A class of stochastic rainfall models known as ‘renewable process rainfall model’ is strong in representing physical patterns found in the rainfall series. A stochastic rainfallmodel based on the renewable process was constructed and possible scaling behavior across different time-resolutions were examined. It was discovered that most of the model parameters obey power-law type scaling. The resultsuggests the possibility of generating synthetic rainfall series of higher resolution from low-resolution observations with these scaling properties.

抄録全体を表示

Recently, a lot of researchers have been interested in ‘scale issues’ in the research area of hydrology.‘Scale issues’ include various questions to be solved, including lots of issues regarding runoff process. For example, the relationships between some hydrological processes which control runoff process and catchmentscale have been studied. Recently, some researchers have tried to clarify the runoff system using mean annual flood (MAF) per unit area and coefficient of variation (CV) of annual flood.
In this study, analysis of runoff process by CV and MAF was carried out. First, CV/MAF versus catchment area were plotted for 285catchments in Japan. Secondly, Eagleson's method was used in order to calculate MAFand CV. The aim of this study is to develop model for numerical analysis of runoff, which will be combined to analysis by the data of 285 catchments. The model used in this study could estimate MAF qualitatively, but further consideration is necessary in regard to CV.

抄録全体を表示

We derived differential equations whose solutions provide the first four momentsof discharge under the condition that rainfall input is mutually dependent random variable using the storage function runoff model proposed by Hoshi et al. In the concrete, we assumed that the deviation from average rainfall is described by AR (1) process based on the statistical analysis of observed rainfall. The validity of proposed theoretical equations was cross-checked by a simulation. It is possible to estimate the probability density function of discharge by the calculated first four moments of discharge. The results of this study can be applied to estimating the design flood.

抄録全体を表示

This paper describes an upper tail point estimation method using the incomplete data by the maximum likelihood estimation method. In some data cases, it happensto occur that the estimates for upper tail points such as 100-year return periodcan be smaller than the observed maximum annual flood datum, even if the number of observed data is smaller than 100; this result of analysis cannot be acceptable from the practioners' viewpoint. Because, adopting such estimates in hydrologic frequency analysis may cause dangerous designs and plans for flood prevention. By weighting much to data in upper tail probability portion, such a phenomenonmay be reduced. Peaks over threshold method (POT) and probability weighted moment method (PWM) are included in such weighting methods. This paper deals with a weighting method by using incomplete data. An example for St. Mary's River data shows the superior points in such a treatment.

抄録全体を表示

Hydrological variables as a series of independent random variables is problematic because a phenomenon of rainfall itself is formed through certain physical processes and the hydrological variables are based on some of those processes.
This paper describes the introduction of a new hydrological parameter, the time variation concentration of rainfall, and shows the homogeneity, of the time concentration of rainfall against total precipitation over many hours. This paper also explains that conventional hydrological frequency analysis should be regarded as an analysis under the condition that does not need to consider the time concentration of rainfall, and finally discusses the method of frequency analysis using the new hydrological parameter with an example of analysis.

抄録全体を表示

Interactions between the atmosphere and the biosphere are important for climate studies. We investigate changes of an atmospheric condition as a result of changing vegetation distribution using an atmospheric general circulation model. Two types of vegetation distribution become available recently. The first is an actual vegetation distribution, which was obtained from remote-sensing data (Kajiwara et al.). The second is a potential vegetation distribution, which was obtainedby natural vegetation models (Box et al.) that estimate vegetation type based onlocal climatological conditions. Two boundary conditions are prepared based on these distributions and each numerical simulation is conducted. It is found that the difference in vegetation has significant impact on the simulated climate. While regions covered with more amount of vegetation mainly tend to have more precipitaion, several regions become dry climate in spite of abundance in vegetation. It is suspected out that the model's deficiency in representing moisture transport by transient weather systems could be a reason for such discrepancy.

抄録全体を表示

Simplified deforestation effects on the climate over Indochina is assessed usinga GCM. In the simulation, a significant decrease in rainfall over Indochina is found in April and May (the beginning of the wet season) as a result of the simplified deforestation. On the contrary, no significant decrease is found in the time series of observed rainfall data in April and May. As the strong sensible heat calculated at forested land surface in Indochina in the dry season is supposedto be inadequate, additional two sets of numerical experiments are carried out with simple modifications to the land surface scheme. However, the decrease in rainfall is still found in the results of the numerical experiments. Change in Bowen ratio doesn't seem to play a major role within “land surface-rainfalrlelationship.”

抄録全体を表示

Time-dependent Reynolds-averaged Navier Stokes equation (RANS) and large-eddy simulation (LES) techniques have been applied to the analysis of flow past smooth topography to evaluate the results of both methods. Though RANS method used is a two-dimensional one with two-equation turbulence model, the results reproduce a time dependent large-scale turbulence structure. It appears to be made possible bysufficiently small grid spacing resolving the near-wall laminar sublayer and a small time step, and is something like an LES simulation with filter average taken in the cross stream direction. The overall accuracy of prediction, however, depends on the representation of the laminar-to-turbulent transition and does not appear to have outpassed standard k-ε A method.

抄録全体を表示

A distribution of atmospheric pressure in which the high pressure area lies to the west and the low pressure area to the east is a typical one covering Japan Sea area in winter. The characteristics of the atmosphere above Fukuoka city undersuch a pressure system have been investigated on the basis of the data obtained from upper-air observations and analyzed by using the one-dimensional k-ε model. Contour line profiles of potential temperature and wind speed drawn in a latitude-height section show that the Siberian cold air mass absorbs a large amount of heat and vapor in flowing down on Japan Sea and a mixed layer develops over 1-2 km height. The analyzed results for the potential temperature and the eastwestcomponent of the horizontal wind velocity agree well with ones obtained from upper-air observations.

抄録全体を表示

Air pollution is getting serious in urban areas by increase of automobile traffic. A variety of methods to control the traffic have been proposed, but efficiency of the methods has not been examined quantitatively yet. It's important to develop a system to simulate a series of processes from an occurrence of automobiletraffic to reaction and deposition of pollutants. In this study, we are trying to construct such a system with HOTMAC of a mesoscale meteorological simulation model and RAPTAD, a sort of random walk model to calculate transport process of pollutants in an urban area. And the mobile source emissions are estimated by using road traffic census data and emission function in RAS-W. Here we simulate behavior of SPM (Suspended Particulate Matter) which is ejected by automobiles in Osaka area under a various meteorological conditions to examine a validity of thesystem.

抄録全体を表示

In order to apply a regional NWP (numerical weather prediction) system to Japan, two submodels are developed to refine the interaction between laiiduse and atmosphere. One is developed to estimate solar radiaticn using the relative humidity profile in the atmosphere, and the other to deal with the heterogeneity of landuse based on flux-equivalence concept. Some other aspects of this system are alsorevised for application in Japan. Incorporating the refinement with the NWP system, two numerical experiments are carried out in Tsurumi riverbasin and central Japan, respectively. The idealized storm case in Tsurumi riverbasin indicates the noticeable effect of surface process to rainfall in a small-scale riverbasin, and the case in central Japan shows the prediction performance of this system inmountainous region.

抄録全体を表示

Water vapor variation has been investigated by using GPS. However, short-term disturbance of water vapor has not been sufficiently understood. Therefore, a method for investigating the short-term disturbance of water vapor is proposed in this study. In this method, power spectrum of atmospheric delay, which is obtained by GPS, is modeled. The parameter of the model and root mean square error (RMS) is used for investigation. The method is applied to the data obtained in Biwako Project '98 held in July 1998. As a result of the research, the difference between power spectra of observed data and power spectrum model shows the mechanismof water vapor disturbance.

抄録全体を表示

In order to investigate the acidification of cloud droplets due to rainout (in cloud scavenging) of air pollutants, the characteristics ofthe acidification of the growing single cloud droplet by the rainout of SO₂(g) are simulated numerically with use of a mathematical model. The mathematical modelis constituted from the conservation equations, the state equation for ideal gas and the equation of drop phase chemidal reactions.(NH₄) ₂SO₄ is selected forthe cloud condensation nucleus (CCN), which is produced from NH₃(g) and SO₂(g) via gas phase chemical reaction in the atmosphere. With use of the model non-steady pH, droplet radius, temperature and concentrations of chemicals are simulated. The major driving force for both of the droplet growth and the absorption of SO₂(g) is the difference of the concentration of (NH₄) ₂SO₄ between droplet and water vapor. It is shown that the salt concentration of CCN controls rainout of pollutants, although little is known about rainout compared with washout (below cloud scavenging).

抄録全体を表示

Field observation was performed to investigate the atmospheric structure and concentration of CO₂, SPM (Suspended Particle Matter) over Tokyo Bay by using Radio Sonde, Doppler Sodar and airplane in summer 1999.
The following results were obtained; 1) There is a descent-flow over Tokyo Bay. The peak value exits at the height of 300m. This expects the existence of circulation flow between Tokyo Bay and surrounding area. 2) The rise in potential temperature in the daytime is caused by the local descent-flow. 3) The vertical and horizontal distribution of SPM and CO₂ is different each other. Vertical gradient of CO₂ is positive over the bay. CO₂ is transported over Tokyo Bay from surrounding high emission area. Vertical gradient of SPM is negative.The profile is affected by the emission of sea-salt at the surface of the bay and Pacific ocean.

抄録全体を表示

Behaviors of sea breeze above Fukuoka City have been investigated on the basis of AMeDAS data and field observations. The land and sea breeze is influenced strongly by the topography near Fukuoka City and blows steady along the northwest-southeast line. Sea breeze observations performed by using a doppler sodar have revealed the existence of a coherent structure consisted of a pair of ascending and descending currents. The cross-correlation coefficients between horizontal andvertical velocities vary with 30 min period and take a value nearly equal to zero when the time lag is 0. Therefore, it is concluded that the coherent structuremay be due to the internal wave motion induced by the shear instability.

抄録全体を表示

Temporal and spatial variability of rainfall distribution over mountainous area is very complicated particularly in Japan. However if hierarchical time-scale structure in dependency of rainfall distribution on topography is taken into the consideration, it is possible that rainfall distribution in time scale greater than a boundary scale is almost uniquely expressed by topographical features. In this study, by analyzing data observed by radars in the southern part of Kyusyu and in K: inki district, it is made clear that the rainfall distribution over mountainous area has a hierarchical time-scale structure, and it is also attempted to explicate the characteristic of hierarchical structure by considering the relation to type of rainfall event.

抄録全体を表示

Through observation of the series of radar images. Meso-β scale rainfall occurring in the Kanto Plain is classified into the following three types, front formation-type, cells-advection type and isolated cell-type. The migration vectors of rain band images are not equal to the advection vectors of rainfall cells measured by PIY method and opposite to the direction of the wind intruding into the atmospheric boundary-layer. The generation mechanism and advection form of spatially large convective rainfall depends on the combination with the wind system in troposphere and local wind(land and sea breeze) in this area.

抄録全体を表示

It is very important for disaster prevention and flood control to predict sever rainfall in mountain regions.The accuracy of rainfall prediction, however, is not enough because of the complexity of meteorologicalcharacteristics caused by the steep mountains and valleys.
To investigate meteorological quantities, experimental observations have been performed 1998-1999 inand around Kurobe-Valley. In this paper, three types of observations 1) Doppler radar to measure rainfallecho around Kurobe-Valley 2) Mini-radar to measure rainfall echo in Kurobe-Valley 3) GPS sonde tomeasure profiles of meteorological quantities (temperature, specific humidity and winds) are presented.It is found that some local phenomena are occurred in steep mountain regions at time of heavy rainfall andnew ideas and instruments using in this experiments are effective to observe that phenomena.

抄録全体を表示

Characteristics of generation of a localized heavy rainfall are investigated using DEM and outputs from an operational numerical weather prediction model named RSM (Regional Spectrum Model), surface wind field observed by the AMeDAS (Automated Meteorological Data Aquisition System) and radar image from a volume scanning radar named Akagiyama radar rainguage. The investigation was conducted based on the classification of event features by their spacial scales such as meso α, β, and γ scales. As a result, relations between some dynamical indices and strom-system generation were made clear, which could be utilized into a physically-based short-term rainfall prediction method.

抄録全体を表示

Almost every year small rivers and drainage basins in urban areas suffer from flooding as a result of large-scale typhoons or concentrated thunderstorms. To minimize damage from such urban flooding, it is very important to predict rainfall and to take appropriate flood-fighting measures quickly. In this study, the relationship between the occurrence of a thunderstorm and the weather condition of the site is investigated. The place where a thunderstorm occ-urs may be related to updraft affected by wind convergence and topography, and to the spatial distribution of temperature. Furthermore, the occurrence of a thunderstorm is influenced by not only the lower-layer short-term weather condition but also the upper-layer condition and the long-term condition.

抄録全体を表示

This paper desribes the method and the result of estimation of rainfall intensity in north eastern Bangladesh using artificial neural networks and GMS images. Based on the observed intensity of rainfall and the temperature of the top of cloud recorded in GMS images, artificial networks are trained. With trained networks, the rainfall intensity is estimated in good accuracy for the data used for the trainings. However, the accuracy is not so good in the estimations for the data not used for trainings.

抄録全体を表示

The present paper shows the relevance of a new approach of using back propagation neural network (BPNN) in storm runoff estimation by using near surface soil moisture. Intensive field observation and field experiment conducted to observe the behavior of a forested catchment in Tono area is presented. The results obtained by numerical experiment using BPNN were tested by the field experiment and catchment observations. Both the experiment and field observations supported the results of the previous studies. The field experiment showed that the importance of litter layer in the direct contribution to runoff was not so significant. It was observed that the highly conductive soil layer underlying the litter layer and overlying the less macroporous soil zone with low hydraulic conductivity was the chief contributor to the total runoff in the study area. The field observation showed that the main contribution to the total storm runoff was from the channel system that received the runoff from such layers as in the field experiment.

抄録全体を表示

A lumped conceptual model, the Stanford Watershed Model (SWM) was used to simulate the runoff processes in the small forest watershed using the observed hydrological data for both the short and long period. Model parameters were calibrated with the runoff hydrograph at rain events only. In the rain runoff events, the changes of soil water vertical distribution were simulated accurately. Moreover, the results of separation of the runoff hydrograph using the SWM showed a good correspondence with those using SiO₂ as tracer. For the long period calculation, the changes of simulated upper zone storage and active groundwater storage on the SWM had the similar periodicity to those of soil water matric potential at 20cm depth and 160cm depth, respectively. However, the runoff hydrograph and lower zone storage could not be simulated well, which suggests that it is necessary to improve each estimation method for the snowmelt process and the evapotranspiration process on the SWM.

抄録全体を表示

In hydrological rainfall runoff simulation, flow routing is one of the most important components. The Muskingum-Cunge routing method is widely used since it is not only conceptually simple, easy to code and efficient to compute, but also has a firm hydraulic basis. However, there are some problems left to be solved before it is applied to a digitized distributed hydrological model. The most important one is the possible occurrence of negative outflows. To avoid it, two methods were developed, the approximation approach and the real-time adjustment of unit space and time intervals. Both were applied to the BTOPMC model (Block-wise use of TOPMODEL with Muskingum-Cunge method) and floods and lowflows of the 3500km² Fujikawa basin in Japan were simulated. The results indicate that both methods are applicable. In addition, two problems relating to the routing parameters K and X are studied and some practical handling methods are suggested

抄録全体を表示

The method to lump a general kinematic wave equation of the slope runoff system is described. The method is as follows: At first, the basin topography is modeled as a set of slope units using digital topographic information. From the topographic model, the spatial distribution of the upslope contributing area is easily obtained. Secondly, the spatial distributions of the discharge and the flow area are calculated assuming that the rainfall-runoff system is under a steady state. Finally, the storage volume of the slope system is calculated by spatially integrating the flow area and then the lumped relation between the storage volume and the outflow discharge is obtained. The flow area can not be always analytically integrated and some numerical computations are required. Then the technique to reduce the numerical computations is also given.

抄録全体を表示

A distributed hydrological model is applied to simulate water balance in the Ebi river catchment (27km²) with a grid size of 50m and a time step of 1 hour. The simulation of 5 years from 1992 to 1996 is performed. The model is verified through comparisons of simulated river discharges and groundwater levels with the observed values. The comparison of water balance at present (1993) with that in future (2035) is also conducted and it shows the impact of urbanization. To conserve hydrological cycle in the catchment implementation of infiltration facilities is thought to be highly required. The effect of infiltration trench is studied. It is found that the hydrological cycle can be improved at same level or even better in future than now if infiltration trench is implemented to infiltrate drainage from urban canopies.

抄録全体を表示

Initialization of soil moisture is a very important problem in numerical weather prediction models. In this study, we evaluate the role of soil moisture in land surface processes by SiBUC model. We carried out several kinds of numerical simulations by using same atmospheric forcing and changing the initial value of the soil moisture.
The key factor that controls heat balance is a relative humidity of soil surface (f_h) for bare soil case, and matric potential in rooting zone (ψ2) for vegetation case. And these two variables change so rapidly in narrow and different range of soil moisture depending on soil type, which leads to complicated reaction of land surface heat budget to soil moisture.

抄録全体を表示

Both land surface models and hydrological models use similar algorithms to describe water movement phenomena such as surface, sub-surface, ground water, etc, at a point. The fundamental difference between two schemes lies in evaporation estimation. Land surface models simulate actual evaporation using the energy balance whereas hydrologic models estimate evapotranspiration from the potential evaporation considering soil and plant properties such as soil moisture variation, leaf area index (LAI), plant root distribution, plant root depth, etc. This paper compares the performance of the land surface model developed at NCAR (LSM) and the hydrological model developed at IIS, University of Tokyo (IISDHM) against field observations from a hydro-meteorological observations (at 10 minutes interval) in an urban catchment. Both the LSM and IISDHM were able to simulate soil moisture variation adequately. Their long term evaporation estimates agree even though the short term patterns are different.

抄録全体を表示

Land surface is much more heterogeneous than atmosphere. To couple land surface hydrological processes with atmospheric dynamics, a model for estimation of spatially averaged hydrological responses over a large land area should be developed by adequate inclusion of the effects of land surface heterogeneity.
In this paper, the seasonal variations of soil moisture heterogeneity and spatially averaged evaporation were investigated by the field observation, process study and modeling in the Tibetan Plateau which has been considered to play an important role in the seasonal and internal variations of the Asian summer monsoon. Spatial distributions of soil moisture are characterized by considering the seasonal march of hydrological processes in the permafrost region. A land surface model which can express the pattern of soil moisture distribution is developed and validated by using the observed data. Two methods for estimation of spatially averaged evaporation are compared; one by using spatially averaged soil moisture and the other by considering the soil moisture heterogeneity. The results of the two methods are quite different during the trasnitionary phase from dry to wet while they are almost equal in the dry period and the wet one.

抄録全体を表示

SiB2, one of the newest Land Surface Models was applied to observational data at a tropical paddy field. Under the case of small Leaf Area Index (LAI), latent heat flux (lE) was underestimated. Because under smaller LAI, evapotranspiration mainly occurs at land or water surface but not at the top of the canopy. Further, surface water is easily lost and evaporation decreases because of low capacity of surface water in SiB2. In order to make up for these defects, SiB2-Pad in which water body is taken into account was developped and applied. As a result, the simulation of the latentheat flux was improved significantly. Ground surface temperature was estimated fairly well, but during nighttime, water temperature was underestimated. Canopy temperature was also lower than observation during nighttime. As a result, slight underestimation of lE in the morning was not improved. Additionally, canopy temperature was sometimes overestimated in the simulations, that caused underestimation of 1E. In order to avoid the underestimation, it was necessary to adjust a parameter representing dependency of stomatal-conductance on leaf temperature.

抄録全体を表示

The dissipation rates of the turbulent kinetic energy and the variance of temperature and humidity were estimated from the turbulence measurements through the relation between the dissipation rates and the second-or third-order structure functions. These estimations of disspation rates are applied to the dissipation methods to estimate turbulent fluxes of sensible/latent heat and momentumn flux from the flat rice paddy field. The estimated flux values are found to be comparable with those estimated with the eddy correlation technique, suggesting the feasibility and applicability of the dissipation methods in the hydrological application.

抄録全体を表示

Micro-meteorological data and data concerning post-irrigation heat and moisture transfer at shallow depths below the surface of a sandy soil were collected in the United Arab Emirates during September 1998. Direct measurement of the evaporation from the soil was carried out using a small removable soil column buried vertically in the ground. From this experiment, the time change of evaporation rate from bare sandy soil after irrigation was obtained. In addition, using the observed evaporation rate, the water vapor transfer coefficient, λ _m was evaluated for the α-β bulk equation, and the correction coefficient for liquid-vapor interfacial area, ξ was evaluated from the diffusion equation. It is concluded that the proposed experimental techniques are appropriate for field measurements of post-irrigation drying phenomena in arid regions.

抄録全体を表示

Natural rainfall has the variation in rainfall intensity during its event. However, the various infiltration models are subjected to rainfall intensities that are higher than the infiltration capacity of the soil at a given location. Diskin and Nazimov (J. Hydrol., 172: 313-330, 1995) proposed recently the infiltration model which is a simple conceptual model and can express the relationship between rainfall intensity and ponding time.‘Ponding time’ is the period from the beginning of rainfall until the occurrence of ponding. This model also can compute the variation in the infiltration capacity for constant or variable rainfall rates. A simple conceptual model is valuable for carrying out the stormwater runoff analysis.
The purpose of this paper is to investigate the ponding time and the infiltration capacity for field infiltration data measured using a rainfall simulator under steady rainfall and to evaluate the above infiltration model proposed by Diskin and Nazimov. Comparison of the model calculations with experimental data shows reasonably good for the relationship between rainfall intensity and ponding time and excellent agreement for the infiltration decay curves.

抄録全体を表示

A series of one-dimensional tracer experiments were carried out in a 20 m long homogeneous sand media to see the scale effect on dispersion. Dispersivity was found increasing with distance. This may be due to the segregation of the smaller sized sand and larger sized sand particles in micro scale. Similar experiments in a 10 m long heterogeneous media, prepared by inserting a number of large permeable blocks into the previous sand media, also showed the similar behavior. However, the rate of increase of the dispersivity is smaller in heterogeneous media.

抄録全体を表示

Solving soil unsaturated flow problems requires knowledge of the water retention θ(ψ) and unsaturated hydraulic conductivity k (θ) relationships.This study introduces a new evaporation method for simultaneous estimation of both retention and unsaturated hydraulic conductivity data. Newton-Raphson iterative method was used to solve non-linear equations in time. Simultaneous transport of liquid and vapor flow in the unsaturated soil was modeled. Evaporation from a vertical column of soil material (tile) was simulated. Hydraulic parameters were estimated by minimizing the sum of squared differences between measured and simulated evaporation rate through the whole period of the experiment. Two laboratory experiments were carried out on the same sample under different conditions to evaluate the ability of this new method to provide good estimation of the retention and unsaturated conductivity curves. The results show that this method is stable, accurate, and can be applied for other types of soil.

抄録全体を表示

Tracer experiment was carried out using a packed bed of fine sand, where groundwater flowed as a single phase under unsaturated conditions. A new apparatus with the new evaporation technique proposed by Mohamed et al. was used to create an upward movement (i. e. upward soil water potential gradient) to estimate the hydrodynamic dispersion coefficient (D) The concentration distribution of the sodium chloride (NaCl) over the depth of the sand column at the end of the experiment could be measured using the electrical potential method. D could be determined by fitting an appropriate numerical solution of onedimensional Convection Dispersion Equation (CDE) to the measured vertical solute concentration through the depth of the unsaturated sand at the end of the experiment using Galerkin Finite Element Method (GFEM). A good agreement was found between the two series. The value of the estimated dispersivity is quite accurate and lies in the range 0.001-0.02m which is suggested by many authors.

抄録全体を表示

Influence of spatial distributions of model parameters on rainfall-runoff simulation results is investigated. Values of hydraulic conductivity and thickness of A-layer are generated according to log normal distribution; each value is assigned randomly to each slope element; runoff simulation is conducted by using a distributed rainfall-runoff model. The above procedure is repeated and simulated hydrographs are compared. As a preliminary result, we obtained that spatially lumped distribution information (mean and variance) of hydraulic conductivity and thickness of A-layer is the most important information to form a hydrograph, and spatially explicit information of the parameters is not always needed under spatially uniform rainfall condition.

抄録全体を表示

Water supply in Kumamoto area is depended only on groundwater. This urban area spreads for the north and east of Kumamoto city by increasing of houses, roads and factories during the last 25 years. As a results, the impervious area has been increased to 104 km² (about 10% of all the area).
This paper reports relation between rainfall and groundwater level using a tank model which considers recharge of paddy field, lateral flow of groundwater and evapotranspiration. As the results, it is possible to calculate the exchange of groundwater level and quantity of springs using the data of rainfall and temperature.
The parameters using this tank model are calculated from observed data which include effect of rainfall and groundwater flow. So it is necessary that these parameters are determined except the influence of interaction between rainfall and groundwater flow.

抄録全体を表示

Wells of the four study areas in Yamanashi Prefecture were grouped on the basis of groundwater qualities. Grouping was based on the scores of principal components of the major ion concentrations. Spatial distribution of grouped wells was consistent with the topography and with the distributions of water temperature and 1, 1, 1-trichloroethene concentration. Similar quality wells grouped by cluster analysis using the principal component scores line up geometrically along the groundwater flow direction estimated with the computer model, USGS MODFLOW. These results supported the hypothesis that the wells of similar quality line up in the direction of the groundwater flow. This characteristic resulted from the human activity which supply the environmental tracers into the groundwater. The semivariogram of the scores of principal component was effective to some extent to find the anisotropy of water quality, if its calculation takes the azimuth into consideration.

抄録全体を表示

“Michi-No-Eki”, HACHI-KITA has been in operation on Route 9 in Muraoka-cho, Hyogo Prefecture, since March 1998.“HACHI-KITA” has two types of snow melting systems using terrestrial heat. One is a Reservoir Heat Collection System (RHCS) applied to a 1120 m² parking lot that is used to put on or take off tire chains. The other is a Bore-hole Heat Exchange System (BHES) used for melting snow on a 310 m² sidewalk. This paper deals with the thermal behavior of the fluid in the water tank and in the surrounding ground, as well as the interaction between them. The snow melting performance of the RHCS was completely satisfactory and this made it possible for people to walk from the parking lot to the “Michi-No-Eki” buildings on a snow-five pavement The fluid temperature was as high as 19.8°C on December 31 and a zone with high ground temperature (17-19°C) existed around the tank in winter, even though the ambient ground temperature was only about 15°C. From these results it was confirmed that the effect of the thermal energy storage during summer persisted until the following winter.

抄録全体を表示

A Bore-hole Heat Exchange System (BHES) has been originally developed for thermal energy storage in rock basin. One of characteristics of the BHES in Fukui University, is that it was built in an alluvial aquifer, and this was the first such system built in Japan. To evaluate the effect of groundwater flow on the thermal performance of the BHES is an important research theme.
This paper describes, both experimentally and theoretically, the thermal behaviors of the fluid in the bore-hole and the surrounding ground temperature in an aquifer (permeable layer) and in an aquitard (semi-permeable layer). The data indicate that the fluid temperature recovery in the bore-hole after shutting off the circulation pump following a snow melting operation was much more rapid at levels with aquifers than at those without. It is concluded that sensible heat associated with groundwater flow contribute substantially to an effective extraction of terrestrial heat by the BHES.

抄録全体を表示

Land surface hydrological conditions have been considered to play an important role in the global and regional climate variability Esspecially, soil moisture, surface temperature and vegetation are the key parameters which should be observed in the global scale. In this paper, an algorithm for these land surface hydrological parameters has been developed by introducing two indices, Soil Wetness Index and Polarization Index which are calculated from a microwave radiative-transfer equation. The algorithm was applied to the air-borne and satellite sensors and validated by using the ground data. The estimated soil moisture, surface temperature and water content of vegetation corresponded reasonably to the observed ones.

抄録全体を表示

This paper investigates the possibility of monitoring of the ground surface condition under the rice crop canopy based on a numerical scattering model preliminarily. The model used here is the Michigan microwave canopy model. In order to apply to the rice paddy field, a developed module for it is added. It is found that the ground surface condition under the canopy can be detected at the incident angle of less than or equal to 25 degree at C-band and at the incident angle between 10 and 50 degree at L-band. It is possible to monitor the ground surface condition under the canopy, if the sensor configuration is designed for its purpose. However most systems mounted on the operational SAR satellites do not suit with the purpose.

抄録全体を表示

The backscattering coefficients observed by satellite-based microwave scatterometer are influenced by surface geometric roughness and incident angles. Land surface information can be obtained using these dependences of backscattering coefficients on a different land cover. The Precipitation Rader (PR) on-board the Tropical Rainfall Measuring Misson (TRMM) offers a global and seasonal data set of backscatter coefficients as a by-product. A set of TRMM-PR2A21 data in whole 1998 is utilized in this present paper to investigate land 3urfacc information. The backscattering coefficients at selected regions which belong to different land cover types are analyzed in order to clarify the dependence of backscattering coefficients on incident angle. It is found that the backscattering coefficients significantly depend on land type and incident angle. The seasonal change of backscattering coefficients at each land type is also assessed which should depend on the seasonal change of soil moisture and vegetation. Then, the PR-data are divided into 3 groups based on incident angle, and a global land cover map is produced by classifying land cover into 16 categolies using the 3 groups. The global land cover map is presented and the characteristics of it is described in detail. It is expected that the seasonal change of global land surface information can be obtained utilizing this method in the future.

抄録全体を表示

The goal of this study is to estimate the surface soil moisture and surface roughness using polarimetric Synthetic Aperture Radar (SAR) data. In this study, a preliminary analysis for approaching, this objective was conducted based on a sensitivity analysis of surface parameters. A numerical scattering model was used, and the results were compared using only like-polarized backscattering coefficients obtained from the data of an experiment conducted simultaneously with an airborne SAR. The surface correlation function was considered in this analysis. Because the problem is site-specific and depends upon the measurement accuracy of both the ground truth data and the SAR system including speckle noise, as well as the model uncertainty, the comparison results did not agree well with measured and inferred values of both the soil moisture and surface roughness. In particular, the moisture was underestimated and the roughness was overestimated.

抄録全体を表示

This paper proposes a new algorithm for precipitation over land by deriving the optical thickness from TMI brightness temperature, in which the effect of land surface emissivity on radiation transfer is taken into account. In turn, soil moisture can be estimated by using the land surface emissivity in addition to precipitation. Based on a microwave radiative transfer equation, two indices, Index of Soil Wetness (ISW) and Polarization Index (PI) are introduced into the algorithm to remove the effect of land surface physical temperature. Surface roughness effects on land surface emissivity is included by using the polarization mixing ratio and r.m.s. height.
The application of the algorithm to the GAME-Tibet meso-scale experimental field shows a good agree-ment with the spatial patterns of precipitation observed by the 3D Doppler radar. The estimated soil moisture shows good correspondence with observed one.

抄録全体を表示

Regional evapotranspiration in the East-Japan is estimated by using NOAA/AVHRR data and GPV (Grid Point Values of meteorological conditions) data based on the heat balance method. Spatial resolutions of those data are different each other.
In or order to get the estimated value of evapotranspiration, following two ways of data arrangement are examined and the results computed from the both ways are compared. At first in the paper, GPV data is interpolated to the scale of NOAA/AVHRR data. In the next, NOAA/AVHRR data is averaged to the scale of GPV data. At last, the authors make discussions on the scale averaging the hydrological conditions for getting more reasonable estimation of regional evapotranspiration.

抄録全体を表示

Using multi-temporal satellite data, the change of land covers in the Doki River basin and its impact on hydrological data for the past 17 years were examined. The land cover classification maps in 1986, 90, and 95 were obtained using multi-temporal Landsat TM. From these results, its observation data were divided into three periods: the first period (1981-86) with the decrease of paddy fields, the second period (1987-92) with the increase of agricultural fields and little urbanization and the third period (1993-97) with golf course development. Through the three periods, deforestation had been carried out and the ratio of forest in the basin decreased from 83 to 76 %. During the observation period, evapotranspiration decreased by 16 % and runoff ratio increased by 13 times. Moreover, seasonal profiles in evapotranspiration showed different patterns each period, which seemed to be affected by different-typed development.

抄録全体を表示

Annual and daily runoffs at most locations of a basin are unknown, which are estimated by the proposed methodology. First a squared region covering the Fuji River basin is divided into 9, 450 grids of nearly 1 km². Annual or daily precipitation data of 27 gauges in the region are used to derive the precipitation at each grid, by applying a spatial interpolation algorithm called spline function. Monthly ordaily mean temperatures at grids are estimated by a step-wise regression method. Second annual water yield at any grid is obtained with Hamon and Pike formulas and the water budget equation. Runoff distribution in the river network drawn out using digital elevation data is estimated. Finally, based on daily rainfall and temperature, the daily runoffs along the rivers are simulated by a distributed hydrologic model. All runoff estimations are checked by the observations in several sites.

抄録全体を表示

Satellite information on spatial and temporal distribution of land cover has been highly requested for watershed management. Data availability of the high spatial resolution sensors is usually limited due to weather conditions, especially in tropics, while the multi-temporal sensors with moderate spatial resolution can not detail information which is required for watershed management. This study is to develop a methodology of watershed management using a mexel (mixed pixel) model which uses Landsat TM and NOAA AVHRR. The area ratio of land cover within a NOAA AVHRR 1.1km pixel can be estimated with reasonable accuracy by applying this model to the Brantus river watershed in Indonesia.

抄録全体を表示