Assessing impervious area ratios of grid-based land-use classifications on the example of an urban watershed

ABSTRACT

When applying a distributed hydrological model in urban watersheds, grid-based land-use classification data with 10 m resolution are typically used in Japan. For urban hydrological models, the estimation of the impervious area ratio (IAR) of each land-use classification is a crucial factor for accurate runoff analysis. In order to assess the IAR accurately, we created a set of vector-based “urban landscape GIS delineation” data for a typical urban watershed in Tokyo. By superimposing the vector-based delineation map on the grid-based map, the IAR of each grid-based land-use classification was estimated, after calculating the IARs of all grid cells in the entire urban watershed. As a result, we were able to calculate the frequency distribution of IAR for each land-use classification, as well as the spatial distribution of IARs for the urban watershed. It is evident from the results that the reference values of IAR for the land-use classifications were estimated very roughly and inherited errors of between about 7% and 70%, which corresponds to more than 100 mm increase of direct runoff for the 1500 mm annual average precipitation.

Editor D. Koutsoyiannis; Guest editor E. Volpi     

印度喀拉拉邦雨影区流域系统形态分析及其水文意义(英文)

The rain shadow regions requisite a comprehensive watershed development and management plan for sustainable water resources management. The Pambar River Basin (PRB) lies on the rain shadow region of the southern Western Ghats, India, where climate showed marked intra-basin variation. A morphometric analysis was done to evaluate the drainage characteristics of PRB using topographical maps and digital elevation data. PRB was divided into eighteen 4th order basins (SB1-SB18), distributed along various climatic gradients. Lower order streams mostly dominate PRB and drainage pattern is a function of relief and structure. The terrain is highly dissected and prone to soil erosion during heavy storms and the elongated shape of PRB enables easier flood management. The influence of climate on drainage characteristics was evidently emphasized in basin morphometry. Four distinctively different classes were identified based on the morphometric similarities. The significance of morphometric analysis on the hydrological characterization is discussed and the relevance of the present study in water harvesting has been explicated.     

Comparison of carbon cycle between the western Pacific subarctic and subtropical time-series stations: highlights of the K2S1 project

A comparative study of ecosystems and biogeochemistry at time-series stations in the subarctic gyre (K2) and subtropical region (S1) of the western North Pacific Ocean (K2S1 project) was conducted between 2010 and 2013 to collect essential data about the ecosystem and biological pump in each area and to provide a baseline of information for predicting changes in biologically mediated material cycles in the future. From seasonal chemical and biological observations, general oceanographic settings were verified and annual carbon budgets at both stations were determined. Annual mean of phytoplankton biomass and primary productivity at the oligotrophic station S1 were comparable to that at the eutrophic station K2. Based on chemical/physical observations and numerical simulations, the likely “missing nutrient source” was suggested to include regeneration, meso-scale eddy driven upwelling, meteorological events, and eolian inputs in addition to winter vertical mixing. Time-series observation of carbonate chemistry revealed that ocean acidification (OA) was ongoing at both stations, and that the rate of OA was faster at S1 than at K2 although OA at K2 is more critical for calcifying organisms.     

Compositional analysis of Yayoi‐Heian period ceramics from Okinawa: Examining the potential for provenance study

In Okinawa, locally produced pottery dates back to the Initial Jomon period (˜6500 ¹⁴C yr B.P.). Later in time, especially during the Early Yayoi‐Heian period (˜300 B.C.–A.D. 300), ceramic assemblages appear to contain mainland (Japan) Yayoi pottery. A greater number of these sherds present in Okinawa over time coincide with an increasing amount of interaction with mainland Japan, as evidenced by other exchange items. In this preliminary study, the authors analyzed sherds from several Early Yayoi‐Heian period deposits from sites in Okinawa using thin‐section petrography and laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS). The objective was to examine the applicability of these techniques for Okinawan ceramic provenance studies, assess intra‐ and intersite variation in mineralogical and chemical composition, and determine whether some sites exhibited a higher frequency of pottery from one locale versus another that might suggest the importation of pottery from mainland Japan. Results are equivocal, suggesting that the region's geological complexity may inhibit successful provenance study of ceramics using these and possibly other compositional techniques. © 2006 Wiley Periodicals, Inc.     

Meshless numerical modeling of brittle–viscous deformation: first results on boudinage and hydrofracturing using a coupling of discrete element method (DEM) and smoothed particle hydrodynamics (SPH)

We have developed a new approach for the numerical modeling of deformation processes combining brittle fracture and viscous flow. The new approach is based on the combination of two meshless particle-based methods: the discrete element method (DEM) for the brittle part of the model and smooth particle hydrodynamics (SPH) for the viscous part. Both methods are well established in their respective application domains. The two methods are coupled at the particle scale, with two different coupling mechanisms explored: one is where DEM particles act as virtual SPH particles and one where SPH particles are treated like DEM particles when interacting with other DEM particles. The suitability of the combined approach is demonstrated by applying it to two geological processes, boudinage, and hydrofracturing, which involve the coupled deformation of a brittle solid and a viscous fluid. Initial results for those applications show that the new approach has strong potential for the numerical modeling of coupled brittle–viscous deformation processes.     

Complex Earthquake Cycle Simulations Using a Two-Degree-of-Freedom Spring-Block Model with a Rate- and State-Friction Law

Numerical simulations of complex earthquake cycles are conducted using a two-degree-of-freedom spring-block model with a rate- and state-friction law, which has been supported by laboratory experiments. The model consisted of two blocks coupled to each other and connected by elastic springs to a constant-velocity, moving driver. By widely and systematically varying the model parameters, various slip patterns were obtained, including the periodic recurrence of seismic and aseismic slip events, and several types of chaotic behaviour. The transition in the slip pattern from periodic to chaotic is examined using bifurcation diagrams. The model system exhibits typical period-doubling sequences for some parameter ranges, and attains chaotic motion. Simple relationships are found in iteration maps of the recurrence intervals of simulated earthquakes, suggesting that the simulated slip behaviour is deterministic chaos. Time evolutions of the cumulative slip distance in chaotic slip patterns are well approximated by a time-predictable model. In some cases, both seismic and aseismic slip events occur at a block, and aseismic slip events complicate the earthquake recurrence patterns.     

High nutrients in the coastal area after heavy rain observed in the central Seto Inland Sea in July 2012

Temporary enhancement of the nutrient concentrations in the coastal area was observed after heavy rain in the central Seto Inland Sea in July 2012. After passage of a stationary front accompanied by heavy rain, the river outflow was enhanced, and low salinity and high nutrient concentrations were detected near the mouths of rivers. The offshore salinity and nutrients increased and decreased, respectively, which suggested that a snapshot event, such as heavy rain, could influence the short-term variation of the coastal marine environmental conditions, such as the salinity and nutrient distributions.     

Interannual variations in the Hawaiian Lee Countercurrent

The Hawaiian Lee Countercurrent (HLCC) is an eastward surface current flowing against the broad westward flow of the North Pacific subtropical circulation. Analyses of satellite altimeter data over 16 years revealed that the HLCC is characterized by strong interannual variations. The strength and meridional location of the HLCC axis varied significantly year by year. The eastward velocity of the HLCC was higher when the location of the axis was stable. Mechanisms for the interannual variations were explored by analyses of the altimeter data and results from a simple baroclinic model. The interannual variations in the strength of the HLCC did not correlate with those of the wind stress curl (WSC) dipole formed on the leeward side of the Hawaii Islands, although the WSC dipole has been recognized as the generation mechanism of the HLCC. Meridional gradients of the sea surface height anomaly (SSHA) across the HLCC generated by baroclinic Rossby waves propagating westward from the east of the Hawaii Islands were suggested as a possible mechanism for the interannual variations in the HLCC. The spatial patterns in the observed SSHAs were reproduced by a linear baroclinic Rossby wave model forced by wind fields from a numerical weather prediction model. Further analysis of the wind data suggested that positive and negative anomalies of WSC associated with changes in the trade winds in the area east of the Hawaii Islands are a major forcing for generating SSHAs that lead to the HLCC variations with a time lag of about 1 year.     

Protoatmospheres and Surface Environment of Protoplanets

Protoatmospheres and surface environment of terrestrial protoplanets during the oligarchic accretion phase and the giant impacts phase are discussed from theoretical points of view. Mars-sized protoplanets form during the stage of the oligarchic growth. Since protoplanets are formed from more or less ‘local’ planetesimals, the surface environment of the accreting protoplanets depends on availability of volatile material in planetesimals. Even if no volatile-bearing planetesimals are available, a gravitationary captured solar composition atmosphere is formed during accretion. In such cases the surface temperature is always kept under the melting temperature of mantle silicate and only a subsurface magma ocean is formed. Core formation proceeds under dry conditions, and volatile elements are not partitioned into metallic iron. Accretion of water-bearing planetesimals results in impact degassing. A surface hydrous magma ocean forms in response to the thermal blanketing effect of the proto-atmosphere. Then, some volatile materials dissolve into the magma ocean. If we consider reaction with metallic iron, the proto-atmosphere is likely to be rich in hydrogen. In addition, a large amount of hydrogen may be partitioned into metallic iron under high pressure, and delivered to the core. In the stage of giant impacts, both dry and water-bearing protoplanets collide on the proto-Earth. Substantial amount of proto-atmosphere (including water vapor) survives giant impacts. Moreover, giant impacts on protoplanets with oceans result in relative concentration of water against other gases.     

Photometric observations of 107P/Wilson-Harrington

We present lightcurve observations and multiband photometry for 107P/Wilson-Harrington using five small- and medium-sized telescopes. The lightcurve has shown a periodicity of 0.2979 day (7.15 h) and 0.0993 day (2.38 h), which has a commensurability of 3:1. The physical properties of the lightcurve indicate two models: (1) 107P/Wilson-Harrington is a tumbling object with a sidereal rotation period of 0.2979 day and a precession period of 0.0993 day. The shape has a long axis mode (LAM) of L₁:L₂:L₃ = 1.0:1.0:1.6. The direction of the total rotational angular momentum is around λ = 310°, β = −10°, or λ = 132°, β = −17°. The nutation angle is approximately constant at 65°. (2) 107P/Wilson-Harrington is not a tumbler. The sidereal rotation period is 0.2979 day. The shape is nearly spherical but slightly hexagonal with a short axis mode (SAM) of L₁:L₂:L₃ = 1.5:1.5:1.0. The pole orientation is around λ = 330°, β = −27°. In addition, the model includes the possibility of binary hosting. For both models, the sense of rotation is retrograde. Furthermore, multiband photometry indicates that the taxonomy class of 107P/Wilson-Harrington is C-type. No clear rotational color variations are confirmed on the surface.