R. L. Mittermeier

A New Bruker IFS 125HR FTIR Spectrometer for the Polar Environment Atmospheric Research Laboratory at Eureka, Nunavut, Canada: Measurements and Comparison with the Existing Bomem DA8 Spectrometer

Abstract A new Bruker IFS 125HR Fourier transform spectrometer has been installed at the Polar Environment Atmospheric Research Laboratory at Eureka, Nunavut, Canada (80.05°N, 86.42°W). This instrument will become the Network for the Detection of Atmospheric Composition Change’s (NDACC’s) primary instrument at Eureka, replacing the existing Bomem DA8 Fourier transform spectrometer, and will operate throughout the sunlit parts of the year. This paper introduces the new instrument and describes the retrieval procedure, including a comprehensive error analysis. Total columns of O3, HCl, HF, HNO3, N2O, CH4, and CO are presented for the first full year of measurements (2007). Perturbations in the total column resulting from the presence of the Arctic polar vortex over Eureka and the chemical processes within it are visible, as are annual cycles driven by photochemistry and dynamics. Enhancements in the CO total column resulting from specific biomass burning smoke events can also be seen. An intercomparison bet...

Ground-based infrared solar spectroscopic measurements of carbon monoxide during 1994 Measurement of Air Pollution From Space flights

Results of the comparison of carbon monoxide ground-based infrared solar spectroscopic measurements with data obtained during 1994 Measurement of Air Pollution From Space (MAPS) flights are presented. Spectroscopic measurements were performed correlatively with April and October MAPS flights by nine research groups from Belgium, Canada, Germany, Japan, New Zealand, Russia, and the United States. Characterization of the techniques and error analysis were performed. The role of the CO a priori profile used in the retrieval was estimated. In most cases an agreement between spectroscopic and MAPS data is within estimated MAPS accuracy of _+ 10%.

Nitric acid measurements at Eureka obtained in winter 2001–2002 using solar and lunar Fourier transform infrared absorption spectroscopy: Comparisons with observations at Thule and Kiruna and with results from three‐dimensional models

[1] For the first time, vertical column measurements of nitric acid (HNO3) above Eureka (80.1N, 86.4W), Canada, have been made during polar night using lunar spectra recorded with a Fourier transform infrared (FTIR) spectrometer, from October 2001 to March 2002. This site is part of the primary Arctic station of the Network for the Detection of Stratospheric Change. These measurements were compared with FTIR measurements at two other Arctic sites: Thule, Greenland (76.5N, 68.8W), and Kiruna, Sweden (67.8N, 20.4E). Eureka lunar measurements are in good agreement with solar ones made with the same instrument. Eureka and Thule HNO3 columns are consistent within measurement error. Differences between HNO3 columns at Kiruna and those at Eureka and Thule can be explained on the basis of available sunlight hours and location of the polar vortex. The measurements were also compared with results from a chemistry-climate model, the Canadian Middle Atmosphere Model (CMAM), and from a three-dimensional chemical transport model, SLIMCAT. This is the first time that CMAM HNO3 columns have been compared with observations in the Arctic. The comparison of CMAM HNO3 columns with Eureka and Kiruna data shows good agreement. The warm 2001–2002winterwithalmostnopolarstratosphericcloudsmakesthecomparisonwiththis version of CMAM, which has a known warm bias, a good test for CMAM under these conditions. SLIMCATcaptures the magnitude of HNO3 columns at Eureka, and the day-today variability, but generally reports higher values than were measured at Thule and Kiruna.

An Intercomparison of Ground-Based Solar FTIR Measurements of Atmospheric Gases at Eureka, Canada

Abstract The authors report the results of an intercomparison of vertical column amounts of hydrogen chloride (HCl), hydrogen fluoride (HF), nitrous oxide (N2O), nitric acid (HNO3), methane (CH4), ozone (O3), carbon dioxide (CO2), and nitrogen (N2) derived from the spectra recorded by two ground-based Fourier transform infrared (FTIR) spectrometers operated side-by-side using the sun as a source. The procedure used to record spectra and derive vertical column amounts follows the format of previous instrument intercomparisons organized by the Network for the Detection of Atmospheric Composition Change (NDACC), formerly known as the Network for Detection of Stratospheric Change (NDSC). For most gases the differences were typically around 3%, and in about half of the results the error bars given by the standard deviation of the measurements from each instrument did not overlap. The worst level of agreement was for HF where differences of over 5% were typical. The level of agreement achieved during this inter...

Toronto-area ozone: Long-term measurements and modelled sources of poor air quality events

The University of Toronto Atmospheric Observatory and Environment Canadas Centre for Atmospheric Research Experiments each has over a decade of ground-based Fourier transform infrared (FTIR) spectroscopy measurements in southern Ontario. We present the Toronto area FTIR time series from 2002 to 2013 of two tropospheric trace gases—ozone and carbon monoxide—along with surface in situ measurements taken by government monitoring programs. We interpret their variability with the GEOS-Chem chemical transport model and determine the atmospheric conditions that cause pollution events in the time series. Our analysis includes a regionally tagged O3 model of the 2004–2007 time period, which quantifies the geographical contributions to Toronto area O3. The important emission types for 15 pollution events are then determined with a high-resolution adjoint model. Toronto O3, during pollution events, is most sensitive to southern Ontario and U.S. fossil fuel NOx emissions and natural isoprene emissions. The sources of Toronto pollution events are found to be highly variable, and this is demonstrated in four case studies representing local, short-, middle-, and long-range transport scenarios. This suggests that continental-scale emission reductions could improve air quality in the Toronto region. We also find that abnormally high temperatures and high-pressure systems are common to all pollution events studied, suggesting that climate change may impact Toronto O3. Finally, we quantitatively compare the sensitivity of the surface and column measurements to anthropogenic NOx emissions and show that they are remarkably similar. This work thus demonstrates the usefulness of FTIR measurements in an urban area to assess air quality.

A Ten-Year Record of Arctic Trace Gas Total Column Measurements at Eureka, Canada, from 1997 to 2006

This paper presents a long-term set of total column densities of N2O, CH4, HF, COF2, HCl, ClONO2, O3, NO, NO2 and HNO3, measured with an ABB Bomem DA8 Fourier transform infrared (FTIR) spectrometer and a consistent methodology, during fall and spring at Eureka (80°N), Nunavut, Canada. The instrumentation, observations and retrievals of the column densities from infrared atmospheric solar absorption spectra are described in detail, including an estimate of the uncertainties in our retrieved column densities. This description also applies to the column data that we have archived on the Data Host Facility of the Network for the Detection of Atmospheric Composition Change (NDACC). The work presented here serves as an introduction to the entire dataset of atmospheric spectra recorded with the DA8 spectrometer at Eureka from 1993 to 2008. A few highlights from the results of our column retrievals for the years 1997 to 2006 are briefly discussed. One of these is the exceptionally low O3, HCl and HNO3 column amounts observed in the spring of 1997 which we ascribe to uptake of gaseous HNO3 on aerosols of type Ib Polar Stratospheric Clouds (PSCs), resulting in appreciable chlorine activation with subsequent chemical ozone depletion. Another is the anomalously high NO columns measured throughout the month of March 2004, the only time this was observed in our ten-year record presented here. We attribute this to the meso-thermospheric contribution by enhanced solar activity. Some comparisons with Ny Alesund observations at 79°N are also discussed.