Water vapor dimers and atmospheric absorption of electromagnetic radiation
Water vapor dimers and atmospheric absorption of electromagnetic radiation
复制标题
水蒸气二聚体和大气对电磁辐射的吸收
DOI：
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
D. Geldart
中科院分区：
文献类型：
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作者：
P. Chylek;D. Geldart
利用基于量子力学谐振子的简单模型，我们估计了六个3500 cm−1宽波段内的平均二聚体吸收截面。在第一频段（1000 ~ 4500 cm−1），截面约为6 × 10−21 cm²，从远红外到可见光部分，随着频率的增加，截面减小约600倍。这种相对缓慢的减少是二聚体内部的非调和力的结果，这削弱了水单体的选择规则。利用前人研究的数值结果，我们将大气中二聚体的浓度参数化，并提供了计算水二聚体对太阳辐射的吸收随总水蒸汽柱数量和温度的函数的形式。当水蒸气柱为1 g/cm²，相对湿度为80%，温度为273 K时，二聚体可吸收约1.6%的入射太阳辐射。吸光度随温度升高而增大，在298 K时达到4.6%左右。我们的估计在四倍以内是准确的。大多数二聚体的吸收发生在红外波长。在被二聚体吸收的太阳辐射中，波长低于0.9µm的只有约5%。
Using a simple model based on a quantum mechanical harmonic oscillator we estimate the average dimer absorption cross sections within six 3500 cm−1 wide bands. The cross section is of the order of 6 × 10−21 cm² in the first frequency band (1000 to 4500 cm−1) and it decreases by a factor of about 600 with increasing frequency from far infrared to visible portion of the spectrum. This relatively slow decrease is a result of anharmonic forces within a dimer, that weaken the selection rules of water monomer. Using numerical results of previous studies, we parameterize the concentration of dimers in the atmosphere and provide the formalism to calculate the absorption of solar radiation by water dimers as a function of total water vapor column amount and temperature. For water vapor column of 1 g/cm² and 80% relative humidity at 273 K, the dimers will absorb about 1.6% of the incident solar radiation. The absorbency increases with increasing temperature to about 4.6% at 298 K. Our estimates are accurate within a factor of about four. Most of the dimer absorption occurs at infrared wavelengths. Only about 5% of solar radiation absorbed by dimers is at wavelengths below 0.9 µm.