  A recent hydrodynamic model, "radiation-driven fountain model" (Wada et al.
2016), presented a dynamical picture that active galactic nuclei (AGNs) tori
sustain their geometrical thickness by gas circulation around AGNs, and
previous papers confirmed that this picture is consistent with multi-wavelength
observations of nearby Seyfert galaxies. Recent near-infrared observations
implied that CO rovibrational absorption lines ($\Delta J=\pm1$, $v=0-1$,
$\lambda \sim 4.7$ $\mathrm{\mu m}$) could probe physical properties of the
inside tori. However, the origin of the CO absorption lines has been under
debate. In this paper, we investigate the origin of the absorption lines and
conditions for detecting them by performing line radiative transfer
calculations based on the radiation-driven fountain model. We find that CO
rovibrational absorption lines are detected at inclination angles
$\theta_\mathrm{obs} = 50-80$ $^{\circ}$. At the inclination angle
$\theta_\mathrm{obs} = 77$ $^{\circ}$, we observe multi-velocity components:
inflow ($v_\mathrm{LOS}=30$ $\mathrm{kms^{-1}}$), systemic ($v_\mathrm{LOS}=0
\, \mathrm{kms^{-1}}$), and outflows ($v_\mathrm{LOS}=-75,\, -95,$ and $-105$
$\mathrm{kms^{-1}}$). The inflow and outflow components ($v_\mathrm{LOS}= 30$
and $-95$ $\mathrm{kms^{-1}}$) are collisionally excited at the excitation
temperature of $186$ and $380$ K up to $J=12$ and $4$, respectively. The inflow
and outflow components originate from the accreting gas on the equatorial plane
at $1.5$ pc from the AGN center and the outflowing gas driven by AGN radiation
pressure at $1.0$ pc, respectively. These results suggest that CO rovibrational
absorption lines can provide us with the velocities and kinetic temperatures of
the inflow and outflow in the inner a-few-pc regions of AGN tori, and the
observations can probe the gas circulation inside the tori.
