抄録
This paper reports a method for measuring and estimating the downward atmospheric radiation flux, AH (kcal/m^2h), under any sky conditions. To measure the global solar radiation flux, TH (kcal/m^2h), and the total downward radiation flux, AH+TH, a pyranometer and an improved pyrgeometer (see Photo-3.1) were used repectively. Observations were carried out at Hakozaki (33°37′N, 130°26′E) in Fukuoka city from October. in 1979 to September. in 1982. Some results obtained with these measuring instruments are compared with the theoretical values, which are calculated by using aerogical data of temperature, humidity and pressure by Radiosonde at Fukuoka District Meteorological Observatory (33°35′N, 130°23′E; 6.4km south-west from Hakozaki) and the radiation chart proposed by G. Yamamoto. Methods for estimating AH are discussed in terms of these observed data. The Brunt type formula under any sky conditions is given by AH/σT^4_0=0.551+0.026CC+(0.056-0.003CC)√<f> where σ=Stefan-Boltzmann constant (=4.88×10^<-8>kcal/m^2hK^4), T_0=outdoor air temperature (K), CC=total cloud amount in tenths, and f=water vapour pressure (mmHg). Another experimental formula is determined as follows; AH=66.05+33.92√<f>+0.2246σT^4_0+5.351CC According to atmospheric radiation AR_<>30> and AR_<>60> (kcal/m^2h) which are observed within h>30°and h>60°respectively (h=altitude of the sky), it is said that atmospheric radiation diffuses downward almost homogeneously. Therefore, when AH is exactly known, the long-wave radiation incident upon a tilted outside surface can be sufficiently estimated by Eq. (6.2).
