ARising air gets compressed and squeezes water out
BRising air cools, and cooler air cannot hold as much water vapor, so the excess condenses into tiny droplets forming a cloud
CRising air gets closer to the Sun, which evaporates more water
DRising air picks up dust that absorbs moisture
As air rises, it expands (because atmospheric pressure decreases with altitude) and cools. Cooler air can hold less water vapor. When the air cools to its dew point — the temperature at which it becomes saturated — the excess water vapor condenses around tiny particles (dust, pollen, sea salt) in the air, forming the visible water droplets or ice crystals that make up a cloud.
Question 2 Short Answer
What determines whether precipitation falls as rain or snow?
Think about your answer, then reveal below.
Model answer: The temperature of the air between the cloud and the ground determines the type of precipitation. If the air is above freezing all the way down, precipitation falls as rain. If it is below freezing all the way down, it falls as snow. If it passes through layers of different temperatures, it can form sleet (freezing rain that re-freezes) or freezing rain (liquid rain that freezes on contact with cold surfaces).
The cloud itself is almost always cold enough for ice crystals to form. The journey from cloud to ground determines what the precipitation looks like when it arrives. This is why weather forecasters pay close attention to temperature profiles at different altitudes — a few degrees can mean the difference between rain and a dangerous ice storm.
Question 3 True / False
Water vapor is visible as the white clouds you see in the sky.
TTrue
FFalse
Answer: False
Water vapor is invisible — it is a gas and you cannot see it. Clouds are made of tiny liquid water droplets or ice crystals that have condensed from water vapor. The steam you see above a boiling pot is also not water vapor — it is tiny water droplets that formed when invisible water vapor immediately condensed in the cooler air above the pot.