Dry ice is solid carbon dioxide. At normal temperature, dry ice is easy to sublimate into gas, and in this process, it absorbs heat, thus playing a role in cooling down. At this time, the water vapor in the high air will condense into small ice particles; After sublimation, the small ice particles melt into liquid state again; Form rain;

So the answer is: sublimation; Absorption; Ninghua; Melting.