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

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 C₂H₆, 0.34 ± 0.21 g kg⁻¹ for C₂H₂, and 2.92 ± 1.30 g kg⁻¹ for HCOOH. The emission factor for CH3OH 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 C₂H₆, 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 H₂CO 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.