An aim of the study is to understand the effect of recent urbanization on the increase of sediment disasters. A case study was done in Nagasaki City and its vicinity, where a severe disaster had occurred in July 1982. The results of this study are summarized as follows: (1) The houses built in the first period locate on the relatively safe morphological units such as lower terrace and gentle foot slope. (2) The houses built in the second period intruded onto the rather risky morphological units; steep slope, valley floor and river bed. These units were not used as a residential area before. (3) The houses built in the last period are settled on the more risky area compared to older settled areas. However the demand for new housing land increased. Thus it was decided to develop the area risky to sediment disaster. 相似文献
Since September 2017, the Kuroshio has taken a large-meander (LM) path in the region south of Japan. We examined characteristics of the 2017–present LM path in comparison with previous LM paths, using tide gauge, altimetric sea surface height, and bottom pressure data. The 2017–present LM path was formed from a path passing through a channel south of Hachijo-jima Island, while a typical LM path originated from a path through a channel north of Miyake-jima Island. The meander trough of this atypical path was found to be shifted far to the east and to vary on a timescale of months. These characteristics are different from those of a typical LM path but they are similar to those of the 1981–1984 LM path. Therefore, we identified two types of LM path; a stable and unstable LM paths. The 2017–present unstable type large meander has a zonal scale greater than that of the 2004–2005 stable type large meander and protrudes from the eastern boundary of the Shikoku Basin, i.e., Izu-Ogasawara Ridge. No significant bottom pressure depression was observed, associated with the formation of the 2017–present LM path, indicating that baroclinic instability was not important in the formation of this LM path. Due to no significant bottom steering, even during the 2017–present LM period, a mesoscale current path disturbance occurred southeast of Kyushu, propagated eastward, and amplified the offshore displacement of the Kuroshio.
Comprehensive global energetics analysis is carried out for the NCAR CCM2 with different horizontal resolutions of R15, T42,
T63, and T106 to assess the effect of various model truncations on the global energetics characteristics in climate models.
Both the energy levels and energy transformations are examined over the zonal wave number domain during a northern winter
and summer. In addition to the simulated atmosphere, the ECMWF global analysis during 1986 to 1990 is analyzed for comparison
using the same diagnostic scheme. Previous studies have revealed that zonal kinetic energy is supplied by synoptic disturbances
in terms of the zonal-wave interactions of kinetic energy. According to our result, however, such an energy flow from eddies
to zonal motions is valid only for zonal wave numbers up to about 30. We find that the zonal-wave interactions of kinetic
energy change sign beyond wave number 30 where the energy is transformed from zonal to eddies for both the ECMWF and CCM2-T106.
The large-scale zonal motions are diffusive against the short waves beyond wave number 30, which may well be parameterized
by various forms of the diffusion schemes. We suggest from this result that the atmospheric disturbances with wave numbers
lower than 30 are necessary to represent accurately the two-way interactions between zonal and eddy motions, because these
waves can actively influence the behavior of the zonal motions. Based on this finding, we suggest that the model resolution
of R15 is inadequate for climate studies from the energetics point of view, and that resolution of T42 is the minimum requirement
to represent the general circulation adequately. Some other discrepancies are discussed in detail for the coarse resolution
climate models.
Received: 15 July 1996/Accepted: 3 January 1997 相似文献
In order to understand the characteristics of shallow very low-frequency (VLF) events as revealed by recent ocean-floor observation studies, we perform a trial simulation of earthquake cycles in the Tonankai district by taking the characteristics of the 1944 Tonankai earthquake and assuming that slow earthquakes occur on numerous small asperities. Our simulation results show that the increase of moment release rate of shallower VLF events in the pre-seismic stage of a megathrust earthquake is higher than that of deeper VLF events. This increase may make leveling change due to VLF swarms detectable at Dense Oceanfloor Network system for Earthquakes and Tsunamis (DONET). We also introduce the time series of hydraulic pressure data at DONET, comparing with the leveling change expected from our numerical simulation. Since leveling change due to shallower VLF swarms is so local as to be incoherent, removal of the moving-averaged data from the data stacked by four nearby observation points in the same node may be useful to detect the short-term local leveling change. 相似文献