Impact of small ice crystal assumptions on ice sedimentation rates in cirrus clouds and GCM simulations
Impact of small ice crystal assumptions on ice sedimentation rates in cirrus clouds and GCM simulations
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小冰晶假设对卷云中冰沉降率的影响和 GCM 模拟
DOI：
10.1029/2008gl033552
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发表时间：
2008
影响因子：
5.2
通讯作者：
T. Nousiainen
中科院分区：
文献类型：
--
作者：
D. Mitchell;P. Rasch;D. Ivanova;G. McFarquhar;T. Nousiainen
在气候变化的预测中，最大的不确定性在于云的表示。冰云尤其具有挑战性，到目前为止，还没有公认的方法来测量较小的冰晶(D<；60μm)。这项研究考察了全球气候模型对不同假设的敏感性，这些假设涉及允许小冰晶影响冰沉积速率时小冰晶的数量和浓度。当它们的浓度相对较高时，GCM预测全球云冰数量将增加12%，卷云覆盖率将增加5.5%。这在热带地区产生了−5 W m−2的净云强迫，并使热带对流层上部3°C以上变暖。与相应的测量不确定性相比，假设的冰晶浓度差异不大，这揭示了全球气候预测中潜在的巨大不确定性来源。
In the prediction of climate change, the greatest uncertainty lies in the representation of clouds. Ice clouds are particularly challenging, and to date there is no accepted method for measuring the smaller ice crystals (D < 60 μm). This study examines the sensitivity of a global climate model to different assumptions regarding the number concentrations of small ice crystals when they are allowed to affect ice sedimentation rates. When their concentrations are relatively high, the GCM predicts a 12% increase in cloud ice amount and a 5.5% increase in cirrus cloud coverage globally. This produces a net cloud forcing of −5 W m−2 in the tropics and warms the upper tropical troposphere over 3°C. Ice crystal concentration differences assumed were modest in comparison to corresponding measurement uncertainties, revealing a potentially large source of uncertainty in the prediction of global climate.