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[地球物理] 臺大熱帶氣旋研究獲美國太空總署專題報導
[地球物理] 臺大熱帶氣旋研究或美國太空總署專題報導
臺大大氣系林依依副教授與其合作伙伴於今年（2009）二月發表在國際期刊《Geophysical Research Letters》的最新研究成果〈Warm Ocean Anomaly, Air Sea Fluxes, and the Rapid Intensification of Tropical Cyclone Nargis (2008)〉,獲得美國太空總署 NASA （2009）年二月二十六日的新聞稿中重點介紹（featured as top story）。
此研究是關於去年造成最大災情的印度洋熱帶氣旋 Nargis。在2008年5月 Nargis 氣旋造成緬甸超過13萬人死亡的災情，為近年來全球最大的天然災害之一。林依依副教授等人研究發現在 Nargis 即將登陸的24小時之內，Nargis 氣旋突然由輕度氣旋增強為強烈氣旋，並且在強度最強的時候登陸，這是重大災害的肇因。此突然增強（sudden intensification）的現象為目前熱帶氣旋（或颱風、颶風）預報的瓶頸，且因應變時間短，造成防災上更加困難。林依依副教授等人及 NASA 科學家 W. Timothy LIU 利用 NASA 衛星測高資料發現這個突然增強過程發生在印度洋北部的海洋暖特徵現象(pre-existing warm ocean anomaly)上面，另外並利用美國大氣與海洋總署(National Oceanic and Atmospheric Administration)的實測水下溫鹽剖面資料 (Argo float profiles)，發現在此海洋暖特徵現象對應著之水下暖水層異常增厚的現象（從70米到100米），使得熱含量顯著增加（從50kJ/cm2 增加到100 kJ/cm2），接著利用海洋混合模式模擬後發現，由於此海洋暖特徵現象，使得海洋深處的冷海水不易被混合或湧升到水表面，因此深層海洋冷海水在颱風增強期間對颱風的負回饋作用被大量降低，以致由海洋到颱風的海氣潛熱及可感熱通量（latent and sensible heat fluxes）顯著增加。在林依依副教授等人的研究估計，此暖特徵現象可提供比在一般情況下高至3倍之海氣通量（300 W/m2到900 W/m2），使 Nargis 之強度快速增強。且因為海洋的熱通量為熱帶氣旋生長及加強的必要條件，因此如果 Nargis 並未通過此海洋暖特徵現象，或是此特徵現象不存在（即一般情況下），Nargis 颱風不可能在24小時內由輕度颱風發展到強烈颱風。此新的研究集合了衛星遙測技術、最新的海洋水下實測探測資料及模式的配合，相關研究成果有助於對目前熱帶氣旋（或颱風,颶風）強度預報的重要議題（即突然增強現象, sudden intensification）的進一步瞭解。
深入資訊：
臺大校訊第954期
美 國太空總署JPL網站 (英文)
美國太空總署NASA介紹研究成果網站(英文)
[Geophysics] Taida's Research on Tropical Cyclone Featured as NASA's Top Story
Taida-Department of Atmospheric Sciences Associate Professor I-I LIN and the team presented the findings “Warm Ocean Anomaly, Air Sea Fluxes, and the Rapid Intensification of Tropical Cyclone Nargis (2008)” in Geophysical
Research Letters, whose content was featured as top story in NASA's newsletter on 26th-Feb., 2009.
The research is about the catastrophic tropical cyclone Nargis in Indian Ocean area. In May 2008, Nargis caused over 130,000 victims in Myanmar (Burma), and was one of the greatest natural disasters in recent years. Professor LIN and the team found, within the twenty-four hours before landing Nargis developed from a minimal suddenly to a severe tropical cyclone and landed in its strongest state, which is the critical cause of the catastrophe. The sudden intensification, ibid., is the bottleneck for forecasting tropical cyclones (such as typhoons or hurricanes), and such difficulty makes precaution and preparedness even more troublesome. With NASA's satellite altimeters data, the team collaborated with NASA scientist W. Timothy LIU, found the sudden intensification co-occurred with pre-existing warm ocean anomaly in Indian Ocean. Besides, the data from the American National Oceanic and Atmospheric Administration's Argo float profiles, which monitor and record the vertical salinity and temperature situation in float, clue the team in that due to the extraordinary thickening of warm layer of ocean water (from 70 meters depth to 100 meters), the heat content is increased from 50 kJ/cm² to 100 kJ/cm². Then, via the simulation analysis of a mixed ocean model, the team concludes that the pre-existing warm ocean anomaly prohibit the cold ocean water in the depth from being mixed or flowing upwards, which decreases the deep cold ocean water's negative effect on typhoon during the development of tropical cyclone's tensity, so that latent and sensible heat fluxes from the ocean water to the cyclone get apparently increased. According to the team's calculation, the Warm Ocean Anomaly provides thrice heat fluxes (from 300 W/m² to 900 W/m²), which consequently makes Nargis extraordinarily stronger and quicker. Also because the existence of heat fluxes is the necessary condition for the growth of tropical cyclones, had Nargis not traverse the ocean in such an anomaly, either as via another course or as the non-existence of the anomaly, Nargis would have no chance to become such a severe typhoon within twenty-four hours. The research is interdisciplinary of satellite monitoring technology, float profiling and ocean models simulation. The result of this research “demonstrates a significant potential benefit of using altimeter data for operational weather forecasting and tropical cyclone intensity predictions," said study co-author Tim LIU of JPL, NASA. "Current hurricane analyses include variations in ocean heat, which can be revealed by ocean altimeters. Satellites like NASA's Jason-1 and Ocean Surface Topography Mission/Jason-2 make important contributions to the operational monitoring and prediction of tropical cyclones, as have other NASA satellites."
Further Information:
National Taiwan University Newsletter Issue 954 (in Chinese)
NASA JPL website
The study featured as top story in NASA JPL Newsletter
臺大大氣系林依依副教授與其合作伙伴於今年（2009）二月發表在國際期刊《Geophysical Research Letters》的最新研究成果〈Warm Ocean Anomaly, Air Sea Fluxes, and the Rapid Intensification of Tropical Cyclone Nargis (2008)〉,獲得美國太空總署 NASA （2009）年二月二十六日的新聞稿中重點介紹（featured as top story）。
此研究是關於去年造成最大災情的印度洋熱帶氣旋 Nargis。在2008年5月 Nargis 氣旋造成緬甸超過13萬人死亡的災情，為近年來全球最大的天然災害之一。林依依副教授等人研究發現在 Nargis 即將登陸的24小時之內，Nargis 氣旋突然由輕度氣旋增強為強烈氣旋，並且在強度最強的時候登陸，這是重大災害的肇因。此突然增強（sudden intensification）的現象為目前熱帶氣旋（或颱風、颶風）預報的瓶頸，且因應變時間短，造成防災上更加困難。林依依副教授等人及 NASA 科學家 W. Timothy LIU 利用 NASA 衛星測高資料發現這個突然增強過程發生在印度洋北部的海洋暖特徵現象(pre-existing warm ocean anomaly)上面，另外並利用美國大氣與海洋總署(National Oceanic and Atmospheric Administration)的實測水下溫鹽剖面資料 (Argo float profiles)，發現在此海洋暖特徵現象對應著之水下暖水層異常增厚的現象（從70米到100米），使得熱含量顯著增加（從50kJ/cm2 增加到100 kJ/cm2），接著利用海洋混合模式模擬後發現，由於此海洋暖特徵現象，使得海洋深處的冷海水不易被混合或湧升到水表面，因此深層海洋冷海水在颱風增強期間對颱風的負回饋作用被大量降低，以致由海洋到颱風的海氣潛熱及可感熱通量（latent and sensible heat fluxes）顯著增加。在林依依副教授等人的研究估計，此暖特徵現象可提供比在一般情況下高至3倍之海氣通量（300 W/m2到900 W/m2），使 Nargis 之強度快速增強。且因為海洋的熱通量為熱帶氣旋生長及加強的必要條件，因此如果 Nargis 並未通過此海洋暖特徵現象，或是此特徵現象不存在（即一般情況下），Nargis 颱風不可能在24小時內由輕度颱風發展到強烈颱風。此新的研究集合了衛星遙測技術、最新的海洋水下實測探測資料及模式的配合，相關研究成果有助於對目前熱帶氣旋（或颱風,颶風）強度預報的重要議題（即突然增強現象, sudden intensification）的進一步瞭解。
from NASA JPL website
深入資訊：
臺大校訊第954期
美 國太空總署JPL網站 (英文)
美國太空總署NASA介紹研究成果網站(英文)
[Geophysics] Taida's Research on Tropical Cyclone Featured as NASA's Top Story
Taida-Department of Atmospheric Sciences Associate Professor I-I LIN and the team presented the findings “Warm Ocean Anomaly, Air Sea Fluxes, and the Rapid Intensification of Tropical Cyclone Nargis (2008)” in Geophysical
Research Letters, whose content was featured as top story in NASA's newsletter on 26th-Feb., 2009.
The research is about the catastrophic tropical cyclone Nargis in Indian Ocean area. In May 2008, Nargis caused over 130,000 victims in Myanmar (Burma), and was one of the greatest natural disasters in recent years. Professor LIN and the team found, within the twenty-four hours before landing Nargis developed from a minimal suddenly to a severe tropical cyclone and landed in its strongest state, which is the critical cause of the catastrophe. The sudden intensification, ibid., is the bottleneck for forecasting tropical cyclones (such as typhoons or hurricanes), and such difficulty makes precaution and preparedness even more troublesome. With NASA's satellite altimeters data, the team collaborated with NASA scientist W. Timothy LIU, found the sudden intensification co-occurred with pre-existing warm ocean anomaly in Indian Ocean. Besides, the data from the American National Oceanic and Atmospheric Administration's Argo float profiles, which monitor and record the vertical salinity and temperature situation in float, clue the team in that due to the extraordinary thickening of warm layer of ocean water (from 70 meters depth to 100 meters), the heat content is increased from 50 kJ/cm² to 100 kJ/cm². Then, via the simulation analysis of a mixed ocean model, the team concludes that the pre-existing warm ocean anomaly prohibit the cold ocean water in the depth from being mixed or flowing upwards, which decreases the deep cold ocean water's negative effect on typhoon during the development of tropical cyclone's tensity, so that latent and sensible heat fluxes from the ocean water to the cyclone get apparently increased. According to the team's calculation, the Warm Ocean Anomaly provides thrice heat fluxes (from 300 W/m² to 900 W/m²), which consequently makes Nargis extraordinarily stronger and quicker. Also because the existence of heat fluxes is the necessary condition for the growth of tropical cyclones, had Nargis not traverse the ocean in such an anomaly, either as via another course or as the non-existence of the anomaly, Nargis would have no chance to become such a severe typhoon within twenty-four hours. The research is interdisciplinary of satellite monitoring technology, float profiling and ocean models simulation. The result of this research “demonstrates a significant potential benefit of using altimeter data for operational weather forecasting and tropical cyclone intensity predictions," said study co-author Tim LIU of JPL, NASA. "Current hurricane analyses include variations in ocean heat, which can be revealed by ocean altimeters. Satellites like NASA's Jason-1 and Ocean Surface Topography Mission/Jason-2 make important contributions to the operational monitoring and prediction of tropical cyclones, as have other NASA satellites."
from NASA JPL website
Further Information:
National Taiwan University Newsletter Issue 954 (in Chinese)
NASA JPL website
The study featured as top story in NASA JPL Newsletter
Edited 3 time(s). Last edit at 04/05/2009 11:14AM by gustav.
(編輯記錄)