Browsing by Author "Wilson, R."

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    An integrated MASS/DIMM monitor based on a low-noise CCD detector
    (2015) Guesalaga Meissner, Andrés Rodrigo; Osborn, J.; Sarazin, M.; Neichel, B.; Perera, S.; Wilson, R.; Wizinowich, Peter
    We propose a novel design for a turbulence profiler. Using a single detector, images of the pupil (scintillation) and stars (image motion) are formed in the detector plane. The instrument is called FASS (Full Aperture Scintillation Sensor), as it uses the full aperture of the telescope. Different processing strategies are evaluated, including spatial segmentation and Fourier analysis. The different approaches are tested via simulation and on-sky data from two telescopes and compared to profiles obtained with the Durham Stereo-SCIDAR monitor. Overall, simulations shows that the method is more accurate that the classical MASS configuration, but it is shown that the photon noise plays an important role in the accuracy of the method, imposing stringent requirements on the pixel size, which must be significantly smaller than the speckle size formed from turbulence close to the ground (Fresnel law for speckle size).
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    The 2015 Chileno Valley glacial lake outburst flood, Patagonia
    (2019) Wilson, R.; Harrison, S.; Reynolds, J.; Hubbard, A.; Glasser, N. F.; Wundrich, O.; Anacona, P. Iribarren; Mao, L.; Shannon, S.
    Glacial Lake Outburst Floods (GLOFs) have become increasingly common over the past century in response to climate change, posing risks for human activities in many mountain regions. In this paper we document and reconstruct the sequence of events and impact of a large GLOF that took place in December 2015 in the Chileno Valley, Patagonia. Hydrograph data suggests that the flood continued for around eight days with an estimated total discharge of 105.6 x 10(6) m(3) of water. The sequence of events was as follows: (1) A large debris flow entered the lake from two steep and largely non-vegetated mountain gullies located northeast of the Chileno Glacier terminus. (2) Water displaced in the lake by the debris flow increased the discharge through the Chileno Lake outflow. (3) Lake and moraine sediments were eroded by the flood. (4) Eroded sediments were redistributed downstream by the GLOF. The post-GLOF channel at the lake outlet widened in some places by >130 m and the surface elevation of the terrain lowered by a maximum of 38.8 +/- 1.5 m. Farther downstream, large amounts of entrained sediment were deposited at the head of an alluvial plain and these sediments produced an similar to 340 m wide fan with an average increase in surface elevation over the pre-GLOF surface of 4.6 +/- 1.5 m. We estimate that around 3.5 million m(3) of material was eroded from the flood-affected area whilst over 0.5 million m(3) of material was deposited in the downstream GLOF fan. The large debris flow that triggered the GLOF was probably a paraglacial response to glacier recession from its Little Ice Age limits. We suggest that GLOFs will continue to occur in these settings in the future as glaciers further recede in response to global warming and produce potentially unstable lakes. Detailed studies of GLOF events are currently limited in Patagonia and the information presented here will therefore help to inform future glacial hazard assessments in this region. (C) 2019 The Author(s). Published by Elsevier B.V.
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    Variability of the capsular anatomy in the rotator interval region of the shoulder
    (2013) Wilson, R.; Magnussen, R.; Irribarra Trivelli, Luis Alfonso; Taylor, D.