Wang Joe

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Wang
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Joe
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Now showing 1 - 6 of 6
  • Article
    Mean structure and variability of the cold dome northeast of Taiwan
    (The Oceanography Society, 2011-12) Jan, Sen ; Chen, Chung-Chi ; Tsai, Ya-Ling ; Yang, Yiing-Jang ; Wang, Joe ; Chern, Ching-Sheng ; Gawarkiewicz, Glen G. ; Lien, Ren-Chieh ; Centurioni, Luca R. ; Kuo, Jia-Yu
    The "cold dome" off northeastern Taiwan is one of the distinctive oceanic features in the seas surrounding Taiwan. The cold dome is important because persistent upwelling makes the region highly biologically productive. This article uses historical data, recent observations, and satellite-observed sea surface temperatures (SST) to describe the mean structure and variability of the cold dome. The long-term mean position of the cold dome, using the temperature at 50 m depth as a reference, is centered at 25.625°N, 122.125°E. The cold dome has a diameter of approximately 100 km, and is maintained by cold (< 21°C) and salty (> 34.5) waters upwelled along the continental slope. The ocean currents around the cold dome, although weak, flow counterclockwise. The monsoon-driven winter intrusion of the Kuroshio current onto the East China Sea shelf intensifies the upwelling and carries more subsurface water up to the cold dome than during the summer monsoon season. On a shorter timescale, the cold dome's properties can be significantly modified by the passage of typhoons, which creates favorable physical conditions for short-term Kuroshio intrusions in summer. The surface expression of the cold dome viewed from satellite SST images is often not domelike but instead is an irregular shape with numerous filaments, and thus may contribute substantially to shelf/slope exchange. As a result of persistent upwelling, typhoon passage, and monsoon forcing, higher chlorophyll a concentrations, and thus higher primary productivity, are frequently observed in the vicinity of the cold dome.
  • Article
    Circulation and intrusions northeast of Taiwan : chasing and predicting uncertainty in the cold dome
    (The Oceanography Society, 2011-12) Gawarkiewicz, Glen G. ; Jan, Sen ; Lermusiaux, Pierre F. J. ; McClean, Julie L. ; Centurioni, Luca R. ; Taylor, Kevin ; Cornuelle, Bruce D. ; Duda, Timothy F. ; Wang, Joe ; Yang, Yiing-Jang ; Sanford, Thomas B. ; Lien, Ren-Chieh ; Lee, Craig M. ; Lee, Ming-An ; Leslie, Wayne ; Haley, Patrick J. ; Niiler, Pearn P. ; Gopalakrishnan, Ganesh ; Velez-Belchi, Pedro ; Lee, Dong-Kyu ; Kim, Yoo Yin
    An important element of present oceanographic research is the assessment and quantification of uncertainty. These studies are challenging in the coastal ocean due to the wide variety of physical processes occurring on a broad range of spatial and temporal scales. In order to assess new methods for quantifying and predicting uncertainty, a joint Taiwan-US field program was undertaken in August/September 2009 to compare model forecasts of uncertainties in ocean circulation and acoustic propagation, with high-resolution in situ observations. The geographical setting was the continental shelf and slope northeast of Taiwan, where a feature called the "cold dome" frequently forms. Even though it is hypothesized that Kuroshio subsurface intrusions are the water sources for the cold dome, the dome's dynamics are highly uncertain, involving multiple scales and many interacting ocean features. During the experiment, a combination of near-surface and profiling drifters, broad-scale and high-resolution hydrography, mooring arrays, remote sensing, and regional ocean model forecasts of fields and uncertainties were used to assess mean fields and uncertainties in the region. River runoff from Typhoon Morakot, which hit Taiwan August 7–8, 2009, strongly affected shelf stratification. In addition to the river runoff, a cold cyclonic eddy advected into the region north of the Kuroshio, resulting in a cold dome formation event. Uncertainty forecasts were successfully employed to guide the hydrographic sampling plans. Measurements and forecasts also shed light on the evolution of cold dome waters, including the frequency of eddy shedding to the north-northeast, and interactions with the Kuroshio and tides. For the first time in such a complex region, comparisons between uncertainty forecasts and the model skill at measurement locations validated uncertainty forecasts. To complement the real-time model simulations, historical simulations with another model show that large Kuroshio intrusions were associated with low sea surface height anomalies east of Taiwan, suggesting that there may be some degree of predictability for Kuroshio intrusions.
  • Technical Report
    Acoustics and oceanographic observations collected during the QPE Experiment by Research Vessels OR1, OR2 and OR3 in the East China Sea in the Summer of 2009
    (Woods Hole Oceanographic Institution, 2010-08) Newhall, Arthur E. ; Lynch, James F. ; Gawarkiewicz, Glen G. ; Duda, Timothy F. ; McPhee, Neil M. ; Bahr, Frank B. ; Marquette, Craig D. ; Lin, Ying-Tsong ; Jan, Sen ; Wang, Joe ; Chen, Chi-Fang ; Chiu, Linus Y. S. ; Yang, Yiing-Jang ; Wei, Ruey-Chang ; Emerson, Chris ; Morton, David ; Abbot, Ted ; Abbot, Philip A. ; Calder, Brian ; Mayer, Larry A. ; Lermusiaux, Pierre F. J.
    This document describes data, sensors, and other useful information pertaining to the ONR sponsored QPE field program to quantify, predict and exploit uncertainty in observations and prediction of sound propagation. This experiment was a joint operation between Taiwanese and U.S. researchers to measure and assess uncertainty of predictions of acoustic transmission loss and ambient noise, and to observe the physical oceanography and geology that are necessary to improve their predictability. This work was performed over the continental shelf and slope northeast of Taiwan at two sites: one that was a relatively flat, homogeneous shelf region and a more complex geological site just shoreward of the shelfbreak that was influenced by the proximity of the Kuroshio Current. Environmental moorings and ADCP moorings were deployed and a shipboard SeaSoar vehicle was used to measure environmental spatial structure. In addition, multiple bottom moored receivers and a horizontal hydrophone array were deployed to sample transmission loss from a mobile source and ambient noise. The acoustic sensors, environmental sensors, shipboard resources, and experiment design, and their data, are presented and described in this technical report.
  • Article
    Observations of a freshwater pulse induced by Typhoon Morakot off the northern coast of Taiwan in August 2009
    (Sears Foundation for Marine Research, 2013-01-01) Jan, Sen ; Wang, Joe ; Yang, Yiing-Jang ; Hung, Chin-Chang ; Chern, Ching-Sheng ; Gawarkiewicz, Glen G. ; Lien, Ren-Chieh ; Centurioni, Luca R. ; Kuo, Jia-Yu ; Wang, Bee
    In this paper we describe large-scale impacts from a typhoon on the circulation over the continental shelf and slope north of Taiwan. Typhoon Morakot was a category 2 tropical storm that landed in central Taiwan, but caused destruction primarily in southern Taiwan from Aug. 8–10, 2009. The typhoon brought record-breaking rainfall; approximately 3 m accumulated over four days in southern Taiwan. River discharge on the west coast of Taiwan increased rapidly from Aug. 6–7 and peaked on Aug. 8, yielding a total volume 27.2 km3 of freshwater discharged off the west coast of Taiwan over five days (Aug. 6–10). The freshwater mixed with ambient seawater, and was carried primarily by the northeastward-flowing Taiwan Strait current to the sea off the northern coast of Taiwan. Two joint surveys each measured the hydrography and current velocity in the Taiwan Strait and off the northeastern coast of Taiwan roughly one week and two and a half weeks after Morakot. The first survey observed an Ω-shaped freshwater pulse off the northern tip of Taiwan, in which the salinity was ∼1 lower than the climatological mean salinity. The freshwater pulse met the Kuroshio and formed a density front off the northeastern coast of Taiwan. The hydrographic data obtained in the second survey suggested that the major freshwater pulse left the sea off the northern and northeastern coasts of Taiwan, which may have been carried by the Kuroshio to the northeast. Biogeochemical sampling conducted after Morakot suggested that the concentrations of nutrients in the upper ocean off the northern coast of Taiwan increased remarkably compared with their normal values. A typhoon-induced biological bloom is attributed to the inputs both from the nutrient-rich river runoff and upwelling of the subsurface Kuroshio water.
  • Article
    Mean structure and fluctuations of the Kuroshio east of Taiwan from in situ and remote observations
    (The Oceanography Society, 2015-12) Yang, Yiing-Jang ; Jan, Sen ; Chang, Ming-Huei ; Wang, Joe ; Mensah, Vigan ; Kuo, Tien-Hsia ; Tsai, Cheng-Ju ; Lee, Chung-Yaung ; Andres, Magdalena ; Centurioni, Luca R. ; Tseng, Yu-Heng ; Liang, Wen-Der ; Lai, Jian-Wu
    The Kuroshio is important to climate, weather prediction, and fishery management along the northeast coast of Asia because it transports tremendous heat, salt, and energy from east of the Philippines to waters southeast of Japan. In the middle of its journey northward, the Kuroshio’s velocity mean and its variability east of Taiwan crucially affect its downstream variability. To improve understanding of the Kuroshio there, multiple platforms were used to collect intensive observations off Taiwan during the three-year Observations of the Kuroshio Transports and their Variability (OKTV) program (2012–2015). Mean Kuroshio velocity transects show two velocity maxima southeast of Taiwan, with the primary velocity core on the onshore side of the Kuroshio exhibiting a mean maximum velocity of ~1.2 m s–1. The two cores then merge and move at a single velocity maximum of ~1 m s–1 east of Taiwan. Standard deviations of both the directly measured poleward (v) and zonal (u) velocities are ~0.4 m s–1 in the Kuroshio main stream. Water mass exchange in the Kuroshio east of Taiwan was found to be complicated, as it includes water of Kuroshio origin, South China Sea Water, and West Philippine Sea Water, and it vitally affects heat, salt, and nutrient inputs to the East China Sea. Impinging eddies and typhoons are two of the principal causes of variability in the Kuroshio. This study’s models are more consistent with the observed Kuroshio than with high-frequency radar measurements.
  • Preprint
    The formation and fate of internal waves in the South China Sea
    ( 2015-03) Alford, Matthew H. ; Peacock, Thomas ; MacKinnon, Jennifer A. ; Nash, Jonathan D. ; Buijsman, Maarten C. ; Centurioni, Luca R. ; Chao, Shenn-Yu ; Chang, Ming-Huei ; Farmer, David M. ; Fringer, Oliver B. ; Fu, Ke-Hsien ; Gallacher, Patrick C. ; Graber, Hans C. ; Helfrich, Karl R. ; Jachec, Steven M. ; Jackson, Christopher R. ; Klymak, Jody M. ; Ko, Dong S. ; Jan, Sen ; Johnston, T. M. Shaun ; Legg, Sonya ; Lee, I-Huan ; Lien, Ren-Chieh ; Mercier, Matthieu J. ; Moum, James N. ; Musgrave, Ruth C. ; Park, Jae-Hun ; Pickering, Andrew I. ; Pinkel, Robert ; Rainville, Luc ; Ramp, Steven R. ; Rudnick, Daniel L. ; Sarkar, Sutanu ; Scotti, Alberto ; Simmons, Harper L. ; St Laurent, Louis C. ; Venayagamoorthy, Subhas K. ; Wang, Yu-Huai ; Wang, Joe ; Yang, Yiing-Jang ; Paluszkiewicz, Theresa ; Tang, Tswen Yung
    Internal gravity waves, the subsurface analogue of the familiar surface gravity waves that break on beaches, are ubiquitous in the ocean. Because of their strong vertical and horizontal currents, and the turbulent mixing caused by their breaking, they impact a panoply of ocean processes, such as the supply of nutrients for photosynthesis1, sediment and pollutant transport2 and acoustic transmission3; they also pose hazards for manmade structures in the ocean4. Generated primarily by the wind and the tides, internal waves can travel thousands of kilometres from their sources before breaking5, posing severe challenges for their observation and their inclusion in numerical climate models, which are sensitive to their effects6-7. Over a decade of studies8-11 have targeted the South China Sea, where the oceans’ most powerful internal waves are generated in the Luzon Strait and steepen dramatically as they propagate west. Confusion has persisted regarding their generation mechanism, variability and energy budget, however, due to the lack of in-situ data from the Luzon Strait, where extreme flow conditions make measurements challenging. Here we employ new observations and numerical models to (i) show that the waves begin as sinusoidal disturbances rather than from sharp hydraulic phenomena, (ii) reveal the existence of >200-m-high breaking internal waves in the generation region that give rise to turbulence levels >10,000 times that in the open ocean, (iii) determine that the Kuroshio western boundary current significantly refracts the internal wave field emanating from the Luzon Strait, and (iv) demonstrate a factor-of-two agreement between modelled and observed energy fluxes that enables the first observationally-supported energy budget of the region. Together, these findings give a cradle-to-grave picture of internal waves on a basin scale, which will support further improvements of their representation in numerical climate predictions.