Understanding uncertainty in future projections for the tropical Atlantic: relationships with the unforced climate
Understanding uncertainty in future projections for the tropical Atlantic: relationships with the unforced climate
复制标题
了解热带大西洋未来预测的不确定性：与非受迫气候的关系
DOI：
10.1007/s00382-008-0466-7
复制
发表时间：
2009
期刊：
影响因子：
4.6
通讯作者：
D. Rowell
中科院分区：
文献类型：
--
作者：
P. Good;J. Lowe;D. Rowell
通过其对海洋ITCZ的控制，未来热带大西洋纬向海表面温度梯度（TAG）的变化可能在区域到全球范围内产生重要影响。我们研究了预测TAG趋势的模型间传播，以应对CO2的增加，使用来自19个耦合GCM的结果参加了IPCC第四次评估。一些模型预测了实质性的变化，最小的变化发生在北方的秋天。有很大的不确定性，甚至在变化的符号中也没有一致性，并且集合平均值接近于零。然而，一个强大的统计关系，发现之间的模拟幅度的TAG趋势和非强制TAG变异。在12月至2月具有较大非受迫变率的模型显示出较大的震级趋势。我们推测，这种关系可能是由于一个潜在的反馈系统，其强度从模型到模型有很大的不同（非受迫性的变化范围由这些模型之间的3倍，模型表现出很大的差异，平均状态）。我们从进一步的分析和文献中提出证据，以表明可能涉及哪些物理机制。特别是，预测较大（较小）的TAG趋势的模型不仅在大西洋，而且在所有三个热带/亚热带海洋，特别是在东海岸附近的南半球，具有较大（较小）的SST变率和较冷（较暖）的平均SST。这些结果可以帮助我们了解当前和未来热带气候的模式误差，并为未来的热带预测提供观测约束。
Through its control on the marine ITCZ, future changes in the tropical Atlantic meridional sea-surface temperature gradient (TAG) could have important impacts, on regional to global scales. We study the inter-model spread of projected TAG trends in response to increasing CO2, using results from 19 coupled GCMs which took part in the IPCC fourth assessment. Some models project substantial changes, with the smallest changes being in boreal autumn. There is substantial uncertainty, with no consistency even in the sign of change, and an ensemble mean close to zero. However, a strong statistical relationship is found between the simulated magnitudes of TAG trends and unforced TAG variability. Models with larger unforced variability in December–February show larger magnitude trends. We speculate that this relationship may be due to an underlying system of feedbacks whose strength varies considerably from model to model (the unforced variability ranges by a factor of 3 amongst these models, and the models exhibit large differences in mean state). We present evidence from further analysis and the literature to suggest which physical mechanisms may be involved. In particular, models projecting larger(smaller) magnitude TAG trends have larger(smaller) SST variability and cooler(warmer) mean SST in not just the Atlantic, but all three tropical/sub-tropical oceans, especially in the southern hemisphere near eastern coasts. These results could assist efforts to understand model errors in present and future tropical climate, and to develop observational constraints on future tropical projections.