Absorption Coefficient of Water Vapour in the Near Infra-red Region

[摘要] In this paper absorption coefficient of water vapour in the near infra-red region between, 1.2 μ and 3.5 μ was calculated by the same method which was employed by us in calculating absorption coefficient of water vapour in the far infra-red region beyond 5 μ. (G. Yamamoto & G. Onishi, Sei. Reports Tohoku Univ. Ser. 5, 1, p. 5 (1949)). In the near infra-red region there are three absorption bands, i. e., 1.4 μ band, 1.8 μ band and the strongest 2.7 μ band which is extending between 2.5 μ and 3.5 μ. For each band the generalized absorption coefficients of Elsasser were calculated basing on the analysed data of Nielsen. The result of calculation was compared with the measurement of Hettner. The comparison shows that in each band Hettner's values are greater than our calculated values and the former values are extending broader to the margin of each band than the latter values. But it must be remembered that Hettner's measurements were carried out on water vapour of 1 atmospheric pressure and 400°A, so that under the temperature of our calculation Hettner's values must be reduced to about 1/4 of their original values. Then it will be said concludingly that both Hettner's measurement and our calculation nearly agree in magnitude in the central part of each band and that measured bands by Hettner are far broader than our calculation. The detailed description in English of this investigation will be published on Sci. Rep, of Tôhoku Univ. Ser. 5 Vol. 2 soon.

[学科分类] 大气科学