  The results on the vertical distribution of optical turbulence above the five
mountains which were investigated by the site testing for the Thirty Meter
Telescope (TMT) are reported. On San Pedro Martir in Mexico, the 13 North site
on Mauna Kea and three mountains in northern Chile Cerro Tolar, Cerro Armazones
and Cerro Tolonchar, MASS-DIMM turbulence profilers have been operated over at
least two years. Acoustic turbulence profilers - SODARs - were also operated at
these sites. The obtained turbulence profiles indicate that at all sites the
lowest 200m are the main source of the total seeing observed, with the Chilean
sites showing a weaker ground layer than the other two sites. The two northern
hemisphere sites have weaker turbulence at altitudes above 500m, with 13N
showing the weakest 16km turbulence, being responsible for the large
isoplanatic angle at this site. The influence of the jetstream and wind speeds
close to the ground on the clear sky turbulence strength throughout the
atmosphere are discussed, as well as seasonal and nocturnal variations. This is
the sixth article in a series discussing the TMT site testing project.
