What is precipitation?

Summary

This educational video script delves into the fascinating world of precipitation, exploring not just rain and drizzle, but also extreme weather events like hailstorms and blizzards. It explains the formation of clouds and precipitation through the condensation of water vapor and the processes of coalescence and aggregation. The script also covers how different weather fronts influence cloud types and precipitation, and it highlights the dynamic nature of hail formation within powerful cumulonimbus clouds. The video encourages viewers to consider the complex journey of raindrops from vapor to cloud droplets, and possibly even hail, before they reach the ground as rain.

Takeaways

• ☁️ Precipitation includes not only rain and drizzle but also extreme weather events like hailstorms and blizzards.
• 🌡️ Clouds form when water vapor in the atmosphere cools and condenses into droplets or ice crystals, depending on the temperature.
• 🌬️ Various processes can cool the air and lead to cloud formation, such as warm fronts, cold fronts, and surface heating.
• 🌦️ Weather fronts often result in cloudy skies, with rain, drizzle, or snow, especially during colder times of the year.
• 💧 Rain and drizzle differ primarily in droplet size, with drizzle consisting of very small droplets that can reduce visibility.
• ❄️ In colder climates, precipitation often begins as ice crystals that form when clouds develop in sub-freezing temperatures.
• 🌨️ The aggregation of ice crystals with supercooled water droplets leads to the formation of snowflakes.
• 🌧️ Rain in temperate climates typically starts as snow but melts before reaching the ground if the air below the cloud is above 2°C.
• ⛈️ Cumulonimbus clouds, driven by strong convection, can produce heavy rain and are characterized by an anvil shape indicating the presence of ice crystals.
• ⚡️ Hailstones form within these clouds through a process of freezing and melting as they are carried up and down by air currents, growing layers like an onion.

Q & A

What is precipitation and why is it not just about rain and drizzle?

Precipitation includes all forms of water that fall from the atmosphere to the Earth's surface, not just rain and drizzle. It also encompasses extreme weather events like hailstorms and blizzards.

How are clouds formed and what role do they play in precipitation?

Clouds form when water vapor in the atmosphere cools and condenses into droplets. They are the starting point for all precipitation as they provide the medium for water droplets or ice crystals to form and grow.

What causes the cooling process that leads to cloud formation?

The cooling process can occur in various ways, such as air rising along a warm front, approaching a cold front, or being heated by the Earth's surface and then rising.

How does the difference in droplet size distinguish rain from drizzle?

Rain and drizzle differ by the size of the droplets involved. Drizzle consists of very small droplets, half a millimeter or less in diameter, while rain involves larger droplets.

What is the process by which drizzle droplets become large enough to fall as rain?

Drizzle droplets merge or coalesce until they become large enough to fall from the cloud under their own weight.

In what conditions does snow form and how does it relate to rain in colder climates?

Snow forms when clouds develop in or move into an area of the atmosphere below freezing. In colder climates, snow can fall but often melts before reaching the ground, resulting in rain.

What is the role of ice crystals and supercooled water droplets in precipitation formation?

Ice crystals and supercooled water droplets are key to precipitation formation. Ice crystals grow rapidly in the presence of supercooled water, and they can aggregate to form snowflakes.

How does the temperature of the air beneath the cloud affect whether snowflakes reach the ground?

If the air between the cloud base and the ground is no warmer than 2°C, snowflakes can reach the ground intact. If the air is above 2°C, the snowflakes will melt and fall as rain.

What are the most energetic cloud types that can produce heavy rain?

The most energetic cloud types that can produce heavy rain are driven by strong convection, often resulting in cumulonimbus or thunderhead clouds.

How are hailstones formed and what is the process like inside a cloud?

Hailstones form inside clouds as small ice crystals and water droplets freeze and aggregate. They can be carried up and down by warm and cold air currents, accumulating layers of ice and growing in size.

What is the largest hailstone ever recorded and where did it occur?

The largest hailstone ever recorded was in Bangladesh in 1986, measuring 15 cm across and weighing over a kilo.

Outlines

00:00

🌧️ Precipitation and Its Formation

This paragraph introduces the topic of precipitation, emphasizing that it encompasses more than just rain and drizzle, including extreme weather events like hailstorms and blizzards. It explains that precipitation originates from clouds, which form when atmospheric water vapor cools and condenses into droplets or ice crystals, depending on the temperature. The paragraph discusses how different atmospheric conditions, such as warm and cold fronts, can lead to the development of various cloud types and subsequent precipitation. It also distinguishes between rain and drizzle based on droplet size and highlights the process of droplet coalescence in tropical climates versus the formation of ice crystals and snowflakes in colder regions. The paragraph concludes with an explanation of how snow melts into rain when it passes through warmer air layers before reaching the ground.

05:00

⛈️ Hailstone Formation and Severe Storms

The second paragraph delves into the formation of hailstones, which occur when small hailstones are carried up and down within a cloud by alternating currents of warm and cold air. This process allows the hailstones to accumulate layers of ice, similar to an onion's structure. The paragraph describes how, in severe storms, this can lead to the formation of large hailstones, with examples including golf ball-sized hail and the record-breaking hailstone from Bangladesh in 1986, which was as large as a tennis ball and weighed over a kilo. The paragraph encourages viewers to consider the complex journey of precipitation from water vapor to cloud droplets, and possibly to hail, before it reaches the ground as rain. It concludes with a prompt to visit the Met Office website for more information on precipitation, weather, and climate.

Keywords

💡Precipitation

Precipitation refers to any form of water that falls from the atmosphere and reaches the ground. In the video, it is not limited to rain but also includes various forms of extreme weather like hailstorms and blizzards. The script explains that all precipitation originates from clouds where water vapor condenses, highlighting precipitation's role in the Earth's water cycle and its impact on weather phenomena.

💡Cloud Formation

Cloud formation is the process by which water vapor in the atmosphere cools and condenses to form visible masses of liquid or ice particles. The script describes how clouds form when air rises and cools, leading to the condensation of water vapor into droplets. This concept is central to understanding how weather patterns develop and how different types of precipitation are produced.

💡Condensation

Condensation is the process where water vapor turns into liquid water, which is a key step in cloud and precipitation formation. The script mentions that condensation occurs as the water vapor cools, leading to the formation of droplets that make up clouds. This process is essential for understanding the development of weather systems and the types of precipitation that result.

💡Ice Crystals

Ice crystals are solid forms of water that form when water vapor freezes directly in the atmosphere, bypassing the liquid phase. The video script explains that when clouds develop in sub-freezing temperatures, ice crystals form and can grow rapidly by attaching supercooled water droplets. Ice crystals are crucial for the formation of snow and play a significant role in the development of hailstones.

💡Supercooled Water Droplets

Supercooled water droplets are water droplets that remain in a liquid state even below the freezing point. The script describes how these droplets can exist in clouds where the temperature is below freezing but have not yet frozen. They are important for the formation of precipitation because they can immediately freeze upon contact with ice crystals, contributing to the growth of snowflakes and hailstones.

💡Aggregation

Aggregation in the context of the video refers to the process where ice crystals combine to form larger structures, such as snowflakes. The script explains that ice crystals aggregate as they come into contact with other ice crystals within a cloud, leading to the formation of snowflakes. This process is essential for understanding how snow develops and the various forms it can take.

💡Glaciation

Glaciation is the process where water droplets in a cloud freeze into ice crystals. The video script mentions that as a cloud grows and passes through the freezing level, the water droplets within it undergo glaciation. This process is significant for the development of precipitation, particularly in the formation of hailstones and the structure of anvil clouds.

💡Anvil Clouds

Anvil clouds, also known as cumulonimbus clouds, are a type of cloud that can produce heavy precipitation, thunderstorms, and even hail. The script describes how these clouds form an anvil shape as they grow beyond the freezing level, indicating the presence of ice crystals. Anvil clouds are a visual indicator of strong convection and intense weather activity.

💡Convection

Convection refers to the movement of air or liquid resulting from the tendency of hotter and therefore less dense material to rise, and colder, denser material to sink. In the video, convection is described as a driving force behind the formation of cumulus clouds and thunderstorms, where warm air rises and cools, leading to the condensation of water vapor and the potential for heavy rain or hail.

💡Hailstones

Hailstones are balls of ice that form in thunderstorm clouds and can fall to the ground. The script explains that hailstones form when small ice crystals and supercooled water droplets combine and are carried up and down by strong air currents within the cloud. This process can repeat many times, with the hailstone accumulating layers of ice, leading to the formation of large hailstones that can cause significant damage.

💡Weather Fronts

Weather fronts are the boundaries between two air masses of different temperatures. The video script discusses how weather fronts, such as warm fronts and cold fronts, can force air to rise, leading to the development of clouds and precipitation. Fronts are critical in understanding how different weather conditions, including rain, drizzle, and snow, are formed and how they change over time.

Highlights

Precipitation includes not only rain and drizzle but also extreme weather events like hail storms and blizzards.

Precipitation forms in clouds where water vapor cools and condenses into droplets or ice crystals.

Clouds form when air is forced to rise, such as along a warm front, creating deep layers of clouds.

Cold fronts can push under warm moist air, lifting it and leading to cloudy skies with rain or snow.

Heated air rising from the Earth's surface can form cumulus clouds, which may develop into cumulonimbus clouds bringing heavy rain or hail.

Rain and drizzle differ only by the size of the droplets, with drizzle being composed of very small droplets.

Drizzle can reduce visibility significantly due to the small and closely packed droplets.

In tropical climates, the coalescing of droplets can produce heavy rain from deep clouds.

Ice crystals and super cooled water droplets mix in clouds below freezing, key to most precipitation formation.

Ice crystals grow rapidly in the presence of super cooled water, leading to the formation of snowflakes.

Snowflakes reach the ground intact if the air below the cloud is no warmer than 2°C.

In warmer conditions, snowflakes melt and arrive as raindrops when the air is above 2°C.

The most energetic cloud types, like cumulonimbus, are driven by strong convection and can produce heavy rain.

Glaciation occurs as water droplets freeze into ice crystals within the cloud, forming an anvil shape typical of thunderhead clouds.

Small hailstones form inside the cloud and can be carried up and down by warm and cold air currents.

Hailstones can grow layers of ice as they travel up and down within the cloud, resembling an onion when cut.

Severe storms with strong air currents can support hailstones as large as golf balls or even tennis balls.

The largest hailstone recorded, from Bangladesh in 1986, was 15 cm across and weighed over a kilo.

Understanding the journey of raindrops from water vapor to precipitation can enhance our appreciation of weather phenomena.

Transcripts

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you might think that precipitation

sounds like a bit of a dull subject but

we're not just talking about rain and

drizzle we experience here in this

country it also includes extreme weather

such as hail storms and blizzards in

this film we're going to be looking at

those examples of extreme weather and

finding out how rain hail and snow are

formed all precipitation develops in

clouds and clouds are formed when water

vapor in the atmosphere cools and

condenses as the water vapor condens SES

it forms droplets and if the cloud

develops within or moves into a part of

the atmosphere that is below freezing

then the droplets form ice crystals the

cooling process which first forms clouds

can happen in many different ways air

may be forced to rise along a warm front

and as it cools deep layers of clouds

can develop sometimes reaching many

thousands of meters all the way down to

ground level air may also be forced to

rise as a cold front approaches in this

instance a wedge of cold dense air push

pushes under the warm moist air ahead of

it lifting it weather fronts tend to

bring generally Cloudy Skies with

relatively long spells of rain and

drizzle or SLE and snow at colder times

of year and finally air may be forced to

rise simply because it's heated by the

Earth's surface and it convex this is

what we often see on a summer's day with

cumulus clouds building up and sometimes

developing into towering cumon nimbus

clouds then we can get very heavy rain

and even hail let's look first at rain

and drizzle the only real difference

between rain and drizzle is the size of

the droplets drizzle is composed of very

small droplets half a millim or less in

diameter the tiny droplets that fall

from the cloud itself merge together or

coales until the droplet size becomes

large enough to fall from the cloud

under its own weight even though drizzle

is made up of small droplets it can

still produce some very poor weather

heavy drizzle can seriously reduce

visibility because the droplets are

small and close together in tropical

climates where deep clouds develop in

warm air this coalescing of droplets can

produce quite heavy rain but in our

latitudes anything more serious than

drizzle usually starts off as ice

crystals high in the atmosphere when

clouds build in air that's below

freezing we often get a mixture of ice

crystals and super cooled water droplets

that is water which is just below

freezing but hasn't yet turned to ice it

is this mix of ice crystals and super

cool droplets that is really the key to

understanding how most precipitation

forms the ice crystals are able to grow

rapidly where there is super cooled

water nearby because as soon as the

supercooled water makes contact with the

Ice Crystal it immediately freezes then

as the crystals drift through the cloud

they connect with other ice crystals in

a process called aggregation and large

snowflakes are formed this process of

aggregation can take place in any fairly

deep Cloud whether it's formed in layers

along a weather front or by the

convective bubbling up process

if the air between the base of the cloud

and the ground is no warmer than 2° C

then the snowflakes reach the ground

intact in warmer conditions when the air

beneath the cloud is above 2° C then the

snowflakes will melt and arrive on the

ground as rain drops this is the way in

which almost all significant rain is

produced in our latitudes it starts as

snow but melts before it reaches the

ground the most energetic cloud types

and the ones that can produce really

heavy rain are driven by strong

convection as the air cools the water

vapor condenses into water droplets

forming clouds as the cloud grows up

through the atmosphere it will soon pass

the freezing level and water droplets

within the cloud will freeze and form

ice crystals that is called glaciation

and an anvil shape is typical of cumulon

nimbus or Thunderhead clouds the fuzzy

edges of an anvil cloud show that there

are ice crystals present and the cloud

has grown well beyond the freezing level

these ice crystals grow as other water

drops nearby freeze onto their surface

creating a coating of ice and small

hailstones are formed inside the cloud

there will be rising currents of warm

air and some quite severe downdrafts of

cold air small hailstones may fall

through the cloud helping to create the

down drafts they can also be carried

back up through the cloud by the rising

currents of warm air this can happen

many times with the Hailstone melting

and freezing and developing fresh coats

of ice during its Journey Through the

Sub-Zero part of the cloud if you're

brave enough to venture into a hail

storm you can actually cut a Hailstone

in half and see how those layers of ice

are built up like an onion as the

Hailstone travels up and down within the

cloud in really severe storms that

process is repeated so often and the

currents of air are so strong that

hailstones as big as golf balls can be

supported in really severe storms

hailstones as big as tennis balls have

been recorded the largest hailstone ever

recorded in recent times came from

Bangladesh in 1986 six and measured a

whopping 15 cm across it weighed over a

kilo that's the same as a bag of sugar

next time you're out in the rain have a

think about what's going on above your

head and the journey those raindrops may

have made from water vapor into Cloud

droplets snow maybe even hail before

falling to Earth as rain if you want to

learn more about precipitation or

anything to do with weather and climate

visit the Met Office website

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