Heat balance at the earth's surface is a base for understanding the nature of the earth surface as Voeikov, Thornthwaite and others had suggested. The study of heat balance hac close relations not only with climatology, but also hydrology, glaciology, geomorphology and biogeography. Regimes of heat and water are two fundamental elements controlling physical features on the earth, and distribution and variation of these elements are explained through the analysis of heat balance. It may be said that heat balance study gives the methodology in physical geography which aims to explain many complex phemomena occurring near the earth's surface. This special volume of the Review is one of the results of activities of “Research Group of Heat Balance Climatology” in our Association. General explanation on heat balance of the earth is illustrated in the figure. Study of heat balance of the earth includes wide fields of the science ranging from satellite climatology to groundwater hydrology, limnology and oceanography. But the papers presented in this volume are mainly concerned with boundary layer climatology and thermal characteristics of the ground surface. These problems are especially important in understand ing the nature of the earth's surface, and they must be studied by geographers who know the complex system of the earth's surface. Recent progress in heat balance studies made by Japanese geographers are briefly reviewed in this article. Papers may be classified into four categories: (1) boundary layer physics; (2) local climatology and urban climatology, (3) hydrology, soil physics and glaciology; and (4) radiation balance. All the papers on heat balance presented in the Review, important papers published in other journals and books on this problem are listed in the bibliography for the last 15 years. The contributions of geographers on this field of the study mainly concentrate to urban climatology, radiation balance and hydrology. As seen from the bibliography, many papers were published in 1970's, and it seems that the heat balance method is getting a foundation in physical geography. For the future development of this method, we have several problems to be solved, for example, curricurum of geography in universities, research fund and application of the method.
Evapotranspiration plays an important role in determining dry and wet conditions of the earth's surface. Many factors consist in the evapotranspiration process and they combine one another in complex ways. Therefore, previous studies of evapotranspiration have been done over uniform surfaces, that is, open water, uniform vegetation, or bare soil surfaces. As advances in the understanding of evapotranspiration process have occurred, it becomes possible to calculate evapotranspiration by adding the soil surface and plant surface com-ponents. A separation of evapotranspiration into soil water evaporation and plant canopy tran-spiration was carried out in this study. Micrometeorological observation was conducted over a pasture field in the Environmental Research Center, University of Tsukuba, during the summer of 1978. The method proposed by Deardorff (1978) was used in computation. Hourly variations of albedo, atmospheric stability and excess resistance were considered in the calculation. The results obtained in this study are summarized as follows. 1. The albedo of pasture and that of bare soil showed hourly variations depending on solar elevation. The hourly albedo values ranged from 0.16 to 0.26. This fact indicates that the hourly variations of albedo should be considered in the analysis of radiation balance for short periods. 2. Soil water evaporation proceeded in the nighttime, even though condensation occurred on pasture leaves. This was caused by the mulching effect of pasture canopy, which pre-vents soil surface from extreme radiative cooling. 3. The soil water evaporation amounted to 25.9% of the total evapotranspiration during the observation period. The proportion of soil water evaporation from a field of pasture was greater than those obtained from other crops.
In the periglacial environment of the Japanese Alps, temperature distributions in surface soil layer are important for the formation of micro topography. However, the lack of soil temperature data in alpine zone of the Japanese Alps are serious. The purposes of this paper are to make clear the diurnal and annual variations of soil temperature on the summit area of the Mt. Tateyama and the Ontake Volcanoes, and the lapse rates along the mountain slopes. Field observations were carried ont in the cooling phase of the year from mid summer to early winter. As we failed to get the data in mid winter, we utilized the data of annual soil temperature change at Tokuyama Village, heavy snow fall area west of the Ontake, combining with the data of the field observations, to obtain empirical equa-tions of annual change of the soil temperature on the several slopes of the Ontake Volcanoes. The lapse rates and the diurnal changes of soil temperature during the field observations are shown in Figs. 4 and 5 and Table 1. Annual change of soil temperature in alpine zone (Tz) is expressed by the Ingersoll's equation as follows; Tz=TM+A0exp (-az)sin(wt-az-γ) where TM mean soil temperature A amplitude of soil surface temperature α;_??_ρ; density of soil, c; specific heat of soil, pkg; Austausch oefficient, ω=22π/p, p; period of temperature cycle, z; depth of soil. Some of the results of the field observations and the estimations by the use of the above equation are shown in Figs. 8_??_10.