This paper discusses a frequently-addressed problem with the aircraft turbulent flux measurements, namely an underestimation of the surface fluxes, and reexamine this underestimation by using recently developed concepts in the boundary layer meteorology. Three possible causes, namely, 1) the vertical distribution of the sensible heat flux within the atmospheric boundary layer, 2) the difference in source area between the aircraft and ground-based measurements, and 3) the average length for the eddy covariance, were taken into account when the fluxes measured with aircrafts were compared with the ground-based measurements.

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Diurnal and seasonal variations of stomatal conductance were observed for six tree species consisting of a warm-temperate secondary forest. Jarvis-type stomatal conductance model was used to derive environmental factors affecting for the stomatal conductance. Sunlit leaves (those exposed to short-wave radiation) provided the highest rate in terms of both magnitude and variability in both diurnal and seasonal variations of stomatal conductance. While shaded leaves (those shaded by sunlit leaves) performed only small conductance and slight variations. In consideration of distinctive characters for sunlit and shaded trees in the responses of stomatal conductance to light intensities, the light response curves were applied for each tree species. They illustrated the maximum stomatal conductance of sunlit leaves much higher light saturation point than those of shaded leaves. Nevertheless, shaded leaves could be reached their maximum points of stomatal conductance by using just small light intensities (large quantum yield), whereas sunlit plant needed much light intensity to reach the maximum.
The statistical analysis of the model usefulness testing (F-test) was used to reduce any insignificant factors from the Jarvis-type model, due to numbers of input variables causing inconvenient experiment. It resulted that in this site soil water potential was not much significant. Therefore, the stomatal conductance were finally estimated by using only three environmental variables composed of photosynthesis photon flux density (PPFD), air temperature, and water vapor pressure deficit (VPD) .
For deciduous plant (Q. serrata), new shooting leaves increased stomatal conductance sharply until reaching the maximum in two months after full leaf expansion. After that, they gradually declined as leaf senescence. Leaves shooting in different years of three evergreen species had distinct difference in stomatal conductance from March through May. These results supposed that leaf age effect should be included in the stomatal conductance model.

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Snow survey was conducted for the years 1939-1967, 1983-1984, and 1996-2000 in Shozawa basin (118 ha, height difference 570 m) of Takaragawa Forest Watershed Experiment Station located in the head water area of Tone River, that is water resources in Tokyo metropolitan area. Full-depth snow density did not depend on an altitude and was expressed as a function of calendar days. As is well known, snow water equivalent SWE has a positive linear relationship with an altitude in a forested area in Japan. The coefficient a, which represents the increment of SWE with an altitude, demonstrated increase trend with time in each winter. For the years 1939-1967 and in 1983 the coefficient a augmented from about 0.5 to 1 mm m^-1 during 40-120 days since 1 January, while in 1984 and for the years 1996-2000 it increased from some 1.8 to 2.5 mm m^-1 during 70-120 days. Though we inspected the relationship between the coefficient a and heavy snow versus light snow years, we could not find any relationships between them. Two possible causes for this increase in a were discussed: first, snow melt promotion in the lower part of the watershed due to temperature rise, and secondly, the effects of silvicultural practices in the basin. Neither of them contributed to the increment of a, and it is concluded that the amount of snow fall increase in the upper part of the basin gave rise to the coefficient a.

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Fresh water in lake has been widely used as valuable water resources in various industries. It is indispensable to investigate and analyze the present situation of lake water quality and quantity for the establishment of sound hydrologic water cycle in a lake basin. The objective of this study is to develop the estimation method of evaporation from a deep lake, Lake Ikeda, Kagoshima. The short and long wave radiation, which are estimated from the observed meteorological data in the vicinity of the lake, agree well with the measured one at the study site. The calculated vertical profiles of lake water temperature and the lake surface temperature are also in good agreement with the measured data. It is concluded that the calculation scheme of evaporation from Lake Ikeda has been established and will be useful for a discussion of the hydrologic budget of the lake as fresh water resources.

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Model calculations are made in order to understand characteristics and response to climate change of runoff from a cold glacier on the Tibetan Plateau. Twenty percent of meltwater was preserved at the snow-ice boundary due to refreezing because glaciers in the middle to northern Tibet are cooled enough during the previous winter. This result suggests that it is not suitable to describe runoff water as same as meltwater at the glacier surface whose procedure has been done well in the previous studies.
Sensitivities to change in meteorolgical parameters revealed that change in air temperature will cause not only increase of melting by sensible heat, but also drastic increase of melting due to albedo lowering since a part of snowfall changes into rainfall. As additional result, it was suggested that an increase of precipitation would cause a decrease of contribution of glacier runoff to the total runoff in the river water.

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Ecological systems and chemical properties of lakes and reservoirs are influenced by the thermal structure process. In the case of agricultural reservoirs, this process is directly associated with the rice crops. Accordingly, it is important to predict correctly this process at the planning stage of a reservoir. In this study, a water column model was proposed for simultaneously estimating vertical profiles of temperature and water level. The model was characterized by substituting a simple water column for complicated geographical features of lakes and reservoirs. The model was applied and tested at Kuzumaru dam reservoir for three months (May∼July 2000). Favorable results could be obtained from the test on the estimation of vertical profile of temperature in a wide range of water depths.

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Surface temperature is one of key physical variables in estimating surface heat fluxes using heat budget method. Therefore, a lot of researches have estimated heat fluxes using thermal-infrared remote sensing data of the 8∼14μm atmospheric window region, namely, thermal-infrared temperature. In this paper, we focus on issues which have occured in investigating the relationship between thermal-infrared temperature and sensible and latent heat fluxes, especially over vegetated surfaces as well as some solution to the issues. Additionally, methods for the atmospheric correction and emissivity correction are described. The former often comes up to problems especially in satellite remote sensing. Combination of remote sensing and numerical models, which is expected to be developed in the near future, is briefly described.

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This paper briefly reviews the history and the scientific achievements of the surface flux measurements using an aircraft equipped with turbulent sensors. Especially, focuses are given to the aircraft measurements linked with large-scale field campaigns that emphasized the land-atmosphere interaction at a large scale.

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