Abstract
Abstract. We present the set-up and a scientific application of the Stratospheric Air Sub-sampler (SAS), a device to collect and to store the vertical profile of air collected with an AirCore (Karion et al., 2010) in numerous sub-samples for later analysis in the laboratory. The SAS described here is a 20 m long 1/4 inch stainless steel tubing that is separated by eleven valves to divide the tubing into 10 identical segments, but it can be easily adapted to collect smaller or larger samples. In the collection phase the SAS is directly connected to the outlet of an optical analyzer that measures the mole fractions of CO2, CH4 and CO from an AirCore sampler. The stratospheric part (or if desired any part of the AirCore air) is then directed through the SAS. When the SAS is filled with the selected air, the valves are closed and the vertical profile is maintained in the different segments of the SAS. The segments can later be analysed to retrieve vertical profiles of other trace gas signatures that require slower instrumentation. As an application, we describe the coupling of the SAS to an analytical system to determine the 17O excess of CO2, which is a tracer for photochemical processing of stratospheric air. For this purpose the analytical system described by Mrozek et al. (2015) was adapted for analysis of air directly from the SAS. The performance of the coupled system is demonstrated for a set of air samples from an AirCore flight in November 2014 near Sodankylä, Finland. The standard error for a 25 mL air sample at stratospheric CO2 mole fraction is 0.56 ‰ (1σ) for δ17O and 0.03 ‰ (1σ) for both δ18O and δ13C. Measured Δ17O(CO2) values show a clear correlation with N2O in agreement with already published data.
Highlights
Monitoring and studying the distribution of greenhouse gases throughout the atmospheric column is an important constituent of understanding contemporary climate change
The initial Valco valve configuration is shown in Fig. 3: V1 and valve 3 (V3) are in position LOAD and valve 2 (V2) is in position INJECT
This article describes the concept of the SAS, a device constructed to recover and store the stratospheric part of air obtained with an AirCore sampler
Summary
Monitoring and studying the distribution of greenhouse gases throughout the atmospheric column is an important constituent of understanding contemporary climate change. The atmospheric profile information in the coil is preserved because of limited gas diffusion inside the long tube. This means that the altitude profiles of various trace gases such as CO2, CH4 and CO can be determined by processing the content of the AirCore through a fast analytical system quickly after recovery of the sampler. The limitation of the method is that the analytical system must be capable of analysing very small air samples, since the total stratospheric fraction of the AirCore profile is only of the order of 250 mL at ambient temperature and pressure, which is split into multiple segments in the SAS.
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