Using Multiple Doppler Radars to Retrieve Typhonic Wind Field

• Main Authors: Yueh-Hsin Liu, 劉岳欣
• Other Authors: 李天浩
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/69790157661781365352

碩士 === 國立臺灣大學 === 土木工程學研究所 === 94 === The GBVTD(Ground-Based Velocity Track Display) technique is the most popular algorithm of single-Doppler retrieval in view of the typhoon. However, it is restricted in a certain part of single-Doppler observation area. Moreover, the algorithm cannot obtain the azimuthal mean-flow and some asymmetric structure wind, so that the analytical wind field is simplified. To estimate tropical cyclone rainfall, there are still some problem with the GBVTD technique and can be improved. On the other hand, the MANDOP (Multiple ANalytical DOPpler) analysis uses multi-Doppler radars to retrieve 3-dimensional wind field. Besides, there is a specific MANDOP analysis with cylindrical coordinate, designed for typhoon circulation system, but it takes too long time to calculate the completed analysis. In order to do real-time forecasting, we have to take some simplification to the MANDOP analysis. This research combines the GBVTD and the MANDOP method, and takes some advantages of both to retrieve horizontal wind field, and make the result can be applied to real-time rainfall forecast model. In the performance of typhoon wind field, a common polar coordinated system is used, and multi-Doppler radar data is sorted by the distance to cyclone center and calculating ring by ring. The horizontal wind is divided into two orthogonal components by tangent and radial direction, then expanded by Fourier series. Finally, by solving Fourier coefficient of tangent and radial wind, we can obtain the analytical wind field.