臺灣東北部山地霧林每日霧水停滯時間之時空變異分析

Assessment of spatiotemporal dynamics of fog daily duration in montane cloud forests of northeast Taiwan

李欣儒(Hsin-Ju Li)

指導教授 ： 黃倬英

國立臺灣大學/理學院/地理環境資源學研究所/碩士(2020年)

https://doi.org/10.6342/NTU202001389

摘要

在全球陸域生態系中，14.2 %的熱帶雨林屬於熱帶山地霧林生態系，山地霧林為林分生長易受環境霧水影響的森林，霧林內霧水長期籠罩，其高濕度環境為許多特有種生物的棲息地，林分攔截之霧水也提供下游地區非常重要的水分來源。近年來，暖化造成溫度上升會改變霧林帶中的霧水時空分布，進而威脅到熱帶山地霧林的生長，因此，量化霧水有助於理解霧林在暖化的時空背景下如何產生變化機制。本研究目的為量化臺灣棲蘭山地區16,775公頃之山地霧林帶，每日的日間霧水停滯時間，本研究利用海拔1151–1810公尺之間的四個空曠地氣象站資料以及高時空解析度向日葵8號衛星圖做為分析資料，其中包含10分鐘解析度的地表與天空中之太陽輻射值比值，以及由現地收集之溫度、相對濕度運算露點溫度差值，作為霧水事件模型(the Fog Event Index)的指標，並使用現地收集之縮時攝影影像作為驗證資料，最終驗證本研究提出之霧水模型可達87%估測正確率。透過此模型可得棲蘭山地區核心的霧林帶很狹窄，主要分布於中海拔地區大約1514–1670公尺，而此主要核心霧林帶內之霧水停滯兩年總時數為其他霧林帶的3.9倍，霧水在秋冬之停滯時間多於春夏，其停滯模式多數為短時間(約1–2小時)停滯，在主要核心霧林帶內較常發生長時間(8小時以上)霧水停滯事件，本研究提出之霧水事件模型有助於估測高空間變異山區霧林之起霧情況。

關鍵字

棲蘭山 ； 露點溫度差 ； 海拔梯度 ； 向日葵8號 ； 相對濕度 ； 太陽輻射 ； 氣溫 ； 縮時攝影

並列摘要

Tropical montane cloud forests (TMCFs) are some of the most unique ecosystems in the terrestrial environments occupying about 14.2% of all tropical forests. Due to their frequent immersion of low altitude cloud (also known as fog) with high humidity, these zones are the major water sources for lowland environments and habitats for many species. Recent studies suggested that elevated temperatures may alter the spatiotemporal dynamics of fog, and cause cascading impacts on TMCFs. Therefore, quantify the occurrence of fog is necessary but rather challenging. This study aims to assess the daytime duration of fog in 16,775 ha TMCFs situated in Chilan Mountain in northeast Taiwan. We installed four open-sky meteorological stations along an elevation gradient of 1151–1810 m a.s.l. We developed a new metric, namely the Fog Event Index (FEI), which integrated the components of solar radiation and dew-point depression. Concurrent photosynthetically active radiation records from a field quantum sensor and Himawari-8 satellite data were required to derive the solar radiation component; in-situ air temperature and relative humidity data were utilized to calculated dew-point depression. The performance of the FEI was satisfactory (87% of accuracy) by comparing with ground truth data recorded by a time-lapse video.

並列關鍵字

Chilan Mountain ； dew point depression ； elevation gradient ； Himawari-8 ； relative humidity ； solar radiation ； temperature ； time-lapse video

參考文獻

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