Adiabatic Cooling-Warming
30C 14C
20C   12C
10C   10C
Dew point decreases with height at a rate of 2oC/km b/c DP varies less with Pressure than Temp.
The rate is much less than cooling rate for air.
Thus, unsaturated air can become saturated    IF it rises far enough.
Red=Temperature Blue=Dew Point
Ahrens, Fig 5.2