ATMOSPHERIC RADIATION FROM CLOUDLESS SKY
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概要
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There are three kinds of methods for knowing atmospheric radiation values, i.e. direct observation with a pyrgeometer, theoretical calculation from aerological data and estimation with empirical formulas from surface weather elements. The first method is not convenient because the observation network and the accuracy are not enough to study radiation climate in Japan. On the other hand, the third method is applicable for most places, but sufficient discussion has not been made on its accuracy. The purpose of this paper is to discuss empirical formulas by using theoretically calculated values of atmospheric radiation. The transfer of atmospheric radiation energy in a cloudless sky can be described by absorption and emission processes. It is possible to calculate the downward long-wave radiation at the surface by solving the radiative transfer equation under the boundary conditions at the earth. For this calculation, the vertical distribution of water vapour and carbon dioxide in the atmosphere is necessary, and it is not possible to calculate atmospheric radiation theoretically without data of radio sounding. In the past 35 years, the theoretical calculation of atmospheric radiation has been done with radiation charts, such as Elsasser chart, Shekhter chart and Yamamoto chart. Recently, as the computer has been developed, many workers' efforts have been directed to numerical programming for this calculation. Source lists of these programs, however, have not been published and we can not use them. In this paper, a FORTRAN program has been developed which calculate atmospheric radiation based on Elsasser's regular band model for water vapour and on Callendar's absorption model for carbon dioxide. Values calculated with this program are found to fit in well with values calculated with radiation charts and with other authors' theoretical calculation pro-grams. They also fit in well with direct observation values at Tateno. At three points in Japan, i.e. Tateno, Wakkanai and Kagoshima, atmospheric radiation from a cloudless sky is calculated with this program at 0900 and 2100 JST from Jan. 1, 1973 to Dec. 31, 1974. These calculated values fit in well with Katayama's formula _??_ but not well with Yamamoto's formula nor with Saito's formula _??_ The Brunt type formulas which are the optimum for theoretical calculation for Tateno, Wakkanai and Kagoshima are given respectively by _??_ In other words, in Japan, the Brunt type formula has the limit of its accuracy, and the P. R. value will not be more than 96%. Especially during winter, the P. R, value decreases markedly. In the course of the discussion, it becomes clear that if a new parameter dt/dp, a lapse rate of temperature, is introduced into the empirical formula, the P. R. value increases up to about 98.5%. This new formula which is the optimum for Tateno is _??_ It must be noted that this formula for dt/dp=0 is nearly equal to the optimum Brunt type formula when water vapour pressure is greater than about 5 mb. If this formula is applied for Wakkanai, the P. E. value will be 95.88%, and for Kagoshima 93.13%. It is possible to estimate atmospheric radiation from a cloudless sky by using the same Brunt type formula for Tateno and Wakkanai, but it is not possible for Kagoshima.
- The Association of Japanese Geographersの論文
The Association of Japanese Geographers | 論文
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