  We apply the helioseismic methodology of Legendre Function Decomposition to
88 months of Dopplergrams obtained by the Helioseismic and Magnetic Imager
(HMI) as the basis of inferring the depth variation of the mean meridional
flow, as averaged between 20 and 60 degrees latitude and in time, in both the
northern and southern hemispheres. We develop and apply control procedures
designed to assess and remove center-to-limb artifacts, using measurements
obtained by performing the analysis with respect to artificial poles at the
east and west limbs. Forward modeling is carried out, using sensitivity
functions proportional to the mode kinetic energy density, to evaluate the
consistency of the corrected frequency shifts with models of the depth
variation of the meridional circulation in the top half of the convection zone.
The results, taken at face value, imply substantial differences between the
meridional circulation in the northern and southern hemisphere. The inferred
presence of a return (equator-ward propagating) flow at a depth of
approximately 40 Mm below the photosphere in the northern hemisphere is
surprising and appears to be inconsistent with many other helioseismic
analyses. This discrepancy may be the result of an inadequacy of our
methodology to remove systematic errors in HMI data. Our results appear to be
at least qualitative similar to those by Gizon et al. (2020) which point to an
anomaly in HMI data that is not present in MDI or GONG data.
