English  |  正體中文  |  简体中文  |  Items with full text/Total items : 67621/67621 (100%)
Visitors : 23029369      Online Users : 351
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/987654321/27408


    Title: Negative correlation between terminal velocity and VHF radar reflectivity: observation and plausible explanation
    Authors: Su,CL;Chu,YH;Lo,IY
    Contributors: 太空科學研究所
    Keywords: RAINDROP SIZE DISTRIBUTION;DOPPLER RADAR;PRECIPITATION;BACKSCATTER;THUNDERSTORM;FREQUENCY;AIR
    Date: 2009
    Issue Date: 2010-06-29 18:37:50 (UTC+8)
    Publisher: 中央大學
    Abstract: The correlation between precipitation backscatter P (or radar reflectivity Z) and reflectivity-weighted terminal velocity V-t has long been thought to be positive. Namely, the larger the magnitude of the terminal velocity is, the stronger the radar reflectivity will be, and vice versa. However, we will show in this article the observational evidences of negative V-t-P correlation made with the Chung-Li VHF radar. It is found that the negative V-t-P correlation can occur in the regions from close to ground to well above the melting layer. In addition, there is a strong tendency for the negative V-t-P correlation to occur around the bright band region. In light of the fact that the conventional model of single drop size distribution cannot explain this negative correlation, it is proposed that the drop size distribution responsible for the negative V-t-Z correlation is composed of two Gamma drop size distributions with respective mean terminal velocities and radar reflectivities. The precipitation particles of these two distributions are assumed to dynamically interact in the way that the total numbers of the precipitation particles of the two Gamma distributions are varied and their reflectivities are also changed accordingly. Theoretical analysis shows that the key factor determining the sign of the V-t-Z correlation is the ratio of the difference between relative changes in the reflectivities of the two Gamma drop size distributions to the change in the total reflectivity. The V-t-Z correlation is negative (or positive) if the ratio is positive (or negative). From these results, it follows that the V-t-Z correlation could be considered to be the result of the redistribution of the radar reflectivies of the two Gamma drop size distributions caused by the interaction of the precipitation particles between them. Different interaction processes of the precipitation particles, such as break-up and coalescence, could give rise to the same V-t-Z correlation, depending on the net change in the total reflectivity. In addition, the results also show that the same interaction process might give opposite V-t-Z correlations. Therefore, great caution is advised when the V-t-Z correlation is employed to interpret the precipitation process.
    Relation: ANNALES GEOPHYSICAE
    Appears in Collections:[太空科學研究所 ] 期刊論文

    Files in This Item:

    File Description SizeFormat
    index.html0KbHTML255View/Open


    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