There have been extensive studies on poleward expansion of the Hadley cells and the associated poleward shift of subtropical dry zones in the past decade. In the present study, we study the trends in the width and strength of the Hadley cells, using currently available simulation results of the Coupled Model Intercomparison Project Phase-6 (CMIP6), and compare the trends with that in CMIP5 simulations. Our results show that the total annual-mean trend in the width of the Hadley cells is 0.13° ± 0.02° per decade over 1970–2014 in CMIP6 historical All-forcing simulations. It is almost the same as that in CMIP5. The trend in the strength of the Northern-Hemisphere (NH) cell shows much greater weakening in CMIP6 than in CMIP5, while the strength trend in the Southern-Hemisphere (SH) cell shows slight strengthening. Single-forcing simulations demonstrate that increasing greenhouse gases cause widening and weakening of both the NH and SH Hadley cells, while anthropogenic aerosols and stratospheric ozone changes cause weak strengthening trends in the SH cell. CMIP6 projection simulation results show that both the widening and weakening trends increase with radiative forcing.

在过去的十年中，人们对哈德莱环流向极地扩张以及相关的亚热带干旱区向极地移动进行了广泛的研究。在本研究中，我们使用耦合模型比较项目第 6 阶段 (CMIP6) 当前可用的模拟结果研究哈德莱环流的宽度和强度趋势，并将这些趋势与 CMIP5 模拟中的趋势进行比较。我们的结果表明，在 CMIP6 历史全强迫模拟中，1970-2014 年哈德莱环流宽度的总年平均趋势为每十年 0.13° ± 0.02°。它与 CMIP5 中的几乎相同。CMIP6 的北半球 (NH) 细胞强度趋势比 CMIP5 弱得多，而南半球 (SH) 细胞的强度趋势略有增强。单一强迫模拟表明，增加的温室气体导致 NH 和 SH Hadley 单元的扩大和减弱，而人为气溶胶和平流层臭氧变化导致 SH 单元的弱加强趋势。CMIP6 投影模拟结果表明，辐射强迫的扩大和减弱趋势均有所增加。