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Contrail Camera Observations These Linear Systems with 3 Unknowns Each Are Solved Numerically EGU Journal Logos (RGB) Open Access Open Access Open Access Advances in Annales Nonlinear Processes Geosciences Geophysicae in Geophysics Open Access Open Access Natural Hazards Natural Hazards and Earth System and Earth System Sciences Sciences Discussions Open Access Open Access Atmospheric Atmospheric Chemistry Chemistry and Physics and Physics Discussions Open Access Open Access Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Atmos. Meas. Tech. Discuss., 6, 7425–7472,Atmospheric 2013 Atmospheric www.atmos-meas-tech-discuss.net/6/7425/2013/Measurement Measurement doi:10.5194/amtd-6-7425-2013 AMTD © Author(s) 2013. CC Attribution 3.0 License.Techniques Techniques Discussions 6, 7425–7472, 2013 Open Access Open Access This discussion paper is/hasBiogeosciences been under review for the journal AtmosphericBiogeosciences Measurement Contrail camera Discussions Techniques (AMT). Please refer to the corresponding final paper in AMT if available. observations Open Access Open Access U. Schumann et al. Contrail study withClimate ground-based Climate of the Past of the Past Discussions cameras Title Page Open Access Open Access 1 2 3 4 1 1 Abstract Introduction U. Schumann , R. HempelEarth, H. System Flentje , M. Garhammer , K.Earth Graf System, S. Kox , H. Lösslein4, and B. Mayer4 Dynamics Dynamics Conclusions References Discussions 1 Deutsches Zentrum für Luft- und Raumfahrt, Institut für Physik der Atmosphäre, Tables Figures Open Access Oberpfaffenhofen, Germany Geoscientific Geoscientific Open Access 2 Deutsches Zentrum für Luft-Instrumentation und Raumfahrt, Simulations- und Softwaretechnik,Instrumentation Cologne, Germany Methods and Methods and J I 3Deutscher Wetterdienst, MeteorologischesData Systems Observatorium Hohenpeissenberg,Data Systems J I Hohenpeissenberg, Germany Discussions Open Access 4 Open Access Meteorologisches Institut, Ludwig-Maximilians-Universität, Munich, GermanyGeoscientific Back Close Geoscientific Model Development Received: 7 August 2013Model – Accepted: Development 8 August 2013 – Published: 19 August 2013 Full Screen / Esc Discussions Correspondence to: U. Schumann ([email protected]) Open Access Open Access Printer-friendly Version Published by Copernicus PublicationsHydrology onand behalf of the European GeosciencesHydrology Union.and Earth System Earth System Interactive Discussion Sciences Sciences Discussions Open Access Open Access Ocean Science Ocean Science 7425 Discussions Open Access Open Access Solid Earth Solid Earth Discussions Open Access Open Access The Cryosphere The Cryosphere Discussions Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Abstract AMTD Photogrammetric methods and analysis results for contrails observed with wide-angle cameras are described. Four cameras of two different types (view angle < 90◦ or whole- 6, 7425–7472, 2013 sky imager) at the ground at various positions are used to track contrails and to derive 5 their altitude, width, and horizontal speed. Camera models for both types are described Contrail camera to derive the observation angles for given image coordinates and their inverse. The observations models are calibrated with sightings of the Sun, the Moon and a few bright stars. The methods are applied and tested in a case study. Four persistent contrails crossing U. Schumann et al. each other together with a short-lived one are observed with the cameras. Vertical 10 and horizontal positions of the contrails are determined from the camera images to an accuracy of better than 200 m and horizontal speed to 0.2 m s−1. With this information, Title Page the aircraft causing the contrails are identified by comparison to traffic waypoint data. Abstract Introduction The observations are compared with synthetic camera pictures of contrails simulated with the contrail prediction model CoCiP,a Lagrangian model using air traffic movement Conclusions References 15 data and numerical weather prediction (NWP) data as input. The results provide tests Tables Figures for the NWP and contrail models. The cameras show spreading and thickening contrails suggesting ice-supersaturation in the ambient air. The ice-supersaturated layer is found thicker and more humid in this case than predicted by the NWP model used. The J I simulated and observed contrail positions agree up to differences caused by uncertain J I 20 wind data. The contrail widths, which depend on wake vortex spreading, ambient shear and turbulence, were partly wider than simulated. Back Close Full Screen / Esc 1 Introduction Printer-friendly Version Contrails are linear clouds often visible to ground observers behind cruising air- craft. The conditions under which contrails form (at temperatures below the Schmidt– Interactive Discussion 25 Appleman criterion) and persist (at ambient humidity exceeding ice saturation) are well known (Schumann, 1996). The dynamics of young contrails depend on aircraft 7426 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | emissions and wake properties and the pattern of contrails changes over their lifetime (Lewellen and Lewellen, 1996; Sassen, 1997; Mannstein et al., 1999; Jeßberger et al., AMTD 2013). Though contrails have been investigated for some time, still little is known about 6, 7425–7472, 2013 the full life cycle of individual contrails (Mannstein and Schumann, 2005; Heymsfield 5 et al., 2010; Unterstrasser and Sölch, 2010; Graf et al., 2012; Minnis et al., 2013; Schu- mann and Graf, 2013). Contrail camera Ground-based contrail observations may help to understand contrail dynamics and observations ice formation (Freudenthaler et al., 1995; Immler et al., 2008). The observable contrail cover can be predicted with contrail simulation models (Stuefer et al., 2005; Duda et al., U. Schumann et al. 10 2009; Schumann, 2012). Such models require numerical weather prediction (NWP) data and traffic data as input and observations for validation. Here, we use NWP data Title Page as available from the Integrated Forecast System (IFS) model of the European Cen- tre for Medium Range Forecasts (ECMWF). Information on air traffic can, since a few Abstract Introduction years, be received online from so-called flight radar data in the internet, including air- Conclusions References 15 craft positions transmitted by Automatic Dependent Surveillance-Broadcast (ADSB), at least from the majority of aircraft which have such equipment (Jackson et al., 2005; de Tables Figures Leege et al., 2012). Wide-angle digital cameras have been used before to observe clouds (e.g. Seiz J I et al., 2007) and contrails (Sassen, 1997; Feister and Shields, 2005; Stuefer et al., 20 2005; Atlas and Wang, 2010; Feister et al., 2010; Mannstein et al., 2010; Shields et al., J I 2013). Whole-sky imagers using fisheye lens image the full sky down or nearly down Back Close to the horizon (Shields et al., 2013). More narrow wide-angle cameras cover only part of the sky but with higher resolution. Besides color cameras also multispectral cam- Full Screen / Esc eras recording in several spectral wavebands are available (Feister and Shields, 2005; 25 Seiz et al., 2007; Shields et al., 2013). Camera observations often reveal interesting Printer-friendly Version cloud properties, but a single camera is insufficient to determine the distance of an observable object (LeMone et al., 2013). A video scene from a single camera allows Interactive Discussion determining the angular but not the linear cloud speed. Horizontal contrail positions can be estimated if the contrail altitude is known from other sources (Atlas and Wang, 7427 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2010). A network of cameras has been used for observations of upper atmosphere clouds (Baumgarten et al., 2009) and other objects (Shields et al., 2013). AMTD In regions with dense air traffic, the sky is often full of contrails, and the assignment of 6, 7425–7472, 2013 individual observed contrails to specific aircraft requires accurate contrail altitudes be- 5 sides traffic information. The analysis of aged contrails requires the trajectory analysis from aircraft flight routes to contrail positions. Contrail camera Here, we report on a case study where we observed contrails with four wide-angle observations cameras, placed several km apart and oriented at fixed positions in the sky, provid- ing digital images every 10 s. If the same cloud detail could be identified in overlap- U. Schumann et al. 10 ping areas of stereo images taken with at least two cameras simultaneously, its three- dimensional position could be determined (Seiz et al., 2007). In our case, the horizontal Title Page distance between the cameras was too large for simultaneous observations, but cloud features moving with about constant speed across the camera view-fields could be Abstract Introduction used for photogrammetric analysis. The results are used to identify the causing air- Conclusions References 15 craft, contrail positions vs. time with respect to NWP data, and to deduce contrail and atmospheric properties. For a direct comparison of simulated contrails with camera ob- Tables Figures servations, we map the computed contrails on synthetic camera images. This requires algorithms which compute spherical coordinates for given pixel coordinates and their J I inverse. 20 The pixel positions of identifiable objects in digital camera images can be determined J I with standard image processing software. However, images of wide-angle cameras Back Close usually are distorted considerably (Weng et al.,
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