Using MIPAS to Characterise Volatile Organic Compound Emissions from Fires
Moore, David P1; Sembhi, Harjinder2; Remedios, John J1; Tereszchuk, Keith3
1NCEO, University of Leicester, UNITED KINGDOM; 2University of Leicester, UNITED KINGDOM; 3University of York, UNITED KINGDOM
Short-lived species emitted from wildfires, such as carbon monoxide (CO) and volatile organic compounds (VOCs), carry a lot of information on atmospheric processes relating to chemistry, convection and emission. These disruptive events, which occur at a surprisingly high frequency, are indirectly a climatological feature of the Earth's atmosphere and its climate response. As a consequence, studying and understanding biomass plume chemistry is vital and accurate measurement of trace gases from these events will also aid improvements in climate/chemistry models.
In this study, we utilise MIPAS and ACE data, in combination with IASI to derive wildfire emissions of VOCs, in the context of two periods; the early 2009 Black Saturday fires and the BORTAS campaign fires. Using the complementary viewing angles of IASI (nadir) and MIPAS/ACE (limb), results will be shown which illustrate observations of aged plume composition, chemistry, distribution and area along with information about vertical distribution.
The Black Saturday fires were a particularly severe event over South-Eastern Australia which burnt an area of 450,000 km2, with up to 400 individual fires being identified on February 7th 2009 alone. Driven by weeks of little or no rainfall and record-breaking temperatures, we show that the plumes from this event, contained enhanced VOC amounts and mixed within the lower stratosphere, reaching altitudes up to 18 km. Enhancement ratios, using CO as a reference, show secondary formation of HCOOH within the plume. We also show the effect inclusion of limb-viewing measurements have on improving tropospheric retrievals from IASI.
The second case study is comparison to results from a recent aircraft campaign over North America in July/August 2011 (BORTAS). The NERC-funded campaign was dedicated to studying the impact of local pollution events over North America and aged plumes originated from Asia and Siberia. In the context of the campaign aims, we investigated CO, VOC chemistry and aerosol signatures in boreal biomass plumes. The most significant event was a series of fires over North-west Ontario which show particularly large enhancements of CO and formic acid. We also derive the time evolution of a variety of VOCs (including PAN) within aged plumes, using comparisons of MIPAS and ACE data. These plumes originate from both the boreal forests of North America and Siberia, and show excellent agreement between these independent datasets. Particularly large enhancements of PAN were discovered from Siberian forest fires in late July 2011. The results exemplify the important science gains from the combination of high vertical resolution limb sounders with nadir sounding data from IASI.