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J. Streicher, C. Münkel, and H. Borchardt

Abstract

Each year fog at airports renders some landing operations either difficult or impossible. In such instances, visibility is the most important information for the pilot of a landing aircraft. Visibility may be constant, decreasing, or increasing with respect to the altitude; however, it is not possible to distinguish this with existing airport sensors. This paper describes a new technique for measuring slant visual range that makes use of a slant scanning device, an eye-safe laser radar.

This device has been tested by the German Meteorological Service in Quickborn, Germany, over a period of one year. A comparison with commercial visibility sensors shows that it is possible to measure visibilities with the slant-looking laser radar in the range from 50 m up to 2000 m and to even distinguish inhomogenities like ground fog. Statistics of the Quickborn measurements show that the atmosphere in that region is not homogeneous in 38% of fog situations, which would at the present lead to a restriction of the air traffic.

The first installation of this instrument at the Hamburg airport is described.

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R. M. Cionco, W. aufm Kampe, C. Biltoft, J. H. Byers, C. G. Collins, T. J. Higgs, A. R. T. Hin, P.-E. Johansson, C. D. Jones, H. E. Jørgensen, J. F. Kimber, T. Mikkelsen, K. Nyrén, D. J. Ride, R. Robson, J. M. Santabarbara, J. Streicher, S. Thykier-Nielsen, H. van Raden, and H. Weber

The multination, high-resolution field study of Meteorology And Diffusion Over Non-Uniform Areas (MADONA) was conducted by scientists from the United States, the United Kingdom, Germany, Denmark, Sweden, and the Netherlands at Porton Down, Salisbury, Wiltshire, United Kingdom, during September and October 1992. The host of the field study was the Chemical and Biological Defence Establishment (CBDE, now part of Defence Evaluation and Research Agency) at Porton Down. MADONA was designed and conducted for high-resolution meteorological data collection and diffusion experiments using smoke, sulphurhexaflouride (SF6), and propylene gas during unstable, neutral, and stable atmospheric conditions in an effort to obtain terrain-influenced meteorological fields, dispersion, and concentration fluctuation measurements using specialized sensors and tracer generators. Thirty-one days of meteorological data were collected during the period 7 September–7 October and 27 diffusion experiments were conducted from 14 to 23 September 1992. Puffs and plumes of smoke and SF6 were released simultaneously for most of the experiments to gauge the resultant diffusion and concentration behavior. Some 44 meteorological and aerosol sensors and four source generators were used during each day of the field study. This array of sensors included 14 towers of wind cups and vanes, 10 sonic anemometer/thermometers, one boundary layer sonde, two lidar, one ion sensor, the CBDE Weather Station, and several one-of-a-kind sensors. Simulations of airflow and diffusion over the MADONA topography (a 9 km by 7.5 km area) were made with a variety of models. Wind fields and wind-related parameters were simulated with several high-resolution (microalpha scale) wind flow models. A tally of the various data-gathering activities indicates that the execution of MADONA was highly successful. Preliminary use of the datasets shows the high quality and depth of the MADONA database. This well-documented database is suitable for the evaluation and validation of short-range/near-field wind and diffusion models/codes. The database was originally placed on CD-ROM in a structured way by CBDE, Porton Down. The database is now available from the Risø National Laboratory, Denmark.

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