Using raindrops to constrain past atmospheric density
Using raindrops to constrain past atmospheric density
复制标题
利用雨滴来限制过去的大气密度
DOI：
10.1016/j.epsl.2014.12.032
复制
发表时间：
2015
影响因子：
5.3
通讯作者：
C. Goldblatt
中科院分区：
文献类型：
--
作者：
L. Kavanagh;C. Goldblatt
早期地球大气的物理性质缺乏限制。Som古密度测量法根据保存在古代地层中的石化雨滴印记的大小来估计古代大气密度的上限，并假设最大的印记是由可能最大的雨滴造成的。使用这种技术Som et al.（2012）提出了太古代大气密度小于2.3 kg m− 3的限制。将这种方法应用于现代雨滴印迹，产生的表面密度上限为0.9 kg m− 3，低于实际值1.2 kg m− 3，反驳了该方法。我们提出了几个变化的方法，其中最重要的是增加最大可能的滴大小从6.8到10毫米，以符合新的大数据集的雨滴观测。通过这些变化，我们现代表面密度的上限变为2.7 kg m− 3，这是一个有效的极限。太古代大气密度的上限于是被修正为11.1 kg m− 3。在一般情况下，我们发现雨滴印迹大小分布更强烈地依赖于降雨率比大气密度，这转化为大的误差。雨滴古密度测量的精度最多也不过是几个到一个数量级。
There exists a dearth of constraints on the physical properties of the early Earth atmosphere. The Som palaeopycnometry method estimates an upper limit on ancient atmospheric density based on the size of lithified raindrop imprints preserved in ancient strata, with the assumption that the largest imprint was made by the largest possible raindrop. Using this technique Som et al.(2012) proposed a constraint on Archean atmospheric density of less than 2.3 kg m− 3. Applying this method to modern raindrop imprints, the upper bound on surface density produced is 0.9 kg m− 3, lower than the actual value of 1.2 kg m− 3, refuting the method. We propose several changes to the method, the most important of which is increasing the maximum possible drop size from 6.8 to 10 mm to be consistent with new large datasets of raindrop observations. With these changes, our upper bound on modern surface density becomes 2.7 kg m− 3, a valid limit. The upper bound on Archean atmospheric density is then revised to 11.1 kg m− 3. In general, we find that raindrop imprint size distribution depends much more strongly on rainfall rate than atmospheric density, which translates into large errors. At best, the precision of raindrop palaeopycnometry will be a factor of a few to an order of magnitude.