ATPL Meteorology - Class 7: Precipitation.

Summary

This meteorology lesson explores various types of precipitation, from drizzle to hail, and their formation due to rising air and temperature changes. Drizzle consists of small droplets under 0.5mm, while rain droplets exceed this size up to 5mm. Freezing drizzle and rain occur when temperatures are below zero but remain liquid. Snow, sleet, and hail are ice-based, with snowflakes varying greatly in size. Sleet is a mix of rain and snow, and hail forms in cumulonimbus clouds with strong updrafts. Precipitation intensity is categorized as slight, moderate, or heavy, based on the hourly rate of fall, with slight rain being under 0.5mm per hour and heavy exceeding 4mm per hour. Duration is described as continuous, intermittent, or in showers, aligning with cloud types and atmospheric conditions.

Takeaways

• 🌧️ Precipitation is any form of water or ice that falls from clouds to the Earth's surface, ranging from light drizzle to heavy hail.
• 💧 Drizzle is characterized by very small water droplets with a diameter of less than 0.5 millimeters.
• 🌦️ Rain consists of larger droplets, with diameters greater than 0.5 millimeters and up to 5 millimeters.
• ❄️ Snow can take various forms including snowflakes, snow grains, and snow pellets, each with different sizes.
• 🌨️ Sleet is a mix of rain and snow, or partially melted snow, and can vary in size and shape.
• ⛈️ Hail forms in strong updrafts within cumulonimbus clouds, where ice pellets rise and fall, colliding and accumulating layers of ice.
• 🌬️ The intensity of precipitation is measured by the amount that falls in an hour, with categories of slight, moderate, and heavy.
• ⏱️ The duration of precipitation can be continuous (over 60 minutes), intermittent (no clear breaks within an hour), or in the form of showers (on-off blocks of precipitation).
• 🌟 Cumuloform clouds, associated with unstable conditions and more rising air, are more likely to produce rain and hail.
• 🌫️ Stratiform clouds, with less rising air, are typically linked to drizzle and are associated with stable atmospheric conditions.
• ❄️ Freezing drizzle and freezing rain occur when droplets are supercooled below zero degrees Celsius but remain in liquid form until they encounter an impurity.

Q & A

What is precipitation and how does it form?

Precipitation is any form of water that falls from clouds back to the Earth's surface. It forms when rising air cools down to below the dew point, causing the air to become fully saturated and form clouds. The suspended water droplets or ice crystals then fall back to Earth as precipitation if they grow large and heavy enough for gravity to overcome the rising air.

What differentiates drizzle from rain in terms of droplet size?

Drizzle is characterized by small water droplets with a diameter of less than 0.5 millimeters. Rain, on the other hand, consists of larger droplets with a diameter larger than 0.5 millimeters but less than 5 millimeters.

How does the intensity of upward air motion affect the size of precipitation droplets?

The more intense the upward motion of the air, the larger the water droplets or ice crystals need to become to be pulled down to the Earth by gravity. This is because they must overcome the force of the rising air.

What types of clouds are associated with drizzle and rain?

Drizzle is more likely to be produced by stratiform clouds with less rising air, while rain generally comes from cumuloform clouds associated with unstable conditions and more rising air.

What is freezing drizzle and freezing rain, and how do they form?

Freezing drizzle and freezing rain occur when rain or drizzle droplets are supercooled to below zero degrees Celsius but remain in liquid form. This happens in very pure air with few impurities for ice crystals to form around. When these supercooled droplets encounter an impurity, they can rapidly freeze.

What are the different types of ice precipitation mentioned in the script?

The script mentions several types of ice precipitation: snow, which includes snowflakes, snow grains, and snow pellets; sleet, which is a combination of rain and snow; and hail, which forms in strong updrafts within cumulonimbus clouds.

How is hail formed and what conditions are necessary for its formation?

Hail forms when an ice pellet rises and falls within a cloud that has a lot of rising air, such as a cumulonimbus cloud. As the ice grows, it collides with more supercooled water droplets or ice particles, and the rising air sends it back up, repeating the process and gaining layers of ice. This requires very high levels of rising air and unstable conditions.

How is the intensity of precipitation measured?

The intensity of precipitation is measured in terms of slight, moderate, and heavy, which refers to the amount of precipitation that falls in an hour. Slight precipitation is less than 0.5 millimeters per hour, moderate is between 0.5 and 4 millimeters per hour, and heavy is anything more than 4 millimeters per hour.

What is the difference between continuous, intermittent, and shower types of precipitation?

Continuous precipitation lasts more than 60 minutes without a break. Intermittent precipitation occurs with no clear breaks within a 60-minute period but is not continuous throughout. Showers are on-off blocks of precipitation with clear gaps of no precipitation and periods of precipitation.

How are the terms 'slight,' 'moderate,' and 'heavy' defined for snowfall?

For snowfall, slight is defined as less than 0.5 centimeters per hour, moderate is between 0.5 and 4 centimeters per hour, and heavy is anything more than 4 centimeters per hour.

Outlines

00:00

🌧️ Understanding Precipitation

This paragraph introduces the concept of precipitation, which includes any form of water that falls from clouds back to the Earth's surface. It can range from light drizzle to heavy hail. The paragraph explains the process of precipitation formation, starting with rising air that cools and becomes saturated, leading to cloud formation. The precipitation falls when water droplets or ice crystals grow large enough to be pulled down by gravity. The size of the droplets determines whether it's classified as drizzle (less than 0.5 mm in diameter) or rain (larger than 0.5 mm up to 5 mm). The intensity of the upward air motion affects the size of the droplets, with more intense updrafts leading to larger droplets. The paragraph also touches on freezing drizzle and rain, which occur when droplets are supercooled below zero degrees Celsius but remain in liquid form until they encounter an impurity. The discussion concludes with the different types of ice precipitation, including snow, snow grains, snow pellets, sleet, and hail, each with unique characteristics and formation processes.

05:00

❄️ Varieties and Intensity of Precipitation

The second paragraph delves into the varieties of precipitation, focusing on the size and formation conditions of different types. It explains that hail forms under conditions of high instability and strong updrafts within cumulonimbus clouds, where ice pellets rise and fall, colliding with supercooled water droplets and growing in size. The intensity of precipitation is measured by the amount that falls within an hour, with slight precipitation being less than 0.5 millimeters per hour, moderate between 0.5 and 4 millimeters per hour, and heavy anything over 4 millimeters per hour. For snow and ice-based precipitation, these measurements are converted into centimeters. The duration of precipitation is categorized as continuous (lasting over 60 minutes), intermittent (no clear breaks within a 60-minute period), or showers (on-off with clear gaps). The paragraph emphasizes the relationship between cloud types and precipitation patterns, with continuous and intermittent precipitation more commonly associated with stratiform clouds and showers with cumuliform clouds. The summary concludes by reiterating the key points about the different types and intensities of precipitation and their relation to atmospheric conditions.

Keywords

💡Precipitation

Precipitation refers to any form of water that falls from clouds back to the Earth's surface. This includes a wide range of phenomena from light drizzle to heavy hail. In the context of the video, precipitation is the central theme, with various types and their characteristics being discussed. The script explains that precipitation occurs when air rises and cools, leading to the formation of water droplets or ice crystals that grow large enough to fall due to gravity.

💡Dew Point

The dew point is the temperature at which air becomes saturated and can no longer hold all the water vapor it contains, leading to condensation. In the video, the dew point is mentioned as the critical temperature at which the air cools down, allowing water vapor to condense and form clouds, which is a precursor to precipitation.

💡Drizzle

Drizzle is a type of precipitation consisting of very fine, light raindrops with a diameter of less than 0.5 millimeters. The script describes drizzle as a mild form of precipitation, often resulting from weaker upward motion of air, and it contrasts it with rain, which has larger droplets.

💡Rain

Rain is a more intense form of precipitation with water droplets larger than drizzle, typically having a diameter larger than 0.5 millimeters but less than 5 millimeters. The video explains that rain is associated with cumuloform clouds and more intense upward motion of air, which allows the water droplets to grow larger before falling to the Earth's surface.

💡Updrafts

Updrafts are currents of air that move upward, often causing the cooling and condensation of water vapor into clouds. The script discusses how the intensity of updrafts affects the size of water droplets that form precipitation, with stronger updrafts leading to larger droplets that can fall as rain.

💡Freezing Drizzle and Freezing Rain

Freezing drizzle and freezing rain occur when supercooled water droplets fall and freeze upon contact with surfaces. The video mentions these types of precipitation as a special case where the temperature is below freezing, but the water remains in liquid form until it encounters an impurity or a cold surface, at which point it freezes.

💡Snow

Snow is a form of precipitation that occurs when water falls as ice crystals. The script describes different forms of snow, including snowflakes, snow grains, and snow pellets, each with distinct sizes and characteristics. Snow is generally associated with colder temperatures and can come from various cloud types depending on atmospheric conditions.

💡Sleet

Sleet is a type of precipitation that is a mixture of rain and snow, or ice pellets. It forms when raindrops freeze before reaching the ground or when snowflakes partially melt and refreeze. The video explains that sleet can vary in size and shape and is not restricted to any particular type of cloud, but rather depends on the temperature profile of the atmosphere.

💡Hail

Hail is a form of precipitation that consists of balls or lumps of ice that form in strong thunderstorms. The script describes the process of hail formation, where ice pellets are carried aloft by powerful updrafts, accumulate layers of ice, and grow in size through repeated cycles of freezing and rising. Hail requires intense updrafts and is associated with cumulonimbus clouds.

💡Intensity of Precipitation

The intensity of precipitation refers to the rate at which it falls, measured in millimeters per hour. The video categorizes precipitation into slight, moderate, and heavy, based on this rate. For example, slight rain is less than 0.5 millimeters per hour, while heavy rain is more than 4 millimeters per hour. This concept is crucial for understanding the potential impact of precipitation on the ground.

💡Duration of Precipitation

The duration of precipitation describes how long it lasts, with the video mentioning continuous, intermittent, and shower types. Continuous precipitation lasts more than 60 minutes without a break, intermittent precipitation occurs with no clear breaks but is not continuous, and showers are on-off periods with clear gaps of no precipitation. These terms help describe the pattern and persistence of rainfall events.

Highlights

Precipitation is any form of water that falls from clouds back to the earth's surface, ranging from light drizzle to large hailstones.

Drizzle is characterized by very fine water droplets with a diameter of less than 0.5 millimeters.

Rain is distinguished from drizzle by having droplets larger than 0.5 millimeters, up to about 5 millimeters.

The size of precipitation droplets is influenced by the intensity of upward air motion; stronger updrafts lead to larger droplets.

Cumuloform clouds, associated with unstable conditions and more rising air, typically produce rain.

Stratiform clouds, with less rising air, are more likely to produce drizzle.

Freezing drizzle and freezing rain occur when supercooled droplets below zero degrees Celsius remain in liquid form until they encounter an impurity.

Snowflakes are a type of ice precipitation that can vary greatly in size, typically a few centimeters.

Snow grains are small ice particles about one millimeter or less in diameter.

Snow pellets are round balls of ice about five millimeters in size.

Sleet is a mixture of rain and snow, or partially melted snowflakes, and can come from various types of clouds.

Hail forms in cumulonimbus clouds with significant rising air, where ice pellets rise and fall, colliding and accumulating layers of ice.

The intensity of precipitation is categorized as slight, moderate, or heavy, based on the amount of precipitation falling in an hour.

Slight rain or drizzle is less than 0.5 millimeters per hour, moderate is between 0.5 and 4 millimeters per hour, and heavy is over 4 millimeters per hour.

For snow and ice-based precipitation, intensity is measured in centimeters per hour, with slight at 0.5 centimeters per hour and moderate up to 4 centimeters per hour.

Precipitation duration is described as continuous (over 60 minutes), intermittent (no clear breaks within 60 minutes), or in showers (on-off blocks of time).

Continuous and intermittent precipitation are more commonly associated with stratiform clouds, while showers are linked to cumuliform clouds.

Transcripts

precipitation is anything that falls

from a cloud back down to the surface of

the earth and it can be as mild as a bit

of light drizzle or as intense as large

heavy hail stones how do we know when to

call it rain or drizzle though and what

is the difference between a light shower

and a moderate shower

let's find out

[Music]

hi i'm grant and welcome to the seventh

class in the meteorology series where

we're going to be taking a quick look at

the various types of precipitation that

fall from the clouds back down to the

surface of the earth precipitation is

formed when rising air cools down to

below the dew point

and the air becomes fully saturated and

clouds are formed it's basically

suspended precipitation at this

point the suspended water droplets or

ice crystals will then fall down back to

earth as precipitation

if they grow large enough and heavy

enough for gravity to pull them down at

a stronger rate than the air is rising

up

this means that the more the air is

rising the larger these water molecules

these water droplets sorry will have to

become to overcome this rising force for

the gravity to pull them down water

droplets or ice crystals will grow

larger by basically colliding into each

other and combining in size

water droplets falling as precipitation

fall into two camps based on the size of

the droplets

if they are small and have a diameter of

less than 0.5 millimeters then this type

of precipitation is known as drizzle

if it is larger than this we call it

rain which has an upper limit of around

5 millimeters

any larger than this and they tend to

break apart into smaller droplets anyway

generally speaking the more intense the

upward motion of the air the more

updrafts the more rising air that we

have the bigger the droplets need to

grow in order to be pulled down to the

earth by the gravity and overcome that

rising air

so you could say that rain

generally comes from cumuloform clouds

the clouds associated with unstable

conditions and more rising air

and then stratiform stable sort of

clouds

with a lot less rising air are more

likely to produce drizzle

it's important to note that we also have

precipitation called freezing drizzle

and freezing rain which is when the

drizzle or rain droplets are supercooled

to below zero degrees celsius but still

in liquid form

this happens because normally ice

crystals form around impurities in the

air like dust

particles and or

other impurities

if the air is very pure that has very

few impurities then the supercooled

droplets can form

and then when these droplets come into

contact with an impurity such as an

aircraft then they will form into ice

crystals and we need to think about

anti-icing the aircraft basically

when the temperature in the cloud is

cold enough to form ice then the

precipitation will fall from the cloud

as ice but it may melt as it heats up

and descends down back to earth there

are a few types of ice precipitation

such as snow snow comes in a few forms

you can think of the typical snowflakes

as being

a few centimeters in size there's

actually so much variance with

snowflakes

um in terms of their size that can be

you know huge or tiny or a range of

things in between but generally a few

centimeters seems about accurate

then you have snow grains which are very

small particles about one millimeter or

less in diameter and then you would have

snow pellets which are like round balls

um around five millimeters in size

and there's no

rule in terms of if this is going to

come from

stratform clouds or cumuloform clouds

there's going to be different levels of

rising air and and it just has to be

cold essentially for snow to form you

also have sleet which is a combination

of rain and snow or it can be snow that

has fallen down and partially melted on

the way down or some of the parts have

melted on the way down so you get a

combination of both water and ice

again this is no strict rule on if this

is going to come from cumuloform or

stratiform clouds it's going to be

different levels of rising air and what

will happen is just the particle size

will tend to be different if you've got

more

stable conditions it'll be smaller

particles more unstable conditions it's

going to be larger particles you also

have hail

which forms when an ice pellet such as

this

rises and falls within a cloud that has

a lot of rising air such as a big

cumulonimbus cloud

as the ice

grows it falls and collides with more

supercooled water droplets or ice

particles on the way down through the

cloud then the rising air sends it back

up to the top

and it falls down again and it gathers

these layers and layers and layers of

ice

so this requires a lot of rising air

this is very high levels of rising air

very unstable conditions very cumuliform

clouds you will get hail in

and hail can grow huge there's

loads of photos online of

massive

hill drops that are the size of tennis

balls and you know even larger than that

so hail pretty serious precipitation if

it can get

because it can get so large basically

intensity of precipitation is measured

in terms of slight moderate and heavy

and it's the amount of precipitation

that falls in an hour

so you can think of rain and slight

as being less than 0.5 millimeters this

is rain or drizzle just water-based

basically

moderate would be between 0.5 and 4

millimeters per hour

and heavy would be anything more than 4

millimeters per hour

and then when you move on to the

ice and snow based precipitation you

basically convert these into centimeters

so slight

snow showers or slight snow would be

0.5 centimeters

per hour

moderate would be 0.5 centimeters to 4

centimeters per hour and heavy would be

anything more than four centimeters per

hour the duration of the precipitation

is described in terms of continuous

which means it lasts more than 60

minutes

intermittent which would mean in a 60

minute period there's no real clear

breaks but it's not continuous the whole

time

or shower which is just on off in blocks

of time

with clear gaps of when there's no

precipitation and clear gaps where there

is precipitation you can think of

continuous and intermittent as

associated more with stratiform clouds

and showers on off sort of precipitation

as more

associated with cumuliform base clouds

like cumulonimbus or cumulus clouds in

general

to summarize then a nice quick class

today short and sharp

you've got different types of

precipitation drizzle

is water that is less than 0.5

millimeters in diameter rain is water

that is less than five millimeters in

diameter

you've got snow in a few forms you've

got the flakes the grains and the

pellets

flakes can be a few centimeters in size

the grains would be about one millimeter

or less and pellets are around five

millimeters

you get sleet which can be various

shapes and sizes it's a combination of

both water and

ice based precipitation so it could be

drizzle and

ice grains for example or ice pellets

and it can also be

caused by

um ice space particles falling down

warming up and some of them melting on

the way down

you also get hail which again can be

various sizes tiny little particles all

the way up to big

tennis ball size things that you get in

some places with extreme weather

and this happens when an ice pellet will

fall and rise within a cloud

colliding with more and more super

cooled water droplets or ice particles

on the way down and it gets sent back up

to the top repeats the process over and

over again gaining layers and layers of

ice and growing in size

and a rule of thumb is the bigger the

droplets the more rising air you have so

think about hail getting all the way up

to that tennis ball size that's going to

be a huge droplet it's not really a

droplet because i suppose a drop is just

of water

but that has a really

high amount of rising air and then

drizzle not that much rising here very

small droplets in terms of intensity

it's all per hour so you get slight

which is 0.5 millimeters per hour

moderate 0.5 to 4 millimeters per hour

and heavy is more than four millimeters

per hour that would be in terms of the

water-based ones rain and drizzle and

then for the snow and ice based ones you

just use centimeters so slight snow or

moderate snow would be 0.5 centimeters

to 4 centimeters and then the duration

if it's anything more than 60 minutes or

60 minutes or more you would call it

continuous precipitation

if it's intermittent it's

kind of a weird one because it's not

continuous

but it's also not as defined as showers

so it's not all the time but there's no

large breaks in the precipitation

and showers are defined on off blocks of

precipitation so if you had a

a moderate rain shower

you would say that there's five

millimeter sized

droplets

there is 0.5 to 4 millimeters depth of

them after an hour and it was on off

throughout that whole hour there was it

wasn't a single period where it was

raining the whole hour it was on off on

off