  The absolute frequency of the $^{87}{\rm Sr}$ clock transition measured in
2015 was reevaluated using an improved frequency link to the SI second. The
scale interval of International Atomic Time (TAI) that we used as the reference
was calibrated for an evaluation interval of five days instead of the
conventional interval of one month which is regularly employed in Circular T.
The calibration on a five-day basis removed the uncertainty in assimilating the
TAI scale of the five-day mean to that of the one-month mean. The reevaluation
resulted in the total uncertainty of $10^{-16}$ level for the first time
without local cesium fountains. Since there are presumably no correlations
among systematic shifts of cesium fountains worldwide, the measurement is not
limited by the systematic uncertainty of a specific primary frequency standard.
