Spectral analysis of the spatial structure of solar subphotospheric convection is carried out for subsurface flow maps. It is found that the horizontal flow scales increase rapidly with depth, from supergranulation to giant-cell values. The total power of the convective flows is found to be anticorrelated with the sunspot number variation over the solar activity cycle in shallow subsurface layers and positively correlated at larger depths.
Forward modeling is applied to numerous global hydrodynamic solar models, and helioseismic measurements on the meridional circulation are made using the forward modeling results. Comparison against the observational measurements shows significant differences, indicating our insufficient knowledge on either the global hydrodynamic modeling or the helioseismic inversions.