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.

抄録全体を表示

1981年12月1日から1982年11月30日までの1年間の観測値のうち,晴天日(曇天日を含む)を選び,草地における熱収支と蒸発散量の関係について解析をした.
ボーエン比は,夏・秋季は0.2近くの値をとり,湖沼や水田の値とほぼ同じであったが,冬季は1.5～2.0の値をとり,湖沼とは大きな相違をみせた.これは,冬季の地表面が乾燥したためと考えられる.日平均値による全短波放射束に対する正味放射束の直線回帰式を求めた結果,勾配の値0.72,切片の値一52.8が得られた.しかし,年変化には大きなヒステリシスが認められた.全短波放射量に対する正味放射量の年間総量の割合は39.4%となった.冬季の12月～2月および春季の4月は,移流等による影響が地表面の熱収支に大きな影響を与えることが認められた.しかし,日平均値をとった場合,5月～11月の夏・秋季には,この影響は他の熱収支項に比べて無視しうる程度に小さいことがわかった.夜間における潜熱交換は,草地においては,地面蒸発が大きく関与し,とくに夏季は凝結による露の生成量を上まわって蒸発が卓越することがわかった.この結果,夜間の正味の凝結量は,年間総量でわずか4mm year^-1程度にしかならなかった.

抄録全体を表示

豪雨時の表層地中の熱環境に着目して,地温変化と降雨浸透にともなう土壌水の移動機構の関係を考察した.その結果,表層土壌中のさまざまな地温変化は,土壌の保水形態にもとづく水の移動形態を反映したものであることが明らかになってきた.すなわち,地表付近の懸垂水帯では,水は土粒子間の接合部に存在する.新たに入った水は,土粒子表面を伝わって降下する移動形態をとる.そのため,地温変化は,降雨発生により生じたぬれ前線の移動にともなって下方へ伝達される.一方,地下水面上方の毛管水帯の水は,毛管力と重力の釣り合いで,平衡水分分布を形成する.そこへぬれ前線が到達すると,圧力平衡は崩れて土壌水の一斉移動が始まる.その時,地温勾配が形成されていると,土壌水の一斉移動に対応して,地温プロファイルは,初期の地温勾配を維持しつつ下方へ移動する.したがって, 1～2mの深度でも,毛管水帯中であれば,その地温変化は急激で,かつ大きいことが土壌水の移動機構の解明により明らかになった.

抄録全体を表示

地表面改変に伴う熱収支構造の変化を把握する研究の一環として,代表的な都市地表面であるアスファルト舗装面を取り上げ,その熱収支特性を考察した.測定装置として, 30cm², 厚さ5cmのアスファルトブロックを積み重ね,各重ね面に熱流板と温度計を埋設し,野外において観測を行なった.その結果,日中アスファルト舗装面では,正味放射量の30～40%が伝導熱流としてアスファルト層内に貯熱されており,日没後の放熱は夜間の都市気温形成の大きな要因となっていると考えられる.一方,アスファルト層の各熱特性値を実測した結果,これまでの定説に反し,熱容量は土壌に比べ小さい値となった.しかしながら,日中の昇温量が大きく,しかも深層まで昇温するため,結果としてアスファルト層は大きな貯熱効果をもち,また舗装面下の地温にも影響を及ぼしている.さらに,早朝まで表面が高温に保たれることから,接地空気層の乾燥と相まって,アスファルト舗装面は,非常に結露しにくい環境となっている.

抄録全体を表示

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.

抄録全体を表示

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 (T_z) is expressed by the Ingersoll's equation as follows;
T_z=T_M+A₀exp (-az)sin(wt-az-γ)
where T_M mean soil temperature A amplitude of soil surface temperature α;_??_ρ; density of soil, c; specific heat of soil, pk_g; 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.

抄録全体を表示