An improved inlet for precisely measuring the atmospheric Ar/N<sub>2</sub> ratio

Blaine, TW, Keeling RF, Paplawsky WJ.  2006.  An improved inlet for precisely measuring the atmospheric Ar/N2 ratio. Atmospheric Chemistry and Physics. 6:1181-1184.

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The atmospheric Ar/N-2 ratio is expected to be useful as a tracer of air-sea heat exchange, but this application has been hindered in part due to sampling artifacts. Here we show that the variability in delta(Ar/N-2) due to thermal fractionation at the inlet can be on the order of 40 - 80 per meg, and we introduce the use of an aspirated solar shield that successfully minimizes such fractionation. The data collected using this new inlet have a mean diurnal cycle of 1.0 per meg or less, suggesting that any residual thermal fractionation effect is reduced to this level.