ATPL Meteorology - Class 7: Precipitation.
Summary
TLDRThis 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
- π§οΈ Precipitation is any form of water or ice that falls from clouds to the Earth's surface, ranging from light drizzle to heavy hail.
- π§ Drizzle is characterized by very small water droplets with a diameter of less than 0.5 millimeters.
- π¦οΈ Rain consists of larger droplets, with diameters greater than 0.5 millimeters and up to 5 millimeters.
- βοΈ Snow can take various forms including snowflakes, snow grains, and snow pellets, each with different sizes.
- π¨οΈ Sleet is a mix of rain and snow, or partially melted snow, and can vary in size and shape.
- βοΈ Hail forms in strong updrafts within cumulonimbus clouds, where ice pellets rise and fall, colliding and accumulating layers of ice.
- π¬οΈ The intensity of precipitation is measured by the amount that falls in an hour, with categories of slight, moderate, and heavy.
- β±οΈ 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).
- π Cumuloform clouds, associated with unstable conditions and more rising air, are more likely to produce rain and hail.
- π«οΈ Stratiform clouds, with less rising air, are typically linked to drizzle and are associated with stable atmospheric conditions.
- βοΈ 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
π§οΈ 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.
βοΈ 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.
Mindmap
Keywords
π‘Precipitation
π‘Dew Point
π‘Drizzle
π‘Rain
π‘Updrafts
π‘Freezing Drizzle and Freezing Rain
π‘Snow
π‘Sleet
π‘Hail
π‘Intensity of Precipitation
π‘Duration of Precipitation
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
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