A new formula is proposed for estimation of net radiation based on the heat balance equation. All effects of various parameters to net radiation are involved in a non-dimensional parameter Rn+, which is derived through normalization with solar radiation and effective longwave radiation flux. Rn+is closely related to the temperature difference between the atmospher and the ground surface. This parameter Rn+on forest in the Tohoku district is calculated with actual climatic data sets. Through the discussion on sensitivity of Rn+to various parameters, it is shown that Rn+can be regarded as a constant under certain condition. Net radiation may be estimated from solar radiation, longwave radiation, air temperature and only one experimental constant Rn+.

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By observing the movement of numerous surface foam on floods photographed by air crafts, the author has discovered that there commonly exist, along the longitudinal axis, parallel cycloidal flows, in which adjacent vortices have opposite directions of rotation. Measuring floats go down along the convergent flow. Also a radio-controlled air boat, which moves around upon the flood flow, acoustic survey system and an automatic dropping device of the floats has been developed. The positions of the floats were measured by LASER track total-station at the river side. The measurement cross section was chosen at a turning point of alternating bars. The accuracy of discharge measurement will be highly improved by studying the ratio of the surface convergent velocity to mean velocity of the parallel cycloidal flows.

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Oikawa model (1985) was improved to simulate annual variations of dry-matter productions of forests. Spatial information such as tree density and canopy closure were included into the model, and the validity of this model were discussed. In terms of qualitative aspects, several kinds of experimental laws of forest growth such as (1) overshooting of leaf biomass during the process of canopy closure, (2) dependence of overshooting periods on tree density, (3) constant final yield, and (4) linear relationship between leaf life-span and leaf biomass, were well simulated. In quantitative view points, simulation results were also compared with the field observation data by Hachiya et al. (1989) for high density stands of Pinus Densiflora. Annual changes of biomass and primary production rate were simulated well, but litterfall rate was not.

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Numerical experiments to investigate the impact of soil moisture on precipitation are carried out with a regional climate model for Eastern Asia in summer. Two independent experiments are carried out at first, one is the 'Wet Run' (soil moisture is saturated) and another is the 'Dry Run' (soil moisture is dry). Comparing both experiments, two kinds of areas are extracted, one is where 'the Wet Run makes much precipitation compared to the Dry Run' (called the 'Area A'), another is where 'the Dry Run makes much precipitation' (called the 'Area B'). To clarify this difference, another experiment (called the 'PW Run') is carried out in which only the 'Area B' is wet.
The analysis of these experiments mainly from a viewpoint of water budget, leads us to the conclusions as follows; (i)Soil moisture affects not only the local precipitation but also the precipitation at the downstream area through the water vapor flux downstream. (ii) This effect on the downstream area depends on '_ΔP/ΔE1or<1'. (_ΔP/ΔE is defined as “the difference of precipitation (Wet Run-Dry Run)/the difference of evaporation (Wet Run-Dry Run) ”) (iii) At the area of '_ΔP/ΔE>1', the vertical profile of θ, (equivalent potential temperature) in the boundary layer is stable in the Dry Run. It is assumed this is owing to the entrainment at the top of the boundary layer. But at the area of '0<_ΔP/ΔE<1', this feature is not detected.

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In order to investigate the hydro-statisticacl charactaristics of annual rainfall amount in cases of three cities, namely, Matsuyama, Fukuoka, and Maebashi for last 100years, (1)Normal Distribution, (2)Logarithmic Normal Distribution with two parameters and (3) With three parameters, and (4) Modified Logarithmic Normal Distribution with three parameters were examined to introduce a better and simpler method for finding the extreme value, maximum or minimum value of annual rainfall, for the design of water resources facilities. In addition, Thomas plotting and Hazen plotting methods were compared for deter-mining expected value of an annual rainfall amount.From the above examination, (4)the Modified Logarithmic Normal Distribution with three parameters showed better re-sults than the other three (1)/(2)/(3) methods. On the other hand, it is clarified that the Hazen plotting method had better adaptability than Thomas plotting method in many cases. However, in case of measuring the long-term amount of rainfall showed a relatively good adaptability even Normal Distribution method.

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Potential effects of urban vegetation on the atmospheric environment in the Kanto area were estimated by coupling the plant-physiological characteristics of Meiji-shrine forest (Kanda et al., 1997a, b) and the output of meso scale meteorological simulation (Fukuda et al, 1997). A total of four functions of vegetation were discussed, which were (1) transpiration (mitigation of urban heat island), (2) photosynthesis (CO2 assimilation) (3) O3 absorption (purification of the atmosphere) and (4) emission of terpene (relaxation effect). The numerical calculation was performed for 27 July in 1995, the calm and clear day in summer. The following results were obtained; 1) The stomatal opening in urban areas was restrained mainly by the larger water vapor deficit of the urban atmos-phere, 2) this lead to the lower level of CO2 assimilation and O3 absorption in urban areas than in rural areas, 3) the emission of terpenes, which were controlled dominantly by leaf temperature, were larger in the urban areas than in rural areas, and (4) Transpiration in urban areas were still higher in spite of stomatal restraint.

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