FGOALS-g2模式模拟和预估的全球季风区极端降水及其变化

利用LASG/IAP（中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室）全球耦合模式FGOALS-g2，评估了其对全球季风区极端气候指标的模拟能力，并讨论了RCP8.5排放情景下21世纪季风区极端气候指标的变化特征。总体而言，模式对季风区总降水和极端气候指标1997～2014年气候态和年际变率的空间分布均具有一定的模拟能力。偏差主要表现在模式低估了亚洲季风强降水中心，低估了中雨（10～20 mm d-1）和大雨（20～50 mm d-1）的频率而高估了暴雨（>50 mm d-1）频率。在RCP8.5排放情景下，由于可降水量的增加，模式预估的全球季风区极端降水、降水总量和降水强度将持续增加。到2076～2095年，极端降水和降水强度在北美季风区增加最显著（约22%和17%），降水总量在澳大利亚增加最显著（约37%）。然而，FGOALS-g2对全球季风区平均的日降水量低于1 mm的连续最大天数（CDD）的预估变化不显著，这是由于预估的CDD在陆地季风区将增加，而在海洋季风区将减少。对各子季风区的分析显示，CDD在南美季风区变长最显著，达到30%，在澳洲季风区变短最显著，达到40%，这与两季风区日降水量低于1 mm的降水事件发生频率变化不同有关。

The FGOALS-g2 Simulation of Global Monsoon Extreme Precipitation and Future Projection

Based on historical simulation and future projection under the RCP8.5 scenario by model FGOALS-g2, the authors have analyzed the extreme climate indices and associated potential future changes in the 21st century over global monsoon region. Results indicate that FGOALS-g2 can reasonably reproduce the spatial pattern of climate state and interannual variability of extreme precipitation indices. However, precipitation is underestimated by FGOALS-g2 in heavy rainfall centers over Asian monsoon region. Due to the overestimation (underestimation) of the frequency of extreme rain (moderate and heavy rain), the extreme precipitation (total precipitation) simulated by FGOALS-g2 is stronger (weaker) than observations. Under the RCP8.5 scenario, extreme precipitation, total precipitation, and precipitation intensity all tend to increase over global monsoon region. The most significant change occurs over North America (22% and 17% for extreme precipitation and precipitation intensity, respectively) and Australia (37% for precipitation amount). The projected increase in extreme precipitation may be attributed to the increase in precipitable water. However, the projected maximum number of consecutive days with daily precipitation less than 1 mm (hereafter CDD) will increase over land areas within global monsoon region but decrease over ocean areas of global monsoon region. To the end of the 21st century (2076-2095), projected CDD will decrease (increase) by 30% (40%) over South America (Australia), which is associated with the increase (decrease) in the frequency of rainfall events with daily precipitation less than 1 mm.