473 research outputs found

    NASA/MSFC ground-based Doppler lidar nocturnal boundary layer experiment (Noblex)

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    During the summer of 1982, NASA/MSFC's ground-based CO2 Doppler Lidar Velocimeter (DLV) was deployed at the Denver Stapleton Airport as part of NASA's participation in the JAWS (Joint Airport Weather Studies) program. Configured to measure the radial wind component within a 10 km radius, the conically scanning lidar was used to examine the evolution of a nocturnal boundary layer under the conditions of cloud free skies and rolling terrain. A valley drainage flow was detected and a two dimension flow visualization constructed. The depth of the gravity current was -700 meters while the depth of the creek valley was -150 meters. This deep drainage flow was detectable for distances of 30 to 40 km from the exit region of the valley. Although the sample period (2000 to 2300 CST) was short and only one nocturnal boundary layer case examined, the usefulness of the DLV was demonstrated as well as the care that must be exercised in interpreting lidar data taken in a stable boundary layer in the vicinity of subtle terrain features

    Influence of coherent mesoscale structures on satellite-based Doppler lidar wind measurements

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    The influence of coherent mesoscale structures on satellite based Doppler lidar wind measurements was investigated. Range dependent weighting functions and the single shot SNR of scan angle are examined and a space shuttle lidar experiment which used a fixed beam and rotating shuttle is simulated

    Evaluation of 2 1-D cloud models for the analysis of VAS soundings

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    Evaluation of the satellite Visual Infrared Spin Scan Radiometer Atmospheric Sounder (VISSR) has begun to document several of its critical shortcomings as far as numerical cloud models are concerned: excessive smoothing of thermal inversions; imprecise measurement of boundary layer moisture; and tendency to exaggerate atmospheric stability. The sensitivity of 1-D cloud models to their required inputs is stressed with special attention to those parameters obtained from atmospheric soundings taken by the VAS or rawinsonde. In addition to performing model experiments using temperature and moisture profiles having the general characteristics of VAS soundings, standard input sensitivity tests were made and 1-D model performance was compared with observations and the results of a 2-D model experiment using AVE/VAS data (Atmospheric Variability Experiment). Although very encouraging, the results are not sufficient to make any specific conclusions. In general, the VAS soundings are likely to be inadequate to provide the cloud base (and subcloud layer) information needed for inputs to current cumulus models. Above cloud base, the tendency to exaggerate the stability of the atmosphere requires solution before meaningful model experiments are run

    Influence of coherent mesoscale structures on satellite-based Doppler lidar wind measurements

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    Efforts to develop display routines for overlaying gridded and nongridded data sets are discussed. The primary objective is to have the capability to review global patterns of winds and lidar samples; to zoom in on particular wind features or global areas; and to display contours of wind components and derived fields (e.g., divergence, vorticity, deformation, etc.). Current considerations in support of a polar orbiting shuttle lidar mission are discussed. Ground truth for a shuttle lidar experiment may be limited to fortuitous alignment of lidar wind profiles and scheduled rawinsonde profiles. Any improvement on this would require special rawinsonde launches and/or optimization of the shuttle orbit with global wind measurement networks

    From/To: Emmitt Channell (Chalk\u27s reply filed first)

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    Portrait of HIV for the east region of Tennessee

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    Optical Holography with Partially Coherent Radiation

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    Holograms can be formed in light of little or no temporal coherence. The coherence requirements for Gabor in‐line holography are examined. It is shown that, with achromatic interferometers formed from diffraction gratings, the coherence requirements for off‐axis holography are equally low. Finally, two basic approaches to the making of holograms in completely white light are described.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87905/2/242_1.pd
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