What happens to the atmospheric pressure acting on a balloon as the balloon rises into the sky

Question

sooobored · Answer

well, the atmosphere get thinner the higher you go

hence the atmosphere/pressure at ground level is greater than the atmosphere/pressure 1 mile up in the sky

osprey · Answer

this is also why high flying aircraft need to have internal pressurising systems to ensure that the pressure on the people in the aircraft is near to ground level value. Otherwise, people would probably suffocate or something else medical.

icrazyaliens · Answer

According the Boyle's law 
the pressure is inversely proportional to the volume.
Once the balloon raises the pressure starts increasing and the volume starts decreasing..