Top row: observed (dashed line) and inverted (solid line) profiles from one pixel within the sunspot during the UF phase (blue) and quiescence (black). Middle row: density map illustrating the inferred temperature stratification during UF (left) and quiescence (right) for a patch inside the umbra. A total of 280 models is shown. Bottom row: same as middle row, for the l.o.s velocity stratification. Negative velocities correspond to upflows.