1] CSIRO Marine and Atmospheric Research, Aspendale, Victoria, Australia [2] School of Earth Sciences, University of Melbourne, Parkville, Victoria, Australia.
CSIRO Marine and Atmospheric Research, Aspendale, Victoria, Australia.
Sci Rep. 2014 Aug 12;4:6034. doi: 10.1038/srep06034.
A positive Indian Ocean Dipole (IOD) tends to have stronger cold sea surface temperature anomalies (SSTAs) over the eastern Indian Ocean with greater impacts than warm SSTAs that occur during its negative phase. Two feedbacks have been suggested as the cause of positive IOD skewness, a positive Bjerknes feedback and a negative SST-cloud-radiation (SCR) feedback, but their relative importance is debated. Using inter-model statistics, we show that the most important process for IOD skewness is an asymmetry in the thermocline feedback, whereby SSTAs respond to thermocline depth anomalies more strongly during the positive phase than negative phase. This asymmetric thermocline feedback drives IOD skewness despite positive IODs receiving greater damping from the SCR feedback. In response to global warming, although the thermocline feedback strengthens, its asymmetry between positive and negative IODs weakens. This behaviour change explains the reduction in IOD skewness that many models display under global warming.
正印度洋偶极子（IOD）往往会在东印度洋产生更强的冷海表面温度异常（SSTA），其影响大于负IOD 阶段发生的暖 SSTA。已经提出了两种反馈作为正IOD 偏态的原因，即正贝克尔尼斯反馈和负 SST-云-辐射（SCR）反馈，但它们的相对重要性存在争议。使用模型间统计数据，我们表明，IOD 偏态最重要的过程是温跃层反馈的不对称性，即在正IOD 阶段，SSTA 对温跃层深度异常的响应比负IOD 阶段更强。尽管正IOD 受到 SCR 反馈的更大阻尼，但这种不对称的温跃层反馈导致了 IOD 偏态。在全球变暖的情况下，尽管温跃层反馈增强，但正IOD 和负IOD 之间的不对称性减弱。这种行为变化解释了许多模型在全球变暖下显示的IOD 偏态减少。
