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arXiv 1601.01147stat.AP
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气候变化条件下降水时空格局的变化

Changes in Spatio-temporal Precipitation Patterns in Changing Climate Conditions

Won Chang, Michael L. Stein, Jiali Wang, V. Rao Kotamarthi, Elisabeth J. Moyer

摘要:

气候模式有力地表明,降水模式将发生一些重大变化。模型一致预测,随着大气含水量的增加,单个降水事件的强度增加约6-7%/K,但总降水量增加较少(瞬时运行中全球平均值为1- 2%/K)。降水事件的某些其他方面必须随之改变,以补偿这种差异。我们在这里开发了一种新的方法来识别单个暴雨和研究其物理特性-包括起始位置,强度,空间范围,持续时间和轨迹-允许识别的补偿机制。我们将这种技术应用于美国邻近地区的降水,这些降水来自基于雷达的数据产品和高分辨率模型运行,模拟了80年的照常变暖。在模式研究中,我们发现,占主导地位的补偿机制是风暴规模的减少。夏季暴雨强度增大,但范围缩小;冬季暴雨仍以收缩为主,但数量减少,持续时间缩短。这些结果意味着,气候变化对洪水的影响将不太严重,预计从降水强度的变化单独。我们还表明,预测的变化小于模型观测偏差,这意味着将它们纳入影响评估的最佳方法是通过“数据驱动的模拟”,将模型预测的变化应用于观测数据。因此,我们开发了一种模拟算法,统计描述模型的变化,降水特征和相应的调整数据,并显示,特别是夏季降水,它优于模拟方法,不包括空间信息。

英文摘要:

Climate models robustly imply that some significant change in precipitation patterns will occur. Models consistently project that the intensity of individual precipitation events increases by approximately 6-7%/K, following the increase in atmospheric water content, but that total precipitation increases by a lesser amount (1-2 %/K in the global average in transient runs). Some other aspect of precipitation events must then change to compensate for this difference. We develop here a new methodology for identifying individual rainstorms and studying their physical characteristics - including starting location, intensity, spatial extent, duration, and trajectory - that allows identifying that compensating mechanism. We apply this technique to precipitation over the contiguous U.S. from both radar-based data products and high-resolution model runs simulating 80 years of business-as-usual warming. In model studies, we find that the dominant compensating mechanism is a reduction of storm size. In summer, rainstorms become more intense but smaller, in winter, rainstorm shrinkage still dominates, but storms also become less numerous and shorter duration. These results imply that flood impacts from climate change will be less severe than would be expected from changes in precipitation intensity alone. We show also that projected changes are smaller than model-observation biases, implying that the best means of incorporating them into impact assessments is via "data-driven simulations" that apply model-projected changes to observational data. We therefore develop a simulation algorithm that statistically describes model changes in precipitation characteristics and adjusts data accordingly, and show that, especially for summertime precipitation, it outperforms simulation approaches that do not include spatial information.

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