• 作者： 朱延祥; 張育銘; 張用穎; 宋俊賢; 莊文治; 林文暉
• 作者服務機構： 中央大學太空科學研究所
• 中文摘要： 利用中壢特高頻雷達進行中氣層之觀測已有多年的歷史。基本上，產生雷達回波之中氣層目標物為背景大氣中的自由電子濃度的紊亂擾動，以及流星離子尾。藉著分析中氣層的雷達回波，一些重要的中氣層參數，例如中氣層之水平風速、高密度流星尾之線電子濃度、和中氣層擴散係數等，均可因此而被測得。在本文中，除了介紹在中壢特高頻雷達上所發展出之中氣層觀測技術之外，並將對於利用中壢雷達觀測中氣層水平風場及擴散係數的結果提出說明。對中氣層風場之個案分析結果顯示，在1988年4月19日下午兩點26分到兩點33分之72公里高度之水平風速為11.2 m/s，其風向為自東北以52度的方向朝西南吹。藉著理論湊配低濃度流星尾回波訊號的動作，中氣層擴散係數亦可測得。結果顯示中氣層擴散係數之數值大都位在0.5 ㎡/s到7 ㎡/s之間，並且以指數型的方式隨高度之增加而增大，其數學關係式可用In D=0.048×Z-4.389描述。中壢雷達所得到的結果與國外其他雷達觀測的結果相當吻合。
• 英文摘要： Mesospheric observations made by using Chung-Li VHF radar have been conducted for many years.The targets which are responsible for the mesospheric radar returns are the turbulent fluctuations of freeelectron density embedded in the background atmosphere and the ionized trail of a meteor. By analyzingthe radar returns from these targets, several important mesospheric parameters, such as mesospherichorizontal wind velocity, electron line density of the overdense meteor trail and the mesospheric diffusivecoefficient, can be measured. In this paper, the radar techniques developed on Chung-Li VHF radar formesospheric observations are introduced. The observed mesospheric wind velocity and diffusive coefficientare also presented By analyzing the intermittent radar returns from electron density fluctuations, themesospheric horizontal wind was measured. The case study shows that a mesospheric wind with a speedof 11.2 m/s from the direction of 52° east of north was observed. By best fitting a theoretical curve tothe observed fading pattern of the echo signals for underdense meteor trail, the mesospheric diffusivecoefficient could be estimated. It is shown that the mesospheric diffusive coefficient is within 0.5 ㎡/s～7㎡/s and increases exponentially with height, following the empirical regression line In D=0.048×Z-4.389. Our results are in good agreement with those obtained by other radars.
• 中文關鍵字： mesosphere; meteor trail; line electron density; diffusive coefficient
• 英文關鍵字： --