A lot of rivers and channels which were cut for water traffic flow through the center of Osaka City. The Dotombori River flows along and across the city's main streets and the landmark of Osaka. However, it is polluted so that it is the target of urban renewal and some measures are carried out. The water quality of this river is controlled by two water gates because more polluted upstream water and saline seawater in which the concentration of dissolved oxygen is very low flow into the river. In the present paper field observation is conducted to clarify the characteristics of the water quality and asses the operation of the water gates in this tidal urban river. The operation is good for the maintenance of the water quality, but the oxygen-deficient seawater intrudes and spreads onto the river bottom and makes influence on the bottom sediment.

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Landslides and debris flows due to heavy rains or earthquakes may block a river flow and create landslide dam naturally. Landslide dams may fail by erosion due to overtopping, abrupt collapse of the dam body or progressive failure. The peak discharge produced by abrupt collapse of the dam is very high compared with other types of failure. However, in-depth knowledge of the mechanism of the dam failures and measured data are still lacking. Numerical simulation and flume experiments were performed to investigate the mechanism of landslide dam failure due to sliding. A stability model coupled with a seepage flow model was used for numerical simulation. Comparison result of numerical simulation and experimental measurement is quite close in terms of movement of moisture in the dam body, predicted critical slip surface and time to failure of the dam body. It shows the potential of the numerical model to be extended for the prediction of flood/debris flow hydrograph by abrupt collapse of the landslide dam.

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The paper presents a mechanistic model for simulation of mass removal during air sparging. Model takes into account several processes which are commonly neglected, suchas air channeling and advection by the water phase. Diffusion of contaminants towards the air channels is modeled as a first order kinetic between the two water compartments. The adopted model of contaminant evaporation at the air-water interface is verified by comparison with reported experimental results. Model is used for simulation of two-dimensional air sparging laboratory experiment conducted by Reddy and Tekola (2004). Good overall agreement is observed. It is showed that natural groundwater flow can influence the efficiency of the air sparging.

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A model simulating reactive transport in natural filter using sawdust as materials to improve the efficiency of filter is developed. The transport part of the model computes the changed in concentration over time caused by the processes of advection and dispersion. The kinetic sub model describes the heterotrophic metabolisms of several groups of bacteria. To model a complete redox sequence (aerobic oxidation, denitrification, Mn (IV) -reduction, Fe (III) -reduction and sulfate reduction) four functional bacterial groups (X1, X2, X3 and X4) are defined. The growth and metabolisms are formulated using the Double Monod kinetic equation. The model takes into account the exchange between the different phases (mobile phase, bio phase and matrix phase). The results from a laboratory soil-sawdust columns experiments are used to verify the simulation results of the model. While the availability of organic carbon is one of the most important factors that affects bacterial activity in natural filter. This study demonstrates that using sawdust as a carbon source can improve the biologically mediated redox processes.

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The assessment of discharge rate and discharge period of dioxins and chlorobenzene which have contaminated the subsurface systems beneath O River, in O City is undertaken through the development of one dimensional transport model employing method of characteristic. The developed model is designed to couple the process of advection, dispersion and retardation of chlorobenzene in vertical direction representing the transport of other contaminants in the site. A variety of scenario based on mass flux and fraction of organic carbon of soil (F_oc) was applied to allow the use of a number of uncertain parameters. The most reasonable simulation result indicated that the contaminants were likely to be released since 1930s until 1975, whereas the transport has been taking place until now. Moreover, the integrated modeling approach may reveal that the migration of hydrophobic compounds (i. e. dioxins) can be significantly enhanced in the presence of a solvent (i. e. chlorobenzene).

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The objectives of this study are to analyze the influence of systematic and random error inrainfall data, discharge data, and the spatial representation of rainfall data on the performance of a distributed hydrologicalmodel, BTOPMC. A framework for uncertainty analysis was developed using a Monte Carlo approach, which was applied to the Kalu River basin in Sri Lanka. Findings show that a systematic error exceeding +/-10% in rainfall or discharge data is detrimental to model results. A random error with standarddeviation is equal to10% ofrainfall or discharge isnot substantial. Calibrationof parameters can compensate for some error. The impact of systematic error in rainfall in terms of Nash-Sutcliffe Efficiency (NSE) is higher than that in discharge. The impact of random error in discharge in terms of NSE is higher than that inrainfall. The impact of the random error is the lowest for the gauge network of the highest density, but the impact of systematic error is not the lowest for this case.

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This study focuses on assessment of the spatial transferability of parameters of a physically based distributed hydrological model, Blockwise use of TOPMODEL with Muskingum-Cunge routing (BTOPMC), to simulate the runoff in different physiographic regions of Nepal. The model was calibrated and validated using different time series data of six basins located in different physiographic regions of Nepal. The model parameters obtained after calibration from six basins were averaged and then applied in other two data limited basins for the jackknife validation of regionalization scheme. The model performance was evaluated by Nash-Sutcliffe efficiency, volume bias and qualitative comparison of observed and simulated hydrograph. The result of model calibration and validation in six basins shows that the model performs well in simulating runoff volume and capturing the seasonal and annual variations. Similarly, the result of model parameter transfer shows that the BTOPMC model parameters can be used to simulate the runoff components in ungauged basins.

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Regionalisation of hydrological model parameters is a simple approach to model ungauged basins. However, uncertainties in model parameters and catchment attributes hinder the regionalisation. In this context, this study proposes a methodology for modeling ungauged basins by pairing the regional model with the posterior distribution of parameters. The performance of regional models are evaluated by comparing the loss in performance and quantifying the uncertainty induced on the result of regionalisation. The study revealed the reduction in inconsistency among various regional models and improvement in performance while the results of regionalisation are constrained by regionalised ranges of parameters. Furthermore, the non-parametetric bootstrap methodology used to quantify of the uncertainty in regional models reveals that the indirect calibration method induced more uncertainty on the result of regionalisation compared to the conventional regionalisation schemes investigated in this study.

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No matter how sophisticated and accurate hydrologic models may be, prediction uncertainty is unavoidable problem in rainfall-runoff modeling and it stems from various components. Therefore, it is essential to identify and reduce sources of uncertainty for more precise agreement between model prediction and observations in the real system. In the context of uncertainty issues, the problem of model structural uncertainty or stability is an issue of increasing interest in recent research. This paper examines a nature of model structural inadequacy using a single-objective global optimization method in hydrological modeling and proposes a framework to assess model structural stability through a comparison of two hydrologic models.

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This study tests whether the lack of conventional ground-based snow observation for Snow Water Equivalent (SWE) can be overcome by using other Hydro-meteorological data. To this end, two different methods are described. The first one is introducing a methodology using a Distributed Hydrological Model (DHM) to estimate SWE, when the available data are just precipitation and river discharge. For the second one, a distributed version of a Temperature-index snow model is developed and applied, when the ground-based data is limited to precipitation and temperature. Two methods are applied in the upstream of Karaj basin (850 km²), which is the most important water resources of Tehran, the capital of Iran. The estimated SWE is used for snow melt runoff forecast. It is found that forecast runoff correlates well with observed natural discharge. This high correlations suggest that a reliable SWE estimation and snowmelt runoff forecasting can be constructed using the methods in the absence of snow observation.

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Few investigations have been made intomodeling snowmeltin data-poor basins; hence, a degree-day method iswidely used and is routinely justified under the auspices that energy-balance models require too many input data. To test this claim, we investigated the utility of merely adopting a full energy approach to model snowmelt. This study first developed so-called “full energy balance snow model” to simulate snowmelt at four sites located in Japan and the USA. The results showed very good agreement between observed and predicted snow water equivalent, R²>0.95. We duplicated the simulations using the approximated version of the model that requires only air temperature and wind speed as input data. Although the original model corresponds better, the performance of its simplified version can be evaluated as good, R²>0.9. These results provide significant information for the development of appropriate approximations in energy balance snowmelt modeling.

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By means of Kalman filter, this study examines recursive updating of a distributed model's state variables, which were the water depths on a fine grid cell, using observed discharges at the basin outlet. The measurement update algorithm of the filter decides the optimal discharge, and the ratio of the optimal discharge to the simulated discharges was applied to every discharge from each cell for a reformation of the distributed state variables with a specific stage-discharge relationship. For the time update algorithm of the filter, Monte Carlo simulation was adopted for the prediction algorithm of the filter. The proposed algorithm offers efficient state variables updating in a distributed hydrologic model.

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The properties of time and space scale invariance of rainfall are investigated and applied to Intensity-Duration-Frequency (IDF) relationships. The hypothesis of the simple scaling is examined in time and space in Yodo River basin and the simple scaling properties in time are confirmed, which is used to derive IDF relationships for short-duration rainfall of several hours from the statistical characteristics of daily data only. The derived IDF matches well with the one derived from historical observed data. Also, the simple scaling properties in space are examined. It is found that two ranges less than 1000 km² and more than 1000 km² show different scale properties.

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The serial application of a stochastic rainfall time series model and a rainfall-runoff model is an effective option in the event when historical discharge records are inadequate for determining quantile flood flows crucial in flood control applications. In this study, the Neyman-Scott clustered Poisson rectangular pulse rainfall model was applied to generate synthetic hourly and daily rainfall time series. This model was evaluated for quantiles for the different areas of Kamishiiba (Kyushu), Naha (Okinawa), and Sapporo (Hokkaido) in Japan. Sets of parameters were determined based on combinations of moments of the historical records. The quantiles of each synthetic time series were compared to the historical counterparts, yielding mixed results. In general, the model proved effective in matching the historical quantile except in periods in which a combination of rainfall sources such as convective, typhoon and/or frontal rainfall was dominant. An ideal combination of historical moments for generating model parameters for the objective was determined for the mentioned study areas, although it is recommended to employ a similar methodical test of moment combinations for regions elsewhere.

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An input delayed neural network (IDNN) for synthetic inflow generation is presented to establish monthly inflow scenarios for the reservoir that supplies water to the city of Matsuyama, Japan. IDNNs are dynamic networks capable of accounting for nonlinearities and representing temporal information of input sequences. In this study, the IDNN model relates the two previousreservoir inflows in order to estimate the current inflow. The inflow scenarios will be used as input to optimization models in order to construct reservoir operation policies. Twenty years of historical inflows were used for calibrating the IDNN and a new 20-year synthetic series was generated. Besides the comparison with the IDNN-generated inflows, the statistics of historical series were also compared with those of synthetic series generated by a second-order autoregressive (AR-2) model. The IDNN modelproved to be capable of preserving the main statistical characteristics of the historical series.

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The purpose of this study is to analyze long-range transport and transformation of acidifying substances over East-Asia. This is done through modeling of emission, meteorology, and atmospheric transport & chemistry. The Models-3 Community Multi-Scale Air Quality Modeling System (Models-3/CMAQ) coupledwith the PSU/NCAR mesoscale model (MM5) is appliedfor this purpose and validated for March 2001. The simulated daily variation of surface SO₂ and NO_x concentrations shows some encouraging agreements with observation at two remote sites. However, underestimates of monthly mean concentration are found at some urban sites where the uncertainty in local emission has larger impact than that at remote and rural sites. Overestimates and larger vertical gradients are found at some sites with complex terrain. Wet depositions of sulfate, nitrate and ammonium are generally underestimated and have some dependence on both precipitation fields and site characteristics.

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The present paper assesses skill of six current Numerical Weather Prediction (NWP) models in simulating the diurnal cycle of precipitation by utilizing the dataset of Enhanced Observing Period (EOP3 from Oct 1, 2002 to Sep 30, 2003) of the Coordinated Enhanced Observation Period (CEOP). Diurnal change of precipitation intensity and frequency of 16 CEOP sites are calculated from observed and modeled data for each site, and then normalized by mean intensity and frequency, respectively. The averaged diurnal cycle of precipitation shows an afternoon peak, a night time peak, and a low intensity in the early evening (18 LST). An analysis using satellite data indicates that the early-evening low intensity is due to rapid cease of convective precipitation in the early evening followed by the start of stratiform precipitation. All the models produce an afternoon peak of precipitation, but the start timing of the afternoon peak is predicted too early in the models. Moreover, no model produces the night time peak and the early-evening low intensity.

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Four dimensional data assimilation (4DDA) system of three-dimensional distributions of radar reflective factor and Doppler velocity by a hydrostatic atmospheric model with a conceptual precipitation model will be proposed. The 4DDA is realized by the variational method for Doppler velocity and the extended Kalman filter for radar reflective factor. The method was applied to a rainfall event observed by two neighboring operational volume-scanning radars one of which is the Doppler radar. As a result, it was found that introducing such the assimilation method improves the prediction accuracy of three hours lead time. However, a limitation of used hydrostatic mesoscale model was also found. In the initial condition after assimilation, there is a little heavy rainfall area at the position different from radar observation. This shows that there is a discrepancy between the time evolution of observations and the time evolution that governing equations of the used model requires.

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Analyses undertaken in this paper show that the Universal Soil Loss Equation (USLE) fails to predict the soil losses during hydrologic events, especially for arid region. The cause is due to the neglect of runoff in predicting the rainfall erosivity index. In this paper, the erosivity index in USLE is modified by relating the kinetic energy with rainfall, infiltration and runoff processes. The modified USLE model is verified to reflect the hydrological processes more accurately and to be capable of estimating event soil losses. As a new approach for modeling the event-based soil erosions in large catchments, the proposed erosion model also takes the channel erosion into account, together with sediment deposition and transport simulations; its application is broadened to model the variations of sediment concentrations during single events. Through a case study in the large arid region -Lushi River basin in China, the designed erosion model is validated to have good performances during most hydrologic events.

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This paper aims to investigate the relations among reservoir sedimentation, rainfall and deforested area in the Omaru River watershed. For this purpose, land-covers of four dams in the Omaru River watershed are classified by using Landsat Thematic Mapper images in 1989-2004 and deforested areas are estimated by Geographic Information System. The relations are analyzed by using statistical regression approaches.
The remote sensing image analyses reveal that the deforested areas of the Dogawa Dam and Matsuo Dam catchment areas are increasing from 1989. Simple regression analyses show that the sedimentations in both dams have positive correlations with the deforested areas. And the results of multiple regression reveal that the deforestations significantly affect the amounts of the sedimentation. These results suggest that the control of deforested area is required in order to reduce the sedimentation in this watershed.

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X-ray powder diffraction (XRD) is widely used for geological analysis of sediment samples. In this study a method for detecting sources of sedimentation using mineral composition obtained by the qualitative phase of XRD is proposed. Possible minerals matching resulted from the Hanawalt's searchmatch method were arranged into binary matrix of mineral composition of each sampling site. Hierarchical cluster analysis was grouped samples into clusters based on mineral similarity and yielded a dendrogram. Using information of sample's environment, the meaning of dendrogram was derived for sediment fingerprinting.
The result showed that sedimentation sources in the Sengguruh reservoir mainly come from 10-30° slope of the Lesti basin and cultivated area downstream of the Brantas origin. Comparing with the field observation and satellite data, a good correlation was obtained.

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This paper investigates the flow and bed deformation around groins under flood conditions in a river restoration project with both experimental and numerical methods. The experiments are based on a large-scale physical model and are able to resolve the local flow and sediment transport phenomena with a relatively high accuracy. The numerical models are formulated on an unstructured mesh and allow the exact representation of complex geometries, in particular the restoration structures such as groins. The numerical results have been compared with those of the experimental measurements. Reasonable agreements have been obtained in terms of both flow patterns and bed variations. The study suggests that the flood had significant impacts on the bed morphologies with quantitative evidences. The numerical models may serve as a promising tool for the decision-making and post-assessment in river restoration.

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Assessing the change in void structure of riverbed material is very important for an ecological issue in rivers. Therefore, we have already developed a framework of the bed variation model available for the analysis of the change of porosity of bed material as well as the bed variation. In this framework, the porosity is assumed to be dependent only on the grain size distribution. Thus, it is necessary to relate the porosity of sediment mixture with the grain size distribution in the model. This study aims to develop a method for obtaining the porosity for different types of grain size distribution. Firstly, grain size distribution of sediment mixture in natural rivers were classified into three types, namely log-normal distribution, Talbot distribution and bimodal distribution, and the parameters on those geometric properties were found out. Secondly, a method for identifying the type of grain size distribution was presented. Thirdly, the relationship between the porosity and the geometric parameter of grain size distribution was obtained by means of a packing model. Finally, the porosity of actual riverbed material was estimated by the presented method. The porosity could be reasonably estimated by means of the presented method and it could be introduced into the bed variation model.

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An explorative study has been carried out within the scope of this paper in order to validate a morphodynamic numerical model with the assessment of model sensitivity to some factors and parameters. The flow model component is a vertical two-dimensional with non-hydrostatic, unsteady free surface flow condition. The flow model has been coupled with sediment transport models. Two different sediment transport approaches have been used, namely Ashida & Michiue's bedload transport formula and a stochastic pick up deposition formulation for non-equilibrium sediment transport proposed by Nakagawa & Tsujimoto. The model performance has been tasted for different turbulence closures, namely a zero-equation, a standard k-ε and a non-linear k-ε models, in the context of morphodynamic simulation. Model performance has been evaluated for the prediction of temporal variation of flow-depth and boundary shear stress induced by bedform evolution based on experimental measurements.

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With the aim of creating navigational channel and river bank stabilization using bandals, flow structures, suspended sediment transport pattern and bed evolution around them under live-bed scour condition were investigated in the laboratory experiment where ten pairs of such structures were installed on both sides of channel banks. The measurements were taken in dynamic equilibrium state of the experiment. A 3D numerical flow model based on unstructured mesh was developed. The model can simulate the flow structures in experiment reasonably well.

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A simple correction model for “subgrid” lubrication force is proposed for fictitious-domain simulation of solid-liquid flow employing the Variable-density Implicit Volumetric forcing. The model is to compensate the unresolved lubrication force for gaps of few grid spacings between the solid surfaces, and is validated with the examination of velocity history and fluid force acting on spherical particles falling under gravity towards a plane wall. The peak particle Reynolds number is from 7 to 58, and relative density between the fluid and the solid is up to 2.9. Excellent agreements have been observed among the simulation results, the experimental ones, and predictions from an analytical model which consists of the lubrication force proposed by Cox & Brenner (1967), the added mass force proposed by Milne-Thomson (1968), and the history term proposed by Mei & Adrian (1992).

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We numerically simulate “bedload transport” of noncohesive sediment by a turbulent liquid flow over an erodible bed using a “fictitious domain” simulation method that employs a fixed Cartesian grid. We report here on comparison with a challenging dense-phase particulate flow, namely a rotating drum partially-filled with spherical particles, through which oil flows to form a free-surface flow. Overall agreement between experimental and simulated values for bed and free-surface angles is found to be quite satisfactory..

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Porosity effects on the hydrodynamic equations are minimal in comparison with other resistance forces like drag and inertia that generated by water flow through vegetation in case of sparsely grown forests. However, in case of densely grown vegetation that have lowest porosity (high blockage) can impose considerable effects on final outcomes. Horizontal two-dimensional depth averaged momentum and continuity equations were derived in first principles with porosity enhancement and it was noticed that new derivations showed considerable contrast with early practiced equations. Two-dimensional numerical simulations were employed to show difference between the results of new and previous equations. It was found that, newly derived equations predicted maximum current velocity was higher than previous equations, maximum water depth was less than previous equations at mid and front of the forest, but maximum water depth was higher than previous equations at behind the forest.

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Internal waves in a two-layer system are simulated using a set of fully nonlinear internal-wave equations, which was derived on the basis of a variational principle without any assumptions of wave nonlinearity and dispersivity. Computational results of interface displacements up to each order on the vertical length scale of motion are compared with calculation results obtained using a Boussinesq-type internal-wave model or the existing experimental data. In a long-wave case, interface displacements obtained by the proposed model with more than two vertically distributed functions of velocity potential are in harmony with those by the Boussinesq-type model, as well as the experimental data especially in the wave number. In an intermediate-wave case, the present model shows different results from those through the Boussinesq-type model, which should not be applied to this case without enough consider- ation of the wave dispersivity.

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As a meshfree particlemethod, the MPS (Moving Particle Semi-implicit) method is an efficient numerical tool for simulating flowswith complicated behavior of water surface, such aswave breaking. In this paper, the MPS method hasbeen applied to solve the Navier-Stokes equation for simulating the breaking and post-breaking of solitary waves on a uniform slope. The high precision of MPS method in the simulation of violent free surface flows, likethebreaking waves, isconfirmed through both quantitative and qualitative comparisons to other numerical results by the BEM or the VOF and experimental data. The process of splashup which ishard to be simulated by conventionalgrid-based methods is alsowell reproduced by the MPS method.

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The objective of the study is to improve the understanding of relationships between multiple spatial scales and the development of micro-habitat as well as its co-dependence with the net-spinning caddisfly (Stenopsyche mamorada). In this study, two target riffles located in the Asa River basin were investigated during the spring of 2006. Three major findings of this research were that; 1. the target specie seems to prefer substrate with median diameters between 3-13 cm because they need medium-sized gravel to create their nests, 2. the abundance of medium-sized gravel in the loose surface layer of riffle bed was observed to be related to the normal flow unit-width discharge because the finer bed material on the surface is washed out during normal flow condition and loose layer is developed, and 3. despite the unstable nature of braided morphology the target specie population was more prevalent and stable because the rough terrain reduce the local shear stress on the riffle bed during small floods.

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Plants require nitrogen (N) within the soil to produce high yields. However, the transport mechanism of nutrients from root medium to plant and the response of plant nitrogen tissue to nitrogen uptake have not been identified so far. The experiments in this study were performed in summer of 2005 and 2006 in order to define the mechanism of nutrient uptake and specify the response of plant nutrient content in Phragmites japonica.
The results suggest that the mayor part of nitrogen absorption is due to an active uptake process. The influx is subject to negative feedback on high external concentration and reaches a maximum uptake rate after 6-8 hours of exposure. The response of leaf N content to NO₃ - uptake not only proves the uptake process based on plant demand but also appears to be independent with external concentration and uptake rate. The results also imply the fact that plants may have sufficient capacity to store nutrients.

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Reduction and control of pollutant load from non-point sources is a key issue to improve the water condition in lakes. In the monitoring of water quality in rivers for this purpose, continuous measurement is required because the pollutant load from non-point sources is highly variable in a process of rain runoff. In practice, however, this requirement is often contradictory to the requirement of data accuracy.
This paper proposes a new idea on the “concept of measurement” in order to develop a “dynamic measurement” of the pollutant load. The point of authors' idea is to use empirical relations found in the field as positively as possible, even if we don't have any scientific reason for the relation. Then, results of a field experiment on the pollutant load monitoring are presented to show the feasibility of the idea.

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This paper proposes a method to evaluate the occurrence of anoxic water in Tokyo Bay, which is a typical enclosed bay in Japan. In Tokyo Bay, seawater exchange with the ocean is revealed to be dominantly controlled by estuarine circulation. Dissolved oxygen (DO) concentrations in the bay head are, thus, expected to be influenced by estuarine circulation. The strength of estuarine circulation changes owing to wind and inflow from rivers. Therefore, we investigated the influence of inflow from rivers on DO concentration around the bay head by using a three-dimensional ecological model. To evaluate the occurrence of anoxic water, we developed a conceptual DO model which was verified through good agreement with the results from a three-dimensional ecological model. As a result, the conceptual DO model has potential in the evaluation of the occurrence of anoxic water around the head of Tokyo Bay.

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Soil moisture is one of the key parameters of land-atmosphere interaction, which affect the seasonal and interannual variations of the global and regional water cycle considerably. To find out a long-term trend of this parameter, a Special Sensor Microwave Imager (SSM/I) algorithm is proposed in this paper by extending an Advanced Microwave Scanning Radiometer (AMSR-E) algorithm. A microwave brightness temperature which was obtained by SSM/I is calibrated to fill in gaps of models.
Although there is disadvantage to estimate soil moisture using SSM/I data, accuracy equal to AMSR-E was obtained through an algorithm validation in the Mongolia reference site of the Coordinated Enhanced Observing Period (CEOP), and a trend of this site was found out by applying the algorithm to the long-term SSM/I data.

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The Huaihe River Basin is vast granary in China, therefore landuse and cropping cycle information are important for water resources and hydrological analysis. In this study, landuse and water usage rule are estimated from satellite remote sensing analysis and field survey, and VSW index method and agricultural statistic data are used for calibration. Estimated landuse data and water usage rule are applied to the LSS (Land Surface scheme) in the Shiguan River Basin (one part of Huaihe River Basin), and the water and heat flux are calculated for 4 months. The calculated runoff and irrigation water in LSS are validated using hydrological data.

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The Asian Summer Monsoon (ASM) onset occurs between late April and early May over inland Indochina, before any transitions occur along the coast. The influence of orography and soil moisture on sub-continental-scale hydrological processes was elucidated by using a regional climate model. The model reproduced many elements of the onset of the Southeast Asia Monsoon (SEAM) associated with land surface conditions, including the early and abrupt onset observed when mountain effects and relatively dry soil conditions were included in the simulations. The nonlinear effects of mountains and ground wetness, combined with realistic increases in precipitation, can modify the hydrological cycle through changes in the surface energy budget. A positive feedback between soil moisture and precipitation increases the moisture source for further precipitation in the transition period.

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The present study conducted investigations using modern methods of time series analysis to clarify how the increase of the atmospheric carbon dioxide is related to the rise in the air temperature. The interrelationship of the global air temperature to the solar activity also was investigated through correlation analysis using time series datasets of them. The results of spectral analysis showed that the variations of the air temperature and atmospheric carbon dioxide have an obvious one-year cycle (seasonal cycle), and that the spectral intensity of the one-year cycle in the air temperature is greater in the polar regions than in low latitudes, while that in the atmospheric carbon dioxide tends to be lower in southward regions. Through coherence analysis, it was found that there are different tendencies between short-term and long-term fluctuations in the interrelationship of the air temperature to the atmospheric carbon dioxide. The long-term fluctuations in the atmospheric carbon dioxide tend to be accompanied by those in the air temperature, and vice versa in the short-term fluctuations.

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A global water resources model was developed to assess the impact of climate change on water resources. The model consists of six modules, namely, land surface, river, agriculture, reservoir operation, environmental flow, and irrigation. One of the primary purposes of this model is to analyze availability of water resources at daily temporal resolution. We estimated the global distribution of water stressed area due to not only the limitation of annual total water resources but also the strong seasonality of them. The results show that the number of population living under water stressed condition reaches its peak around 2050 and remains high until the end of 21^st century under SRES A1B scenario.

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We developed a new global river discharge model by merging existing methods and tuning parameters in the model for better reproduction of observed monthly river discharges. The developed model enabled us to estimate amount of renewable water resource witha spatially finer scale than the previous studies. After verifying the effect of the parameter tuning, we appliedthe developed model to the assessment of water scarcity. The regions judged to have high risk of water scarcityare Sahara desert, Arabian Peninsula, Indus river basin, the northern part ofChile and California Peninsula. Though the regions judged to have high risk of water scarcity were similar to the results of the previous studies, we additionally succeeded in depicting inhomogeneous distribution of water scarcity risk inside the river basins. Since the developed model estimates monthly renewable water resources, monthly variation of water scarcity can be also assessed.

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Turbulent organized structure (TOS) above urban canopies has not been clarified. In order to investigate it, we observed the horizontal distribution of TOS at COSMO (Comprehensive Outdoor Scale Model experiment for urban climate). The horizontal dimension of COSMO was 50m x 100m, with 1.5m cubic roughness blocks arranged uniformly. 60 thermo couples and 8 sonic anemometers were arranged.
A new quantitative analysis to characterize the size of TOS has been conducted by using OSIM (Organized Structure Identification Method). OSIM detects the area of large turbulent motion and quantified the span-wise width and the time duration of the motion. In this study, we explained the algorithm of OSIM and applied it to COSMO data.

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The present study investigated the vertical profiles of the turbulent statistics over the reduced urban scale model in a neutral stratification. The experiment was conducted under the planetary boundary layer so that the corrected data was always affected by the outer layer turbulence more or less. We compared the surface layer turbulence statistics in the scale model with that in urban, which are velocity spectra, momentum co-spectra and nondimensional velocity variances and so on.
A scale effect was apparent in the statistics related with the horizontal velocity variance. The scale effect came from the discrepancy of the ratio of outer layer (i. e. planetary boundary layer) scale with the surface layer scale of the scale model and with that of urban. Although the former scale is always same order, the latter scale is different in urban and in the scale model. Therefore we considered that the scale effect is an evidence of the influence of the outer layer turbulence in the surface layer.

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The interception of rainfall was observed at an outdoor urban scale model site. The model dimensions were 50 x 100 m, with 1.5-m cubic roughness blocks arranged uniformly. The amounts of rainfall and runoff within the area of 6 x 6 m were measured. In this study, we introduced the specification of the facility and preliminary results of rain events which were obtained in September 2006. Mean rainfall intensity of the rainfall events ranged from 0.6 to 1.4 mm hour^-1. Under these rain events, the ratio of runoff to rainfall decreased as the rainfall decreased. This tendency was commonly found in both the total rainfall and the real-time rainfall intensity.

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This paper reports on the evaluation of Simple Urban Energy Balance for Mesoscale Simulation (SUMM) to two cities (i. e. Kugahara, Japan; Basel, Switzerland) in winter, spring and summer. This new version of SUMM is incorporated with vegetation scheme to meet the existence of vegetation fraction in real city. SUMM simulated the urban energy balance and radiative temperature (Tr) generally well in Kugahara and Basel. However, SUMM slightly underestimated Tr in the nighttime and overestimated Tr in the daytime in Basel.

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Datasets of energy fluxes and surface temperature were obtained from Comprehensive Outdoor Scale Model Experiment (COSMO) in winter and spring-early summer. Daytime and daily total statistics of the ratio of heat storage (dQs) to net all-wave radiation (Q*) were investigated. We obtained following major findings. i) Daytime (Q* ≥ 0) dQs/Q* in winter were larger than those of spring-early summer. ii) Daytime dQs/Q* was slightly dependent on wind velocity and decreased with increasing wind velocity. iii) Daily total dQs/Q* was negative in winter and positive in summer, since daily total Q* was positive regardless of seasons while daily total dQs was negative in winter and positive in summer. The value of daily total dQs was strongly related to net daily increment of surface temperature.

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This paper shows the seasonal dependency of vertical profile of air temperature, CO₂, and H₂O within and above a suburban canopy and the turbulent diffusivity of the scalars. The results were derived from field measurements of the vertical profiles and fluxes, which were conducted in a residential area (the mean height of canopy is 7.3 m) of Tokyo, Japan. The vertical profile of CO₂ in the daytime drastically varied with the season; the CO₂ concentration within the canopy was lower than that above the canopy in summer but was slightly higher in winter. The seasonal change of the daytime CO₂ profile is likely due to the effect of photosynthesis by vegetation in backyards. The normalized turbulent diffusivity of air temperature and CO₂ depended on height and atmospheric stability, which is similar to that for vegetated canopies. In contrast, the normalized turbulent diffusivity of H₂O was relatively smaller than that of heat and CO₂. Although the correlation coefficients indicated that the transfer efficiencies of CO₂ were generally smaller than that of heat, the magnitude of normalized turbulent diffusivity of air temperature and CO₂ was almost same.

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Rainfall prediction technique based on short-range forecasts requires the construction of physically meaningful relationships between numerical model outputs and rainfall. However, it is questionable whether conventional rainfall prediction models incorporate the physically meaningful relationships because inherent horizontal scale in a meteorological field inducing a rainfall is not fully considered. Therefore, in our study, in order to relate meteorological elements (Precipitable water, Convergence, CAPE) to rainfall, a horizontal scale of a target area for extracting them was considered. As a result, a larger target area led to the construction of physically meaningful relationships between meteorological elements and rainfall. Therefore, it should be emphasized that the specification of the horizontal scale of target area, considering horizontal features of meteorological fields, plays an important role in constructing a reliable rainfall prediction model for practical use.

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This study statistically analyzed the dependence of heavy rainfall on elevation in mountain areas, using long-term precipitation data observed by raingauges installed densely at railway stations of East Japan Railway Company and meteorological stations of Japan Meteorological Agency. Total rainfall amount of heavy rainfall depends on elevation, and the increasing rate of total rainfall amount is 5-10% /100m. Maximum hourly precipitation of heavy rainfall cased by typhoon and front depends on elevation, and the increasing rate of maximum hourly precipitation is 10-20% /100m. However, maximum hourly precipitation of heavy rainfall cased by thunderstorm dose not depend on elevation. Furthermore, the frequency of heavy rainfall cased by typhoon and front depends on elevation.

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Linear or non-linear system equations have been applied for the modeling of hydrological time series. However, the estimation of optimal parameters in the system is one of the most difficult processes in hydrological modeling, because the slight perturbation of the parameters in the system can cause remarkable difference of system solutions. Thereby, in order to assure the reliability of estimated system parameters, it is crucial to investigate the response of the system solutions against perturbation of the system parameters.
In this study, we conducted sensitivity analysis for the perturbation of parameters in non-linear system, using Self-Organizing Map. As the results, the time series generated from semi-optimal parameters were classified depending on their similarities. The parameters which generated approximately actual time series were partially visualized on the 2-Dimentional map.

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The present paper investigates the estimation of the frequency analysis of the annual maximum monthly precipitation (AMMP) in East Asia based on a dynamical ensemble approach with an atmospheric global climate model. The model used is the latest version of the MRI/JMA 98 with about 300-km horizontal resolution with 30 vertical layers. 130-year integration was performed with the ensemble size of six. Two formulation of the frequency analysis for the ensemble dataset are first introduced: ensemble mean and composite estimators. The estimation of the AMMP for 50-and 200-year retrun period from the comoposite model outputs basically reproduces that of the observation. Further analysis demonstrates that each member of the ensemble can be combine into one based on the statical F-test and that natural variablity significantly affect the estimation error of the extreme values.

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