Effects of Snowfall on Drifting Snow and Wind Structure Near a Surface     

Masaki Nemoto  Takeshi Sato  Kenji Kosugi  Shigeto Mochizuki 《Boundary-Layer Meteorology》2014,152(3):395-410

Wind-tunnel and numerical experiments were performed to investigate the effects of snowfall on the wind profile and the development of drifting snow. Wind profiles and mass-flux profiles of drifting snow were measured with and without artificial snowfall over a snow surface within the tunnel. Wind and shear-stress profiles and the impact speeds of the snowflakes during snowfall were also investigated numerically. During snowfall, snowflakes transfer part of their horizontal momentum to the air, which increases the stress close to the snow surface; however, the resultant modifications of the wind profiles are small. Because snowflakes have large momentum, the decomposed snow crystals that result from their collision with a surface can form a saltation layer, even over a hard snow surface where entrainment of the grains from the surface does not occur. Additionally, during snowfall, the threshold friction velocity can be lower than the impact threshold because snowflake fragmentation facilitates snow drifting. The broken crystals contribute to the increase in the number of drifting snow grains, even below the impact threshold.  相似文献   

Subduction of the Woodlark Basin at New Britain Trench, Solomon Islands region   总被引：1，自引：0，他引：1  

Shinji Yoneshima  Kimihiro Mochizuki  Eiichiro Araki  Ryota Hino  Masanao Shinohara  Kiyoshi Suyehiro 《Tectonophysics》2005,397(3-4):225-239

The Woodlark Basin, located south of the Solomon Islands arc region, is a young (5 Ma) oceanic basin that subducts beneath the New Britain Trench. This region is one of only a few subduction zones in the world where it is possible to study a young plate subduction of several Ma. To obtain the image of the subducting slab at the western side of the Woodlark Basin, a 40-day Ocean Bottom Seismometer (OBS) survey was conducted in 1998 to detect the micro-seismic activity. It was the first time such a survey had been performed in this location and over 600 hypocenters were located. The seismic activity is concentrated at the 10–60 km depth range along the plate boundary. The upper limit just about coincides with the leading edge of the accretionary wedge. The upper limit boundary was identified as the up-dip limit of the seismogenic zone, whereas the down-dip limit of the seismogenic zone was difficult to define. The dip angle of the plate at the high seismicity zone was found to average about 30°. Using the Cascadia subduction zone for comparison, which is a typical example of a young plate subduction, suggests that the subduction of the Woodlark Basin was differentiated by a high dip angle and rather landward location of the seismic front from the trench axis (30 km landward from the trench axis). Furthermore, as pointed out by previous researchers, the convergent margin of the Solomon Islands region is imposed with a high stress state, probably due to the collision of the Ontong Java Plateau and a rather rapid convergence rate (10 cm/year). The results of the high angle plate subduction and inner crust earthquakes beneath the Shortland Basin strongly support the high stress state. The collision of the Ontong Java Plateau, the relatively rapid convergence rate, and moderately cold slab as evidenced by low heat flow, rather than the plate age, may be dominantly responsible for the geometry of the seismogenic zone in the western part of the Woodlark Basin subduction zone.  相似文献   

Linear inversion of geomagnetic inclination and declination     

E. Mochizuki 《Geophysical Journal International》1994,119(1):349-351

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Interannual variability of North Pacific eastern subtropical mode water formation in the 1990s derived from a 4-dimensional variational ocean data assimilation experiment     

T. Toyoda  T. Awaji  S. Masuda  N. Sugiura  H. Igarashi  T. Mochizuki  Y. Ishikawa 《Dynamics of Atmospheres and Oceans》2011,51(1-2):1-25

The interannual variability of eastern subtropical mode water (ESTMW) formation in the North Pacific is examined using a new ocean dataset constructed by a 4-dimensional variational data assimilation experiment covering the decade of the 1990s. The volume of newly formed ESTMW varies due to interannual variability in the following three physical processes taking place in the surface layer: (1) convergence in the transport of surface saline water induced by Ekman flow in the vicinity of the formation region, (2) thermal stratification in the preconditioning phase in association with the insolation anomaly induced largely by low-level cloud coverage, and (3) wintertime surface cooling in the eastern subtropics. We find that, in addition to the surface forcing, the properties of both the ESTMW and the upper mixed-layer water are broadly controlled by the volume of the new ESTMW component, and that the variations in the upper mixed-layer water affect the properties of ESTMW formed in the following winter. Due to the combined effect of these processes, the ESTMW subducts down to subsurface layers with a wide range of σ_θ values lying between 24.8 and 25.4 and with significant interannual variation in water mass formation.  相似文献   

2011年日本东北近海地震震源上方的位移     

M.Sato  T.Ishikawa  N.Ujihara  S.Yoshida  M.Fujita  M.Mochizuki  A.Asada  万永革 《世界地震译丛》2011,(3)

2011年3月11日,一次大的板间地震(MW9.0)发生在日本东北宫城县附近的板块交界处。根据余震分布推测的震源区为约500km长、200km宽的近海区(Japan Meteo-rological Agency,2011)。  相似文献   

Assessing the designs and effectiveness of Japan's emissions trading scheme     

Junko Mochizuki 《Climate Policy》2013,13(6):1337-1349

After years of discussions and trials, Japan's domestic emissions trading scheme remains purely voluntary. The newly elected Democratic Party of Japan (DPJ) has taken a firmer stance on climate change, initially intending to establish a nationwide mandatory cap-and-trade as early as 2011. This has promoted several questions regarding the possible designs and feasibility of such a scheme. This article describes the key features of the two trial schemes implemented, thus far, assesses the effectiveness of their implementation and discusses what will be the likely areas of contention should the Japanese government introduce a mandatory cap-and-trade in the future. The analyses indicate that the initial years of ‘Japan's Voluntary Emissions Trading Scheme’ (JVETS) implementation have shown positive performance, although its scale has remained limited. The ‘Trial Implementation of an Integrated Domestic Market for Emissions Trading’ emerged as a hybrid scheme, one that incorporated varying interests. Significant institutional developments have taken place in recent years, however the effectiveness of the present trial scheme also seems restricted.  相似文献   

Ray tracing of body waves in an anisotropic medium     

E. Mochizuki 《Geophysical Journal International》1987,90(3):627-634

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Spherical harmonic decomposition of an elastic tensor     

E. Mochizuki 《Geophysical Journal International》1988,93(3):521-526

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Palaeointensities of the Auckland geomagnetic excursions by the LTD-DHT Shaw method     

Nobutatsu Mochizuki  Hideo Tsunakawa  John Cassidy 《Physics of the Earth and Planetary Interiors》2006,154(2):168-179

We report new palaeointensity results concerning the Auckland geomagnetic excursions using the double heating technique of the Shaw method with low temperature demagnetisation (LTD-DHT Shaw method). The excursional palaeodirections recorded in six volcanoes of the Auckland volcanic field, New Zealand, have been classified into three groups: north-down (ND), west-up (WU) and south-up (SU) directions. In the present study, five to six consistent palaeointensities have been obtained from each of five volcanoes recording the Auckland geomagnetic excursions. The Wiri (27 ka), Crater Hill and Puketutu volcanoes (ND group) yielded mean palaeointensities of 10.6 ± 1.2 (1σ), 11.8 ± 2.8 and 11.1 ± 0.4 μT, respectively. The Hampton Park volcano (55 ka; WU group) gave 9.5 ± 1.2 μT while the McLennan Hills volcano (SU group) gave 2.5 ± 0.5 μT. It is notable that consistent palaeointensities have been obtained from the three different volcanoes which have almost the same palaeodirections (ND group), possibly supporting the reliability of the palaeointensity data. These five palaeointensities for the Auckland geomagnetic excursions correspond to virtual dipole moments (VDMs) of 0.6-2.1 × 10²² A m², whereas three mean palaeointensities obtained from the Auckland volcanoes having non-excursional palaeodirections are 13.1-40.0 μT giving stronger VDMs of 2.1-6.9 × 10²² A m². These results suggest that the dipole component of the geomagnetic field reduced to about 2 × 10²² A m² or less during the Auckland geomagnetic excursions.  相似文献   

Paleotectonic structures and their influence on recent seismo-tectonics in the south Kuril subduction zone     

Junzo  Kasahara  Toshinori  Sato  Kimihiro  Mochizuki Kazuo  Kobayashi 《Island Arc》1997,6(3):267-280

Abstract Bathymetric data from south of Hokkaido obtained during a cruise of R/V Hakuho-Maru are summarized, and their correlation with earthquake occurrence is discussed. There are structural lineations on the seaward slope of the Kuril Trench, oblique to the Kuril Trench axis and parallel to the magnetic lineations in the Pacific plate. The structural lineations comprise horst-grabens generated by normal faulting. This suggests that Cretaceous tectonic structures originating at the spreading centre affect present seismotectonics around the trench axis. The structural-magnetic relation is compared to the case of the Japan Trench. North-east of the surveyed area, there are two major fracture zones (Nosappu Fracture Zone and Iturup Fracture Zone) that divide the oceanic plate into three segments. If the fracture zones (FZ) and the zone of paleo-mechanical weakness, represented by magnetic lineations, can control the direction of normal faults at a trench, the extent of the resulting topographic roughness on the seaward slope of the trench would be different across an FZ because of the differences in ages. By studying recent large earthquakes occurring in the south Kuril region, it is shown that several main-aftershock distributions for large earthquakes in this region are bounded by the Nosappu FZ and the Iturup FZ. Two models (Barrier model and Rebound model) are presented to interpret earthquake occurrence near the south Kuril Islands. The Barrier model explains seismic boundaries seen in several examples for earthquake occurrence in the south Kuril regions. The fracture zone forming the boundary of two segments with different magnetic lineations is also the boundary of two different normal fault systems on their ocean bottom, and the difference in sea-bottom roughness between two normal fault systems should affect the seismic coupling at a plate interface. Due to the difference of seismic coupling, earthquake occurrence is controlled by an FZ and then the FZ acts as a seismic boundary (Barrier model). Existing normal faults created by plate bending of subducting oceanic plate should rebound after its subduction (Rebound model). This rebound of normal faults may cause intraplate earthquakes with a high-angle reverse-fault mechanism such as the 1994 Shikotan Earthquake. The energy released by an intraplate earthquake generated by normal-fault rebounding is not directly related to that of interplate earthquakes such as low-angle thrust earthquakes. It is a reason why large earthquakes occurred in the same region during a relatively short period.  相似文献