臺灣高山地區霧雨雪之水象特色

Abstract

本研究主要分析2012年~2016年雪山地區降雨、雲霧發生以及冬季降雪觀測資料，同時蒐集中央氣象局玉山北峰，海拔3,858公尺氣象資料，來瞭解臺灣南北兩大主峰水象因子的季節與年際差異程度；此外，本研究也在臺灣山區不同海拔進行雲霧攔截實驗，並透過個案分析來推估其相對於降水的貢獻程度。 分析結果發現臺灣高山地區雨量於春夏時期高於秋冬時期，以海拔3,180公尺的雪山三六九山莊為例，2012年至2016年研究期間五年平均雨量為3,046.5mm；春雨和梅雨季(3~6月)佔總平均雨量45.7%，夏季(7~10月)佔34.7%的雨量貢獻，秋冬季(11~2月)最少僅佔19.6%。然而在同一山區海拔3,593公尺的雪山圈谷，五年平均總雨量為1,408.3mm；夏季佔總平均雨量45%，其次是春雨和梅雨季佔40%，秋冬季最少僅佔15%。研究期間共歷經28次颱風，在三六九山莊SP3與圈谷SP1測站，由颱風所挾帶的平均雨量貢獻分別為690.7mm佔總平均雨量22.6%與407mm佔總平均雨量28.9%，由此可見颱風對於高山地區生態與水資源收支的貢獻不容小觑。 雲霧出現頻率的季節性變化與雨量因子雷同，仍是呈現春夏季節高於秋冬季節。研究期間雪山地區(白晝期間)平均總雲霧發生時數為1,844小時；季節性特徵是，春雨、梅雨季(3~6月)有731.8小時(40%)、夏季587.1小時(32%)、秋冬季518.8小時(28%)。綜合雪山山區雨水(垂直性降水)與雲霧(水平降水)季節變化特徵，顯示山區具有為春夏季(3~10月)多雨多霧，以及秋冬季(11~隔年2月)少雨少霧的乾溼差異特性。 至於臺灣南北兩大主峰(玉山北峰與雪山圈谷)降水量的差距，以2012年~2016年總累積降雨量（玉山2,970mm，雪山1,408.3mm)來說，玉山北峰高於雪山一倍以上；然而，雪季(12~4月)降雪量(延遲降水)卻是雪山高於玉山一倍以上(玉山242cm，雪山524cm)。 在不同海拔進行雲霧攔截實驗個案資料分析，顯示新北市雙溪泰平里的雲霧攔截收集率為65.9ml/m2/hour；苗栗三義地區雲霧收集率則為312.4ml/m2/hour；南投溪頭地區雲霧攔截收集率為48.4ml/m2/hour；至於雪山三六九山莊個案資料，顯示雨水加上雲霧水的總蒐集率可達49.9L/m2/hour，一場大霧可有310 ml/m2/hour，假設持續相同霧水濃度，則可有7.4 L/m2/day攔截量，因此雖然該地海拔已超過3,000公尺的高度，但是雲霧水攔截效率仍有全球各地霧水蒐集率(3~10L/m2/day)的中上數值。 本研究針對臺灣高山的垂直降水(降雨)、水平降水(雲霧)與延遲降水(降雪)三種水象因子進行初步觀測分析，期盼能引起國人與管理單位持續重視高山水文氣象資訊蒐集，以及在全球極端氣候威脅議題下，臺灣山區水資源管理上能有拋磚引玉的效果。

In this study we use our observing rainfall, cloud-fog and snowfall data at Shei-Shan from 2012 to 2016, and compare them with Yu-San (elevation 3858m) weather Station of Central Weather Bureau (CWB) to analyze the seasonal & annual difference of hydrological factors between these two summits at Taiwan. We also use some cases in our cloud-fog harvest experiments at different elevation in Taiwan to estimate the contribution of fog water supply related to rainfall. The results show that rainfall at Spring-Summer season is more than Autumn-Winter season. For example, rainfall at 369 Cabin (3180m elevation, called SP3) has 3046.5mm per year. Spring rainfall and Meiyu rainfall (March to June) cover 45.7%, Summer rainfall has 34.7% (July to October) and only 19.6% occurs during Autumn to Winter (November to February). Nevertheless, another higher site (Shei-Shan Cirque, elevation 3593m, called SP1) above 369 Cabin only has 1408.3mm per year with different seasonal ratio(Summer 45%，Spring-Meiyu 40%，Autumn-Winter 15%)。During our data analysis period, there are 28 typhoons passing Taiwan and Typhoon event could contribute 22.6 % (690.7mm at SP3) to 28.9% (407mm at SP1). It means typhoon event plays significant hydrological role at Shei-Shan region. The seasonal variation of cloud-fog frequency is similar to rainfall factor and which is higher at Spring-Summer and lower at Autumn-Winter. We found there is 1844 hours/year at daytime of SP3 site. 40% happens at Spring-Meiyu, 32% happens at summertime and 28% happens at Autumn-Winter. In summary, the rainfall (vertical precipitation) and the cloud-fog water (horizontal precipitation) provide the wet season (Marcj-Octoer) to dry season (November to February) exchange in Shei-Shan mountain region. The rainfall amount at Yu-Shan weather station for five years (2012~2016) is near double than Shei-Shan Cirque has (2970mm/year vs. 1408.3mm/year), but the snowfall amount only half oppositely (242cm/year vs. 524 cm/year). For the cloud-fog harvest experiments at different elevation sites in Taiwan, we got 65.9ml/m2/hour at Shuang-Xi (New Taipei City), 312.4ml/m2/hour at San-Yi (Maioli County) and 48.4ml/m2/hour at Xitou (Nantou County). The harvest rate including rainfall at 369 Carbin (SP3) gives 49.9L/m2/hour, and one dense fog with no rain could provides 310 ml/m2/hour. If we assume this fog intensity keep one-day and there will have 7.4 L/m2/day harvest amount which is the medium level around the world (3~10 L/m2/day). We have surveyed characteristics of three precipitation patterns (rainfall for vertical precipitation, cloud-fog for horizontal precipitation and snowfall for delayed precipitation) at Taiwan mountain region, and we expect this study could rise the attention on the continuous monitor on mountain hydrological measurement at Taiwan, and more studies on water resource management under the impact of global climate change.