利用GPS訊號反演對流層天頂向濕延遲量之研究

Study on the zenith wet delay of troposphere measured by GPS technology

簡士詠(Shih-Yung Chine)

指導教授 ： 葉大綱

共同指導教授 ： 陳春盛

健行科技大學/研究學院/空間資訊與防災科技研究所/碩士(2009年)

https://doi.org/10.6824/UCH.2009.00032

摘要

台灣是個海島型氣候的國家，天氣變化相當豐富，雖然現今氣象科技相當進步，但有時還是不是很準確，本研究利用GPS信號來反演對流層天頂向的濕延遲量，觀察天頂向濕延遲量與降雨量之間的關係，並用水氣微波輻射儀所觀測到的濕延遲量來驗證GPS訊號的濕延遲量是否有誤並觀察其關係，本研究利用國內15個衛星追蹤站及15氣象站相互配對，並針對梅雨季及雙颱兩個案例來做比較，希望可以對氣象方面有所幫助。在梅雨季及雙颱兩個案例發現到水氣微波輻射儀與Bernese 4.2所計算出來的天頂向延遲量趨勢非常一致，其相關系數很高，但都會有數公分的平均偏差，而且大部分降雨來時濕延遲量會明顯的升高，當晴天時延遲量會變低，但有時有明顯的降雨濕延遲量卻明顯的下降，其原因可能對流層的的水氣凝結成雨滴掉落至地面，使對流層水氣含量變少所致。本研究初步發現其實降雨量與濕延遲量並沒有絕對關係，高的延遲量不ㄧ定會產生降雨，因為影響降雨的因素有很多，大氣中的含水量只是降雨因素的其中之ㄧ；未來在比對GPS、水氣微波輻射儀與降水關係時，於個案選擇上必須更為小心，選擇弱綜觀環境之個案可能較為妥當。

關鍵字

全球定位系統 ； 水氣微波輻射儀 ； 對流層 ； 濕延遲 ； 降雨量

並列摘要

In order to determine the accuracy of the atmospheric precipitable water vapor derived from ground-based GPS data, projected measurements were made and compared against the reference data collected from corresponding weather stations and Water Vapor Radiometer (WVR) stations. As to ensure that comparable data were obtained, the distance between GPS stations and its corresponding weather stations were no more than 20 km apart. In total, 15 such pairings were employed. Periods of significant rainfall were preferred for this study. Thus, the GPS and the hourly rainfall records from the Central Weather Bureau (CWB) in Taiwan for the months of June and August 2006 were utilized. Moreover, the WVR observations measured at the Yangmingshan (northern Taiwan) and Beigang (western Taiwan) were collected to validate the precipitable water vapor estimates derived from ground-based GPS data. The Zenith Wet Delay (ZWD) of each station was calculated using Bernese 4.2 software. The data was processed relative to the TSKB station (Japan) to avoid the high correlation within the atmosphere and to eliminate systematic errors. The ZWD derived from GPS matched with the measurements of the WVR, with a slight offset by about 5 mm. Furthermore, it is observed that significant rainfall often results in a large decrease in the calculated ZWD. In the future, the upgrade of the data processing algorithm and the study of the relationships between ZWD and rainfall are our next efforts.

並列關鍵字

GPS ； WVR ； troposphere ； zenith wet delay ； precipitable water vapor

參考文獻

1. 鄧忠民，1998。利用全球定位系統估算大氣濕延遲量，國立中央大學太空科學研究所碩士論文。

2. 蔡亦證，2005。近即時估計台灣GPS追蹤站網之對流層延遲效應，國立宜 蘭大學土木工程學系碩士論文。

3. 李佳霖，1994。網路RTK定位精度模擬分析，逢甲大學土地管理學系碩士論文 。

4. 劉基余、李征航、王躍虎、桑吉章，1993。全球定位系統原理與其應用，測繪出本社，北京。

5. 儲慶美，1995。全球定位系統之原理與應用。第23屆國軍軍事著作金像獎著作，11月。