Evaluating metrics derived from Landsat 8 OLI imagery to map crop cover     

Rei Sonobe  Yuki Yamaya  Hiroshi Tani  Xiufeng Wang  Nobuyuki Kobayashi  Kan-ichiro Mochizuki 《国际地球制图》2019,34(8):839-855

Developing techniques are required to generate agricultural land cover maps to monitor agricultural fields. Landsat 8 Operational Land Imager (OLI) offers reflectance data over the visible to shortwave-infrared range. OLI offers several advantages, such as adequate spatial and spectral resolution, and 16 day repeat coverage, furthermore, spectral indices derived from Landsat 8 OLI possess great potential for evaluating the status of vegetation. Additionally, classification algorithms are essential for generating accurate maps. Recently, multi-Grained Cascade Forest, which is also called deep forest, was proposed, and it was shown to give highly competitive performance for classification. However, the ability of this algorithm to generate crop maps with satellite data had not yet been evaluated. In this study, the reflectance at 7 bands and 57 spectral indices calculated from Landsat 8 OLI data were evaluated for its potential for crop type identification.  相似文献   

Origin and fate of particulate organic matter in the southern Beaufort Sea – Amundsen Gulf region,Canadian Arctic     

Cédric Magen  Gwénaëlle Chaillou  Sean A. Crowe  Alfonso Mucci  Bjørn Sundby  Aiguo Gao  Ryosuke Makabe  Hiroshi Sasaki 《Estuarine, Coastal and Shelf Science》2010

To establish the relative importance of terrigenous and marine organic matter in the southern Beaufort Sea, we measured the concentrations and the stable isotopic compositions of organic carbon and total nitrogen in sediments and in settling particles intercepted by sediment traps. The organic carbon content of surface sediment in the Chukchi and southern Beaufort Seas ranged from 0.6 to 1.6% dry wt., without a clear geographical pattern. The C_ORG:N_TOT ratio ranged from 7.0 to 10.4 and did not vary significantly downcore at any one station. Values of δ¹³C_ORG and δ¹⁵N_TOT in the sediment samples were strongly correlated, with the highest values, indicative of a more marine contribution, in the Amundsen Gulf. In contrast, the organic matter content, elemental (C_ORG:N_TOT ratio) and isotopic (δ¹³C_ORG and δ¹⁵N_TOT) composition of the settling particles was different from and much more variable than in the bottom sediments. The isotopic signature of organic matter in the Beaufort Sea is well constrained by three distinct end-members: a labile marine component produced in situ by planktonic organisms, a refractory marine component, the end product of respiration and diagenesis, and a refractory terrigenous component. A three-component mixing model explains the scatter observed in the stable isotope signatures of the sediment trap samples and accommodates an apparent two-component mixing model of the organic matter in sediments. The suspended matter in the water column contains organic matter varying from essentially labile and marine to mostly refractory and terrigenous. As it settles through the water column, the labile marine organic matter is degraded, and its original stable isotope signature changes towards the signature of the marine refractory component. This process continues in the bottom sediment with the result that the sedimentary organic matter becomes dominated by the refractory terrigenous and marine components.  相似文献   

The basement geology of Japan from A to Z     

Simon R. Wallis  Ken Yamaoka  Hiroshi Mori  Akira Ishiwatari  Kazuhiro Miyazaki  Hayato Ueda 《Island Arc》2020,29(1)

The Precambrian and lower Paleozoic units of the Japanese basement such as the Hida Oki and South Kitakami terranes have geological affinities with the eastern Asia continent and particularly strong correlation with units of the South China block. There are also indications from units such as the Hitachi metamorphics of the Abukuma terrane and blocks in the Maizuru terrane that some material may have been derived from the North China block. In addition to magmatism, the Japanese region has seen substantial growth due to tectonic accretion. The accreted units dominantly consist of mudstone and sandstone derived from the continental margin with lesser amounts of basaltic rocks associated with siliceous deep ocean sediments and local limestone. Two main phases of accretionary activity and related metamorphism are recorded in the Jurassic Mino–Tanba–Ashio, Chichibu, and North Kitakami terranes and in the Cretaceous to Neogene Shimanto and Sanbagawa terranes. Other accreted material includes ophiolitic sequences, e.g. the Yakuno ophiolite of the Maizuru terrane, the Oeyama ophiolite of the Sangun terrane, and the Hayachine–Miyamori ophiolite of the South Kitakami terrane, and limestone‐capped ocean plateaus such as the Akiyoshi terrane. The ophiolitic units are likely derived from arc and back‐arc basin settings. There has been no continental collision in Japan, meaning the oceanic subduction record is more complete than in convergent orogens seen in intracontinental settings making this a good place to study the geological record of accretion. Hokkaido lacks most of the Paleozoic history recognized in Honshu, Shikoku, Kyushu, and the Ryukyu Islands to the south and its geology reflects the Cenozoic development of two convergent domains with volcanic arcs, their approach, and eventual collision. The Hidaka terrane reveals a cross section through a volcanic arc and the main accretionary complex of the convergent system is represented by the Sorachi–Yezo terrane.  相似文献   

Seasonal Patterns of Vertical Distribution between Meiofaunal Groups in Relation to Phytodetritus Deposition in the Bathyal Sagami Bay, Central Japan   总被引：2，自引：0，他引：2  

Motohiro Shimanaga  Hiroshi Kitazato  Yoshihisa Shirayama 《Journal of Oceanography》2000,56(4):379-387

Temporal changes in the vertical distribution of metazoan meiofaunal groups were examined at a bathyal site (depth 1450 m) in Sagami Bay from December 1996 to August 1998. Among major meiofaunal groups, the vertical distributions of copepods (adults and copepodites), and kinorhynchs changed seasonally and they concentrated in the shallower part in the sediment profile when CPE concentrations were higher. Seasonal changes in the vertical distributions of ovigerous females and nauplii of copepods were not related to CPE concentrations, but related to that of total copepods. On the other hand, nematodes, ostracods, and polychaetes did not show seasonal migrations. These results suggest that there is a difference in the response to the sedimentation of organic matter between metazoan meiofaunal taxa.  相似文献   

Effects of Larval Settlement and Post-Settlement Mortality on the Distribution Pattern and Abundance of the Spirorbid Tube Worm Neodexiospira brasiliensis (Grube) (Polychaeta) Living on Seagrass Leaves     

Kyoko Hamamoto  & Hiroshi Mukai 《Marine Ecology》1999,20(3-4):251-272

Abstract. The role of larval settlement, post-settlement mortality and competition with a red algae in determining the patterns of abundance and distribution of the spirorbid tube worm Neodexiospira brasiliensis (Grube) (Polychaeta: Spirorbidae) on leaves of three seagrass species: Zostera marina Linnaeus, Zostera asiatica Miki and Phyllospadix iwatensis Makino were examined in Aininkap, Akkeshi Bay, Akkeshi, Hokkaido, Japan. Field collections of seagrass shoots were made at about 1-week intervals. The density of newly settled larvae (< 0.3 mm in tube diameter) increased significantly on Z. asiatica and P. iwatensis , but not on Z. marina during the sampling period. It was highest on Z. asiatica among the three seagrass species, followed by P. iwatensis and Z. marina . Newly settled larvae occurred more on the basal part of younger leaves of each seagrass species. Mortality tended to be high on Z. marina , followed by Z. asiatica and P. iwatensis , although the differences were not great. Size-specific mortality showed the existence of high mortality in early post-settlement stages on Z. asiatica and P. iwatenisis . Relatively high mortality was also suffered by individuals with a tube diameter over 1.5 mm. Growth in tube diameter of N. brasiliensis was slower on P. iwatensis than on the other two seagrasses. The effect of a calcareous red algae on larval settlement was investigated with removal experiments; however, no effect of red algae was detected. Patterns in the distribution and abundance of N. brasiliensis on leaves of three seagrass species resulted from the heterogeneity of larval settlement rather than from post-settlement mortality or competition with red algae. Different densities of larval settlement among the three seagrass species or on a leaf are likely to relate to larval behaviour, such as negative phototaxis.  相似文献   

Overview of the 1990–1995 eruption at Unzen Volcano     

Setsuya Nakada  Hiroshi Shimizu  Kazuya Ohta 《Journal of Volcanology and Geothermal Research》1999,89(1-4)

Following 198 years of dormancy, a small phreatic eruption started at the summit of Unzen Volcano (Mt. Fugen) in November 1990. A swarm of volcano-tectonic (VT) earthquakes had begun below the western flank of the volcano a year before this eruption, and isolated tremor occurred below the summit shortly before it. The focus of VT events had migrated eastward to the summit and became shallower. Following a period of phreatic activity, phreatomagmatic eruptions began in February 1991, became larger with time, and developed into a dacite dome eruption in May 1991 that lasted approximately 4 years. The emergence of the dome followed inflation, demagnetization and a swarm of high-frequency (HF) earthquakes in the crater area. After the dome appeared, activity of the VT earthquakes and the summit HF events was replaced largely by low-frequency (LF) earthquakes. Magma was discharged nearly continuously through the period of dome growth, and the rate decreased roughly with time. The lava dome grew in an unstable form on the shoulder of Mt. Fugen, with repeating partial collapses. The growth was exogenous when the lava effusion rate was high, and endogenous when low. A total of 13 lobes grew as a result of exogenous growth. Vigorous swarms of LF earthquakes occurred just prior to each lobe extrusion. Endogenous growth was accompanied by strong deformation of the crater floor and HF and LF earthquakes. By repeated exogenous and endogenous growth, a large dome was formed over the crater. Pyroclastic flows frequently descended to the northeast, east, and southeast, and their deposits extensively covered the eastern slope and flank of Mt. Fugen. Major pyroclastic flows took place when the lava effusion rate was high. Small vulcanian explosions were limited in the initial stage of dome growth. One of them occurred following collapse of the dome. The total volume of magma erupted was 2.1×10⁸ m³ (dense-rock-equivalent); about a half of this volume remained as a lava dome at the summit (1.2 km long, 0.8 km wide and 230–540 m high). The eruption finished with extrusion of a spine at the endogenous dome top. Several monitoring results convinced us that the eruption had come to an end: the minimal levels of both seismicity and rockfalls, no discharge of magma, the minimal SO₂ flux, and cessation of subsidence of the western flank of the volcano. The dome started slow deformation and cooling after the halt of magma effusion in February 1995.  相似文献   

Comparison of Kuroshio surface velocities derived from satellite altimeter and drifting buoy data   总被引：2，自引：0，他引：2  

Hiroshi Uchida  Shiro Imawaki  Jian-Hwa Hu 《Journal of Oceanography》1998,54(1):115-122

Sea-surface geostrophic velocities for the Kuroshio region calculated from TOPEX/POSEIDON altimetry data together within situ oceanographic data are compared with surface velocities derived from drifting buoy trajectories. The geostrophic velocities agree well with the observed velocities, suggesting that the Kuroshio surface layer is essentially in geostrophic balance, within measurement error. The comparison is improved a little when the centrifugal acceleration is taken into account. The observed velocities are divided into the temporal mean and fluctuation components, and the partitioning of velocities between these two components is examined. For the Kuroshio region, most of the fluctuation components of the velocities derived from drifting buoys are found to be positive. This result suggests that Eulerian mean velocities for the Kuroshio region estimated from drifting buoy data tend to be larger than actual means, due to the buoy’s tendency to sample preferentially in the high-velocity Kuroshio.  相似文献   

鲈鱼生长催乳素的分离纯化与N-末端序列分析   总被引：1，自引：1，他引：0  

徐斌  张培军  苗宏志  李德尚  森山俊介  川内浩司 《海洋学报》1998,20(2):83-89

生长催乳素(SL)是生长激素/催乳素家族的一种新的脑垂体蛋白质激素,本研究首次从鲈鱼脑垂体中分离得到.鲈鱼脑垂体在碱性条件下,经葡聚糖凝胶(SephadexG-100)过滤和反相高效液相色谱(rpHPLC)分离出纯化的鲈鱼生长催乳素,(sbSL),并与大麻哈鱼生长催乳素(sSL)抗体发生特异性的Western免疫印迹交叉反应证实.SDS-聚丙烯酰胺凝胶电泳(SDS-PAGE)分析,发现鲈鱼生长催乳素分别是由分子量为23.2×103和28.4×103u两种形式组成(后者可能是一种糖基化形式).根据Edman降解原理,测得鲈鱼生长催乳素的N-末端16个氨基酸的序列,它与已知鱼类生长催乳素的N-末端序列比较,具有较高的同源性;由此进一步证实,分离纯化得到的鲈鱼生长催乳素是正确的.  相似文献   

Observation of the abyssal current in the West Mariana Basin   总被引：1，自引：1，他引：1  

Noriya Yoshioka  Masahiro Endoh  Hiroshi Ishizaki 《Journal of Oceanography》1988,44(1):33-39

In order to investigate long-term variations of deep sea currents and temperature in the western North Pacific, a direct current measurement was made at 12.5°N, 137°E from July 1985 to July 1986. The current meter was moored at a depth of about 4,000 m (bottom depth 4,604 m) in the West Mariana Basin, very close to the deep water passage to the North Pacific Basin. Throughout the observed period, the current flows southward with an average speed of 0.8 cm sec^–1. There are significant variations of both currents and temperature within the period of 60 days. For the shorter time scales, in addition to the tidal oscillations with one day and half day periods, there is a notable spectral peak of the current with a clockwise rotation at a period of 2.2 days, which is slightly shorter than the local inertial period of 2.3 days.The observed southward current seems to indicate that the deep sea water in the West Mariana Basin flows out through the sill which is deeper than 4,000 m and is located about 200 km southeast of the mooring point. A simple analysis of the linear plane wave indicates that the medium time-scale variation with a period of 60 days is associated with the barotropic Rossby wave whose wavelength is 390 km and whose trough direction is 30° clockwise from the north.  相似文献   

Direct measurements of mid-depth circulation in the Shikoku basin by tracking SOFAR floats   总被引：1，自引：0，他引：1  

Keisuke Taira  Shoji Kitagawa  Katsuto Uehara  Hiroshi Ichikawa  Hiroyuki Hachiya  Toshihiko Teramoto 《Journal of Oceanography》1990,46(6):296-306

Mid-depth circulation of the Shikoku Basin was measured by tracking four SOFAR floats drifting at the 1,500 m layer. Two floats were released on 17 April 1988 at 30°N, 135°59E and tracked for 433 days. Another two were released on 3 November 1988 at 29°52N and 133°25E, and tracked for 234 days. Two floats flowed clockwise around the Shikoku Warm Water Mass with a diameter of 400 km centered at 31°N and 136°E and a mean drift speed of 4.5 cm sec^–1. One of the floats showed about ten counterclockwise rotations with a period of about 8 days and a maximum speed of 80 cm sec^–1 in the sea area west to the Izu Ridge. In the east to Kyushu, a southward flow was observed under the northward flowing Kuroshio. The southward flow of 4 cm sec^–1 drift speed was considered to be a part of the counterclockwise circulation at deep layers along the perimeter of the Shikoku Basin. One float remained for 234 days in a limited area of 100 km by 150 km in the western part of the basin.  相似文献