基于物理约束的中国日极值气温预估订正

Correction of Projected Daily Extreme Temperatures in China Based on Physical Constraints

  • 摘要: 未来日极值气温变化预估是评估气候风险、制定减排策略与适应方案的核心依据,可信的未来预估结果非常重要。选取西伯利亚地区海平面气压和印度洋海表温度作为约束因子,采用涌现约束法与帕累托最优集合方案,对CMIP6(Coupled Model Intercomparison Project Phase 6)多气候模式未来预估结果进行订正,以期研究在全球2 ℃温控情景下,碳达峰后的21世纪中期中国日极值气温的未来变化情况。结果表明:两种方法均能有效降低多模式未来预估结果间的不确定性,其中基于三变量因子的帕累托最优集合方案订正效果最显著。三变量帕累托最优集合方案订正后,中国日最高(最低)气温未来预估的不确定性范围降为 1.26~2.10 ℃(1.12~2.06 ℃),较订正前降低约 36.8%(32.9%),中国大部分地区日极值气温预估变化的信噪比提升明显,21世纪中期,我国日最高气温大部分地区升温低于2 ℃,仅在西南东部和华东北部地区升温超过2 ℃,日最低气温全国不超过2 ℃。

     

    Abstract: The ongoing rise in greenhouse gas emissions is leading to a sharp increase in global surface temperatures and more frequent extreme weather events, which has intensified the fluctuation range of daily extreme temperatures and increased the difficulty of prediction. Research on forecasting changes in daily extreme temperature can provide reliable scientific data for assessing future disaster risks and support decision-making. Due to limitations in the performance and sensitivity, current global climate models (GCM) exhibit considerable uncertainty in predicting extreme temperatures, increasing the difficulty of predicting future trends. It is necessary to correct the direct prediction results of GCMs to obtain more reliable prediction results. Therefore, Siberian sea level pressure and the sea surface temperature of the Indian Ocean, both of which have significant impacts on the daily extreme temperature changes in China, are selected as physical factors for correction. Two methods, emergent constraints and Pareto optimal ensemble, are employed to correct GCM’ predictions of daily extreme temperature changes in China under the SSP1-2.6 scenario for the middle of the 21st century. A comparison of results before and after correction reveals that both methods could effectively reduce the inter-model uncertainty of future daily extreme temperature changes. Among them, Pareto optimal ensemble scheme, which integrates three-variable factors-daily extreme temperature in China, Siberian sea level pressure, and the Indian Ocean sea surface temperature,proves most effective in minimizing inter-model uncertainty. The range of multi-model predictions of daily maximum (minimum) temperature changes in China for the mid-21st century, as corrected by the three-variable Pareto optimal ensemble scheme, is narrowed to 1.26 ℃ to 2.10 ℃ (1.12℃ to 2.06 ℃). The uncertainty range is reduced by approximately 36.8% (32.9%) compared to the uncorrected results. Moreover, the signal-to-noise ratio of the predicted daily extreme temperature changes increase in most areas of China, rising from below 1 without correction to above 1. At the same time, corrected results based on three-variable Pareto optimal ensemble scheme show significant regional differences, adjusting the magnitude of warming differentially over the Qinghai-Xizang Plateau, Northwest China, and Sichuan Basin. Overall, employing physical constraint derived from selected constraint factors to correct predictions of future daily extreme temperature changes in China is shown to be useful and feasible.

     

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