Plain Of Taiwan Research Articles

Effects of the Northeast Monsoon on Different Terrain of the Taipei Basin and Lanyang Plain in Taiwan

The Taipei Basin (TPB) and the Lanyang Plain (LYP) are geographically similar, both situated in northern Taiwan. However, significant differences in heat transfer processes arise between the two regions due to local terrain influences under the Northeast Monsoon. Precipitation patterns in the TPB and LYP, especially during the case study of 26 November 2021, differ markedly due to the distinctive dustpan-shaped terrain of the LYP. Our study, based on the WRF model, reveals that while both the TPB and LYP are characterized by downward cold air transfer, the TPB exhibits stronger atmospheric boundary layer mixing and a higher mixing layer height compared to the LYP. Turbulent kinetic energy (TKE) in the TPB is higher during the morning and evening, while vertical heat flux is more pronounced in the LYP. The average sensible heat flux is greater in the TPB, whereas latent heat flux is higher in the LYP. In addition, the amount of water vapor transported into the LYP by the Northeast Monsoon is greater than in the TPB. In the TPB, the wind field, influenced by the terrain, shifts predominantly from northeast to northeasterly and southeasterly. However, upon entering the LYP, the same environmental wind field is affected by the dustpan-shaped terrain, resulting in a counterclockwise near-surface wind pattern. The wind field transitions from northeasterly in the north to westerly, southwesterly, or northwesterly in the south. This difference in wind field causes precipitation in the TPB to be confined mainly to the windward side of the mountainous areas whereas, in the LYP, precipitation occurs both on the windward side and, more abundantly, in the plains. The effect of different types of terrain under the Northeast Monsoon is quite obvious.

地下水模拟中识别参数结构的差分进化优化方法的应用

Parameter structure identification is formulated in terms of solving an inverse problem, which allows for a determination of an appropriate level of parameter structure complexity, and the identification of its pattern and the associated parameter values. With the increasing complexity of parameter structure identification in groundwater modeling, demand for robust, fast, and accurate optimizers is on the rise among researchers from groundwater hydrology fields. A novel global optimizer, differential evolution (DE), has been proposed to solve the parameter-structure-identification problem. The Voronoi tessellation is adopted for the automatic parameterization. The stepwise regression method and the error covariance matrix are used to determine the optimal structure complexity. Numerical experiments with a continuous hydraulic conductivity distribution are conducted to demonstrate the proposed methodology. The results indicate that the DE can identify the global optimum effectively and efficiently. A sensitivity analysis of the control parameters and mutation schemes implemented in the DE is employed to examine their influence on the objective function. The comparison between DE and genetic algorithm shows the advantage of DE in terms of robustness and efficiency. The proposed methodology is also applied to a real groundwater system, Pingtung Plain in Taiwan, and the properties of aquifers are successfully identified.

Evapotranspiration Estimation with Remote Sensing and Various Surface Energy Balance Algorithms—A Review

With the advent of new satellite technology, the radiative energy exchanges between Sun, Earth, and space may now be quantified accurately. Nevertheless, much less is known about the magnitude of the energy flows within the climate system and at the Earth’s surface, which cannot be directly measured by satellites. This review surveys the basic theories, observational methods, and different surface energy balance algorithms for estimating evapotranspiration (ET) from landscapes and regions with remotely sensed surface temperatures, and highlights uncertainties and limitations associated with those estimation methods. Although some of these algorithms were built up for specific land covers like irrigation areas only, methods developed for other disciplines like hydrology and meteorology, are also reviewed, where continuous estimates in space and in time are needed. Temporal and spatial scaling issues associated with the use of thermal remote sensing for estimating evapotranspiration are also discussed. A review of these different satellite based remote sensing approaches is presented. The main physical bases and assumptions of these algorithms are also discussed. Some results are shown for the estimation of evapotranspiration on a rice paddy of Chiayi Plain in Taiwan using remote sensing data.

Multiple Diving Waves and Steep Velocity Gradients in the Western Taiwan Coastal Plain: An Investigation Based on the TAIGER Experiment

Seismic data collected during explosion experiments performed as part of the TAiwan Integrated GEodynamics Research (TAIGER) project provide an excellent opportunity to obtain high‐resolution images of the structure of the crust and upper mantle beneath Taiwan. The most significant feature observed at near‐source stations located on the western coastal plain in Taiwan is high‐energy later arrivals. These high‐amplitude multiples almost completely mask the lower‐amplitude signals (seismic refraction and wide‐angle reflection) from the deep crust. The later arrivals are identified as free‐surface‐reflected multiples. The nature and generation of these high‐energy, multiple diving waves are demonstrated using synthetic examples. Their generation requires the presence of a steep velocity gradient in the shallow crust. A detailed analysis of the observation data provided information on the velocity gradients in this region. An accurate layer‐velocity model, including the boundary orientation and its depth, and velocity gradient, was constructed based on a 1D waveform simulation and 2D seismic raytracing modeling for travel times. The present results indicate that the thick sediment in the survey area dips shallowly to the east, has a surface P ‐wave velocity of ![Graphic][1] , and an average velocity gradient of about 0.72/s from the surface to 3.0‐km depth. The thick sediment of the 2D model shows lateral variations in velocity gradient, increasing from west to east. This velocity model may provide useful information for future data processing to reduce multiple diving waves with the aim of enhancing the deep‐surface refraction/reflection signal. The velocity gradient calculated for the thick sediment of the western coastal plain may require a revision of the regional seismic velocity model developed for southwestern Taiwan, to improve the accuracy of regional hypocenter determinations, and to predict the strong ground motions produced by large earthquakes beneath this region. [1]: /embed/inline-graphic-1.gif

Establishing an irrigation management plan of sustainable groundwater based on spatial variability of water quality and quantity

Summary Conditions of water quality and quantity are two key factors impacting groundwater utilization for irrigation. To obtain pristine groundwater and reduce pumping impacts on aquifers, this study establishes an irrigation management plan of sustainable groundwater in the Pingtung Plain in Taiwan based on the spatial variability of water quality and quantity parameters. According to an irrigation water quality standard, multivariate indicator kriging (IK) was adopted to estimate the integration of hydrochemical parameters in groundwater. IK was also used to grade transmissivity fields representing the pumping capacity of aquifers. Six risk categories of recommended groundwater used for irrigation were spatially delineated based on combinations of five levels of groundwater quality and quantity determined by estimated probabilities. The analyzed results indicate that 54.4% of aquifers are recommended to extract groundwater for irrigation. The aquifers belonging to excellent categories are the optimal locations, where groundwater can be used for irrigation without dilution. The aquifers belonging to ordinary categories are the regions, where groundwater mixed with surface water is appropriate for use in irrigation.

Evaluation of surface heat fluxes in Chiayi plain of Taiwan by remotely sensed data

Surface energy processes have an essential role in regional weather, climate and hydrosphere cycles, as well in regulating urban heat redistribution. The Chiayi urban area of Taiwan and its surrounding agricultural plains are an appropriate complex for studying land surface parameters and energy fluxes of different land cover/land use types in an urban heat island. In this study, three micro-meteorological stations were established over Chiayi Plain to collect in situ reference observations from 2006. In order to properly characterize the surface heat fluxes over a regional scale by point measurement, Moderate Resolution Imaging Spectroradiometer (MODIS) satellite images and images acquired by a high resolution airborne campaign in conjunction with meteorological data were used to estimate the surface heat fluxes over a large area. The analytical results indicated that surface heat fluxes determined from both airborne and satellite images were feasible for estimating surface heat flux. The correlation coefficient of surface heat fluxes with in situ corresponding observations exceeded 0.80. On the other hand, satellite-observed surface skin temperature and land surface energy fluxes were the core factors analysed in different land cover types. The urban surface was rather dry as half of net radiation is converted to sensible heat flux for heating the surface, whereas over 90% net radiation is converted to latent heat flux at wet surfaces such as evergreen broadleaf or water. Surface heat flux was also proven to be an indicator of the magnitude of urban heat island effect and the findings of this study encouraged further use of remotely sensed imagery for assessing the urban heat island effect.

Primary Geologic Sources of Arsenic in the Chianan Plain (Blackfoot Disease Area) and the Lanyang Plain of Taiwan

The area that includes Beimen and the immediate surrounding villages of southwestern Taiwan is recognized as the home of the world's only well-documented Blackfoot Disease (BFD) occurrence—where extremely high concentrations of arsenic (As) have been found in the artesian wells from the Chianan Plain that were previously used as a drinking water supply. In the past decade, very high levels of arsenic have also been discovered in the potable water from the Lanyang Plain of northeastern Taiwan, but BFD does not occur there. From regional geological/geophysical field investigations in these two areas and a literature survey of arsenic problems in the drinking water of other countries, we have identified five potential primary geologic sources of the As for the BFD area and six sources for the Lanyang Plain. We also report measurements of arsenic in two "new" areas: (1) the sea water west of the BFD area (three samples with As levels of 2.32, 7.46, and 9.71 μg/L; and (2) stream bed deposits east of the BFD area (two samples with As concentrations of 0.00485 wt% and 0.23000 wt%). With the current information available, it seems most plausible that the primary source of the arsenic in the BFD area is from fluid escape from the accretionary prism of Taiwan or from in situ formation of arsenic-laden sulfide minerals in the water-rich coastal sediments, whereas the most likely sources of the high concentrations of arsenic in the Lanyang Plain are hydrothermal venting in the Okinawa Basin and/or weathering of sulfide minerals associated with gold and copper ores along the Lishan fault to the south. Although oxidation is known to play a role in the formation of some arsenic compounds, most of these 11 primary sources and their associated rocks and minerals are originally related to reducing environments; however, continued research is necessary to fully explain each source's expulsion mechanism (mobility), transport (if any), and final concentration or enrichment of arsenic in the groundwater of Taiwan.

Risk characterization and exposure assessmentin arseniasis-endemic areas of Taiwan

This paper examines the age-specific human health risks exposed to inorganic arsenic through arsenic-contaminated farmed fish/shrimp and groundwater consumptions in arseniasis-endemic areas of blackfoot disease (BFD)-endemic area and Lanyang Plain in Taiwan, based on an probabilistic integrated risk assessment framework. We employ an age-dependent predictive physiologically-based pharmacokinetic model to account for arsenic concentrations in target organs. We reconstruct age-specific dose-response profiles for arsenicosis and arsenic-induced cancers by best fitting a pharmacodynamics-based three-parameter Hill equation model to published epidemiological data from West Bengal and Taiwan. The predicted median arsenic concentrations in age group-specific skin, lung, and bladder ranged from 2.24-5.70, 3.76-9.46, and 5.11-20.71 micro g g(-1) in BFD-endemic area, whereas 4.98-12.04, 8.23-19.92, and 11.07-43.45 micro g g(-1) in Lanyang Plain, respectively. Risk analysis indicates that consumption of arsenic-contaminated farmed fish/shrimp and groundwater in arseniasis-endemic areas may increase threat to prevalence of arsenicosis for all age groups, whereas adults may undergo potential risks of arsenic-induced skin, lung and bladder cancers. We show that peoples in Lanyang Plain are more readily associated with higher morbidities for arsenicosis and skin cancer as well as fatalities for lung and bladder cancers than that of peoples in BFD-endemic area. Here we report the first case in which theoretical human health risks for consuming As-contaminated farmed fish/shrimp and groundwater in the arseniasis-endemic areas are alarming under a conservative condition based on a probabilistic risk assessment framework.

Designing an optimal multivariate geostatistical groundwater quality monitoring network using factorial kriging and genetic algorithms

The optimal selection of monitoring wells is a major task in designing an information-effective groundwater quality monitoring network which can provide sufficient and not redundant information of monitoring variables for delineating spatial distribution or variations of monitoring variables. This study develops a design approach for an optimal multivariate geostatistical groundwater quality network by proposing a network system to identify groundwater quality spatial variations by using factorial kriging with genetic algorithm. The proposed approach is applied in designing a groundwater quality monitoring network for nine variables (EC, TDS, Cl−, Na, Ca, Mg, SO 4 2− , Mn and Fe) in the Pingtung Plain in Taiwan. The spatial structure results show that the variograms and cross-variograms of the nine variables can be modeled in two spatial structures: a Gaussian model with ranges 28.5 km and a spherical model with 40 km for short and long spatial scale variations, respectively. Moreover, the nine variables can be grouped into two major components for both short and long scales. The proposed optimal monitoring design model successfully obtains different optimal network systems for delineating spatial variations of the nine groundwater quality variables by using 20, 25 and 30 monitoring wells in both short scale (28.5 km) and long scale (40 km). Finally, the study confirms that the proposed model can design an optimal groundwater monitoring network that not only considers multiple groundwater quality variables but also monitors variations of monitoring variables at various spatial scales in the study area.

Arsenic and humic substances of groundwater in the southwestern coastal plain of Taiwan

concentration of 150 pM was observed at the sediment water interface (SWI) and the samples were close to 20 pM in the anoxic zone. Maximum of 450 pM concentration of dissolved total Cd was detected at the SWI of site P2. The labile fraction of Cd at this SWI varied between 85 and 177 pM. Below the SWI the total dissolved Cd was 695 pM. Thereafter it decreased to 30 pM in the anoxic zone, which indicates that Cd was removed from the pore water as precipitate (sulfide) and higher concentration below the SWI at site P2 is probably not associated with the reduction of Fe and Mn oxides.

Study on the transverse structures across Taiwan Strait

The mountain ranges are almost NE- or NNE-trending in mainland and Taiwan island across the strait. But a number of correspondent transverse structures across Taiwan Strait have been identified on the basis of morphology, surface structure, deep seismic survey and gravity field etc. Moreover, it is inferred from the square or/and rectangular shape of the isoseist maps of 8 M≥ 6 earthquakes occurring in the western foothill plain of Taiwan that there is an apparent segmentation of the Taiwan Island along the N-S orientation. This has been verified from the GPS’s results of the ground motions measured during the Chi-Chi earthquake in 1999. As a matter of fact, the transverse structures within the Taiwan Island could be correlated with more salient NW- and EW-trending structures in the mainland of Fujian than in Taiwan. The investigation of the transverse structures across Taiwan Strait is conducive to realizing the geology within the strait. Hence, the tectonic sketch map of the strait as well as mainland and island drawn in this context shows NW- and EW-trending structures for the study area.

Surface wave excitation in the western coastal plain of Taiwan during the 1999 Chi‐Chi earthquake

During the 1999 Chi‐Chi Taiwan Earthquake, long‐period surface waves were excited in the western coastal plain of middle Taiwan. The seismic signals were well recorded by the Central Weather Bureau's strong motion seismometers. The surface wave period was between 2 and 10 seconds. Although there was no report on direct damage caused by surface waves, they were still very dangerous for structures like long‐period bridges and elevated railroad systems built for high‐speed bullet trains. In this study, we focus on simulating the factors that control the generation of long period surface waves in the western plain of middle Taiwan. The numerical method used is the pseudo‐spectral method. We use two criteria to justify the simulation results. The first criterion is the permanent displacement around the surface outcrop produced by a rupture fault. The second criterion is to match the Airy phase or the energy trains. We tested several parameters to see the effects on generating surface wave signals. The tested parameters are the rupture velocity, fault dip angle, and whether the fault rupture arrives at the ground surface or not. In this study, we reach three conclusions. First of all, if a medium‐sized earthquake occurs in the foothills of central Taiwan, long‐period surface waves can be generated in the western coastal plain only if the fault rupture has reached the top low velocity sediments or the ground surface. Second, rupture velocity will strongly control the duration of surface waves. Third, the excitation of surface waves is mostly controlled by the near surface fault rupture; the deeper part of the rupture will only affect body wave signals.

Characteristics of environmental geochemistry in the arseniasis area of the Inner Mongolia of China

In China, endemic arseniasis attributable to the geological-geochemistry environment is mainly found in the plain of the Great Bend of the Yellow River and the Hu-Bao plain in the Inner Mongolia Autonomous Region, in the Datong basin of Shanxi Province, the floodplain of the northern side of the Tian Mountain of Xinjiang Uygur Autonomous Region, and in the southwest coastal plain of Taiwan. These areas share many similar characteristics including widespread occurrences, a large population being affected, and the magnitude of risk involved. The population living in these areas is estimated to be around 5.5 × 105, of which of 2.5 × 105 are resident in Inner Mongolia. Based on our systematic research and comparison of various areas, we found the different types of arseniasis are often associated with different regions. The neural arseniasis is distributed in Xinjiang Uygur Autonomous Region and Shanxi Province, caused by inorganic arsenic in drinking water while the cycling-obstacle arseniasis is mainly found in Inner Mongolia and Taiwan, associated with organic arsenic in water. The distribution of arsenic affected villages in Inner Mongolia exhibits orientation and focus on low-lying land in the subsiding centre of the Great Bend basin, which was enriched with humus in the lake and limnetic deposits. Much CH4 gas can be detected in the water of shallow and deep wells in these villages. Some of the wells with higher concentrations of CH4 can even be ignited. This is a typical reductive geochemical environment. We tested the total amount of arsenic (ΣAs), As3+, and methyl arsenate in all types of water sources. It is found that the number of arseniasis cases is not clearly related to the total amount of arsenic (ΣAs) in the water. However, it is related to the ratio of As3+ plus methyl arsenic to the total amount of arsenic (ΣAs). The higher the ratio, the higher the number of people affected and the more serious the illness. The statistical results also indicate that good drinking water accounts for 60% of the drinking water source while the arsenic contaminated water makes up about 25% of the drinking water in the study area. This research reveals that the local geochemical environment is responsible for the spreading of the endemic arseniasis in the area and thus suggests a new direction of how to prevent such disease.

Transition from oblique subduction to collision in the northern Luzon arc‐Taiwan region: Constraints from bathymetry and seismic observations

We systematically study the detailed bathymetry, seismicity, and source parameters of large‐ and moderate‐sized earthquakes that occurred in the northern Luzon arc‐Taiwan region between 1964 and 1996. The purpose is to characterize the transition from oblique subduction to regional collision in terms of the distribution of morphological features, the characteristics of seismogenic structures, and the corresponding state of strain. To the south of 21.5°N, the existence of a subduction zone is clearly shown by both bathymetry and seismicity. The subducted Eurasia slab reaches a maximum depth of ∼200 km, and the depth decreases sharply as it approaches Taiwan. Focal mechanisms indicate that the subducted slab is in downdip extension for depths <150 km but switches to downdip compression at greater depths. To the north of 23°N, collision is clearly the predominant process with broad deformation on both sides of the suture. In between, the transition is accommodated by a distributed thrust deformation zone in the frontal portion of the accretionary prism, closure of the forearc basin, and the right‐lateral NE‐SW striking Taitung canyon fault zone (TCFZ). These structures resolve the differential movements between the subduction and collision zones and will repeatedly change their positions as the collision propagates southwestward. The present‐day plate boundary follows the axis of the Manila trench in the south, broadens significantly in the zone of transition, and finally becomes a zone of several tens of kilometers in width across eastern Taiwan. The deformation front, on the other hand, is located between the Western Foothills and Coastal plain in Taiwan, then connects to the Manila trench to the south. Seismic strain tensors indicate that the region to the north of TCFZ has a compression rate ∼15 times larger than that to the south. The northern Luzon arc shows characteristics of oblique subduction, but the effects of collision are not as significant within the subducted Eurasian lithosphere, as comparing to the subducted Philippine Sea plate beneath the southernmost Ryukyu arc.

Zoophilic Schistosomiasis on Taiwan: Reestablishment of Schistosoma japonicum Subsequent to Drastic Alteration of Habitats by Flood

Drastic alterations in the habitats of Schistosoma japonicum in the enzootic area of Taiwan practically eliminated the parasite in the focus studied. Observations over a period of several years allowed a comparison of the status of host-parasite relationships before and after interruption of the parasite cycle by natural causes. Although excessive flooding reduced the snail (Oncomelania formosana) population and the parasite infection in definitive hosts (lower vertebrates) to near nil, Oncomelania populations returned to near normal after approximately 1 year, followed by appearance of infection in rodents. An unusual compensation in biological productivity seemed to allow for rapid reestablishment of the schistosome cycle after abnormal circumstances had placed the parasite-snail-definitive host associations in jeopardy. The inability of the Taiwan strain of Schistosoma japonicum to infect man has been a biological curiosity for years, especially since the island is geographically located near the center of a broad arc of the Orient in which schistosomiasis is a disease of great concern. Confinement to a few small areas, plus a number of other biological factors, separate the species on Taiwan from a morphologically similar parasite designated by the same name in Japan, mainland China, the Philippines, and other areas of Southeast Asia. Continuation of the cycle under adverse conditions has added to the uniqueness of the schistosome situation. S. japonicum continues to propagate itself in spite of very low biotic potentials and other uncertain circumstances relating to zoophilic schistosomiasis on the island. During the past decade Dr. H. F. Hsii and associates (1952, 1962) have elucidated the various peculiarities which differentiate the Taiwan species from others in the Far East. Their early field observations revealed the low rates of infection in Oncomelania formosana in most of the localities studied in Pu-yen Hsiang (township) near Chang-hua. Subsequent observations over a Received for publication 29 March 1965. * Research task MR. 005.09-1601.3, Bureau of Medicine and Surgery, Navy Department. This study was supported in part by funding under Public Law 480, Section 104 (c). The opinion and assertions herein are those of the author and are not to be construed as official or reflecting the views of the Navy Department or Naval Service at large. period of several years in the same area by the present author have similarly indicated rates of infection so low in the snail and lower mammalian hosts that continuation of the cycle appears all but impossible. Factors such as the seasonal reduction of infection rates in mollusks during the winter months, unpredictable drying or man-imposed alterations of snail habitats for parts of the year, intensive rodent control campaigns which eliminate a number of the infected vertebrate hosts, etc., in the enzootic areas, add to the precariousness of host-parasite associations. Hairston (1962) has presented the problems relating to population ecology and has graphically illustrated the mathematical complexities to be surmounted for maintenance of the schistosome cycle in the Philippines, where conditions, though regulated by a multitude of natural variables, probably are more favorable for parasite survival than in Taiwan. During the course of field studies, a natural disaster altered the majority of schistosome habitats and practically eliminated the infection on the west-central coastal plain of Taiwan. For approximately 1 week the S. japonicum habitats were covered as a result of flooding after excessive rains. This occurred in August (1959), the season at which parasite transmission potentials are at their height. Biological activities relating to the parasite cycle within habitats were greatly reduced and temporarily suspended as the rich, well-cultivated and irrigated, alluvial plain of Pu-yen was submerged in 2 to 6 ft of fast-flowing

Land Reform in Taiwan: Its Effect on Rural Social Organization and Leadership

The Hokkien village of Hsin Hsing where the writer carried on field research for 16 months in 1957 and 1958, is in Chang-hua Hsien (county) on the west-central coastal plain of Taiwan. It is a wet-rice agricultural village whose population of 650 persons comprises descendants of Chinese who emigrated approximately 170 years ago from Fukien (near Amoy) in southeastern China.