010 are on average 4 × 1014  molec cm−2 and exceed 1 × 1015  molec cm−2 for individual grid cells. Assuming a NOx lifetime of 4 h, this corresponds to soil NOx emissions in the range of 6 up to 65 ng N m−2 s−1, which is in good agreement with literature values. Apart from the clear first-day peak, NO2 VCDs are moderately enhanced (2 × 1014  molec cm−2) compared to the background over the following 2 weeks, suggesting potential further emissions during that period of about 3.3 ng N m−2 s−1. The pulsed emissions contribute about 21–44 % to total soil NOx emissions over the Sahel.

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We present a top-down approach to infer and quantify rain-induced emission pulses of nitrogen oxides from soils using satellite-borne measurements of NO2. We found strong enhancements of NO2 induced by the first intense precipitation after prolonged droughts in many semi-arid regions of the world, in particular in the Sahel. Apart from the clear first-day peak, NO2 VCDs are moderately enhanced compared to background over the following 2 weeks suggesting potential further emissions.
We present a top-down approach to infer and quantify rain-induced emission pulses of nitrogen...
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