Calculation of average, uncertainty range, and reliability of regional climate changes from AOGCM simulations via the "reliability ensemble averaging'' (REA) method
Calculation of average, uncertainty range, and reliability of regional climate changes from AOGCM simulations via the "reliability ensemble averaging'' (REA) method
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DOI：
10.1175/1520-0442(2002)015
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发表时间：
2002-05-15
影响因子：
4.9
通讯作者：
Mearns, LO
中科院分区：
文献类型：
--
作者：
Giorgi, F;Mearns, LO
本文介绍了利用不同的大气-海洋环流模式（AOGCM）模拟的集合计算次大陆尺度气候变化的平均值、不确定性范围和可靠性度量的“可靠性集合平均”（REA）方法。该方法考虑了两个“可靠性标准”：模型再现当今气候的性能（“模型性能”标准）和模型之间模拟变化的收敛性（“模型收敛”标准）。REA方法适用于21世纪后几十年的平均季节温度和降水量变化，覆盖世界22个陆地区域，这是最近针对两种人为排放情景（政府间气候变化专门委员会的A2和B2情景）进行的一组9个AOGCM实验模拟的。在A2情景中，REA平均区域温度变化在各区域之间约为2至7 K，它们都在估计的自然变率之外。通过+/-REA均方根差（rmsd）测量的REA平均变化的不确定性范围在1和4 K之间变化，可靠性主要在0.2和0.8之间（范围从0到1）。对于降水量，大约一半的区域REA平均变化，无论是正的还是负的，都在估计的自然变率之外，它们在大约-25%和+30%之间变化（以现今降水量的百分比为单位）。这些变化的不确定性范围（+/- rmsd）主要在10%和30%之间变化，相应的可靠性在不同地区之间变化很大。B2情景的模拟变化显示出与A2情景的高度一致性。与更简单的方法相比，REA方法允许通过最小化“离群值”或表现不佳的模型的影响来减小模拟变化中的不确定性范围。该方法还产生了一个定量测量的可靠性，表明这两个标准需要满足的模拟，以增加模拟的变化的整体可靠性。
The "reliability ensemble averaging'' (REA) method for calculating average, uncertainty range, and a measure of reliability of simulated climate changes at the subcontinental scale from ensembles of different atmosphere-ocean general circulation model (AOGCM) simulations is introduced. The method takes into account two "reliability criteria'': the performance of the model in reproducing present-day climate ("model performance'' criterion) and the convergence of the simulated changes across models ("model convergence'' criterion). The REA method is applied to mean seasonal temperature and precipitation changes for the late decades of the twenty-first century, over 22 land regions of the world, as simulated by a recent set of nine AOGCM experiments for two anthropogenic emission scenarios (the A2 and B2 scenarios of the Intergovernmental Panel for Climate Change). In the A2 scenario the REA average regional temperature changes vary between about 2 and 7 K across regions and they are all outside the estimated natural variability. The uncertainty range around the REA average change as measured by +/- the REA root-mean-square difference (rmsd) varies between 1 and 4 K across regions and the reliability is mostly between 0.2 and 0.8 (on a scale from 0 to 1). For precipitation, about half of the regional REA average changes, both positive and negative, are outside the estimated natural variability and they vary between about -25% and +30% (in units of percent of present-day precipitation). The uncertainty range around these changes (+/- rmsd) varies mostly between about 10% and 30% and the corresponding reliability varies widely across regions. The simulated changes for the B2 scenario show a high level of coherency with those for the A2 scenario. Compared to simpler approaches, the REA method allows a reduction of the uncertainty range in the simulated changes by minimizing the influence of "outlier'' or poorly performing models. The method also produces a quantitative measure of reliability that shows that both criteria need to be met by the simulations in order to increase the overall reliability of the simulated changes.