Solar meridional circulation is an axisymmetric flow system, extending from the equator to the poles (\(\sim \)20 m/s at the surface, \(\approx \)1% of the mean solar rotation rate), plunging inwards and subsequently completing the circuit in the interior through an equatorward return flow and a radially outward flow back up to the surface. This article reviews the profound role that meridional circulation plays in maintaining global dynamics and regulating large-scale solar magnetism. Because it is relatively weak in comparison to differential rotation (\(\sim \)300 m/s, \(\approx \)7% of the mean solar rotation rate) and owing to numerous systematical errors, accurate surface measurements were only first made in 1978 and initial inferences of interior meridional circulation were obtained using helioseismology two decades later. However, systematical biases have made it very challenging to reliably recover flow in the deep interior. Despite numerous advances that have served to improve the accuracy of inferences, the location of the return flow and the full extent of the circulation are still open problems. This article follows the historical developments and summarises contemporary advances that have led to modern inferences of surface and interior meridional flow.

太阳经向环流是一个轴对称的流动系统，从赤道延伸到两极（表面速度\(\sim\) 20 m/s， \(\approx \)平均太阳自转速度的1%），向内急速延伸，随后通过赤道返回流和径向向外流返回地面来完成内部回路。本文回顾了经向环流在维持全球动态和调节大范围太阳磁力方面所发挥的深远作用。由于它与微分自转相比相对较弱（ \(\sim \) 300 m/s， \(\约 \)平均太阳自转速率的 7%），并且由于存在大量系统误差，因此准确的表面测量只是第一个1978 年进行了这项研究，二十年后利用日震学对内部经向环流进行了初步推论。然而，系统偏差使得可靠地恢复内部深处的流动变得非常具有挑战性。尽管在提高推论准确性方面取得了许多进展，但回流的位置和循环的整体范围仍然是悬而未决的问题。本文跟踪历史发展并总结当代进展，这些进展导致了表面和内部经向流的现代推论。