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STATUS:
10.19.2021
Instrument Status:
SOFIE
SOFIE is currently collecting sunset science observations, and housekeeping parameters all indicate a stable and healthy instrument. SOFIE V1.3 data are available online.
An improved SOFIE sunrise signal calibration resulted in meteoric smoke extinction retrievals in the Northern Hemisphere (NH), for the first time. The SOFIE meteoric smoke record now spans 2007-present in both hemispheres, as recently described by Hervig et al., [2021]. The new observations are in good agreement with SOFIE Southern Hemisphere (SH) measurements, and with Whole Atmosphere Community Climate Model (WACCM) simulations. Comparing SOFIE with WACCM requires knowledge of smoke composition, to relate the optical and physical smoke properties. Based on SOFIE multi-wavelength observations combined with recent theoretical and laboratory work, the present study assumes that smoke in the mesosphere exists purely as Fe-rich olivine (Mg0.8Fe1.2SiO4). With this assumption, SOFIE indicates a global mean ablated meteoric influx of 7.3 ± 2.2 t d-1 (total influx of 24.7 ± 7.3 t d-1), in good agreement with a recent and independent study from the University of Leeds that used models and observations to derive an ablated influx of 8.3 ± 4.7 t d-1 (total influx of 28.0 ± 16 t d-1).
The SOFIE time series of mesospheric smoke shows a hemispheric asymmetry with more smoke in the NH winter compared to the SH (see Figure). This asymmetry is consistent with stronger transport in the NH winter vs. the SH, and is also present (although weaker) in WACCM smoke. This hemispheric difference is confirmed by wintertime mesospheric H2O, with both SOFIE and WACCM showing ∼10% hemispheric differences (SH > NH), again consistent with stronger transport in the NH winter. The open issue is that the asymmetry in smoke is greater in SOFIE than in WACCM. The SOFIE hemispheric difference is not attributed to sunrise - sunset observational biases, because the difference persists after 2018 when sunrise switched from the NH to SH (vice versa for sunset; see Figure). The asymmetry is thus taken to indicate a missing component in our understanding of meteoric processes. One candidate is incomplete chemistry or microphysics in the smoke simulations. Another is an asymmetry in meteoric influx that is not represented in the current model. NASA Wind/WAVES measures meteoric flux near the first Lagrange point, and shows a seasonal variation that was attributed to interstellar particles. The WIND asymmetry is similar to that indicated by SOFIE, and current efforts are thus exploring these comparisons further, and the possibility of an interstellar dust component in Earths mesosphere.
Hervig, M. E., Plane, J. M. C., Siskind, D. E., Feng, W., Bardeen, C. G., Bailey, S. M. (2021). New global meteoric smoke observations from SOFIE: Insight regarding chemical composition, meteoric influx, and hemispheric asymmetry. Journal of Geophysical Research: Atmospheres, 126, e2021JD035007. https://doi.org/10.1029/2021JD035007 (article).
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