利用中壢VHF雷達測量大氣垂直速度並分析大氣結構之初步研究－個案分析

A Preliminary Study of the Measurement of Atmospheric Vertical Wind Speed and Its Fine Structure by Chung-Li VHF Radar-Case Study

朱延祥(Yen-Hryang Chu)

《大氣科學》 14卷1期 (1986/09) Pp. 91-102

摘要

中壢特高頻雷達已於民國74年5月正式建造完成。經多次的測試及改良，本雷達目前正順利的運轉中。本研究係分析民國74年6月2日0629 LT到0705 LT以垂直向發射及接收的雷達回波訊號，分別利用都卜勒頻譜法及自相關相位法，來計算大氣的垂直運動速度，並比較二者的差異。結果發現當訊號雜訊比大峙，二者所算出的風速幾乎完全一致，但當訊號雜訊比小時，自相關相位法所求出的風速值，則較都卜勒頻譜法合理。同時由垂直風速的時間序列中亦可明顯的看出大氣重力波的存在及其傳播的情形。此外，本研究亦根據雷達回波的統計特性，來探討回波的可能機制。大致而言，在本次觀測中，對流層的高層（8－10公里）及低層（3－5公里）的回波，呈明顯的反射特性，而中層（5－8公里）的回波特性則以散射為主。此次個案分析研究，由於缺乏微觀之大氣結構探空資料，故無法於觀測資料中，驗證分析所得。未來研究將運用此次經驗，配合實際觀測，探討台灣上空大氣結構。

並列摘要

The Chung-Li VHF radar was set up in May 1985. After testing and modification, this equipment is now operating normally, In this research, the radar returns of vertical beam observed during 2 June 0629 LT ~ 0705 LT 1985 were analyzed. By using Doppler spectral method and autocorrelation phase method, the vertical wind velocity were calculated respectively. The results show that the verticle wind speeds are fluctuated very seriously, but the mean values are small. The values calculated from autocorrelation phase method are more reasonable than those from Doppler spectral method. From the height-time plot of vertical wind fluctuation, the internal gravity waves can be detected easily. Based on the statistical properties of radar returns, the echo mechanism were also discussed It can be concluded that echo mechanism at upper (7 Km to 10 Km) and Lower (3 Km to 5 Km) trosphere is dominated by partial reflection and turbulent scattering is the major echoes mechanism of middle (5 Km to 7 Km) troposphere.Due to the lack of the sounding data, the verification of the current research result can not be performed. In the future, the VHF radar data will be combined with the atmospheric observation data to analyze the atmospheric structure above the Taiwan island.