Browsing by Author "Russell, James M. III"

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    High Precision Refraction Measurements By Solar Imaging During Occultation: Results From Sofie
    Gordley, Larry L.; Burton, J.; Marshall, B. T.; McHugh, M.; Deaver, L.; Nelsen, J.; Russell, James M. III; Bailey, Scott M. (Optical Society of America, 2009-09-01)
    A new method for measuring atmospheric refraction angles is presented, with in-orbit measurements demonstrating a precision of +/-0.02 arcsec (+/-0.1 mu rad). Key advantages of the method are the following: (1) Simultaneous observation of two celestial points during occultation (i.e., top and bottom edges of the solar image) eliminates error from instrument attitude uncertainty. (2) The refraction angle is primarily a normalized difference measurement, causing only scale error, not absolute error. (3) A large number of detector pixels are used in the edge location by fitting to a known edge shape. The resulting refraction angle measurements allow temperature sounding up to the lower mesosphere. (C) 2009 Optical Society of America
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    Large ice particles associated with small ice water content observed by AIM CIPS imagery of polar mesospheric clouds: Evidence for microphysical coupling with small-scale dynamics
    Rusch, D. W.; Thomas, G.; Merkel, A.; Olivero, J.; Chandran, A.; Lumpe, J. D.; Carstans, J.; Randall, C.; Bailey, S.; Russell, James M. III (2017-09)
    Observations by the Cloud Imaging and Particle Size (CIPS) instrument on the Aeronomy of Ice in the Mesosphere (AIM) satellite have demonstrated the existence of Polar Mesospheric Cloud (PMC) regions populated by particles whose mean sizes range between 60 and 100 nm (radii of equivalent volume spheres). It is known from numerous satellite experiments that typical mean PMC particle sizes are of the order of 40-50 nm. Determination of particle size by CIPS is accomplished by measuring the scattering of solar radiation at various scattering angles at a spatial resolution of 25 km(2). In this size range we find a robust anti-correlation between mean particle size and albedo. These very-large particle-low-ice (VLP-LI) clouds occur over spatially coherent areas. The surprising result is that VLP-LI are frequently present either in the troughs of gravity wave-like features or at the edges of PMC voids. We postulate that an association with gravity waves exists in the low-temperature summertime mesopause region, and illustrate the mechanism by a gravity wave simulation through use of the 2D Community Aerosol and Radiation Model for Atmospheres (CARMA). The model results are consistent with a VLP-LI population in the cold troughs of monochromatic gravity waves. In addition, we find such events in Whole Earth Community Climate Model/CARMA simulations, suggesting the possible importance of sporadic downward winds in heating the upper cloud regions. This newly-discovered association enhances our understanding of the interaction of ice microphysics with dynamical processes in the upper mesosphere. Published by Elsevier Ltd.
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    Trends in the polar summer mesosphere temperature and pressure altitude from satellite observations
    Bailey, Scott M.; Thurairajah, Brentha; Hervig, Mark E.; Siskind, David E.; Russell, James M. III; Gordley, Larry L. (2021-09-01)
    Time series of mesospheric temperature and pressure altitude are produced through combining observations by the Halogen Occultation Experiment (HALOE), Sounding of the Atmosphere Using Broadband Emission Radiometry (SABER), and Solar Occultation for Ice Experiment (SOFIE) instruments. Time series of both temperature and pressure altitude are produced through the combination of HALOE/SABER providing 29 years in length and HALOE/SOFIE providing 22 years in length. The different sampling of the three instruments constrains the time series to June in the northern hemisphere and December in the southern hemisphere and 6470 degrees in both hemispheres. We interpret the time series by fitting them to simple descriptions of the variations including solar, intra-hemispheric, inter-hemispheric, and linear trend terms. The inferred intra- and inter-hemispheric terms show that dynamical influences rival solar variability in the mesosphere. We find a robust result that the mesosphere is in general cooling at most altitudes at approximately 1-2 K per decade in response to greenhouse gas increases. That cooling leads to a shrinking of the atmosphere on the order of 100-200 m per decade. The shrinking leads to a reduction in cooling and eventually a warming near 0.005 hPa due to hydrostatic contraction.