Integrated Research System for Sustainability Science and Transdisciplinary Initiative for Global Sustainability, University of Tokyo, Tokyo 113-8654, Japan.
Proc Natl Acad Sci U S A. 2010 Jan 12;107(2):571-5. doi: 10.1073/pnas.0903186107. Epub 2009 Dec 22.
Precipitation extreme changes are often assumed to scale with, or are constrained by, the change in atmospheric moisture content. Studies have generally confirmed the scaling based on moisture content for the midlatitudes but identified deviations for the tropics. In fact half of the twelve selected Intergovernmental Panel on Climate Change (IPCC) models exhibit increases faster than the climatological-mean precipitable water change for high percentiles of tropical daily precipitation, albeit with significant intermodel scatter. Decomposition of the precipitation extreme changes reveals that the variations among models can be attributed primarily to the differences in the upward velocity. Both the amplitude and vertical profile of vertical motion are found to affect precipitation extremes. A recently proposed scaling that incorporates these dynamical effects can capture the basic features of precipitation changes in both the tropics and midlatitudes. In particular, the increases in tropical precipitation extremes significantly exceed the precipitable water change in Model for Interdisciplinary Research on Climate (MIROC), a coupled general circulation model with the highest resolution among IPCC climate models whose precipitation characteristics have been shown to reasonably match those of observations. The expected intensification of tropical disturbances points to the possibility of precipitation extreme increases beyond the moisture content increase as is found in MIROC and some of IPCC models.
降水极值变化通常被认为与大气水汽含量的变化成比例，或者受到其限制。研究普遍证实了基于水汽含量的中纬度地区的这种尺度关系，但也发现了热带地区的偏差。事实上，在 12 个选定的政府间气候变化专门委员会（IPCC）模型中，有一半的模型表现出比气候学平均可降水量变化更快的增长，尽管存在显著的模型间离散度，对于热带地区每日降水的高百分位数而言。降水极值变化的分解表明，模型之间的差异主要归因于上升速度的差异。发现垂直运动的幅度和垂直分布都对降水极值有影响。最近提出的一种包含这些动力效应的标度可以捕捉到热带和中纬度地区降水变化的基本特征。特别是，热带降水极值的增加明显超过了气候模式综合研究（MIROC）中的可降水量变化，MIROC 是 IPCC 气候模型中分辨率最高的耦合大气环流模型，其降水特征已被证明与观测结果相当吻合。热带扰动的预期加剧表明，降水极值的增加可能超过 MIROC 和一些 IPCC 模型中发现的水汽含量增加。
