Five years of CO, HCN, C<sub>2</sub>H<sub>6</sub>, C<sub>2</sub>H<sub>2</sub>, CH<sub>3</sub>OH, HCOOH and H<sub>2</sub>CO total columns measured in the Canadian high Arctic

Abstract

Abstract. We present a five-year time series of seven tropospheric species measured using a ground-based Fourier transform infrared (FTIR) spectrometer at the Polar Environment Atmospheric Research Laboratory (PEARL; Eureka, Nunavut, Canada; 80 • 05 N, 86 • 42 W) from 2007 to 2011. Total columns and temporal variabilities of carbon monoxide (CO), hydrogen cyanide (HCN) and ethane (C 2 H 6 ) as well as the first derived total columns at Eureka of acetylene (C 2 H 2 ), methanol (CH 3 OH), formic acid (HCOOH) and formaldehyde (H 2 CO) are investigated, providing a new data set in the sparsely sampled high latitudes.Total columns are obtained using the SFIT2 retrieval algorithm based on the optimal estimation method. The microwindows as well as the a priori profiles and variabilities are selected to optimize the information content of the retrievals, and error analyses are performed for all seven species. Our retrievals show good sensitivities in the troposphere. The seasonal amplitudes of the time series, ranging from 34 to 104 %, are captured while using a single a priori profile for each species. The time series of the CO, C 2 H 6 and C 2 H 2 total columns at PEARL exhibit strong seasonal cycles with maxima in winter and minima in summer, in opposite phase to the HCN, CH 3 OH, HCOOH and H 2 CO time series. These cycles result from the relative contributions of the photochemistry, oxidation and transport as well as biogenic and biomass burning emissions.Comparisons of the FTIR partial columns with coincident satellite measurements by the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) show good agreement. The correlation coefficients and the slopes range from 0.56 to 0.97 and 0.50 to 3.35, respectively, for the seven target species.Our new data set is compared to previous measurements found in the literature to assess atmospheric budgets of these tropospheric species in the high Arctic. The CO and C 2 H 6 concentrations are consistent with negative trends observed over the Northern Hemisphere, attributed to fossil fuel emission decrease. The importance of poleward transport for the atmospheric budgets of HCN and C 2 H 2 is highlighted. Columns and variabilities of CH 3 OH and HCOOH at PEARL are comparable to previous measurements performed at other remote sites. However, the small columns of H 2 CO in early May might reflect its large atmospheric variability and/or the effect of the updated spectroscopic parameters used in our retrievals. Overall, emissions from biomass burning contribute to the day-to-day variabilities of the seven tropospheric species observed at Eureka.

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

“…Time series are obtained from February to October since the FTIR measurements require the sun as the light source. The seasonal cycles of CO, HCN, C 2 H 6 , C 2 H 2 , CH 3 OH, HCOOH, and H 2 CO are representative of their differing transport, emissions, lifetimes, and oxidation rates, and have been discussed in detail in Viatte et al (2014) with reference to the Eureka data set.…”

“…Then, total and tropospheric partial columns (between 0 and 10.25 km) are recalculated from the smoothed model profiles. Typical FTIR averaging kernels of the seven tropospheric can be seen in Viatte et al (2014). The FTIR retrievals have different vertical sensitivities for each species, characterized by the degrees of freedom for signal (DOFS), ranging on average over 4454 and 1747 measurements from 2.6 to 0.9 for CO and H 2 CO at Eureka, respectively.…”

“…Details about the seven tropospheric species error budget can be seen in section 2.6 of Viatte et al (2014). Time series are obtained from February to October since the FTIR measurements require the sun as the light source.…”

“…For CO, HCN, and C 2 H 6 , retrieval parameters are based on the NDACC-IRWG standard parameter definitions (NDACC Infrared Working Group, http://www.acd.ucar.edu/irwg/). Details of the retrievals of the seven tropospheric species at Eureka are described in Viatte et al (2014). A priori profiles of the target species are derived from the mean of 40 year runs from the Whole Atmosphere Community Climate Model, version 6 (WACCM, http://www2.cesm.ucar.…”

“…Seven tropospheric species (CO, HCN, C 2 H 6 , C 2 H 2 , CH 3 OH, HCOOH, and H 2 CO) released by biomass burning were monitored from 2008 to 2012. Complete descriptions of the methodologies and characterizations of the retrievals are found in Viatte et al (2014). These species were selected because of their differing anthropogenic, biogenic, fossil fuel burning and biomass burning source fractions, as well as their widely differing lifetimes, sinks, and secondary production rates.…”