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STATUS:
05.11.2017
Instrument Status:
The AIM spacecraft continues to perform well.
SOFIE
The AIM orbit beta angle is currently high enough that the sun does not rise or set as viewed from the satellite. SOFIE measurements are not possible under these conditions, and sampling will be interrupted from February 24, 2017 until early October, 2017. The SOFIE instrument is being monitored and all science and housekeeping parameters are normal. SOFIE V1.3 data are available online through February 2017.
Rong et al. [2016] recently described an investigation of SOFIE methane observations, including comparisons with independent observations. SOFIE CH4 random errors are ~0.1–1% up to ~50 km, increasing to ~9% at ∼ 70 km. The systematic errors are ~4% throughout the stratosphere and lower mesosphere. Comparisons with CH4 from ACE-FTS and MIPAS show agreement to within ~15% in the altitude range ~30–60 km (see example comparisons in the Figure below). Below ~25 km SOFIE CH4 is systematically higher (≥20%), while above ~65 km it is lower by a similar percentage. Methane, H2O, and 2CH4 + H2O yearly differences from their values in 2009 are examined using SOFIE, with MIPAS CH4 and Aura MLS H2O. It is concluded that 2CH4 + H2O is conserved with altitude up to an upper limit between ~35 km and ~50 km depending on the season. In summer this altitude is higher. In the Northern Hemisphere the difference relative to 2009 is the largest in late spring and the established difference prevails throughout summer and fall, suggesting that summer and fall are dynamically quiet. In both hemispheres during winter there are disturbances (with a period of ~1 month) that travel downward throughout the stratosphere with a speed similar to the winter descent.
Rong, P., J. M. Russell III, B. T. Marshall, D. E. Siskind, M. E. Hervig, L. L. Gordley, P. F. Bernath, and K. A. Walker (2016), Version 1.3 AIM SOFIE measured methane (CH4): Validation and Climatology, J. Geophys. Res. Atmos., 121, doi:10.1002/2016JD025415.
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