近幾年的研究顯示，從太陽表面延伸到對流層底都可以觀測到子午流的存在。次表面的子午流在黑子週期上扮演了重要的角色。這篇論文主要是研究太陽”子午流隨深度、緯度及時間的變化”。所使用的數據從1994年到2000年，包含了2000年的黑子極大期，及1996年的黑子極小期。研究的深度達太陽半徑的13%。在1994年到1997年間黑子逐漸減少，相對的子午流的強度增加。1997年到2000年黑子逐漸增加，有一個新的子午流分量，以緯度20度為中心，在南北半球產生。這個新子午流分量由其中心向南北方向流動。並使得原本赤道附近向極軸方向的子午流變為往赤道方向。這個新增加的子午流的速度隨深度有增加的現象（在0.9R☉內）。這種次表面的子午流隨黑子週期的變化，顯示子午流在黑子週期中扮演重要的角色。我們也許可以利用子午流的變化來研究對流區底部或內部的磁場。

Recent observation have shown that the axisymmetric flow in Sun`s surface to the base of the convection zone. The subsurface meridional flow plays an important role in the dynamics of the sunspot cycle. It is of importance to learn how the subsurface meridional flow varies with the eleven-year sunspot cycle. Here we report the study of subsurface meridional flow as a function of latitude and depth down to a depth of 13% of the solar radius in the period from 1994 to 2000 covering the solar minimum in 1996 and maximum in 2000. We find that the velocity of meridional flow increased as sunspot number decrease from 1994 to 1997.As the sunspot number increased from 1997 to 2000,a new component of meridional flow,centered at about 20° latitude,was created in each hemisphere. It moves away from the center. This additional component changes the observed meridional flow from poleward to equatoward near the equator in both hemispheres. The velocity of the additional meridional flow increase with depth at least down to a depth of 70000 km,~10% of the solar radius. The variation of the subsurface meridional flow plays an important dynamical role in the sunspot cycle. It can be used as a tool to probe the magnetic fields deep in the convection zone.

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