On Nocturnal Radiation

[摘要] The equation for the radiative transfer was solved on earth's atmosphere to calculate the incoming radiation at the ground level. Different formulae were obtained for the incoming radiations due to absorption of water vapour both in the intermediate region where the change of absorption coefficient with wave-length is smooth and in the absorption bands where the absorption coefficient fluctuates rapidly with wave-length. The formula which is available for mixed gas of H2O and CO2 (or O3) was derived too.Using the values of the absorption coefficient of water vapour calculated by Yamamoto-Onishi and by Elsasser, and those of Co2 and O3 properly assumed, the incoming radiations were calculated for several weather conditions appropriate to clear skies. The comparison of calculations with observations shows that the calculated values based on Yamamoto-Onishi's absorption coefficient agree fairly well with observations, and that those based on Elsasser's absorption coefficient are generally smaller than the observed values.By formulating the calculated values the following formula was obtained: where G (O) is the incoming radiation and W is the amount of water vapour in the air column in cm unit of precipitable water. When the vapour pressure at the ground level, ε0 in mb, is taken as abscissa, the empirical formula of Brunt's type agree with many observations as a whole.The possibility of deriving these formulae was discussed also.

[学科分类] 大气科学