Oggers,
Look at those variations though, and consider their nature. At constant height above sea level / geoid, they are very modest, requiring days of data from satellite orbit measurements to measure. The differences are typically at the 10 ppm level, and up to about 60 ppm.
See
GRACE Gravity Model- Gravity Recovery and Climate Experiment Gravity Model for a description of the GRACE mission and its products. GOCE produced more too.
If the author is including GRACE maps is his fluttering debris data, then he's missing the wood for the trees.
Is he using pressure altitude to start his simulation? If so, then he should have a further think about the "variable gravity" bit and where isobars lie in 3D.