  We measure and model the wavelength dependence of the PSF in the Hyper
Suprime-Cam (HSC) Subaru Strategic Program (SSP) survey. We find that PSF
chromaticity is present in that redder stars appear smaller than bluer stars in
the $g, r,$ and $i$-bands at the 1-2 per cent level and in the $z$ and
$y$-bands at the 0.1-0.2 per cent level. From the color dependence of the PSF,
we fit a model between the monochromatic PSF trace radius, $R$, and wavelength
of the form $R(\lambda)\propto \lambda^{b}$. We find values of $b$ between -0.2
and -0.5, depending on the epoch and filter. This is consistent with the
expectations of a turbulent atmosphere with an outer scale length of $\sim
10-100$ m, indicating that the atmosphere is dominating the chromaticity. We
find evidence in the best seeing data that the optical system and detector also
contribute some wavelength dependence. Meyers and Burchat (2015) showed that
$b$ must be measured to an accuracy of $\sim 0.02$ not to dominate the
systematic error budget of the Large Synoptic Survey Telescope (LSST) weak
lensing (WL) survey. Using simple image simulations, we find that $b$ can be
inferred with this accuracy in the $r$ and $i$-bands for all positions in the
LSST field of view, assuming a stellar density of 1 star arcmin$^{-2}$ and that
the optical PSF can be accurately modeled. Therefore, it is possible to correct
for most, if not all, of the bias that the wavelength-dependent PSF will
introduce into an LSST-like WL survey.
