Diurnal cycle and multi-decadal trend of formaldehyde in the remote atmosphere near 46° N

Abstract

Only very few long-term records of formaldehyde (HCHO) exist that are suitable for trend analysis. Furthermore, many uncertainties remain as to its diurnal cycle, representing a large short-term variability superimposed on seasonal and inter-annual variations that should be accounted for when comparing ground-based observations to, e.g., model results. In this study, we derive a multidecadal time series (January 1988-June 2015) of HCHO total columns from ground-based high-resolution Fourier transform infrared (FTIR) solar spectra recorded at the highaltitude station of Jungfraujoch (Swiss Alps, 46.5 • N, 8.0 • E, 3580 m a.s.l.), allowing for the characterization of the midlatitudinal atmosphere for background conditions. First we investigate the HCHO diurnal variation, peaking around noontime and mainly driven by the intra-day insolation modulation and methane (CH 4 ) oxidation. We also characterize Published by Copernicus Publications on behalf of the European Geosciences Union. Chem. Phys., 16, 4171-4189, 2016 www.atmos-chem-phys.net/16/4171/2016/ Atmos.

Decreasing Trend in Formaldehyde Detected From 20‐Year Record at Wollongong, Southeast Australia

“…The observed regional‐scale increase in OMI HCHO during this period is likely linked to changes in global CH 4 abundance, as seen elsewhere (Franco et al, ). The decreasing trend at Wollongong, however, is inconsistent with this increasing trend—suggesting that the greater regional increase in HCHO is being overpowered by local changes at Wollongong that cannot be attributed to CH 4 .…”

“…Changes in background CH 4 abundance have been shown to affect HCHO observed at other sites and could be impacting the HCHO observations at Wollongong. At Jungfraujoch, for example, Franco et al () found 1998–2015 changes in HCHO and CH 4 were strongly correlated. Using FTIR measurements, the authors found a decrease in HCHO abundance of −3.68 ± 1.00%/year from 1996–2002, the period when global CH 4 levels stabilized (Aydin et al, ; Dlugokencky et al, ; Simpson et al, ), and an increase in HCHO abundance of +0.81 ± 0.62%/year from 2003–2015, when CH 4 levels were stable followed by resumed growth (Kirschke et al, ; Nisbet et al, ).…”

“…In addition, the timing of the observed HCHO trends is not consistent with the timing of changes in global CH 4 abundance. From 2003–2015, when methane levels were stable then increasing (Nisbet et al, ) and HCHO increased at Jungfraujoch (Franco et al, ), Wollongong HCHO observations showed a large decrease of −2.6 [−3.0, −2.2] %/year.…”

“…Between 1910 and 2010 temperatures in Australia increased 0.8 °C (Pink, ), and both biogenic emissions and oxidative chemistry would be sensitive to this change. Globally, methane abundance increased over the years 1984–1999, stayed almost steady from 1999–2006, and then resumed growing from 2007 onwards (Nisbet et al, ) with implications for HCHO production (Franco et al, ). Decreases in biomass burning emissions have been suggested to explain trends in carbon monoxide over Australia from 2002–2011 (Yin et al, ), and declining industrial emissions from 1997–2009 have been shown to affect both carbon monoxide and ethane at nearby sites in New Zealand and Antarctica (Zeng et al, ); both of these emission trends could also impact HCHO in southeast Australia.…”

Changes in ambient air quality and atmospheric composition and reactivity in the South East of the UK as a result of the COVID-19 lockdown

“…Average daily levels of formaldehyde (both a primary and secondary pollutant in sub/urban air; e.g. Parrish et al, 2012 ; Franco et al, 2016 ; Fu et al, 2019 ) did not differ significantly during the lockdown period compared to previous years, i.e. the average daily formaldehyde concentration after lockdown increased by only ~0.2 μg m −3 , to values 102% of those observed across the same time period during previous years.…”