OMI air-quality monitoring over the Middle East

Abstract. Using Ozone Monitoring Instrument (OMI) trace gas vertical column observations of nitrogen dioxide (NO₂), formaldehyde (HCHO), sulfur dioxide (SO₂), and glyoxal (CHOCHO), we have conducted a robust and detailed time series analysis to assess changes in local air quality for over 1000 locations (focussing on urban, oil refinery, oil port, and power plant targets) over the Middle East for 2005–2014. Apart from NO₂, which is highest over urban locations, average tropospheric column levels of these trace gases are highest over oil ports and refineries. The highest average pollution levels over urban settlements are typically in Bahrain, Kuwait, Qatar, and the United Arab Emirates.

We detect 278 statistically significant and real linear NO₂ trends in total. Over urban areas NO₂ increased by up to 12 % yr⁻¹, with only two locations showing a decreasing trend. Over oil refineries, oil ports, and power plants, NO₂ increased by about 2–9 % yr⁻¹. For HCHO, 70 significant and real trends were detected, with HCHO increasing by 2–7 % yr⁻¹ over urban settlements and power plants and by about 2–4 % yr⁻¹ over refineries and oil ports. Very few SO₂ trends were detected, which varied in direction and magnitude (23 increasing and 9 decreasing). Apart from two locations where CHOCHO is decreasing, we find that glyoxal tropospheric column levels are not changing over the Middle East. Hence, for many locations in the Middle East, OMI observes a degradation in air quality over 2005–2014. This study therefore demonstrates the capability of OMI to generate long-term air-quality monitoring at local scales over this region.