Long-term tropospheric formaldehyde concentrations deduced from ground-based fourier transform solar infrared measurements

Abstract

Abstract. We report a 13-year (1992-2005) dataset of total column measurements of formaldehyde (HCHO) over Lauder, New Zealand, inferred from solar infrared spectra measured using a high-resolution Fourier Transform Spectrometer (FTS). Ambient HCHO concentrations at this rural location are often close to levels typical of remote marine environments (<250 ppt), which are close to the detection limit using standard techniques. Consequently we develop a new method that successfully produces HCHO columns with sufficient sensitivity throughout the whole season. HCHO columns over Lauder have a strong seasonal cycle (±50%), with a mean column of 4.9×10 15 molecules cm −2 , peaking during summer months. A simple box model of CH 4 oxidation reproduces the observed broad-scale seasonal cycle, but significantly underestimates the seasonal peak HCHO ground concentrations during summer. This suggests the existence of an additional significant source of HCHO, possibly isoprene that cannot be explained by oxidation of CH 4 alone. The ground-based FTS column data compare well with collocated HCHO column measurements from the Global Ozone Monitoring Experiment (GOME) satellite instrument during the operational period of GOME (1996)(1997)(1998)(1999)(2000)(2001), r 2 =0.65, mean bias=10%, n=48).

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

“…Indeed, the new spectroscopic intensities have been increased by around 30 % in the spectral region employed here ), leading to a significant decrease of the retrieved total columns. In addition, Jones et al (2009) Our low H 2 CO total columns measured in late winter might also reflect the large atmospheric variability of H 2 CO, given its small lifetime, with no local sources in winter at Eureka. However, our data show a strong seasonal cycle consistent with the FTIR measurements at Ny Ålesund (Albrecht et al, 2002) and in situ measurements at Alert (Canada; 82 • N, 63 • W), which range from 30 to 700 pptv (De Serves, 1994 and the degradation mechanisms of non-methane hydrocarbons , which need to be better understood in model simulations (Millet et al, 2008;Parker et al, 2011;Paulot et al, 2011).…”

“…Isoprene has also been suggested as an additional significant source of H 2 CO (Jones et al, 2009 and references therein). In addition, secondary H 2 CO formation in biomass burning plumes has been proposed (Paton-Walsh et al, 2010).…”

“…For HCOOH and H 2 CO, the a priori VMRs in the boundary layer are about 8 and 30 pptv and then decrease to 1 and 10 pptv around 30 km for HCOOH and H 2 CO, respectively. However, the sinks and sources are not as well understood (Paulot et al, 2011;Jones et al, 2009), especially in the polar region, so the interpretation of the a priori profiles has to be done carefully.…”

“…CH 3 OH and HCOOH have been measured in a limited number of ground-based FTIR studies (Paton-Walsh et al, 2005Rinsland et al, , 2009Zander et al, 2010;Paulot et al, 2011). The first FTIR data sets of H 2 CO were obtained in remote areas (Mahieu et al, 1997;Notholt et al, 1997a, b) and were then extended to urban areas (Hak et al, 2005) and the Southern Hemisphere (Jones et al, 2009;Vigouroux et al, 2009;Paton-Walsh et al, 2010).…”

NDACC harmonized formaldehyde time-series from 21 FTIR stations covering a wide range of column abundances

“…a positive bias of 30% or even 50% is found at Reunion Island if the settings of Franco et al (2015) or Jones et al (2009) are used, respectively, instead of those from Vigouroux et al (2009). Although these high biases are consistent with the uncertainty budgets, it is important, to facilitate the interpretation of a satellite or model validation, to harmonize the settings 20 among the stations.…”