Lecture 7: Forms of Precipitation

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What is the primary issue with cloud droplets forming precipitation by themselves?

Cloud droplets are extremely tiny and fall in still air incredibly slowly, requiring a growth in volume by 1 million times for precipitation to occur.

What is the role of ice crystals in the Bergeron process?

Ice crystals grow larger at the expense of supercooled droplets, increasing their weight until they fall, and accumulating more cloud droplets through accretion.

How does the Collision-Coalescence process occur in warm clouds?

Larger cloud droplets fall faster, collide with smaller droplets, and merge through coalescence, facilitated by opposite electrical charges and aided by updrafts that allow for more time to grow.

What is the significance of terminal velocity in the context of raindrop formation?

Terminal velocity is the constant speed at which a falling raindrop reaches, where air resistance equals the pull of gravity, and larger drops fall faster due to their smaller surface-area-to-weight-ratio. Signup and view all the answers

What is the difference in falling speed between a typical cloud droplet and a typical raindrop?

A typical raindrop falls over 600 times faster than a typical cloud droplet. Signup and view all the answers

What is the process of ice crystals colliding and sticking together called?

Aggregation. Signup and view all the answers

What is the primary difference between rain and drizzle in terms of drop size?

Raindrops have a diameter equal to or greater than 0.5 mm, while drizzle has a diameter less than 0.5 mm. Signup and view all the answers

What happens to raindrops when they encounter rapidly rising air?

The raindrops do not reach the ground because the updraft causes them to evaporate or remain suspended in the air. Signup and view all the answers

What is the term for the maximum speed at which a falling object can travel through the air, in this case, a raindrop?

Terminal velocity Signup and view all the answers

What type of cloud is associated with continuous rain and has weaker, more shallow vertical air currents?

Nimbostratus cloud Signup and view all the answers

What determines the size, shape, and concentration of snowflakes?

The temperature at which they form Signup and view all the answers

What is the difference between sleet and freezing rain?

Sleet forms when raindrops freeze before reaching the ground, while freezing rain forms when supercooled raindrops freeze upon contact with the ground. Signup and view all the answers

What are the necessary conditions for hail to form?

Large cumulonimbus clouds with strong updrafts and a lot of supercooled water Signup and view all the answers

What is the primary role of updrafts in the formation of hail?

Updrafts carry hailstones upward, allowing them to grow through the accumulation of supercooled water droplets. Signup and view all the answers

What is the term for the streaks of precipitation that evaporate before reaching the ground?

Virga Signup and view all the answers

What is the primary difference between cumulonimbus clouds and nimbostratus clouds?

Cumulonimbus clouds have strong, deep convection currents, while nimbostratus clouds have weaker, more shallow vertical air currents. Signup and view all the answers