未来极端降水对气候平均变暖敏感性的蒙特卡罗模拟试验

Monte Carlo experiments on the sensitivity of future extreme rainfall to climate warming.

中文关键词:  极端降水, 概率分布, 随机模拟

英文关键词:Extreme rainfall, Probability distribution, Stochastic simulation

中文摘要:

      利用Weibull分布拟合逐日降水的原始分布模式，并基于统计降尺度和蒙特卡罗随机模拟方法，对中国东部区域各站逐日极端降水量在未来气候变暖条件下的响应特征进行统计数值试验。结果表明，在全球变暖背景下，区域平均温度的改变即可导致区域极端降水概率分布特征的变动。从两个典型代表区域的预估结果中可见，长江中下游南部平均降水量对平均温度升高有正响应，模拟得到的区域极端降水概率分布曲线有明显的向右平移，导致大量级的极端降水的再现期缩短即概率增大。山东及渤海湾区域平均降水量对平均温度升高有负响应，模拟得到的区域极端降水概率密度分布尺度参数变小更明显，即方差增大，表现为左右两侧概率密度增加，同样导致大量级的极端降水再现期缩短即概率增大。本文仅考察了气候均值改变条件下，未来区域气候极端值的概率预估的可行性方案。对于未来气候方差的变化并未作试验，但理论上已经证明，未来气候极端值的概率对于气候方差变化的敏感性可能更大。由于目前尚未整理出考察方差变化的较为完整的实际观测资料，该问题还有待进一步深入研究。

英文摘要:

      Based primarily on a probability distribution model of daily rainfall fitted by using Weibull distribution together with Monte Carlo simulation and statistical downscaling methods, statistical simulation experiments are carried out for studying the responses of the regional extremes of daily station rainfall over eastern China to future climate warming. The results show that the change of mean temperature under the backgruond of global warming may lead to variations in the probability distribution features of extreme daily rainfall. For example, there is a positive response of precipitation amount to the average temperature change south of the lower middle reaches of the Yangtze River, because the simulated probability distribution curve of regional extreme rainfall events is obviously shifted rightward, which indicates the shortening of the return period for intense extreme rainfall, or the increase of the extremes' probability. But, in the Shandong and Bohai Bay area, there is a nagtive response of precipitation amount to the average temperature change, due to a significant reduction in the scale paremeter of the probability density function for regional extreme rainfall over there. The reduced scale parameter means larger variance, which is represented by enhanced probability density function in both right and left ends. This also leads to the increase of the probability of intense extreme rainfall. This paper only investigates the effect of the change of climatic mean temperature on regional extreme rainfall. The extreme rainfall may be more sensitive to the climatic temperature variance change, sensitivity which needs to be further investigated.