Why does the angle of descent increase in a constant headwind while decreases in a sudden encounter with a headwind, in a descend? I'm currently studying aerodynamics.
I have realized that a sudden encounter with a headwind during descent
will result in the aircraft generating more lift, thus angle of descent decreases. 
I haven't studied the descent in a constant headwind, but through research I've come across that a constant headwind during descent will increase the angle of descent.
This does not make sense. Shouldn't the angle of descent decrease in both situations? Will appreciate it if someone could explain this.
Consider descending in zero wind, trimmed to an airspeed of 80m/s (288km/h) and a sink rate of 2m/s. You won't touch stick, trim tabs or throttles during the descent, but you will encounter a headwind at a later time. For now, ground speed is equal to airspeed and the angle of descent is 1:40.

You suddenly encounter a headwind of 20m/s. Ground speed remains at 80m/s due to inertia; Airspeed rises to 100m/s. The rise in airspeed increases lift and reduces sink rate to 1m/s. The angle of descent is now much shallower, at 1:80.

After a couple of seconds, airspeed bleeds off and the aircraft resumes its trimmed state at an airspeed of 80m/s and a sink rate of 2m/s. This time, the ground speed is only 60m/s due to the headwind and the angle of descent is now 1:30.