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Chia Chou - One of the best experts on this subject based on the ideXlab platform.
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Changes in precipitation frequency and intensity in the vicinity of Taiwan: typhoon versus non-typhoon events
Environmental Research Letters, 2013Co-Authors: Chia ChouAbstract:The hourly rainfall at 21 ground stations in Taiwan is used to investigate changes in the frequency, intensity, and duration of rainfall, which can be divided into typhoon and non-typhoon rainfall, in the period of 1970‐2010. As a whole, the frequency of rainfall shows a decreasing trend for lighter rain and an increasing trend for heavier rain. Also, the typhoon rainfall shows a significant increase for all intensities, while the non-typhoon rainfall exhibits a general trend of decreasing, particularly for lighter rain. In rainfall intensity, both typhoon and non-typhoon rainfall extremes become more intense, with an increased rate much greater than the Clausius‐Clapeyron thermal scaling. Moreover, rainfall extremes associated with Typhoons have tended to affect Taiwan rainfall for longer in recent decades. The more frequent, intense and long-lasting typhoon rainfall is mainly induced by the slower translation speed of the Typhoons over the neighborhood of Taiwan, which could be associated with a weakening of steering flow in the western North Pacific and the northern South China Sea.
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an abrupt increase of intense Typhoons over the western north pacific in early summer
Environmental Research Letters, 2011Co-Authors: Chia Chou, Ping Huang, Ronghui HuangAbstract:The frequency and intensity of Typhoons have been a focus in studying typhoon-related climate changes. In this study, we focus on a seasonal cycle of intense Typhoons (category 4 and 5) over the western North Pacific, particularly changes in the number of intense Typhoons in early summer. In general, 81% of intense Typhoons occur in July–November (JASON), with maxima in September and October. Our analysis shows that intense Typhoons have tended to occur more frequently in May since the year 2000. Before 2000, intense Typhoons seldom occurred in May, with a frequency of around once per decade. After 2000, however, the frequency of intense Typhoons has become much higher in May—almost once per year. We have also examined changes in the large-scale environment in the past few decades. The results show that the large-scale environment did become more favorable for intense Typhoons in the 2000s, which is consistent with a larger tropical cyclone genesis index. The changes include warmer sea surface temperature, higher sea surface height, larger upper-ocean heat content, weaker vertical wind shear, increased tropospheric water vapor, and greater water vapor in the mid-troposphere. The last two might be more important than the others.
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the abrupt shift of typhoon activity in the vicinity of taiwan and its association with western north pacific east asian climate change
Journal of Climate, 2009Co-Authors: Jienyi Tu, Chia ChouAbstract:Bayesian analysis is applied to detect changepoints in the time series of seasonal typhoon counts in the vicinity of Taiwan. An abrupt shift in the typhoon count series occurs in 2000. On average, 3.3 Typhoons per year have been noted before 2000 (1970‐99), with the rate increasing to 5.7 Typhoons per year since 2000 (2000‐06). This abrupt change is consistent with a northward shift of the typhoon track over the western North Pacific‐East Asian region and an increase of typhoon frequency over the Taiwan‐East China Sea region. The northward shift of the typhoon track tends to be associated with typhoon-enhancing environmental conditions over the western North Pacific, namely, the weakening of the western North Pacific subtropical high, the strengthening of the Asian summer monsoon trough, and the enhanced positive vorticity anomalies in the lower troposphere. Based on observational analysis and model simulations, warm sea surface temperature anomalies over the equatorial western and central Pacific appear to be a major factor contributing to a northward-shifted typhoon track.
Danling Tang - One of the best experts on this subject based on the ideXlab platform.
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increase in fish abundance during two Typhoons in the south china sea
Advances in Space Research, 2013Co-Authors: Danling Tang, Zirong Huang, Guobao ChenAbstract:A fish monitoring program was conducted in the northern region of the South China Sea from March 2009 to December 2010. During this period, two Typhoons, GONI and Koppu, hit this region consecutively in August and September 2009. The fish and satellite data were analyzed to understand the influence of the Typhoons on fish activities. The results showed that the fish species number (FSN) increased by approximately 14.29% and 14.81% after the two Typhoons, GONI and Koppu, respectively. The five increased fish species included three estuarine species and two shallow sea species. However, one shallow sea species was also absent. In the nearshore (near the Pearl River Estuary) and offshore (along the typhoon's track) regions after GONI, the FSN increased by approximately 24% (nearshore) and 52.63% (offshore), with estuarine species accounting for 42.86% (nearshore) and 33.33% (offshore) of the fish species; after Koppu, the FSN increased by approximately 15.38% (nearshore) and 163.64% (offshore), with estuarine species accounting for 60% (nearshore) and 26.32% (offshore) of the fish species. In the increased records, small and medium-sized fish species were dominant nearshore, and small fish species were dominant offshore. The FSN increased to a maximum value between the 5th and the 10th days after the typhoon nearshore and between the 3rd and 8th days after the typhoon offshore. The results indicated that river discharge, triggered by the typhoon's nearshore rainfall, as well as offshore upwelling nutrients, also triggered by the Typhoons, and may have played important roles in the variability of fish species. This research found that the increase in the FSN was associated with the Typhoons in the northern South China Sea. 2012 COSPAR. Published by Elsevier Ltd. All rights reserved.
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phytoplankton blooms near the pearl river estuary induced by typhoon nuri
Journal of Geophysical Research, 2009Co-Authors: Hui Zhao, Danling Tang, Dongxiao WangAbstract:The authors investigate two phytoplankton blooms near or off the Pearl River Estuary (PRE) triggered by Category 2 Typhoon Nuri with moderate wind intensity in the South China Sea using both remotely sensed and in situ data sets. An offshore triangular phytoplankton bloom (chlorophyll a (Chl a) > 0.5 mg m(-3)) was observed near Dongsha Archipelago along Nuri's track, prolongating southeastward to 18 degrees N 1 week after the typhoon's passage; a stronger nearshore phytoplankton increase (Chl a > 1.5 mg m(-3)) with high total suspended sediment appeared southwest of the PRE from the coast toward the South China Sea. After the typhoon's passage, sea surface cooling (similar to 3 degrees C), strong wind (> 20 m s(-1)), and heavy rainfall (> 100 mm d(-1)) were also observed in the region, especially offshore. In addition, the freshwater discharge from the PRE during the typhoon passage increased fivefold in comparison with the August climatology in the nearshore bloom region. The nearshore bloom was probably due to the increased discharge from the PRE and favorable current, as well as mixing, upwelling, and near-inertial resonance driven by strong typhoon wind. The offshore bloom may be triggered by upwelling and entrainment induced by strong typhoon wind and the topography of islands and islets. The present study suggests that one typhoon may nourish phytoplankton biomass by inducing transport of nutrient-rich water from both the Pearl River Estuary to offshore and the sublayer to surface.
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comparison of phytoplankton blooms triggered by two Typhoons with different intensities and translation speeds in the south china sea
Marine Ecology Progress Series, 2008Co-Authors: Hui Zhao, Danling Tang, Yuqing WangAbstract:Two phytoplankton blooms in the South China Sea (SCS), triggered by 2 Typhoons with different intensities and translation speeds, were compared using remotely sensed chlorophyll a (chl a), sea surface temperature (SST), vector wind field, and best-track typhoon data. Typhoon Ling-Ling in 2001 was strong, with a maximum sustained surface wind speed of 59 m s(-1), and fast-moving with a mean translation speed of 4.52 m s(-1). Typhoon Kai-Tak in 2005 was weak with a maximum sustained surface wind speed of 46 m s(-1), and slow-moving with a mean translation speed of 2.87 m s(-1). The weak, slow-moving typhoon Kai-Tak induced phytoplankton blooms with higher chl a concentrations, while the strong, fast-moving typhoon Ling-Ling induced blooms over a larger area. On average, about 7 Typhoons per year affect the SCS, among which 41% are strong (> 50 m s(-1)) and 59% are weak, while 64% are fast-moving (>4.4 m s(-1)) and 36% are slow-moving. We conservatively estimate that typhoon periods may account for 3.5% of the annual primary production in the oligotrophic SCS.
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offshore and nearshore chlorophyll increases induced by typhoon winds and subsequent terrestrial rainwater runoff
Marine Ecology Progress Series, 2007Co-Authors: Guangming Zheng, Danling TangAbstract:The response of phytoplankton chlorophyll to Typhoon Damrey in the South China Sea (SCS) in September 2005 was studied by remote sensing. Chl a concentration increased in 2 areas after the typhoon: (1) An offshore bloom along Damrey's track exhibited a chl a peak (4 mg m(-3)) 5 d after the typhoon's passage. It was preceded by sea-surface cooling (-5 degrees C), mainly on the right side of the typhoon track, and sea-level decrease (-25 cm) along the typhoon track 1 d post-typhoon. The offshore bloom was due to nutrient increase from mixing and upwelling, (2) A nearshore chl a increase succeeded typhoon rain (> 300 mm on 26 September) on Hainan Island in the northwest SCS. In the bloom region, the water was rich in suspended sediments, phytoplankton, and colored dissolved organic matter, and was entrained by an eddy. This nearshore feature may have resulted from rainwater discharge and seaward advection by a typhoon-induced current. By these 2 mechanisms, both typhoon winds and rain can enhance production of marine phytoplankton.
I I Lin - One of the best experts on this subject based on the ideXlab platform.
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typhoon induced phytoplankton blooms and primary productivity increase in the western north pacific subtropical ocean
Journal of Geophysical Research, 2012Co-Authors: I I LinAbstract:[1] Using multiple satellite observations and series of numerical experiments, this work systematically studied phytoplankton blooms induced by tropical cyclones in the western North Pacific subtropical ocean (WNPSO) because WNPSO is among the world oceans where most number of intense tropical cyclones are found. All eleven typhoon cases passing the study domain in 2003 were examined in detail. It was observed that only two Typhoons (18%) were able to induce phytoplankton blooms (chlorophyll-a concentration increased from ≦0.1 mg m−3 to 0.4–0.8 mg m−3) and strong sea surface temperature cooling of −2.5 to −6°C. The other nine Typhoons, including the most intense tropical cyclone on Earth in 2003 (i.e., supertyphoon Maemi), were not able to induce phytoplankton blooms and the associated sea surface temperature cooling was weak (0 to −1.5°C). Using series of numerical experiments, it was found that the presence of warm ocean eddy can effectively isolate the cold, nutrient-rich water to be entrained to the surface ocean. Under this situation, even category 5 typhoon Maemi at its peak intensity of 150 kts could not induce phytoplankton bloom in the WNPSO. The weak responses of the other eight Typhoons were due to insufficient wind intensity and transit time (caused by relatively small storm size and fast translation speed) in this deep nutricline/mixed layer ocean. As a result, the total annual primary production increase induced by Typhoons in the WNPSO was estimated to be ∼3.27 × 1012 g C (0.00327 Pg), equivalent to 0.15% of the global annual anthropogenic CO2 uptake. This suggests that though WNPSO has the highest number and intensity of tropical cyclones among the world oceans, tropical cyclones in the WNPSO have little contribution to enhance biological carbon fixation in the context of global carbon-climate system.
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validation and application of altimetry derived upper ocean thermal structure in the western north pacific ocean for typhoon intensity forecast
IEEE Transactions on Geoscience and Remote Sensing, 2007Co-Authors: Iamfei Pun, I I Lin, W T LiuAbstract:This paper uses more than 5000 colocated and near-coincident in-situ profiles from the National Oceanic and Atmospheric Administration/Global Temperature and Salinity Profile Program database spanning over the period from 2002 to 2005 to systematically validate the satellite-altimetry-derived upper ocean thermal structure in the western North Pacific ocean as such ocean thermal structure information is critical in typhoon-intensity change. It is found that this satellite-derived information is applicable in the central and the southwestern North Pacific (covering 122-170degE, 9-25degN) but not in the northern part (130-170degE, 25-40degN). However, since > 80% of the Typhoons are found to intensify in the central and southern part, this regional dependence should not pose a serious constraint in studying typhoon intensification. Further comparison with the U.S. Naval Research Laboratory's North Pacific Ocean Nowcast/Forecast System (NPACNFS) hydrodynamic ocean model shows similar regional applicability, but NPACNFS is found to have a general underestimation in the upper ocean thermal structure and causes a large underestimation of the tropical cyclone heat potential (TCHP) by up to 60 kJ/cm2. After validation, the derived upper ocean thermal profiles are used to study the intensity change of supertyphoon Dianmu (2004). It is found that two upper ocean parameters, i.e., a typhoon's self-induced cooling and the during-typhoon TCHP, are the most sensitive parameters (with R 2~0.7) to the 6-h intensity change of Dianmu during the study period covering Dianmu's rapid intensification to category 5 and its subsequent decay to category 4. This paper suggests the usefulness of satellite-based upper ocean thermal information in future research and operation that is related to typhoon-intensity change in the western North Pacific
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dropwindsonde observations for typhoon surveillance near the taiwan region dotstar an overview
Bulletin of the American Meteorological Society, 2005Co-Authors: Pohsiung Lin, Sim D Aberson, Tienchiang Yeh, Weipeng Huang, Kunhsuan Chou, Jingshan Hong, Chintzu Fong, Kuanchien Hsu, I I Lin, Pay-liam LinAbstract:DOTSTAR (Dropwindsonde Observations for Typhoon Surveillance near the Taiwan Region) is an international research program conducted by meteorologists in Taiwan partnered with scientists at the Hurricane Research Division (HRD) and the National Centers for Environmental Prediction (NCEP) of the National Oceanic and Atmospheric Administration (NOAA). The experiment is based on successful surveillance missions conducted in the Atlantic with NOAA's Gulfstream-IV jet aircraft. During the experiment, GPS dropwindsondes are released from a jet aircraft flying above 42000 ft in and around tropical cyclones approaching Taiwan to collect critical meteorological data for improving the analysis and the prediction of Typhoons. After one-year of training, development and installation of all the needed software and hardware in the aircraft, the DOTSTAR research team initiated typhoon surveillance in 2003. Two missions (in Typhoons Dujuan and Melor) were conducted successfully,and seven or eight missions are expected to be conducted annually during the 2004 and 2005 typhoon seasons. The current manuscript provides an overview of the scientific objectives of DOTSTAR including operational plans, organization, data management, and data archiving. Preliminary results of the two missions in the first season in 2003 are presented. The experiment marks the beginning of typhoon surveillance in the western North Pacific and is expected to yield impressive improvements in typhoon research, observations and forecasting.
Hui Zhao - One of the best experts on this subject based on the ideXlab platform.
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phytoplankton blooms near the pearl river estuary induced by typhoon nuri
Journal of Geophysical Research, 2009Co-Authors: Hui Zhao, Danling Tang, Dongxiao WangAbstract:The authors investigate two phytoplankton blooms near or off the Pearl River Estuary (PRE) triggered by Category 2 Typhoon Nuri with moderate wind intensity in the South China Sea using both remotely sensed and in situ data sets. An offshore triangular phytoplankton bloom (chlorophyll a (Chl a) > 0.5 mg m(-3)) was observed near Dongsha Archipelago along Nuri's track, prolongating southeastward to 18 degrees N 1 week after the typhoon's passage; a stronger nearshore phytoplankton increase (Chl a > 1.5 mg m(-3)) with high total suspended sediment appeared southwest of the PRE from the coast toward the South China Sea. After the typhoon's passage, sea surface cooling (similar to 3 degrees C), strong wind (> 20 m s(-1)), and heavy rainfall (> 100 mm d(-1)) were also observed in the region, especially offshore. In addition, the freshwater discharge from the PRE during the typhoon passage increased fivefold in comparison with the August climatology in the nearshore bloom region. The nearshore bloom was probably due to the increased discharge from the PRE and favorable current, as well as mixing, upwelling, and near-inertial resonance driven by strong typhoon wind. The offshore bloom may be triggered by upwelling and entrainment induced by strong typhoon wind and the topography of islands and islets. The present study suggests that one typhoon may nourish phytoplankton biomass by inducing transport of nutrient-rich water from both the Pearl River Estuary to offshore and the sublayer to surface.
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comparison of phytoplankton blooms triggered by two Typhoons with different intensities and translation speeds in the south china sea
Marine Ecology Progress Series, 2008Co-Authors: Hui Zhao, Danling Tang, Yuqing WangAbstract:Two phytoplankton blooms in the South China Sea (SCS), triggered by 2 Typhoons with different intensities and translation speeds, were compared using remotely sensed chlorophyll a (chl a), sea surface temperature (SST), vector wind field, and best-track typhoon data. Typhoon Ling-Ling in 2001 was strong, with a maximum sustained surface wind speed of 59 m s(-1), and fast-moving with a mean translation speed of 4.52 m s(-1). Typhoon Kai-Tak in 2005 was weak with a maximum sustained surface wind speed of 46 m s(-1), and slow-moving with a mean translation speed of 2.87 m s(-1). The weak, slow-moving typhoon Kai-Tak induced phytoplankton blooms with higher chl a concentrations, while the strong, fast-moving typhoon Ling-Ling induced blooms over a larger area. On average, about 7 Typhoons per year affect the SCS, among which 41% are strong (> 50 m s(-1)) and 59% are weak, while 64% are fast-moving (>4.4 m s(-1)) and 36% are slow-moving. We conservatively estimate that typhoon periods may account for 3.5% of the annual primary production in the oligotrophic SCS.
Chiaying Ko - One of the best experts on this subject based on the ideXlab platform.
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decadal phytoplankton dynamics in response to episodic climatic disturbances in a subtropical deep freshwater ecosystem
Water Research, 2017Co-Authors: Chiaying Ko, Fuh-kwo ShiahAbstract:Abstract Information of the decadal timescale effects of episodic climatic disturbances (i.e., Typhoons) on phytoplankton in freshwater ecosystems have received less attention and fewer seasonal evaluations partly due to the lack of long-term time-series monitoring data in typhoon prevailing areas. Through field observations of a total 36 typhoon cases in a subtropical deep freshwater ecosystem in the period of 2005–2014, we quantified phytoplankton biomass, production and growth rate in response to meteorological and hydrological changes in the weeks before, during and after Typhoons between summer and autumn, and also investigated the effects of typhoon characteristics on the aforementioned phytoplankton responses. The results showed that phytoplankton exposed to typhoon disturbances generally exhibited an increasing trend over the weeks before, during and after Typhoons in summer but varied in autumn. The correlations and multivariate regressions showed different contributions of meteorological and hydrological variables to individual phytoplankton responses before, during and after Typhoons between seasons. The post-typhoon weeks (i.e., within two weeks after a typhoon had passed) were especially important for the timeline of phytoplankton increases and with a detectable seasonal variation that the chlorophyll a concentration significantly increased in autumn whereas both primary production and growth rate were associated with significant changes in summer. Additionally, phytoplankton responses during the post-typhoon weeks were significantly different between discrete or continuous types of typhoon events. Our work illustrated the fact that Typhoons did influence phytoplankton responses in the subtropical deep freshwater ecosystem and typhoon passages in summer and autumn affected the phytoplankton dynamics differently. Nevertheless, sustained and systematic monitoring in order to advance our understanding of the role of Typhoons between seasons in the modulation of phytoplankton productivity and functioning is required because such episodic climatic disturbances are projected to have intense magnitude and inconsistent frequency under 21st century climate change.
