Parameterization of contrails in the UK Met Office Climate Model
Parameterization of contrails in the UK Met Office Climate Model
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DOI：
10.1029/2009jd012443
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发表时间：
2010-05
影响因子：
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通讯作者：
A. Rap;P. Forster;A. Jones;O. Boucher;J. Haywood;N. Bellouin;R. R. Leon-R.
中科院分区：
文献类型：
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作者：
A. Rap;P. Forster;A. Jones;O. Boucher;J. Haywood;N. Bellouin;R. R. Leon-R.
据信，持续的尾迹目前对气候具有相对较小但显著的正辐射强迫。随着航空旅行预计将在未来几年继续快速增长，航迹对气候的变暖效应预计会增加。然而，目前对尾迹辐射强迫的估计仍有很大的不确定性。尾迹的形成主要取决于飞机在足够冷和潮湿的气团中飞行。迄今为止，大多数研究都依赖于使用平均气象条件的简单参数化。在本文中，我们通过为英国气象局气候模式开发一个在线轨迹参数化来考虑背景云量的短期变化。利用这一参数化方法，我们估计2002年空中交通的年平均线性轨迹覆盖率约为0.11%。假设全球平均尾迹光学深度为0.2或更小，并假设六边形冰晶，计算得出在全天条件下相应的尾迹辐射强迫小于10 mW m（-2）。我们发现自然云对尾迹的遮蔽效应可能比以前认为的要高得多。这个新的结果可以用这样一个事实来解释：飞机尾迹似乎更倾向于在多云的条件下形成，这将使它们对气候的总体影响减少了大约40%。
Persistent contrails are believed to currently have a relatively small but significant positive radiative forcing on climate. With air travel predicted to continue its rapid growth over the coming years, the contrail warming effect on climate is expected to increase. Nevertheless, there remains a high level of uncertainty in the current estimates of contrail radiative forcing. Contrail formation depends mostly on the aircraft flying in cold and moist enough air masses. Most studies to date have relied on simple parameterizations using averaged meteorological conditions. In this paper we take into account the short-term variability in background cloudiness by developing an on-line contrail parameterization for the UK Met Office climate model. With this parameterization, we estimate that for the air traffic of year 2002 the global mean annual linear contrail coverage was approximately 0.11%. Assuming a global mean contrail optical depth of 0.2 or smaller and assuming hexagonal ice crystals, the corresponding contrail radiative forcing was calculated to be less than 10 mW m(-2) in all-sky conditions. We find that the natural cloud masking effect on contrails may be significantly higher than previously believed. This new result is explained by the fact that contrails seem to preferentially form in cloudy conditions, which ameliorates their overall climate impact by approximately 40%.