Study of method for synthetic precipitation data for ungauged sites using quantitative precipitation model

A method was developed to estimate a synthetic precipitation record for ungauged sites using irregular coarse observations. The proposed synthetic precipitation data were produced with ultrahigh hourly resolution on a regular 1 × 1 km grid. The proposed method was used to analyze selected real-time observational data collected in South Korea from 2010 to the end of 2014. The observed precipitation data were measured using the Automatic Weather System and Automated Synoptic Observing System. The principal objective of the proposed method was to estimate the additional effects of orography on precipitation introduced by ultrahigh- resolution (1 × 1 km) topography provided by a digital elevation model. The Global Forecast System analysis of the National Centers for Environmental Prediction was used for the upper-atmospheric conditions, necessary for estimating the orographic effects. Precipitation data from 48 of the more than 600 observation sites used in the study, which matched the grid points of the synthetic data, were not included in the synthetic data estimation. Instead, these data were used to evaluate the proposed method by direct comparison with the real observations at these sites. A bias score was investigated by comparison of the synthetic precipitation data with the observations. In this comparison, the number of Hit, False, Miss, and Correct results for 2010-2014 was 74738, 25778, 7544, and 367981, respectively. In the Hit cases, the bias score was 1.22 and the correlation coefficient was 0.74. The means of the differences between the synthetic data and the observations were 0.3, -3.9, -14.4, and -34.9 mm h^-1 and the root mean square errors (RMSEs) were 2.7, 8.3, 19.3, and 39.6 mm h^-1 for the categories of 0.5-10.0, 10.0-30.0, 30.0-50.0, and 50.0-100.0 mm h^-1, respectively. In addition, in each range, the 60% difference between the synthetic precipitation data and the observation data was -1.5 to +1.5, -5.0 to +5.0, -17.0 to +17.0, and -33.0 to +33.0 mm h^-1, respectively. Overall, the correlation coefficient of the synthetic precipitation data was > 0.7 for 43 of the 48 test stations and the RMSE was < 4 mm h^-1 at 31 stations. The results are significant at all evaluation stations at the 0.05 significance level.     

Residential mobility in the Seoul metropolitan region, Korea

The spatial pattern of residential mobility in Korea is found to be one of intraregional rather than interregional movement. Net inmigration has taken place only in the Seoul metropolitan region (SMR) since 1970. People from the Cholla region have formed the main stream of net inmigration into the SMR. The decentralization of population from Seoul to Kyonggi and Inchon has generated a transformation of the Seoul urban fringe since 1970. This metropolitanization process is accompanied by residential and employment suburbanization to 45kms from the center of Seoul. Residential mobility in the SMR is the result of metropolitan job opportunities, availability of housing, and the effects of the various regional policies. Availability of transportation between Seoul and its urban fringe encouraged the wide expansion of the urban areas and population redistribution within the SMR.     

Observation of the Degradation Characteristics and Scale of Unevenness on Three-dimensional Artificial Rock Joint Surfaces Subjected to Shear

The present study explores the degradation characteristics and scale of unevenness (small-scale roughness) on sheared rock joint surfaces at a low-stress regime. While the degradation characteristics of unevenness and the normal stress are mutually interrelated, an understanding of the degradation patterns of the three-dimensional roughness of rock joints is one of the important components needed to identify asperity failure characteristics and to quantify the role of damaged unevenness in establishing a shear strength model. A series of direct shear tests was performed on three-dimensional artificial rock joint surfaces at different normal stress levels. After shearing, the spatial distributions and statistical parameters of degraded roughness were analysed for the different normal stress levels. The length and area of the degraded zones showed bell-shaped distributions in a logarithmic scale, and the dominant scale (or the most frequently occurring scale) of the damaged asperities (i.e., unevenness) ranged from approximately, 0.5 to 5.0 mm in length and 0.1–10 mm² in area. This scale of the damaged unevenness was consistent regardless of the level of normal stress. It was also found that the relative area of damaged unevenness on a given joint area, and thus the contribution of the mechanical asperity failure component to shear strength increased as normal stress increased.     

The effect of tides on the volume of sea ice in the Arctic Ocean

Tides are believed to drive vertical mixing in the Arctic Ocean, thereby helping heat to reach the bottom of the sea ice layer, especially in regions with thick ice covers. However, tides are usually not included in ocean models. We investigated the effect of tides on sea ice in the Arctic Ocean using an ice-coupled ocean model that includes tides simultaneously. We found that with tidal forcing, the volume of sea ice increased by 8.5% in Baffin Bay, whereas it decreased by 17.8% in the Canadian Arctic Archipelago. The increase in sea ice volume in Baffin Bay results from the convergence of sea ice, driven by tidal residual currents. In contrast, the decrease in ice volume in the Canadian Archipelago is due to the suppression of ice formation in winter, especially in areas with steep topography, where the vertical mixing of temperature is enhanced by tides. Our results imply that tides should be directly included into the oceanic general circulation model (OGCM) to realistically reproduce the distribution of sea ice in the Arctic Ocean.     

Use of Lade's Single Surface Work-Hardening Model to Investigate Mechanical Behavior of Decomposed Soils

In this study, it was attempted to assess soil parameters necessary for Lade's single surface work-hardening model that reviewed the physical and mechanical properties of granite soil located in Korea based on the results of triaxial compression tests. In addition, finite element analyses coupled with the determined soil parameters as inputs were conducted based on Lade's single surface work-hardening model and the results were compared with element test results. It could be seen that, in predicting undrained mechanical behavior, the single surface model was reproducing the stress-strain relation obtained through element tests at high accuracy. It is worthwhile to inform that these differences in the initial loading stage and the impossibility to predict swelling behavior are caused by the fact that there is no prediction model for changes in shear properties, especially in dilatancy properties due to particle crushing occurring while element tests are conducted. Hence, it is concluded that, to expand the applicability of Lade's single surface work-hardening constitutive model to practical problems, the model should be modified in relation to the dilatancy of soils.     

Channel capacity in bits per joule

Underwater acoustic telemetry has a total input energy constraint, since the energy is stored in the transmitter's batteries. This work is primarily rephrasing the work in channel capacity in terms ofC_{J}bit/J as compared toCbit/s, to emphasize the energy efficiency and to deemphasize the speed of the telemetry. The energy channel capacityC_{J}, for any waveform channel with well-defined capacityCbit/s at signal powerSwatts, is defined asC/Sbit/J. It is shown that for coherent binary frequency shift keying (BFSK) and waveform channels, the supremum ofC_{J}overSis approached asSapproaches zero. For the Gaussian channel the best coding uses narrow bands with the highest S/N.     

Variations in the abundance of fisheries resources and ecosystem structure in the Japan/East Sea

Evidence supports the hypothesis that two climatic regime shifts in the North Pacific and the Japan/East Sea, have affected the dynamics of the marine ecosystem and fisheries resources from 1960 to 2000. Changes in both mixed layer depth (MLD) and primary production were detected in the Japan/East Sea after 1976. The 1976 regime shift appears to have caused the biomass replacement with changes in catch production of major exploited fisheries resources, including Pacific saury, Pacific sardine and filefish. Both fisheries yield and fish distribution are reflected in these decadal fluctuations. In the 1960s and 1990s, common squid dominated the catches whereas in the 1970s and 1980s, it was replaced by walleye pollock. In the post-1988 regime shift, the distribution of horse mackerel shifted westward and southward and its distributional overlap with common mackerel decreased. The habitat of Pacific sardine also shifted away from mackerel habitats during this period. To evaluate changes in the organization and structure of the ecosystem in the Japan/East Sea, a mass-balanced model, Ecopath, was employed. Based on two mass-balanced models, representing before (1970–75) and after (1978–84) the 1976 regime shift, the weighted mean trophic level of catch increased from 3.09 before to 3.28 after. Total biomass of species groups in the Japan/East Sea ecosystem increased by 15% and total catch production increased by 48% due to the 1976 regime shift. The largest changes occurred at mid-trophic levels, occupied by fishes and cephalopods. The dominant predatory species shifted from cephalopods to walleye pollock due to the 1976 regime shift. It is concluded that the climatic regime shifts caused changes in the structure of the ecosystem and the roles of major species, as well as, large variations in biomass and production of fisheries resources.     

An identification of wave propagation based on a single-point measurement

This study presents the identification of wave propagation using the information measured at a fixed point. The mathematical model used to carry out this research is an integral equation. The equation turned out to be a Fredholm integral equation of the first kind. The discretized matrix equation yielded an ill-conditioned system. To secure the stability of the system, Tikhonov regularization was applied to the ill-conditioned system. The analysis of the numerical computation proved that the regularization was able to retain the target spectrum.     

An analytical model with three sub-regions for m2 tide in the yellow sea and the East China Sea

In this study an analytical tide model of uniform width with three sub-regions is presented. The three-subregions model takes into account step-like variations in depths in the direction of the channel as a way to examine the M₂ tide of the East China Sea (ECS) as well as the Yellow Sea (YS). A modified Proudman radiation condition has been applied at the northern open head, while the sea surface elevation is specified at the southern open boundary. It is seen that, due to the presence of an abrupt change in depth, co-amplitude lines of the M₂ tide are splitted to the east and west near the end of the ECS shelf region. Variations in depths, bottom friction and the open head boundary conditions all contribute to the determination of formation of amphidromes as well as overall patterns of M₂ tidal distribution. It is seen that increasing water depth and bottom friction in the ECS shelf results in the westward shift of the southern amphidrome. There is however no hint at all of the well-known degenerated tidal pattern being formed. It is inferred that a lateral variation of water depth has to be somehow incorporated to represent the tidal patterns in ECS in a realistic manner. Regarding the radiation factor introduced by Fang et al. (1991), use of a value larger than one, possibly with a phase shift, appears to be a proper way of incorporating the reflected waves from the northern Yellow Sea (NYS). Key words - analytical model, M₂ tide, Kelvin wave, Yellow Sea, East China Sea