溪頭地區霧分布特性初探

Preliminary Studies on Fog Characteristics at Xitou Region of Central Taiwan

魏聰輝(Tsong-Huei Wey) ； 賴彥任(Yen-Jen Lai) ； 張振生(Cheng-Sheng Chang) ； 沈介文(Chien-Wen Shen) ； 洪志遠(Chi-Yuan Hong) ； 王亞男(Ya-Nang Wang) ； 陳明杰(Ming-Chieh Chen)

《國立臺灣大學生物資源暨農學院實驗林研究報告》 25卷2期 (2011/06) Pp. 149-160

https://doi.org/10.6542/EFNTU.201106_25(2).0006

摘要

本研究首先在溪頭農業氣象站設置三只Decagon Device Inc.（Washington State, USA）所產製葉濕感應器，其中兩只以豎立式、上方遮蔽方式安裝，一只以裸露而水平式安裝；遮蔽式、裸露式各一只連結於EM50型記錄器，另一只遮蔽式連結於CR10x記錄器。不同型號記錄器觀測結果顯示，兩型記錄器所獲致觀測值隨著霧之發生而震盪得相當一致，相關性分析呈現正相關，r^2為0.9494，回歸式為y = 0.1472x - 64.748；相關研究或測站，可依據此回歸式推廣至已設置Campbell系列記錄器之測站選擇應用。葉濕感應器可有效偵測大氣水分狀態，唯應將感應器採取豎立式安裝，並在上方遮蔽方式施行觀測，方可排除垂直向降水之影響，以符合偵測霧之發生頻率與時間的研究目的。本研究另於觀景平臺安裝一只自動相機，依據相機所拍攝影像判讀霧之發生與消散時間，進而統計成霧總時數、霧日；結果為溪頭地區在此一年間成霧總時數為2,009.8小時、霧日為292日，成霧頻率平均為每日6.8小時。其中能見度小於500 m濃霧的成霧時間為1,405.3小時、霧日為276日，成霧頻率平均為每日4.9小時。依據霧之發生頻率、時間與消散時刻之分布特性，推判溪頭地區霧之種類為升坡霧。

關鍵字

葉濕感應器 ； 光學能見度感應器 ； 成霧時間 ； 霧日 ； 升坡霧 ； 溪頭

並列摘要

This research aims to explore fog characteristics at Xitou. To investigate the frequency of the fog occurrence, three Leaf Wetness Sensors (LWS) are set up at Agricultural Weather Station, Xitou. Two LWSs are shielded to exclude precipitation and frost, and the third one exposes in the open-air. A shielded LWS is connected with CR10x data logger and the other two LWSs are linked to EM50 data logger. The results show that two types of data logger has a significant relationship (r^2 = 0.9494, y = 0.1472x - 64.748) on recording vibration of fog occurrence. This relationship can further apply to similar studies as well as the use of CR10 series data logger in weather stations. The LWS is sensitive enough to detect miniscule amount of moisture in the air. However, authors recommend using shielded approach to exclude vertical precipitation and dew on measuring fog duration and frequency. Additionally, an automatic camera is also installed on sightseeing platform to determine the time of fog occurrence and dissipation. The cumulative hours of fog occurrence are 2,009.8 hours per year (22.94% of the annual hours), and the days of fog occurrence are 292 days per year (75.62% of the annual days). The average frequency of fog occurrence is 6.8 hours per day. In which, the occurrence time of dense fog with the visibility less than 500 m is 1,405.3 hours per year and 276 days per year respectively. The average time of occurring frequency of dense fog is 4.9 hours per day. From these indicators, the dominant fog type in Xitou is ”Upslope Fog.”

並列關鍵字

Leaf Wetness Sensor (LWS) ； Optical Fog Sensor (OFS) ； fog occurring duration ； fog days ； upslope fog ； Xitou Region