1136 In Situ Measurements of Sulfur Hexafluoride (SF6) and Age of Air from NH Sources during the Atmospheric Tomography (ATom) Global Airborne Survey

Wednesday, 10 January 2018
Exhibit Hall 3 (ACC) (Austin, Texas)
James W. Elkins, NOAA, Boulder, CO; and F. L. Moore, E. J. Hintsa, E. A. Ray, G. S. Dutton, J. D. Nance, B. D. Hall, C. Sweeney, S. A. Montzka, E. Dlugokencky, and P. A. Newman

Atmospheric SF6 is an excellent tracer of atmospheric transport in the troposphere, because of its long lifetime (850 years), mostly northern hemispheric (NH) emissions (95%), and high atmospheric growth rate (~4%/yr.). The gas is used in the distribution of electrical power, because it is an excellent insulator. It is primarily released through its use (leaking and refilling) in high voltage power transformers.

Two NOAA/GMD airborne, in situ gas chromatographs (GCs), PAN and other Trace Hydrohalocarbons ExpeRiment (PANTHER) and UAS Chromatograph for Atmospheric Trace Species (UCATS), operated on the first two circuits of the Atmospheric Tomography Mission (ATom-1 & ATom-2). Both instruments measure nitrous oxide (N2O) and sulfur hexafluoride (SF6) once every 70 seconds using a very sensitive electron capture detector (ECD). We combined data from both instruments into one data set for analysis, since both use the same standards and their measurements are comparable.

The main purpose of ATom is to study the influence of air quality on climate during the four seasons; two seasons are completed so far. The altitude-latitude cross sections of SF6 mixing ratios during the ATom-1 shows sources (left) are mostly located in the NH (~95%). The upper troposphere indicates inter-hemispheric mixing. High altitude, polar regions mixes in older stratospheric air. Using the procedure described by Waugh et al., (2013) [JGR-Atmos. 10.1002/jgrd.50189] and a recent growth rate of 0.32 ppt yr-1, we have calculated the mean age of each SF6 measurement from its source at ground level in the NH, (lat. range of 30-50°N). The contours of age (right) are in agreement with the mean inter-hemispheric exchange time (τNS) of ~1.2 yr and higher ages in the polar stratosphere (2-3 yr).

Figure Caption: Representative latitudinal cross sections of SF6 and age from the NH source region from two airborne GCs during ATom-1.

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