Determination of the atmospheric lifetime and global warming potential of sulfur hexafluoride using a three-dimensional model
Determination of the atmospheric lifetime and global warming potential of sulfur hexafluoride using a three-dimensional model
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DOI：
10.5194/acp-17-883-2017
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发表时间：
2016-08
影响因子：
6.3
通讯作者：
T. Kovács;W. Feng;Anna Totterdill;J. Plane;S. Dhomse;J. Gómez-Martín;G. Stiller;F. Haenel;
中科院分区：
文献类型：
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作者：
T. Kovács;W. Feng;Anna Totterdill;J. Plane;S. Dhomse;J. Gómez-Martín;G. Stiller;F. Haenel;
抽象的。我们使用了全大气社区气候模式(WACCM)，并对损失过程进行了最新处理，以确定六氟化硫(SF6)的大气寿命。该模型包括以下SF6去除过程：光解、电子附着和与中间层金属原子的反应。索丹基拉离子化学(SIC)模型被结合到WACCM的标准版本中，以产生具有团簇离子和负离子的详细D区离子化学的新版本。这被用来确定标准WACCM中电子密度的纬度和高度相关的比例因子，以便进行多年的SF6模拟。该模型给出了11年太阳周期(τ)的平均寿命为1278年(范围为1120年到1475年)，这比目前广泛使用的3200年的数值要短得多，这是因为模型中的电子密度对大气总损失的贡献率较大(97.4%)。通过与中间层金属原子(Na和K)反应，SF6的损失太慢，不会影响寿命。我们研究了这种较短的大气寿命如何影响使用SF6来计算平流层空气年龄。与被动的SF6示踪剂相比，在20公里的极地纬度，这种寿命较短的SF6示踪剂产生的空气年龄要长9%。我们还提供了SF6的红外光谱的实验室测量结果，并发现与以前的研究结果很好地一致。我们计算得到的辐射作用力和辐射效率，平均而言，与以前报道的非常相似。我们对20年、100年和500年全球变暖潜势的数值分别为18000、23800和31300。
Abstract. We have used the Whole Atmosphere Community Climate Model (WACCM), with an updated treatment of loss processes, to determine the atmospheric lifetime of sulfur hexafluoride (SF6). The model includes the following SF6 removal processes: photolysis, electron attachment and reaction with mesospheric metal atoms. The Sodankyla Ion Chemistry (SIC) model is incorporated into the standard version of WACCM to produce a new version with a detailed D region ion chemistry with cluster ions and negative ions. This is used to determine a latitude- and altitude-dependent scaling factor for the electron density in the standard WACCM in order to carry out multi-year SF6 simulations. The model gives a mean SF6 lifetime over an 11-year solar cycle (τ) of 1278 years (with a range from 1120 to 1475 years), which is much shorter than the currently widely used value of 3200 years, due to the larger contribution (97.4 %) of the modelled electron density to the total atmospheric loss. The loss of SF6 by reaction with mesospheric metal atoms (Na and K) is far too slow to affect the lifetime. We investigate how this shorter atmospheric lifetime impacts the use of SF6 to derive stratospheric age of air. The age of air derived from this shorter lifetime SF6 tracer is longer by 9 % in polar latitudes at 20 km compared to a passive SF6 tracer. We also present laboratory measurements of the infrared spectrum of SF6 and find good agreement with previous studies. We calculate the resulting radiative forcings and efficiencies to be, on average, very similar to those reported previously. Our values for the 20-, 100- and 500-year global warming potentials are 18 000, 23 800 and 31 300, respectively.