Radiative transfer in CO2‐rich atmospheres: 1. Collisional line mixing implies a colder early Mars
Radiative transfer in CO2‐rich atmospheres: 1. Collisional line mixing implies a colder early Mars
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富含二氧化碳大气中的辐射传输：1. 碰撞线混合意味着早期火星较冷
DOI：
10.1002/2015je004871
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
I. Halevy
中科院分区：
文献类型：
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作者：
N. Ozak;O. Aharonson;I. Halevy
快速而准确的辐射传输方法对于模拟富含二氧化碳的大气是必不可少的，这些大气与早期地球和火星、今天的金星和一些系外行星的气候有关。尽管这样的模型已经存在，但随着更好的理论和实验约束条件的出现，它们的精度可能会得到改善。在这里，我们开发了一个一维辐射传输程序，用于富含二氧化碳的大气，使用关联k方法，重点是模拟早期火星。我们的模型与现有模型的不同之处在于，它在逐线吸收系数的计算中考虑了CO2碰撞线混合的影响。与以前的研究结果相比，包含这些影响导致模型大气对红外辐射更透明，因此在辐射-对流平衡时表面温度更低。由于较弱的早期太阳下的低大气温度，模型大气中包含水蒸气导致可以忽略不计的变暖，这转化为气候上不重要的水蒸气浓度。总体而言，这些结果表明，如果大气中只含有二氧化碳和水蒸气，火星早期的持续变暖是不可能的，这表明目前的模型中没有火星早期气候系统的其他组成部分，或者温暖的条件并不持久。
Fast and accurate radiative transfer methods are essential for modeling CO2‐rich atmospheres, relevant to the climate of early Earth and Mars, present‐day Venus, and some exoplanets. Although such models already exist, their accuracy may be improved as better theoretical and experimental constraints become available. Here we develop a unidimensional radiative transfer code for CO2‐rich atmospheres, using the correlated k approach and with a focus on modeling early Mars. Our model differs from existing models in that it includes the effects of CO2 collisional line mixing in the calculation of the line‐by‐line absorption coefficients. Inclusion of these effects results in model atmospheres that are more transparent to infrared radiation and, therefore, in colder surface temperatures at radiative‐convective equilibrium, compared with results of previous studies. Inclusion of water vapor in the model atmosphere results in negligible warming due to the low atmospheric temperatures under a weaker early Sun, which translate into climatically unimportant concentrations of water vapor. Overall, the results imply that sustained warmth on early Mars would not have been possible with an atmosphere containing only CO2 and water vapor, suggesting that other components of the early Martian climate system are missing from current models or that warm conditions were not long lived.