The increase of bare areas has certain effects on climate change. For this reason, it would seem that a better understanding of soil moisture would be useful in the solution of thermal balance. Changes in soil moisture are brought about by shifts of liquid and vapor in soil. The liquid permeated into the soil by the difference between matric potential and gravity. This study derives the behavioral model of moisture by using a dimensional unsaturated analysis which accounts for hysteresis of soil moisture. This model is the method used for shifting vapor in soil. Through the use of this model, the environment of soil moisture may be better understood.

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Miyakejima Island is a small volcanic island, like a cone about 8.7 km in diameter and 814 m in height. To clarify the spatial and temporal changes in precipitation and oxygen isotope ratio, 14 precipitation collectors were set all over the island, and rain samples were collected 10 times from Jul.1994 to Jul.1995.As a result, in spite of the same trend of temporal change in oxygen isotope ratio of precipitation to Japan mainland, the alti-tude effect in Miyakejima Island, -0.10∼-0.17%/100m, was smaller than that at other areas in Japan mainland (-0.2∼-0.25‰/100m). However, according to the data reported from other areas in the world, altitude effect depends on the eleva-tion. Taking this result into consideration, the altitude effect on Miyakejima Island is not small specially.There were remarkably the spatial changes in both annual precipitation and weighted averaged isotope ratio. The maximum precipitation was found at about 400∼600m above sea level on the windward slope. But the lightest isotope ratio was found at about 400∼600m on the lee side slope.From the result above, it is cleared that spatial and temporal changes in oxygen isotope ratio of precipitation on Miyakejima Island, is predominantly affected by amount effect, altitude effect. Furthermore, the phenomenon which may represent rain shadowing effect was confirmed.

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We analyzed temperature, specific humidity and vertical velocity observed in the surface boundary layers of very flat paddy field and wide orchard. It was obtained that the characteristics of turbulent intensities of the temperature and specific humidity are consisted with the one-third power law on the unstable condition, and the empirical coefficients were in agreement with that given in previous studies. However, for a near neutral condition, the turbulent intensities of the vertical velocity didn't follow with the one-third power law. Further, we proposed a simplified method for flux estimation, in which the mean wind velocity instead of vertical velocity is used. Compared with the variance method, i.e. power-law method, our method was shown to estimate the temperature and humidity fluxes much better, and we also found the estimation for the temperature flux more accurately than that of the humidity flux in each method.

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Estimation of latent heat flux and of evapotranspiration rate over regional scale has been one of the important subjects addressed in Hydrology, Climatology, and Meteorology. For estimating regional latent heat flux, the remote sensing technologies are essential. The measurements of the surface fluxes at grassland, paddy, and at copse were carried out, to understand the relationships between the spectral reflectances derived from a satellite and the latent fluxes. Observations were made in 1997 and in 1998. The grassland site is located within Environmental Research Center, University of Tsukuba. The paddy site is located within Agricultural and Forestry Research Center, University of Tsukuba. The copse site is located in the west of University of Tsukuba. Latent and sensible heat fluxes were estimated by the energy balance equation using eddy correlation method at the grassland, and by the energy balance equation using Bowen ratio at the paddy field and the copse, respectively. Results are summarized as follows: At paddy field, definite increase trends were confirmed in the seasonal changes both in the surface albedo and in the evaporative fraction. This synchronization indicated that rice plants phenology affected to the surface fluxes. There were confirmed in the time series of the surface albedo at grassland, one was a decreasing trend from April to May, the other was an increasing trend until the middle of June. The former trend in surface albedo is thought to be affected by the increase of Absorbed Photosynthesis Active Radiation (APAR), and the latter by the increase of reflectance in the near infrared wavelength with increase of Leaf Area Index (LAI). These periods accorded with increasing period in the evaporative fraction.

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Estimations of the surface fluxes, particularly inferring the evapotranspiration rates over regional scale, have been one of the important subjects addressed in Hydrology, Climatology, and Meteorology. For estimating regional surface fluxes, the remote sensing technologies are essential. This study carried out the comparisons of the vegetation index derived from a satellite with the latent heat flux (lE) measured at the surface. And We considered the regarding factors that influence on these relationships. SPOT (Systeme Probatoire d'Observation de la Terre) HRV (High Resolution Visible) data was used for this study, and NDVI (Normalized Difference Vegetation Index) was estimated from SPOT data. Results are summarized as follows: 1) Seasonal variations in digital numbers of red and near-infrared, and in NDVI indicated the phonologies and the changes in the land surface status at each land cover. 2) A positive correlationship was confirmed from the relationship between NDVI and lE at grassland and at copse. However, no relationship was confirmed this relationship at paddy. 3) In the period of the increase in NDVI (i.e., growing stage of the plant), a very good correlationship was found in the relation between NDVI and lE. An inferring error of lE from NDVI was approximately 10 Wm-2, therefore, NDVI was a good indicator for inferring lE. 4) On the other hand, after growing of the plant, it was difficult to infer lE from NDVI only. it have to consider a “Synergism” use of the satellites for inferring lE.

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The indirect method and stochastic method are efficient and accurate in the inverse groundwater modeling in a small research area but inefficient in a large scale basin. Because the Kanto Plain is a large scale basin, to develop an inverse groundwater model in this basin, we are forced to turn to the direct method. The direct method is a conceptually simple method, but also faced by the ill-posedness problem that makes this method yield no solution in a large scale basin if the traditional optimization solution scheme is adopted. Therefore, the authors developed a non-optimization solution scheme, the NODMIP, to eliminate the ill-posedness problem, while overcoming the difficulties in groundwater modeling in a large scale basin at the same time . To do so, the following five steps are taken: 1) solving the governing equations one time step by one time step, 2) imposing constrains of the prior information while the equations are being solved, 3) eliminating the pumping term and the residual term in the discretized equation, 4) interpolating water table data by Kriging technique, 5) estimating the unique aquifer parameters by simple arithmetic averaging method. This model is validated by an application in the Kanto Plain.

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