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基于CMIP6模式的中国未来极端降水变化预估

Future changes in precipitation extremes across China based on CMIP6 models

[2021-08-12]


  【中文介绍】

   

  极端降水事件往往会带来严重危害,对经济、社会、人类健康等造成严重威胁,因而对中国极端降水事件未来变化趋势的研究一直受到广泛关注。第六次全球耦合模式比较计划(CMIP6)模式已对外发布,那么相比于CMIP5模式,CMIP6模式对中国极端降水变化的模拟能力如何?在未来变暖情景下中国极端降水又将如何变化?


  我们的研究表明,CMIP6与CMIP5多模式集合均可以很好地再现中国极端降水的空间分布特征;CMIP6模式的模拟偏差相对减小,尤其是南方地区的负偏差得到较明显改善。我们进而选择14个CMIP6模式与相应的CMIP5旧版本模式进行比较研究,发现CMIP6模式在模拟中国极端降水指数方面总体表现出更优的性能,CMIP6模式模拟的大多数极端降水指数变化的不确定性范围也相对较小。此外,两个CMIP版本模式的多模式集合结果均优于单个模式。然而,与 CMIP5模式相比,仍有部分CMIP6 模式对个别极端降水指数的模拟性能有所降低。七种再分析资料在刻画这些极端降水指数变化时也存在很大的不确定性,因而在利用再分析资料评估模式模拟性能时需要谨慎选择。随着未来的持续增温,中国地区总降水量 (PRCPTOT)、五日连续最大降水量 (RX5day)和强降水日数 (R20mm)都将显著增加。但是,连续干日 CDD呈现下降趋势,这意味着由降水异常引起的干旱状况将得到缓解。然而,未来极端降水变化预估结果仍然存在较大的不确定性,其不确定性主要来自于模式和情景之间的差异。

 

  【英文介绍】

   

   Recently, CMIP6 model outputs are openly released. A comparison assessment of model capabilities in simulating precipitation extremes across China was first implemented by using 30 models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) and using 36 CMIP6 models. The results indicate that the multimodel median ensembles (MME) of both the CMIP5 and CMIP6 models can reasonably reproduce the climate means for the period from 1986 to 2005, and the biases are lower in most CMIP6 models compared to the CMIP5 models, especially over southern China. To provide further comparisons, 14 CMIP6 models are selected and compared with their predecessors in CMIP5. The results show that the CMIP6 models generally exhibit superior skill in simulating the extreme precipitation indices over China. The model spreads for most of the extreme indices in the CMIP6 version are also smaller. Additionally, the MMEs of the two CMIPs outperform individual models. However, some CMIP6 models also exhibit weaker skill levels in simulating some particular indices compared with those in CMIP5, which merits further investigation. The results from seven reanalyses further show large uncertainties for these indices; therefore, care should be taken in comparison with reanalyses. For future changes in precipitation extremes, total wet day precipitation (PRCPTOT), maximum 5-day precipitation (RX5day) and very heavy precipitation days (R20mm) are projected to clearly increase across China over the coming century under the shared socioeconomic pathway (SSP) 2-4.5 and SSP5-8.5 scenarios. However, the dry condition index of consecutive dry days (CDD) exhibits a decreasing tendency in the future, which implies that the dry conditions induced by precipitation anomalies will be mitigated. However, large uncertainties are still observed for future changes, which are primarily sourced from inter-model and scenario variabilities, especially for the projected changes at the end of the 21st century.


  【关键图表



图:在 SSP2-4.5 和 SSP5-8.5 情景下,CMIP6多模式集合预估的未来中国地区(a) PRCPTOT,(b) RX5day,(c) R20mm,(d) CDD相对于1986-2005年的变化。
Figure. Temporal evolution of the projected changes in (a) PRCPTOT, (b) R20mm, (c) RX5day, and (d) CDD for CMIP6 models over China under SSP2-4.5 and SSP5-8.5 scenarios for the future years relative to the reference period of 1986-2005. The shading signifies the interquartile model spread ranging from the 25th to 75th quantiles. The time series are smoothed by the Butterworth low-pass filtering method with a 21-year window.

                                

  引用格式       

              

  Xu HW, Chen HP and Wang HJ. 2021. Future changes in precipitation extremes across China based on CMIP6 models. Int. J. Climatol. DOI: 10.1002/joc.7264















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