Oceanographic Institute, University of São Paulo, São Paulo, Brazil.
Climate Change Research Centre, The University of New South Wales, Sydney, Australia.
Sci Rep. 2020 Aug 10;10(1):13458. doi: 10.1038/s41598-020-68884-5.
Thermodynamic arguments imply that global mean rainfall increases in a warmer atmosphere; however, dynamical effects may result in more significant diversity of regional precipitation change. Here we investigate rainfall changes in the mid-Pliocene Warm Period (~ 3 Ma), a time when temperatures were 2-3ºC warmer than the pre-industrial era, using output from the Pliocene Model Intercomparison Projects phases 1 and 2 and sensitivity climate model experiments. In the Mid-Pliocene simulations, the higher rates of warming in the northern hemisphere create an interhemispheric temperature gradient that enhances the southward cross-equatorial energy flux by up to 48%. This intensified energy flux reorganizes the atmospheric circulation leading to a northward shift of the Inter-Tropical Convergence Zone and a weakened and poleward displaced Southern Hemisphere Subtropical Convergences Zones. These changes result in drier-than-normal Southern Hemisphere tropics and subtropics. The evaluation of the mid-Pliocene adds a constraint to possible future warmer scenarios associated with differing rates of warming between hemispheres.
热力学观点表明，在温暖的大气中，全球平均降雨量会增加；然而，动力学效应可能导致区域降水变化的多样性更加显著。在这里，我们利用 Pliocene Model Intercomparison Projects 阶段 1 和 2 的输出结果和敏感性气候模型实验，研究了中更新世暖期（约 300 万年前）的降雨变化，当时的温度比工业化前高 2-3°C。在中更新世的模拟中，北半球更高的升温速率造成了半球间的温度梯度，使南北向跨赤道能量通量增加了高达 48%。这种能量通量的加强重新组织了大气环流，导致热带辐合带向北移动，南半球亚热带辐合带减弱并向极地移动。这些变化导致南半球热带和亚热带地区比正常情况干燥。中更新世的评估为与半球间升温速率不同相关的未来可能更温暖的情景增加了一个约束。
