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41.
Takashi Abe 《Planetary and Space Science》1984,32(7):903-906
A theoretical consideration is given to the critical ionization velocity. A macroscopic theory is constructed, assuming that (1) the newly born ions have an unstable velocity distribution and (2) the resultant fluctuating electric field heats the electrons. For the critical ionization velocity to operate in the case of , the initial values of high speed ion (or newly ionized ion) density and suprathermal electron energy density should be above a certain threshold. This threshold depends upon the velocity diffusion co-efficient and the collisional loss rate of the newly ionized ion. 相似文献
42.
Netrananda Sahu Swadhin K. Behera Yosuke Yamashiki Kaoru Takara Toshio Yamagata 《Climate Dynamics》2012,39(7-8):1673-1680
Extreme stream-flow events of Citarum River are derived from the daily stream-flows at the Nanjung gauge station. Those events are identified based on their persistently extreme flows for 6 or more days during boreal fall when the seasonal mean stream-flow starts peaking-up from the lowest seasonal flows of June–August. Most of the extreme events of high-streamflows were related to La Ni?a conditions of tropical Pacific. A few of them were also associated with the negative phases of IOD and the newly identified El Ni?o Modoki. Unlike the cases of extreme high streamflows, extreme low streamflow events are seen to be associated with the positive IODs. Nevertheless, it was also found that the low-stream-flow events related to positive IOD events were also associated with El Ni?o events except for one independent event of 1977. Because the occurrence season coincides the peak season of IOD, not only the picked extreme events are seen to fall under the IOD seasons but also there exists a statistically significant correlation of 0.51 between the seasonal IOD index and the seasonal streamflows. There also exists a significant lag correlation when IOD of June–August season leads the streamflows of September–November. A significant but lower correlation coefficient (0.39) is also found between the seasonal streamflow and El Ni?o for September–November season only. 相似文献
43.
Hideo Shiogama Masahiro Watanabe Masakazu Yoshimori Tokuta Yokohata Tomoo Ogura James D. Annan Julia C. Hargreaves Manabu Abe Youichi Kamae Ryouta O’ishi Rei Nobui Seita Emori Toru Nozawa Ayako Abe-Ouchi Masahide Kimoto 《Climate Dynamics》2012,39(12):3041-3056
In this study, we constructed a perturbed physics ensemble (PPE) for the MIROC5 coupled atmosphere–ocean general circulation model (CGCM) to investigate the parametric uncertainty of climate sensitivity (CS). Previous studies of PPEs have mainly used the atmosphere-slab ocean models. A few PPE studies using a CGCM applied flux corrections, because perturbations in parameters can lead to large radiation imbalances at the top of the atmosphere and climate drifts. We developed a method to prevent climate drifts in PPE experiments using the MIROC5 CGCM without flux corrections. We simultaneously swept 10 parameters in atmosphere and surface schemes. The range of CS (estimated from our 35 ensemble members) was not wide (2.2–3.2?°C). The shortwave cloud feedback related to changes in middle-level cloud albedo dominated the variations in the total feedback. We found three performance metrics for the present climate simulations of middle-level cloud albedo, precipitation, and ENSO amplitude that systematically relate to the variations in shortwave cloud feedback in this PPE. 相似文献
44.
Takanori Shimizu Koji Tamai Ikuhiro Hosoda Shoji Noguchi Yuji Kominami Toshio Abe Kenzo Kitamura Ushio Kurokawa Delphis F. Levia Tayoko Kubota Naoki Kabeya Shin'ichi Iida Tatsuhiko Nobuhiro Shinji Sawano Sho Iwagami Akira Shimizu Yoshio Tsuboyama 《水文研究》2021,35(10):e14376
This data note introduces a database of long-term daily total precipitation and stream discharge data for seven forested watersheds in Japan that have been continuously monitored by the Forestry and Forest Products Research Institute. Three of the watersheds started data collection in the 1930s. Forest cover across the sites ranges from cool to warm temperate regions with the latitude spanning from 31 to 44° N and annual precipitation ranging from 1200 to 3000 mm yr−1. The effects of vegetation change via clearcutting, thinning and forest fire (among other stressors) on stream discharge can be analysed from the long-term observation sites. Moreover, this multi-site dataset allows for inter- and intra-site comparisons of annual water loss (difference of annual precipitation and stream discharge). These long-term datasets can provide comprehensive insights into the effects of climate change and other stressors on forested ecosystems, not only in Japan but across a spectrum of forest types, if combined with other long-term records from other forested watersheds across the world. 相似文献
45.
For efficient and targeted management, this study demonstrates a recently developed non-point source (NPS) pollution model for a year-long estimation in the Pingqiao River Basin (22.3 km2) in China. This simple but physically reasonable model estimates NPS export in terms of land use by reflecting spatial hydrological features and source runoff measurements under different land-use types. The NPS export was separately analysed by a distributed hydrological model, a spatial hydrograph-separation technique, and an empirical water quality sub-model. Simulation results suggest that 57 890 kg of total nitrogen (TN) and 1148 kg of total phosphorus (TP) were delivered. The results, validated with observed stream concentrations, show relative errors of 23.3% for TN and 47.4% for TP. Countermeasures for urban areas (5.3% of total area) were prioritized because of the high contribution rate to TN (14.1%) and TP (26.2%) which is caused by the high degree of runoff (8.5%) and pollution source. 相似文献
46.
Diets of Steller sea lions off the coast of Hokkaido,Japan: An inter‐decadal and geographic comparison 下载免费PDF全文
Yoko Goto Akihiko Wada Noboru Hoshino Takahiro Takashima Masaki Mitsuhashi Kaoru Hattori Orio Yamamura 《Marine Ecology》2017,38(6)
Inter‐decadal and geographic variations in the diets of Steller sea lion, Eumetopias jubatus, were examined based on the contents of 408 stomachs collected from coastal areas around Hokkaido Island during the periods 1994–1998 and 2005–2012. The most important prey species in the 1990s were gadid fishes (walleye pollock [Gadus chalcogrammus], Pacific cod [Gadus microcephalus] and saffron cod [Eleginus gracilis]). The frequency of occurrence and gravimetric contribution of gadids decreased in the 2000s latter period at three study sites (Rausu, Shakotan and Rebun) and were replaced by Okhotsk Atka mackerel (Pleurogrammus azonus) and smooth lumpsucker (Aptocyclus ventricosus). However, analysis based on gravimetric composition indicated that the dietary diversity of prey showed only a slight inter‐decadal difference, reflecting the wide diversity of prey ingested during both study periods. These results indicate that Steller sea lions along the Hokkaido coast are opportunistic feeders that utilize a wide variety of prey, and appear to feed mainly upon prey that is easily obtained. 相似文献
47.
Volume transports proceeding to the Kuroshio Extension region and recirculating in the Shikoku Basin 总被引:4,自引:1,他引:3
Akira Nagano Kaoru Ichikawa Hiroshi Ichikawa Masanori Konda Kiyoshi Murakami 《Journal of Oceanography》2013,69(3):285-293
The volume transport of the Kuroshio, the western boundary current of the North Pacific subtropical gyre, varies vigorously due to merging of disturbances propagating from the entire North Pacific. Taking into account the recirculation in the Shikoku Basin by the zonal observation line at 30°N to the west of the Izu–Ogasawara Ridge, we estimated the volume transport in the top 1,000 m layer toward the Kuroshio Extension region. The volume transport of the local recirculation gyre in the Shikoku Basin increases associated with the westward extension of the gyre, particularly in the period of the large meandering path of the Kuroshio south of Japan. Meanwhile, most of the transport variations toward the Kuroshio Extension region correspond to those of the Kuroshio transport on the continental slope south of Japan, which vary independently of those of the recirculation gyre. 相似文献
48.
Large ageostrophic currents in the abyssal layer southeast of Kyushu, Japan, by direct measurement of LADCP 总被引:1,自引:1,他引:0
Akira Nagano Kaoru Ichikawa Hiroshi Ichikawa Yasushi Yoshikawa Kiyoshi Murakami 《Journal of Oceanography》2013,69(2):259-268
With full-depth LADCP velocity data collected in a wide area southeast of Kyushu, Japan, large velocity currents, occasionally exceeding 15 cm s?1, were observed in a thick, 500–1,500 m, near-homogeneous density layer below approximately 3,000 m depth around the steep topographies. The currents were found not to flow along the topographic contours, and to be strongly ageostrophic. The directions of the bottom-layer currents are rather related with phase of the semi-diurnal tides, suggesting deeply intruded internal tides generated at the steep topographies. 相似文献
49.
Blair Thornton Seiki Ohnishi Tamaki Ura Naoteru Odano Shun Sasaki Tsuneo Fujita Tomowo Watanabe Kaoru Nakata Tsuneo Ono Daisuke Ambe 《Marine pollution bulletin》2013
An estimated 3.5 ± 0.7 × 1015 Bq of 137Cs is thought to have been discharged into the ocean following the melt down at Fukushima Dai-ichi Nuclear Power Plant (F1NPP). While efforts have been made to monitor seafloor radiation levels, the sampling techniques used cannot capture the continuous distribution of radionuclides. In this work, we apply in situ measurement techniques using a towed gamma ray spectrometer to map the continuous distribution of 137Cs on the seafloor within 20 km of the F1NPP. The results reveal the existence of local 137Cs anomalies, with levels of 137Cs an order of magnitude higher than the surrounding seafloors. The sizes of the anomalies mapped in this work range from a few meters to a few hundreds of meters in length, and it is demonstrated that the distribution of these anomalies is strongly influenced by meter scale features of the terrain. 相似文献
50.
The microstructural state and evolution of fault gouge has important implications for the mechanical behaviour, and hence
the seismic slip potential of faults. We use 3D discrete element (DEM) simulations to investigate the fragmentation processes
operating in fault gouge during shear. Our granular fault gouge models consist of aggregate grains, each composed of several
thousand spherical particles stuck together with breakable elastic bonds. The aggregate grains are confined between two blocks
of solid material and sheared under a given normal stress. During shear, the grains can fragment in a somewhat realistic way
leading to an evolution of grain size, grain shape and overall texture. The ‘breaking up’ of the fault gouge is driven by
two distinct comminution mechanisms: grain abrasion and grain splitting. The relative importance of the two mechanisms depends
on applied normal stress, boundary wall roughness and accumulated shear strain. If normal stress is sufficiently high, grain
splitting contributes significantly to comminution, particularly in the initial stages of the simulations. In contrast, grain
abrasion is the dominant mechanism operating in simulations carried out at lower normal stress and is also the main fragmentation
mechanism during the later stages of all simulations. Rough boundaries promote relatively more grain splitting whereas smooth
boundaries favor grain abrasion. Grain splitting (plus accompanying abrasion) appears to be an efficient mechanism for reducing
the mean grain size of the gouge debris and leads rapidly to a power law size distribution with an exponent that increases
with strain. Grain abrasion (acting alone) is an effective way to generate excess fine grains and leads to a bimodal distribution
of grain sizes. We suggest that these two distinct mechanisms would operate at different stages of a fault’s history. The
resulting distributions in grain size and grain shape may significantly affect frictional strength and stability. Our results
therefore have implications for the earthquake potential of seismically active faults with accumulations of gouge. They may
also be relevant to the susceptibility of rockslides since non-cohesive basal shear zones will evolve in a similar way and
potentially control the dynamics of the slide. 相似文献