ENTROPIE (UMR 9220), IRD, Univ. de la Réunion, CNRS, Nouméa, Nouvelle-Calédonie.
LOCEAN-IPSL, Sorbonne Universités, UPMC, Université Paris 06, CNRS-IRD-MNHN, Paris, France.
Sci Rep. 2020 Mar 16;10(1):4838. doi: 10.1038/s41598-020-61570-6.
Climate model projections generally indicate fewer but more intense tropical cyclones (TCs) in response to increasing anthropogenic emissions. However these simulations suffer from long-standing biases in their Sea Surface Temperature (SST). While most studies investigating future changes in TC activity using high-resolution atmospheric models correct for the present-day SST bias, they do not consider the reliability of the projected SST changes from global climate models. The present study illustrates that future South Pacific TC activity changes are strongly sensitive to correcting the projected SST changes using an emergent constraint method. This additional correction indeed leads to a strong reduction of the cyclogenesis (-55%) over the South Pacific basin, while no statistically significant change arises in the uncorrected simulations. Cyclogenesis indices suggest that this strong reduction in the corrected experiment is caused by stronger vertical wind shear in response to a South Pacific Convergence Zone equatorward shift. We thus find that uncertainty in the projected SST patterns could strongly hamper the reliability of South Pacific TC projections. The strong sensitivity found in the current study will need to be investigated with other models, observational constraint methods and in other TC basins in order to assess the reliability of regional TC projections.
气候模式的预测通常表明，人为排放增加会导致热带气旋（TC）数量减少，但强度增加。然而，这些模拟存在长期存在的海表温度（SST）偏差。虽然大多数使用高分辨率大气模型研究未来 TC 活动变化的研究都纠正了当前的 SST 偏差，但它们并没有考虑到全球气候模型预测的 SST 变化的可靠性。本研究表明，使用新兴约束方法纠正预测的 SST 变化，未来南太平洋 TC 活动的变化将高度敏感。这种额外的校正确实导致南太平洋盆地的气旋生成减少了 55%，而在未校正的模拟中没有出现统计学上的显著变化。气旋生成指数表明，这种在校正实验中的强烈减少是由于南太平洋辐合带向赤道移动导致的更强的垂直风切变引起的。因此，我们发现，预测 SST 模式的不确定性可能会严重阻碍南太平洋 TC 预测的可靠性。本研究发现的强烈敏感性需要在其他模型、观测约束方法和其他 TC 海域中进行研究，以评估区域 TC 预测的可靠性。
