English  |  正體中文  |  简体中文  |  Items with full text/Total items : 67621/67621 (100%)
Visitors : 23052691      Online Users : 302
RC Version 7.0 © Powered By DSPACE, MIT. Enhanced by NTU Library IR team.
Scope Tips:
  • please add "double quotation mark" for query phrases to get precise results
  • please goto advance search for comprehansive author search
  • Adv. Search
    HomeLoginUploadHelpAboutAdminister Goto mobile version

    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/27433

    Title: An investigation of 19.5 GHz sky noise temperature over Taiwan area
    Authors: Chu,YH;Shih,SP
    Contributors: 太空科學研究所
    Date: 1999
    Issue Date: 2010-06-29 18:38:24 (UTC+8)
    Publisher: 中央大學
    Abstract: A number of ground-based instruments, including 19.5 GHz radiometer, optical raingauge, portable weather station, and high resolution disdrometer, were set up to conduct the Ka band propagation experiment of the Experimental Communication Payload (ECP) for ROCSAT-1. In this article, 19.5 GHz background sky noise temperatures measured at Chung-Li and Tainan sites are presented and investigated. Long-term statistics of the 19.5 GHz background sky noise temperature observed by a vertically pointed radiometer in precipitation-free condition over the Taiwan area shows that the percentages of time that the sky noise temperature exceeds 20 K, 30 K, 40 K and 50 K are, respectively, 98%, 85%, 53%, and 27%. However, in precipitating environments, statistics shows that the percentage of time that the sky noise temperature exceeds 55 K, 100 K, 150 K, and 200 K are, respectively, 22%, 13%, 4.5%, and 2%. The statistics of sky noise temperatures observed at different zenith angles under environments without precipitation is also made. The results show that 80% of the observed sky noise temperatures at zenith angles of 100, 300, 500 and 70 degrees are, respectively, in the ranges of 92 - 180 K, 39 - 52 K, 26 - 33 K, and 21 - 27 K. In addition, a comparison between surface rainfall rate recorded by the optical raingauge and sky noise temperature measured by 19.5 GHz radiometer shows that the former lags behind the latter by about 5 minutes, implying non-uniform and inhomogeneous distribution of precipitation in the air. In order to measure the precipitation aloft, the Chung-Li VHF radar was operated simultaneously. Champaign observation shows that there is no latency between sky noise temperature and VHF backscatter from precipitation. This result implies that the VHF backscatter from precipitation can be employed to validate the observed sky noise temperature. In addition, we also find that the sky noise temperature may be as high as 155 K (corresponding to 3.6 dB attenuation) under an environment without surface precipitation. This feature is attributed to the dense water vapor and heavy cloud.
    Appears in Collections:[太空科學研究所 ] 期刊論文

    Files in This Item:

    File Description SizeFormat

    All items in NCUIR are protected by copyright, with all rights reserved.

    社群 sharing

    ::: Copyright National Central University. | 國立中央大學圖書館版權所有 | 收藏本站 | 設為首頁 | 最佳瀏覽畫面: 1024*768 | 建站日期:8-24-2009 :::
    DSpace Software Copyright © 2002-2004  MIT &  Hewlett-Packard  /   Enhanced by   NTU Library IR team Copyright ©   - Feedback  - 隱私權政策聲明