Investigation of CO, C<sub>2</sub>H<sub>6</sub> and aerosols in a boreal fire plume over eastern Canada during BORTAS 2011 using ground- and satellite-based observations, and model simulations

Abstract

We present the results of total column measurements of CO, C₂H₆ and fine mode aerosol optical depth (AOD) during the "Quantifying the impact of <i>BOR</i>eal forest fires on <i>T</i>ropospheric oxidants over the Atlantic using <i>A</i>ircraft and <i>S</i>atellites" (BORTAS-B) campaign over Eastern Canada. Ground-based observations, using Fourier transform spectrometers (FTSs) and sun photometers, were carried out in July and August 2011. These measurements were taken in Halifax, Nova Scotia, which is an ideal location to monitor the outflow of boreal fires from North America, and also in Toronto, Ontario. Measurements of fine mode AOD enhancements were highly correlated with enhancements in coincident trace gas (CO and C₂H₆) observations between 19 and 21 July 2011, which is typical for a smoke plume event. In this paper, we focus on the identification of the origin and the transport of this smoke plume. We use back-trajectories calculated by the Canadian Meteorological Centre as well as FLEXPART forward-trajectories to demonstrate that the enhanced CO, C₂H₆ and fine mode AOD seen near Halifax and Toronto originated from forest fires in Northwestern Ontario that occurred between 17 and 19 July 2011. In addition, total column measurements of CO from the satellite-borne Infrared Atmospheric Sounding Interferometer (IASI) have been used to trace the smoke plume and to confirm the origin of the CO enhancement. Furthermore, the emission ratio (ER_C₂H₆/CO) and the emission factor (EF_C₂H₆) of C₂H₆ (with respect to the CO emission) were estimated from these ground-based observations. These C₂H₆ emission results from boreal fires in Northwestern Ontario agree well with C₂H₆ emission measurements from other boreal regions, and are relatively high compared to fires from other geographical regions. The ground-based CO and C₂H₆ observations were compared with outputs from the 3-D global chemical transport model GEOS-Chem, using the Fire Locating And Monitoring of Burning Emissions (FLAMBE) inventory. Agreement within the stated measurement uncertainty was found for the magnitude of the enhancement of the total columns of CO (~3%) and C₂H₆ (~8%) between the measured and modelled results. However, there is a small shift in time (of approximately 6 h) of arrival of the plume over Halifax between the results

Origin, variability and age of biomass burning plumes intercepted during BORTAS-B

“…We use airborne CO measurements from phase B of the Quantifying the Impacts of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites (BORTAS-B) project, July 2011. The overall objective of BORTAS was to better understand the production of tropospheric ozone with respect to the chemical evolution of plumes from boreal forest fires, which was achieved by integrating aircraft Le Breton et al, 2013;O'Shea et al, 2013), surface (Gibson et al, 2013;Griffin et al, 2013), sonde (Parrington et al, 2012), and satellite measurements ) of atmospheric composition. Phase A of BORTAS was conducted without aircraft in July 2010 (Parrington et al, 2012).…”

“…Figure 7 shows an example ofĀ on 20 July 2011, which is used as a case study in other BORTAS studies (e.g. Griffin et al, 2013;Franklin et al, 2014). Figure 7a shows longitudinal and latitudinal cross-section views of emissions as they are transported from the Thunder Bay region (50 • N, 88 • W).…”

“…Figure 7a shows longitudinal and latitudinal cross-section views of emissions as they are transported from the Thunder Bay region (50 • N, 88 • W). By the time the plume is observed on 20 July by ground-based observatories over Toronto (43.70 • N, 69.40 • W) (Griffin et al, 2013) and Halifax (44.6 • N, 63.59 • W) (Franklin et al, 2014) the plume is approximately 5-7 days old, corresponding to an emission on 14-15 July. Figure 7b shows that the transported air, intercepted at 63 • W, is composed of a young plume (4-5 days old) surrounded by older air (7 days old) over 47-55 • N. Previous BORTAS-B studies have used the NOAA HYbrid Single-Particle Lagrangian Integrated Trajectory (HYS-PLIT) model (Draxler and Hess, 1998), driven by meteorological reanalyses data from the National Center for Environmental Prediction (NCEP) Global Data Assimilation Program (GDAS) to interpret ground-based remote-sensing data collected during BORTAS-B (Griffin et al, 2013;Franklin et al, 2014).…”

“…Figure 7b shows that the transported air, intercepted at 63 • W, is composed of a young plume (4-5 days old) surrounded by older air (7 days old) over 47-55 • N. Previous BORTAS-B studies have used the NOAA HYbrid Single-Particle Lagrangian Integrated Trajectory (HYS-PLIT) model (Draxler and Hess, 1998), driven by meteorological reanalyses data from the National Center for Environmental Prediction (NCEP) Global Data Assimilation Program (GDAS) to interpret ground-based remote-sensing data collected during BORTAS-B (Griffin et al, 2013;Franklin et al, 2014). We find that our Eulerian age of emissions estimates are typically a day older than those determined by the the HYSPLIT model during 19-21 July 2011, when groundbased observations reported elevated concentrations due to biomass burning (Gibson et al, 2013;Griffin et al, 2013;Franklin et al, 2014). Figure 8 shows thatĀ averaged over all BORTAS-B flights is generally consistent with the associated median photochemical age of 6 days, determined using NMVOC ratios .…”

Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites (BORTAS) experiment: design, execution and science overview

“…During BORTAS-B precipitation was generally drier than climatology over Maritime Canada and across Western Canada. An example of the role of precipitation in the transport of pyrogenic aerosol during BORTAS-B is reported by Griffin et al (2013) and Franklin et al (2013).…”