  This paper aims at revisit the physical and dynamical properties of the warm
atomic gas in the inner disk region of classical T Tauri stars (CTTs) and
relate them to the properties of the outer dusty disk. We used the high
resolution (R=115,000) spectra of 36 CTTs observed as part of the GHOsT project
and analysed the profile and luminosity of the brightest optical forbidden
lines, namely [OI]630 and 557nm, [SII]406 and 673nm, and [NII]658nm. We find
that in about 40% of sources the so-called narrow low-velocity component (NLVC)
display a peak velocity compatible with the stellar velocity. In these sources,
that typically show lower mass accretion rates and the absence of a jet, the
[OI]630nm profiles are well fitted by a simple Keplerian disk model, indicating
that the emission from the disk is dominant with respect to the wind
contribution. For transitional disks (TD), no correlation is found between
$R_{kep}$, derived from the line HWHM, and the size of the dust cavity. We also
see an anti-correlation between the [OI] 557/630 nm ratio and $R_{kep}$, which
suggests that the [OI] emitting region expands as the gas cools and becomes
less dense. We confirmed previous findings on the density and temperature
ranges implied by the line ratios, and additionally constrained the ionisation
fraction in the NLVC to be < 0.1. We however discuss the limits of applying
this diagnostic to winds that are not spatially resolved. For the outflow
component, we estimated the mass-loss for both the disk winds and jets and
compared the results with X-ray photoevaporative models. We conclude that
without better knowledge of the wind geometry, and given the limitation of the
diagnostics, the mass-loss in the wind traced by the LVC cannot be constrained
better than a factor of 100, with a mass-loss/mass-accretion ratio spanning
between ~ 0.01 and more than 1.
