地球科學系(含 海洋環境科技研究所)
Permanent URI for this communityhttp://rportal.lib.ntnu.edu.tw/handle/20.500.12235/59
本系設立的宗旨,首在養成學生具備地球科學五大學術領域–地質學、大氣科學、海洋科學、天文學和地球物理–充分之本職學能;本系的教育目標,則首重致力培養有志從事地球科學之專精人才,以培育優秀之地球科學研究人才和實務工作的專業人才為主軸,並以培養優良的中學地球科學師資為輔。特別是在國內各地球科學相關系所中,本系是唯一同時涵蓋五大地球科學研究領域,並擁有師範大學在科學教育專業基礎的高等學術機構,此為本系之特色。若志在從事中等學校地科教學,本系亦可提供地科教學知能和教育專業知識,充分培育健全之地球科學師資。
在課程上,為營造更優質的學習與研究環境,本系已適度調整原以師資培育目標為主的舊有課程架構,整合各地球科學次領域之基礎課程,降低本系必、選修課程之比例,大幅減少各次領域之必修課程學分,以增加學生在各次領域課程選修之自由度及彈性,進而充分落實各次領域之專業進階課程。此外本系並積極鼓勵學生,實際參與實驗、撰寫論文、從事專題計畫研究等,以豐富其研究經驗,訓練學生使其具備獨立研究之精神與能力。經由選修本系提供之更多進階專業課程,進而厚植學生之理論基礎、充實其專業背景,並強化其選定目標次領域之學術養成和專業訓練;連同充足的研究經驗,本系學生的未來發展,將更具時代性與面對挑戰時的競爭力,進一步達到「博而精、廣而深」的終極目標。近來本系更積極增聘優秀外籍專任師資,以全英語教學方式授課,期能增加學生之國際觀與國際競爭力。
本系在碩、博士班研究所的教育上,採一系多所之架構,除地球科學研究所外,還包括海洋環境科技研究所。本系研究所的研究重點與發展方向,首在地球科學各領域之深耕與研究發展,並加強各次領域間之跨學門合作,以進一步提升本系之學術研究及國際化,並為本系學生的訓練和學習,提供全面全方位的考量,以訓練學生從容面對多變的世界,因應未來的挑戰。
News
Browse
Search Results
Item 南海與呂宋海峽渦漩動力之研究(2009) 許瑋真Satellite observations have shown the abundance of generally westward-propagating eddies in the subtropical regions in the North Pacific Ocean, especially north of 10°N. Eddies transport mass, and can significantly impact the circulation as well as the heat, salt and nutrient balances of the western Pacific marginal seas. This study uses a numerical model to examine the conditions when eddies can or cannot freely propagate westward through the Luzon Strait into the South China Sea (SCS). Composite analyses on the 10-year model data show that the fates of eddies depend on the strength and path of the Kuroshio. In one path which exists mostly during fall and winter, the Kuroshio loops westward into the SCS, the potential vorticity (PV) across the current is weak, and eddies are likely to propagate freely through the Luzon Strait. In another path which exists mostly during spring and summer, the Kuroshio tends to leap directly northward bypassing the SCS, the PV across it strengthens, and eddies are then blocked and are constrained to also follow the northward path. Nonlinear eddy-current interaction and the existence of a cyclone north of the Luzon Island during the looping phase explain why eddies of both signs can pass through the strait. It is shown also that the upstream state of the Kuroshio in the western tropical Pacific plays an important role in dictating the different paths of the Kuroshio. The looping (leaping) path is caused by a weakened (stronger) Kuroshio transport related to the northward (southward) shift of the North Equatorial Current in wintertime (summertime). During El Niño/Southern Oscillation (ENSO) events, the Kuroshio weakens and a large portion of the Philippine Sea water passes through the Luzon Strait. The intensity of the Kuroshio is capable of influencing the seasonal upwelling in the SCS. Seasonal upwelling events along the east coast of Vietnam and west coast of Luzon have been demonstrated by satellite data. In a normal year, a strong eastward jet is associated with the cooling and upwelling off Vietnam. Strong ENSO events have been recorded in the years 1997 and 1998: the satellite data clearly show a vigorous upwelling off Vietnam in August 1997, but a wan one in August 1998. Abnormal warming interrupts the normal upwelling generated off Vietnam and Luzon. Two defined indicators of sea surface temperature anomaly (SSTA), the upwelling off the coast of East Vietnam in summer and off the coast of west Luzon Island, reveal seasonal upwelling activities. Both these upwellings appear in normal years, but they diminish during the active warming period. The seasonal upwelling dynamics is dependent on ENSO and is also coherent with the South Eastern Tropical Indian Ocean (SETIO). The intensity of prevailing monsoon varies the proportion of the response to oceanic circulation and heat content, that is, weak monsoons do not promote water in vertical motion and less heat is released. The ocean heat content anomaly (OHCA) indicates whether the budgets for both the ascending and descending heat content are initiated at the western boundary. Although the OHCA in conjunction with the vortex has not been directly reported, the results of model dynamics studies are favorably comparable with the satellite data. Large-scale Indian-Pacific Ocean meteorological variations have certain strong impacts on the SCS. The teleconnection between ocean and atmosphere shows that the seasonal upwelling is controlled by the complex interplay between the internal and external sea-air interacting processes. The regional monsoon system changes rapidly in response to oceanic variations. The weak wind stress curl during the evolution of the La Niña cycle of 1998 affects the atmosphere-ocean coupling and hampers the generation of the upwelling. Variations in both the large-scale air-sea interaction and the strength of the Kuroshio transport impact (1) the generation of vortices over the SCS and (2) the path of movement vortices in the Luzon Strait.Item 台灣周邊海域海流之數值研究(2008) 辛宜佳; Yi-Chia HsinA multiple grid-size nesting ocean model system is developed in this work to perform studies on the variations of the flow in the Taiwan Strait and the Kuroshio east of Taiwan. The transport in the Taiwan Strait is studied using the East Asian Marginal Seas (EAMS) model. Three model experiments using different wind data sets (ERA40, NCEP Reanalysis version 2, and QuikSCAT/NCEP blend wind) were performed. Model experiments suggested that the best simulation is achieved when the model is driven by the QuikSCAT/NCEP blend wind forcing. Involving the strong wintertime southward flow events in the Taiwan Strait, the annual averaged modeled transports through the Taiwan Strait is 1.09 Sv (1 Sv=106 m3/s). The result suggests that shipboard Acoustic Doppler Current Profiler (sb-ADCP) observations are biased toward estimates in summer and fair weather since bad weather during the winter northeast monsoon often prevents seagoing observations. Linear regression lines are also proposed to give simple relations between transport and wind stress for roughly evaluating the transport through a known wind stress value. The spatial and temporal variations of the Kuroshio east of Taiwan are investigated using model outputs, surface drifter trajectories, satellite-based altimetric data, and wind data. From the simulation of the EAMS model over a span of 24 years from 1982 to 2005, the variability of the Kuroshio east of Taiwan is studied in detail. Between 22 and 25°N, the mean state and variability of the Kuroshio, such as the two paths observed in the trajectories of surface drifters southeast of Taiwan and the branching of the Kuroshio northeast of Taiwan, are well reproduced by the model. Southeast of Taiwan, the Kuroshio is mostly in the top 300 m in the inshore path but extends to 600 m in the offshore path. Northeast of Taiwan, the Kuroshio follows the shelf edge in the East China Sea, but sometimes branches along a path south of the Ryukyu Islands. The latter path often meanders southward, and a significant portion of the Kuroshio transport may be diverted to this path. The Kuroshio extends from the coast to 123°E ~ 123.5°E between 22°N ~ 25°N with currents reaching a depth of 1000 m at some latitudes. The Kuroshio transports averaged over five sections east of Taiwan are 28.4 ± 5.0 Sv and 32.7 ± 4.4 Sv with and without the contribution from the countercurrent, respectively. Using satellite data and the Seas Around Taiwan (SAT) model simulation, the intra-seasonal variation of the Kuroshio southeast of Taiwan is further studied. Superimposed with the main stream of the Kuroshio, two intra-seasonal signals longer than 2 weeks are revealed in the study region, 20 ~ 30 days and 40 ~ 90 days. The variation of 20 ~ 30 days is only significant between Taiwan and the Lan-Yu Island. Amechanism is proposed to describe how the wind stress curl in the northeastern South China Sea modulates the circulation southeast of Taiwan on this timescale. The fluctuation with a longer period of 40 ~ 90 days is resulted from the westward propagating eddies.Item 台灣北部夏季午後降雨機制與地形影響之探討(2010) 歐安祥為了瞭解夏季台灣北部午後降雨機制,本研究以WRF Model針對2008年夏季午後降雨個案進行數值模擬,共挑選3個午後強降雨個案進行天氣分析,分別為2008年6月28日、8月17日以及8月23日。研究結果顯示,數值模式可掌握北部區域午後對流胞的生成、移動到消散之環境動力與熱力機制,且發現夏季對流系統發展受北部地形影響明顯,包括環境風場與地形輻合作用、淡水和基隆河口於白天海風的建立、午後雪山山脈西側下坡風的發展,以及台北盆地日間之增溫效應等。 利用模擬氣流線變化,發現上游氣流遇中央山脈南端地形分流角度不同,於台灣北部海域合流位置也有所不同,於台灣西南海域之氣流越接近南-北走向,下游合流區越靠近台灣北方海域,若西南海域風場之西風分量較多,合流位置則較靠近宜蘭東方海域,綜觀環境流場與合流區位置不同,將影響台灣北部風場結構,進而改變對流激發型態與發展趨勢。模擬近地面風場受地形影響之強輻合帶比較,發現對流發展期近地面輻合帶位置各不相同,隨後對流發展與此時輻合帶位置有密切關係。 發現上午盆地加熱率增加,建立平原往盆地之風場,對於盆地風場變化扮演重要角色。由對流垂直結構分析,發現對流胞內有強盛上升氣流,且中層有水平強風區存在時,環流風場隨高度向水平風下游方向傾斜,並將部分雨滴帶到雲區下游,使降雨範圍延伸較廣。而海風環流與山風界面於模擬中有一鋒區存在,依空氣性質差異,區分為淡水河口至雪山山脈切面的山風鋒區,與台北盆地至基隆河口切面的海風鋒區,鋒區上方垂直速度較強,並於近地面伴隨強輻合區,因此強對流胞多發生於鋒區位置。Item 奈格颱風引起遠距降雨之個案研究(2014) 林士然; LIN SHIH-JAN秋颱奈格(Nalgae)於2011年10月1日至3日間影響臺灣,颱風中心距離臺灣甚遠,但臺灣東北部地區降下超大豪雨,排汛不及造成水災。本研究利用WRF模式模擬,藉以分析臺灣東北部劇烈降雨成因、測試颱風存在與否對環境氣流及水氣傳輸的影響,並改變臺灣地形高度進行敏感度實驗,此外,亦選取同年份相似路徑之納莎(Neseat)颱風做環境場之對照比較,討論環境場與臺灣地區降雨的關聯。 模擬結果顯示,臺灣東半部發生強降水可分為兩個時期,第一為颱風環流與來自太平洋的東風輻合後形成對流,對流隨氣流方向進入臺灣陸地,在迎風面降下豪雨;第二為颱風東側的南風環流與東風氣流匯合後,兩者北偏與乾冷之東北季風輻合,發展出旺盛對流,加以宜蘭地區的地形效應,使該處出現劇烈降水。另外,若將颱風移除,臺灣南側暖溼氣流北送的情勢減弱,使累積雨量降低、降水區域改變。而將奈格颱風與納莎颱風的環境場相互對照後發現,東北季風對於東北部出現超大豪雨有重要貢獻。 歸納上述結果,本個案造成臺灣出現遠距降水之原因有:(1)颱風環流將南邊的暖濕水氣北送。(2)南來的暖溼氣流與乾冷的東北季風交會提供對流發展之有利條件。(3)對流系統移入時,受到地形抬升而增強。(4)宜蘭地區之地形利於氣流匯集,輻合現象顯著。Item 蘇迪勒颱風(2015)之數值模擬與研究(2017) 張君瑋; Chang, Chun-Wei摘要 臺灣夏季常受到颱風侵襲,因中央山脈地勢高聳,地形因素使颱風路徑預報困難。本研究以蘇迪勒颱風(2015)進行個案研究,利用WRF模式針對蘇迪勒颱風進行數值模擬實驗,同時也使用Nguyen and Chen(2011)的颱風初始化模組(簡稱NC2011)進行模擬測試,改善颱風初始結構偏弱的狀態,並針對模擬結果進行分析。 研究結果指出NC2011方法可以加強颱風初始強度,在模式初期不論是颱風(CTL組)的水平結構和垂直結構均較未經過初始化的颱風(NCI組)完整,使颱風整體結構更接近真實颱風,且渦漩結構在海上可以維持一段時間。 本研究也針對地形高度進行敏感度測試,在颱風結構的方面,發現當地形越高,颱風環流受到破壞的程度較嚴重,出海後的中心氣壓也較高;而地形越低,颱風環流受到破壞的程度較小,出海後的中心氣壓相對較低。在颱風路徑方面,當颱風強度越強、結構越深,駛流對路徑造成的效應大於通道效應,使颱風在登陸後路徑南偏;當地形加高,通道效應大於駛流對路徑造成的效應,使颱風在登陸前路徑南偏。Item 季內振盪對颱風伴隨西南氣流之影響(2017) 陳怡秀; Chen, Jennifer摘要 颱風離臺後所伴隨的西南氣流,往往同時伴隨長時間的強降雨,有時甚至比颱風本身造成之降雨更為劇烈。然而並非所有颱風個案皆與西南氣流共伴,為瞭解大尺度環境(包括MJO、QBWO等季內振盪)是否在其中扮演重要角色,本研究選取發生西南氣流共伴之颱風個案,如敏督利(2004)、卡玫基(2008)、鳳凰(2008)、莫拉克(2009)、潭美(2013),使用WRF模式模擬,並進行系集平均分析。 移除MJO環流後對颱風駛流的改變並不顯著,但臺灣海峽附近之西風、水氣量、水氣通量的輻合均變小,使西南氣流降雨減少。而QBWO對伴隨西南氣流颱風個案最顯著之影響在於路徑與駛流,當移除QBWO後,使颱風路徑改變,颱風環流與南海的豐沛水氣無法互相連結,且西南風不足的情況下無法將對流雨帶推往陸地;亦或是颱風路徑大幅偏離,導致颱風中心遠離臺灣,皆致使大量降雨發生於海面上。而路徑差異較小之個案,移除QBWO後的模擬結果在臺灣海峽之西南氣流強度明顯不如移除MJO之結果,故臺灣西南方的共伴降雨大幅減少。以中尺度之觀點分析,QBWO對颱風伴隨西南氣流的影響明顯大於MJO。歸納上述,季內振盪改變亞洲與西北太平洋地區大尺度環境場,產生有利颱風伴隨西南氣流之條件,進而使共伴降雨增強。關鍵字:颱風,季內振盪,西南氣流,數值模擬Item 不同氣候情境對長江流域暖季東移雨帶的影響與評估(2016) 張鳳茹; Chang, Feng-Ru觀測資料顯示,5月至7月在青藏高原東部產生的降雨,常有沿長江流域(29°N–34°N, 100°E–120°E) 向東邊傳播的現象。針對此現象,本論文主要探討的議題有二。其一為利用Weather Research and Forecasting (WRF) 區域模式,對2009年5月的長江流域東移雨帶進行三種不同氣候條件下的模擬,以求瞭解氣候變遷對長江流域東移雨帶可能造成的影響。其二為探討在計算資源充足的情況下,如何有效提高WRF模式模擬長江流域東移雨帶個案的能力。 針對議題一,本論文的研究結果發現: (1) 在現今的氣候條件下(現代情境),WRF對長江流域東移雨帶的模擬結果與觀測資料相似; (2) 在加入過去氣候變異的情況下(過去情境),WRF模擬的東移雨帶個數明顯減少,東移距離明顯變短,降雨強度明顯變弱; (3) 在加入未來氣候變異的情況下(未來情境),WRF模擬的東移雨帶個數、東移距離與現代情境下的模擬結果無明顯差異,但降雨強度明顯增強。分析平均環流場的差異顯示,在過去情境下,高層西風的減弱會造成東移雨帶個數減少與東移距離變短,而水氣傳輸的減弱是造成降雨強度變弱的主因。在未來情境下,因為高層西風無明顯變化,所以東移雨帶個數與東移距離與現代情境下的模擬結果無明顯差異,而水氣傳輸的增強(減弱)會造成東移雨帶降雨強度變強(變弱)。針對議題二,本論文選用不同解析度、不同嵌套方式、不同積雲參數法及雲物理方案,對WRF模擬長江流域東移雨帶的能力進行敏感度測試。結果證明提高水平解析度最能夠顯著改善模擬長江流域東移雨帶的結果。在相同解析度的情況下,雙向嵌套優於單向嵌套。而使用不同的積雲參數法或雲物理方案,則對模擬結果無顯著影響。Item 台灣地形對冬季冷鋒個案影響之數值研究(2003) 林勝峰摘要 本文使用MM5模式針對1996年1月7日至9日的冬季冷鋒個案進行數值模擬,以探討台灣地形對冬季冷鋒之影響。該冷鋒呈東北東—西南西走向之淺鋒面結構,在1月7日2200UTC以後抵達台灣,導致溫度驟降,形成寒潮爆發。衛星雲圖及地面的觀測均顯示該鋒面受台灣地形阻擋,造成在東西部鋒面的強度及移動速度上出現差異。地面觀測顯示鋒面在西岸自梧棲以南逐漸減弱並且移速減慢,東部則較能維持原來之鋒面結構。鋒面出海後受到洋面之地表通量影響而產生變性,使鋒後低層呈現濕冷的環境,在抵達台灣之後受地形阻擋的抬昇作用影響,北部迎風面以及東部沿岸出現零星的降雨;而台灣西南部在鋒面通過期間並沒有雲冪及降雨現象的發生。 中尺度模式 MM5的模擬結果顯示,通過台灣東西部之鋒面受地形影響的機制並不相同。跨越大陸武夷山之鋒前氣流受台灣地形阻擋而轉為北風,造成台灣在西南部及海峽上鋒前北風提前增強的現象。其次,台灣西南部地表受日間輻射增溫的影響,使得鋒面之結構變得不顯著且移速減慢,但海峽處之鋒面則受管道效應影響而加速南移。在東部沿海由於冷空氣受地形阻擋而形成高壓脊,加強了花蓮沿海之非地轉北風的強度,並造成鋒面在蘇澳以南加速南移。 以台灣地形及地表通量為變因所進行的敏感度測試中,顯示在沒有中央山脈的阻擋下,通過台灣本島之鋒面結構較為完整。並且鋒後之風場並未出現受地形增強的現象,鋒面的移動速度則隨著鋒面南移而減慢。而在無地表通量的模擬中,鋒面的溫度梯度並未受到暖洋面的影響而減弱,因此在低層具有較強的壓力梯度與水平風切,顯示出較強且淺的鋒面結構。而鋒後更穩定之環境則減弱了對流的強度並使鋒後降水強度明顯減弱,可見地表通量在冬季冷鋒出海之後對鋒面結構之修正扮演極為重要的角色。