Context :

Aims : We focus on detecting and studying quasi-periodic propagating features that have been interpreted both in terms of slow magneto-acoustic waves and of high speed upflows .

Methods : We analyze long duration spectroscopic observations of the on-disk part of the south polar coronal hole taken on 1997 February 25 by the SUMER spectrometer aboard SOHO .
We calibrated the velocity with respect to the off-limb region and obtain time–distance maps in intensity , Doppler velocity and line width .
We also perform a cross correlation analysis on different time series curves at different latitudes .
We study average spectral line profiles at the roots of propagating disturbances and along the propagating ridges , and perform a red-blue asymmetry analysis .

Results : We find the clear presence of propagating disturbances in intensity and Doppler velocity with a projected propagation speed of about 60 \pm 4.8 km s ^ { -1 } and a periodicity of \approx 14.5 min .
To our knowledge , this is the first simultaneous detection of propagating disturbances in intensity as well as in Doppler velocity in a coronal hole .
During the propagation , an intensity enhancement is associated with a blue-shifted Doppler velocity .
These disturbances are clearly seen in intensity also at higher latitudes ( i.e .
closer to the limb ) , while disturbances in Doppler velocity becomes faint there .
The spectral line profiles averaged along the propagating ridges are found to be symmetric , to be well fitted by a single Gaussian , and have no noticeable red-blue asymmetry .

Conclusions : Based on our analysis , we interpret these disturbances in terms of propagating slow magneto-acoustic waves .