Identifying fire plumes in the Arctic with tropospheric FTIR measurements and transport models

Abstract

Abstract. We investigate Arctic tropospheric composition using ground-based Fourier transform infrared (FTIR) solar absorption spectra, recorded at the Polar Environment Atmospheric Research Laboratory (PEARL, Eureka, Nunavut, Canada, 80 • 05 N, 86 • 42 W) and at Thule (Greenland, 76 • 53 N, −68 • 74 W) from 2008 to 2012. The target species, carbon monoxide (CO), hydrogen cyanide (HCN), ethane (C 2 H 6 ), acetylene (C 2 H 2 ), formic acid (HCOOH), and formaldehyde (H 2 CO) are emitted by biomass burning and can be transported from mid-latitudes to the Arctic.By detecting simultaneous enhancements of three biomass burning tracers (HCN, CO, and C 2 H 6 ), ten and eight fire events are identified at Eureka and Thule, respectively, within the 5-year FTIR time series. Analyses of Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model back-trajectories coupled with Moderate Resolution Imaging Spectroradiometer (MODIS) fire hotspot data, Stochastic Time-Inverted Lagrangian Transport (STILT) model footprints, and Ozone Monitoring Instrument (OMI) UV aerosol index maps, are used to attribute burning source regions and travel time durations of the plumes. By taking into account the effect of aging of the smoke plumes, measured FTIR enhancement ratios were corrected to obtain emission ratios and equivalent emission factors. The means of emission factors for extratropical forest estimated with the two FTIR data sets are 0.40 ± 0.21 g kg −1 for HCN, 1.24 ± 0.71 g kg −1 for C 2 H 6 , 0.34 ± 0.21 g kg −1 for C 2 H 2 , and 2.92 ± 1.30 g kg −1 for HCOOH. The emission factor for CH 3 OH estimated at Eureka is 3.44 ± 1.68 g kg −1 .To improve our knowledge concerning the dynamical and chemical processes associated with Arctic pollution from fires, the two sets of FTIR measurements were compared to the Model for OZone And Related chemical Tracers, version 4 (MOZART-4). Seasonal cycles and day-to-day variabilities were compared to assess the ability of the model to reproduce emissions from fires and their transport. Good agreement in winter confirms that transport is well implemented in the model. For C 2 H 6 , however, the lower wintertime concentration estimated by the model as compared to the FTIR observations highlights an underestimation of its emission. Results show that modeled and measured total columns are correlated (linear correlation coefficient r>0.6 for all gases except for H 2 CO at Eureka and HCOOH at Thule), but suggest a general underestimation of the concentrations in the model for all seven tropospheric species in the high Arctic.

Determination of enhancement ratios of HCOOH relative to CO in biomass burning plumes by the Infrared Atmospheric Sounding Interferometer (IASI)

“…The Siberian ER (HCOOH/CO) (4.4 × 10 −3 mol mol −1 ± 0.09 × 10 −3 ) is found to be in good agreement with the wide range of values obtained by Tereszchuk et al (2013) and Viatte et al (2015). This ER (HCOOH/CO) is, however, lower than the ratios calculated by R' Honi et al (2013), who focused on the extreme fire event that occurred in 2010.…”

Emission of trace gases and aerosols from biomass burning – an updated assessment

“…Dry grassland fires, for example, are dominated by flaming combustion and a rapid passage of the fire front, with little residual smoldering. Forest fires, on the other hand, especially those in fuels with relatively high fuel moisture and large diameters, have a long phase of residual smoldering combustion (RSC), during which larger-diameter fuels are consumed over time spans of up to several days (Ward and Hardy, 1991;Ward et al, 1992;Yokelson et al, 1997;Bertschi et al, 2003;Hao and Babbitt, 2007;Burling et al, 2011;Akagi et al, 2013;Geron and Hays, 2013;Urbanski, 2014;Reisen et al, 2018). The smoldering mode of combustion can become dominant in peat fires, which often proceed without a flaming phase and below ground Stockwell et al, 2016b).…”

Intercomparison of atmospheric water vapour measurements at a Canadian High Arctic site

“…The 125HR records highresolution solar absorption spectra (0.0035 cm −1 ) during clear-sky conditions while the sun is above the horizon (late February until late October). Its wide spectral range enables the 125HR to detect many trace gases, including NO y species (Lindenmaier et al, 2011), stratospheric ozone chemistry species , and biomass burning products (Viatte et al, 2015). The 125HR can also measure atmospheric water vapour and is the most northern measurement site of the NDACC, Total Carbon Column Observing Network (TCCON), and MUSICA networks.…”