潘吉亚超大陆时期的哈德雷环流

The Hadley circulation in the Pangea era

潘吉亚超大陆时期,是地球历史上的一个独特阶段.在约2.5亿年前,全球大陆汇聚成一块从南极延伸至北极的超级大陆,其面积约占地球表面积的35%,与现代大陆面积(约30%)相比要大得多.此时地球处于温室气候,全球平均地面温度约为26℃,二氧化碳浓度远高于现代.本文通过气候模拟研究了这一地质时期的哈德雷环流.结果表明,潘吉亚的哈德雷环流强度较弱,边界纬度较宽.一个最为显著的特征是,北半球和南半球冬季的哈德雷环流上升支分别位于23°S和18°N,比现代的上升支远离赤道得多.这是副热带较大的陆地面积以及与之相关的极高温度造成的.

The Pangea era is an exceptional phase in Earth’s history.It is characterized by its hothouse climate state and the latest supercontinent.Thus,it is expected that atmospheric circulation in the Pangea era was largely different from that of the modern world.Here,we study the Hadley circulation in the Pangea era and compare it with that of the present,by performing climate simulations.Our results show that the annual mean Hadley cells are about 20%and 45%weaker than that in the pre-industrial(PI)climate,and their poleward edges are about 2°wider in latitude.The austral winter cell is weakened by 27%and expanded by 2.6°,while the changes of the boreal winter cell are not significant.One distinctive feature is that the ascending branches of the boreal and austral winter cells shift to 23°S and 18°N,respectively,which are much more poleward than their present locations.Our analyses demonstrate that the weakening and widening of the Hadley circulation is due to increasing tropical and subtropical static stability,and that the poleward shifts of the ascending branches of the winter cells are associated with the geographic configuration of the supercontinent Pangea.