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Version 1.3 AIM SOFIE measured methane (CH 4 ): Validation and seasonal climatology
Author(s) -
Rong P. P.,
Russell J. M.,
Marshall B. T.,
Siskind D. E.,
Hervig M. E.,
Gordley L. L.,
Bernath P. F.,
Walker K. A.
Publication year - 2016
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2016jd025415
Subject(s) - mesosphere , microwave limb sounder , altitude (triangle) , atmospheric sciences , environmental science , aeronomy , northern hemisphere , atmospheric sounding , stratosphere , southern hemisphere , climatology , atmosphere (unit) , meteorology , physics , geology , geometry , mathematics
The V1.3 methane (CH 4 ) measured by the Aeronomy of Ice in the Mesosphere (AIM) Solar Occultation for Ice Experiment (SOFIE) instrument is validated in the vertical range of ~25–70 km. The random error for SOFIE CH 4 is ~0.1–1% up to ~50 km and degrades to ~9% at ∼ 70 km. The systematic error remains at ~4% throughout the stratosphere and lower mesosphere. Comparisons with CH 4 data taken by the SCISAT Atmospheric Chemistry Experiment‐Fourier Transform Spectrometer (ACE‐FTS) and the Envisat Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) show an agreement within ~15% in the altitude range ~30–60 km. Below ~25 km SOFIE CH 4 is systematically higher (≥20%), while above ~65 km it is lower by a similar percentage. The sign change from the positive to negative bias occurs between ~55 km and ~60 km (or ~40 km and ~45 km) in the Northern (or Southern) Hemisphere. Methane, H 2 O, and 2CH 4 + H 2 O yearly differences from their values in 2009 are examined using SOFIE and MIPAS CH 4 and the Aura Microwave Limb Sounder (MLS) measured H 2 O. It is concluded that 2CH 4 + H 2 O 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.