1997–2007 CO trend at the high Alpine site Jungfraujoch: a comparison between NDIR surface in situ and FTIR remote sensing observations

Abstract

Abstract. Within the atmospheric research community, there is a strong interest in integrated datasets, combining data from several instrumentations. This integration is complicated by the different characteristics of the datasets, inherent to the measurement techniques. Here we have compared two carbon monoxide time series (1997 till 2007) acquired at the high-Alpine research station Jungfraujoch (3580 m above sea level), with two well-established measurement techniques, namely in situ surface concentration measurements using Non-Dispersive Infrared Absorption technology (NDIR), and ground-based remote sensing measurements using solar absorption Fourier Transform Infrared spectrometry (FTIR). The profile information available in the FTIR signal allowed us to extract an independent layer with a top height of 7.18 km above sea level, appropriate for comparison with our in situ measurements. We show that, even if both techniques are able to measure free troposphere CO concentrations, the datasets exhibit marked differences in their overall trends (−3.21 ± 0.03 ppb year −1 for NDIR vs.−0.8 ± 0.4 ppb year −1 for FTIR). Removing measurements that are polluted by uprising boundary layer air has a strong impact on the NDIR trend (now −2.62 ± 0.03 ppb year −1 ), but its difference with FTIR remains significant. Using the LAGRANTO trajectory model, we show that both measurement techniques are influenced by different source regions and therefore are likely subject to exhibit significant differences in their overall trend behaviour. However the observation that the NDIR-FTIR trend difference is as significant before as after 2001 is at odds with available emission databases which claim a significant Asian CO increase after 2001 only.

Representativeness of the IAGOS airborne measurements in the lower troposphere

“…In agreement with numerous other studies (e.g. Dils et al, 2011;Worden et al, 2013;Petetin et al, 2016a), this decrease over Europe is mainly due to the reduction of CO anthropogenic emissions over the last decades (Yoon and Pozzer, 2014;Strode et al, 2016). The strongest decrease is observed at the traffic stations with best estimates of the trend ranging from -5.5 to -10% yr -1…”

Tracking isotopic signatures of CO<sub>2</sub> at the high altitude site Jungfraujoch with laser spectroscopy: analytical improvements and representative results

“…Other related tracers, e.g., δ(O 2 /N 2 ) (Uglietti et al, 2011), carbon monoxide (Dils et al, 2011), and carbonyl sulfide that are routinely measured at Jungfraujoch, can provide additional information on the sources and sinks of CO 2 . Combining these data with an isotope specific regional model might allow for emission specific classifications.…”

A review of atmospheric chemistry observations at mountain sites

“…The site has been shown to be excellent for studies on new particle formation (Bianchi et al 2016) or aerosol-cloud interaction, including mixed-phase and glaciated clouds Verheggen et al 2007). In addition, remote sensing investigations have been performed by FTIR spectroscopy, which allows for quasisimultaneous investigation of total column concentrations of a large number of gaseous constituents (e.g., Barret et al 2002Barret et al , 2003aDe Mazière et al 1999;Dils et al 2011;Duchatelet et al 2009Duchatelet et al , 2010Krieg et al 2005;Mahieu et al 1997;Melen et al 1998;Rinsland et al 1991Rinsland et al , 1992Rinsland et al , 1996Rinsland et al , 2000Rinsland et al , 2008Vigouroux et al 2007;Zander et al 2008Zander et al , 2010. JFJ is exposed mostly to FT air masses in autumn and winter.…”

“…4e), KVV at~180 ppb (Fig. 4d), and JFJ at~140 ppb Balzani Dils et al 2011;Forrer et al 2000;Gilge et al 2010;Zellweger et al 2009; Fig. 4c).…”

“…They stated that further studies are needed in order to understand the trends and the contributions from anthropogenic emissions and possible changes in atmospheric chemistry through reactions with OH radicals. Few records of continuous observations of CO are available beginning in the 1990s at high-altitude stations other than MLO (Novelli et al 1998(Novelli et al , 2003 and JFJ (Dils et al 2011;Gilge et al 2010;Zellweger et al 2009). The trend of CO at JFJ for the period 1996-2007 has been determined to be −3.36 ± 1.08 ppb year −1 ) and −2.65 ± 0.04 ppb year −1 (Zellweger et al 2009) calculated using background data, respectively.…”