霧及水平降水之多重策略觀測

Abstract

本研究利用多重的觀測策略來針對雪霸國家公園觀霧遊憩區的雲霧量、滯留時間與季節變化以及水平降水的程度，進行定量上的觀測調查。首先，我們將針對觀霧地區1988~2007年的觀測資料進行分析，以期了解地區的氣象特徵。其次，我們利用自行設計的整合式「霧觀測與攔截裝置(FDID, Fog Detection and Interception Device)」在雪霸國家公園觀霧管理站進行實際的野外觀測，其中包括了兩款霧偵測器(RFD與OFD)、自動相機定時自動拍照(TLI)以及兩款霧水收集器(SFC與CFC)。同時，我們也利用能見度儀與自行研發的「霧風洞」進行FDID的校驗工作，用以評估FDID中各元件的表現能力。 研究結果顯示，FDID的確具有針對霧事件的發生、濃度及其造成之水平降水進行定量觀測的能力。自動相機的TLI方法，在135日觀測中偵測到114日曾有霧事件的發生，並利用RGB資料分析將霧事件區分輕、大、濃三種不同的程度。我們也由霧水收集器的資料估計觀霧地區的年水平降水量約可達到年雨量的20%。此外，藉由結合水平降水及風場資料，我們發現觀霧地區霧事件的平均液態水含量(LWC)為0.12g/m3，主要分布在0~0.05、0.05~0.1及0.15~0.2 g/m3的範圍。整體來說，霧事件發生之頻率、濃度及其造成之水平降水三者間的結果具有良好的一致性，因此本研究所提出的FDID為一經濟可行的霧事件觀測策略。

This study tried to quantify the fog and HP amount, its existence length and monthly variation at Kuan-Wu recreation area in Shei-Pa National Park. The 20-year (1988~2007) record length of meteorological data at Kuan-Wu was analyzed first to build up the background information of the local weather. Then, we have designed an integrated Fog Detection and Interception Device (FDID) and launched measurement from June of 2008. FDID includes two types of fog detectors (RFD and OFD), an constant time lapse image (TLI) from digital camera and two different fog collectors (SFC and CFC) for fog detection and HP quantification. All the components of FDID were validated by visibility meter in the field and a indoor self-build fog tunnel. The results show that some components of FDID present the capability on the fog event detection and could give quantitative amount of fog and HP. The digital images detected ~84% happening of fog event in 135 valid observation days. Through the further RGB diagnosis of digital images, the fog events can be distinguished into light, medium and heavy fog events. The estimation of HP from SFC is about ~20% of water amount compared with to the annual rainfall. Combining HP and wind field data, LWC is also estimated ~0.12g/m3 for average. In general, the result of fog frequency, HP and LWC of fog event provided by camera image, SFC and wind field data show good consistence in field observation. FDID could be one of the economical and workable solution for fog observation.