GEOGRAPHY GRADE 12| SUBTROPICAL ANTICYCLONES |LINE THUNDERSTORMS|COASTAL LOW|BERG WINDS |MADE SIMPLE

Summary

The video script offers an in-depth exploration of subtropical anticyclones and their associated weather patterns, focusing on their impact on South Africa. It covers the formation and characteristics of three main anticyclones: the South Atlantic, the Kalahari, and the South Indian, detailing how they influence the country's weather, particularly the production of warm moist air from the Indian Ocean and cold dry air from the Atlantic Ocean. The script delves into the effects of ocean currents, topography, and latitudinal position on South Africa's climate. It also discusses the phenomena of the inversion layer and its role in preventing warm moist air from the Indian Ocean from penetrating the interior during winter, leading to stable and sunny weather. The impacts of line thunderstorms, coastal lows, and Berg winds are examined, including their positive and negative effects on the region, such as water restoration, nitrogen fixation, flooding, property damage, and the encouragement of veld fire spread. Strategies to combat these impacts, like wetting the soil and evacuating people and livestock, are suggested. The script emphasizes the importance of understanding these weather systems for predicting and preparing for their effects.

Takeaways

• 🌍 The video discusses subtropical anticyclones and their associated weather conditions, focusing on South Africa's weather system.
• 🌀 Three main factors affect South Africa's weather: ocean currents, topography, and the country's latitudinal position.
• 🔥 The warm Mozambique Current and the cold Benguela Current are significant ocean currents influencing the region's climate.
• 🏞️ The topography of South Africa, including the high plateau and escarpments, plays a crucial role in the country's weather patterns.
• 🌡️ South Africa is situated in the subtropical high-pressure belt, leading to the formation of three anticyclones.
• ⏱️ The strength of the Kalahari High, one of the anticyclones, changes with the seasons, affecting the country's weather.
• 🌦️ The inversion layer, formed by the interaction of warm moist air and cold air, acts as a barrier to cloud formation and rainfall.
• ⚡️ Line thunderstorms are a summer phenomenon in South Africa, bringing both positive impacts, like water restoration and nitrogen fixing, and negative impacts, such as flooding and property damage.
• 🌊 Coastal lows are low-pressure systems that develop year-round and move along the coastline, influencing weather conditions with onshore and offshore winds.
• 🍂 Berg winds, or hot and dry winds, result from the interaction between the Kalahari High and coastal lows, leading to uncomfortable conditions and an increased risk of wildfires.
• 🛡️ Strategies to combat the negative impacts of weather phenomena include wetting the soil to prevent fire spread, evacuating people and livestock, and ensuring emergency services are well-equipped and efficient.

Q & A

What are the three factors that affect South Africa's weather?

The three factors that affect South Africa's weather are ocean currents, the topography of the country, and the latitudinal position of the country.

What are the two different ocean currents mentioned in the script and what are their effects?

The two different ocean currents are the warm Mozambique current and the cold Benguela current. The Mozambique current on the eastern side of the country is responsible for high temperatures and the production of warm moist air after evaporation, while the Benguela current on the western side results in the production of cold dry air.

What is the significance of the Kalahari High's position during different seasons?

The position of the Kalahari High changes with the seasons. During winter, it is strong with a high pressure system, leading to stable and sunny weather in the interior. In summer, it is weak with low pressure, allowing warm moist air from the Indian Ocean to penetrate inland, leading to rainfall and thunderstorms.

Line thunderstorms form during summer when warm moist air from the South Indian High meets cold dry air from the South Atlantic High along a moisture front. The impacts include heavy rainfall leading to water restoration in dams, nitrogen fixing which acts as a natural fertilizer, but also negative impacts such as flooding, property damage from hail, and potential injuries or fatalities from lightning.

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What is the Coastal Low and how does it affect the weather conditions along the coast?

The Coastal Low is a low-pressure system that develops along the coast and moves from west to east. It brings different weather conditions on either side; on the western side, it brings cold dry air from the Atlantic Ocean, while on the eastern side, it brings warm moist air from the Indian Ocean, leading to rainfall.

What are Berg winds and how do they form?

Berg winds are hot and dry winds that develop in winter as a result of the interaction between the strong Kalahari High and a coastal low. As air moves from the high pressure Kalahari High towards the coastal low, it descends the escarpment, warming up adiabatically and losing moisture, resulting in hot and dry conditions at the coastal settlements.

What is the inversion layer and how does it impact the weather during winter and summer?

The inversion layer is a layer where the temperature increases with increasing height, which is the opposite of the normal decrease in temperature with height. During winter, the strong subsidence of cold air from the Kalahari High pushes the inversion layer down, preventing warm moist air from the Indian Ocean from penetrating inland and resulting in stable sunny weather. In summer, the inversion layer is lifted above the escarpment, allowing warm moist air to rise, cool, and form clouds, leading to rainfall.

How do the three anticyclones in South Africa affect the country's weather?

The three anticyclones—the South Atlantic, Kalahari, and South Indian—create high pressure systems that influence the country's weather. The South Atlantic anticyclone brings cold and dry air, the Kalahari anticyclone is strong in winter and weak in summer, and the South Indian anticyclone brings warm and moist air. Their movement and strength change with the seasons, affecting weather patterns such as rainfall and temperature.

What is the role of the intertropical convergence zone (ITCZ) in the migration of weather systems?

The ITCZ moves northwards and southwards depending on the season, following the hemisphere that experiences summer. As the ITCZ moves, it drags along weather systems such as cyclones and anticyclones. This migration affects the proximity of these systems to South Africa, influencing the country's weather during different seasons.

What strategies can be used to combat the negative impacts of Berg winds?

To combat the negative impacts of Berg winds, strategies include wetting the soil to prevent fire spread, evacuating people and livestock to safer areas, ensuring emergency services are well-equipped and efficient for a quick response, and providing sufficient water to fight fires and hydrate victims.

How can one identify the three anticyclones on a synoptic or satellite image?

On a synoptic weather map, anticyclones are represented by an 'H' indicating high pressure. The South Atlantic anticyclone can be identified by its position on the Namibian coast or the Atlantic Ocean. The Kalahari anticyclone is located in the interior on the plateau and is usually strong during winter. The South Indian anticyclone is situated on the Indian Ocean and will show anticlockwise movement of air. On satellite images, one would look for specific cloud formations and weather patterns associated with each anticyclone.

Outlines

00:00

🌍 Introduction to Subtropical Anticyclones

The video begins with an introduction to subtropical anticyclones, discussing their formation and associated weather conditions. It emphasizes the importance of understanding the factors affecting South Africa's weather, such as ocean currents, topography, and the country's latitudinal position. The warm Mozambique current and the cold Benguela current are highlighted for their roles in creating warm moist air from the Indian Ocean and cold dry air from the Atlantic Ocean, respectively.

05:01

🌀 Characteristics and Formation of Anticyclones

The second paragraph delves into the characteristics of anticyclones, explaining that they form due to sinking air which creates high pressure. The South Atlantic anticyclone, situated on the Namibian coast, is identified as the strongest of the three anticyclones due to its association with cold air. The effects of the anticyclones' movement, particularly during the summer, are also discussed, including their impact on the country's weather.

10:02

🔥 Kalahari Anticyclone and Its Seasonal Variations

The Kalahari anticyclone, located in the country's interior, is described as being weak during summer due to weak subsidence and strong during winter due to strong subsidence. The paragraph explains how the Kalahari anticyclone's strength changes with the seasons, influencing South Africa's weather patterns, particularly the formation of an inversion layer that affects the movement of warm moist air from the Indian Ocean.

15:02

🌬️ Impact of Kalahari High on South African Weather

This section discusses the Kalahari High's impact on South Africa's weather, particularly during winter and summer. The strong subsidence during winter leads to stable, sunny weather due to the inversion layer acting as a barrier to warm moist air. In contrast, during summer, the weak subsidence allows the inversion layer to lift, enabling warm moist air to penetrate the interior and result in rainfall and thunderstorms.

20:03

⚡ Positive and Negative Impacts of Line Thunderstorms

The video outlines the positive and negative impacts of line thunderstorms, which occur during summer. Positive aspects include water restoration in dams and nitrogen fixing through lightning, which acts as a natural fertilizer. Negative impacts include the potential for flooding and property damage due to hail and lightning. The formation of line thunderstorms is linked to the interaction between the South Atlantic High and the South Indian High, leading to the development of a moisture front and subsequent thunderstorm activity.

25:03

🌊 Coastal Low and Its Effects on Weather Conditions

Coastal lows are discussed as another type of traveling disturbance that can develop in both summer and winter. These low-pressure systems move along the coastline from west to east, causing different weather conditions on either side. On the eastern side, warm moist air from the Indian Ocean can lead to rainfall, while the western side experiences warm dry conditions due to offshore winds. The paragraph also addresses how to identify coastal lows in synoptic weather maps.

30:05

🔥 Formation and Impact of Berg Winds

Berg winds, or B winds, are hot and dry winds that develop in winter due to the interaction between the strong Kalahari High and a coastal low. As air moves from the high pressure towards the low pressure, it descends and warms up adiabatically, losing moisture and resulting in hot and dry conditions. These winds can lead to the spread of veld fires, property destruction, loss of livestock and equipment, and even loss of life. Strategies to combat these impacts include wetting the soil to prevent fire spread, evacuating people and livestock, and ensuring emergency services are well-equipped and efficient.

35:08

✅ Conclusion and Preview of Upcoming Topic

The video concludes with a summary of the concepts covered under subtropical anticyclones and associated weather patterns. It stresses the importance of understanding these weather phenomena and their impacts. The host also previews the next topic, which will be valley climates, and encourages viewers to apply the foundational principles discussed throughout the series.

Keywords

💡Tropical Cyclones

Tropical Cyclones are rotating, organized systems of clouds and thunderstorms that form over warm oceans and exhibit the characteristics of intense low pressure. In the video, they are mentioned in the context of previous content where general characteristics, formation areas, and necessary factors for their formation were discussed, setting a foundation for understanding other weather phenomena.

💡Subtropical Anticyclones

Subtropical Anticyclones are large areas of high atmospheric pressure that rotate in a clockwise direction in the Southern Hemisphere. They are characterized by sinking air, leading to clear skies and stable weather conditions. In the video, they are a central topic, with the discussion focusing on their impact on South Africa's weather and how they form due to the country's latitudinal position.

💡Ocean Currents

Ocean Currents are the continuous, directed movement of seawater generated by various factors including wind, temperature, and salinity. The video discusses two significant currents affecting South Africa: the warm Mozambique Current and the cold Benguela Current, which play a crucial role in determining the country's climate by influencing the production of warm moist air from the Indian Ocean and cold dry air from the Atlantic Ocean.

💡Topography

Topography refers to the physical and structural features of the landscape, which can influence climate and weather patterns. The video describes South Africa's topography as a high plateau with escarpments, which affects the movement of air masses and contributes to the formation of weather phenomena such as the inversion layer.

💡Latitudinal Position

A region's latitudinal position refers to its location relative to the equator, which affects the climate due to variations in the angle of sunlight and the presence of climatic zones. South Africa's position along the 30° South latitude places it within the subtropical high-pressure belt, leading to the formation of anticyclones.

💡Inversion Layer

An Inversion Layer is a layer of the atmosphere where temperature increases with an increase in altitude, which is the opposite of the normal decrease in temperature with altitude. In the video, it is explained that this phenomenon prevents warm moist air from the Indian Ocean from penetrating the interior during winter, leading to stable and sunny weather conditions in South Africa's interior.

💡Traveling Disturbances

Traveling Disturbances are meteorological phenomena that move across the landscape, affecting weather conditions as they pass. The video discusses three types: line thunderstorms, coastal lows, and Berg winds. These disturbances are significant for their impact on weather, such as causing rainfall, storms, and in the case of Berg winds, contributing to fire hazards.

💡Line Thunderstorms

Line Thunderstorms are a type of severe weather phenomenon that occurs during the summer. They form along a moisture front where warm moist air from the Indian Ocean meets cold dry air from the Atlantic Ocean, leading to the lifting of the warm air, condensation, and the formation of towering cumulonimbus clouds that result in heavy rainfall and thunderstorms, particularly on the eastern side of the front.

💡Coastal Low

A Coastal Low is a low-pressure system that forms along the coastline and moves from west to east. It is characterized by a clockwise rotation of air in the Southern Hemisphere, leading to different weather conditions on either side of the system. The Coastal Low brings cold dry air inland on one side and warm moist air on the other, influencing the local weather and potentially causing rainfall on the eastern side.

💡Berg Winds

Berg Winds are hot and dry downslope winds that occur in winter as a result of the interaction between the strong Kalahari High and a coastal low. As air descends from the high plateau towards the coast, it warms adiabatically and loses moisture, leading to uncomfortable and hazardous conditions that can increase the risk of wildfires, affecting human settlements, the environment, and agriculture.

💡Pressure Gradient

The Pressure Gradient is the difference in atmospheric pressure over a certain distance, which influences the movement of air from high-pressure areas to low-pressure areas. In the context of the video, the pressure gradient is discussed in relation to the movement of air from the South Atlantic High and the South Indian High towards the thermal low in the interior of South Africa during summer, contributing to the formation of line thunderstorms.

Highlights

The video discusses subtropical anticyclones and their associated weather conditions, including traveling disturbances like line thunderstorms, coastal low-pressure cells, and South African back winds.

Three main factors affecting South Africa's weather are identified: ocean currents, topography, and the country's latitudinal position.

The warm Mozambique current and the cold Benguela current are key ocean currents influencing South Africa's climate.

The topography of South Africa, featuring a plateau and escarpments, plays a significant role in the country's weather patterns.

South Africa is situated in the subtropical high-pressure belt, leading to the formation of three anticyclones.

The South Atlantic anticyclone is the strongest of the three due to its association with cold air from the Atlantic Ocean.

The Kalahari anticyclone, located on the plateau, is weak during summer and strong during winter due to variations in subsidence.

The South Indian anticyclone brings warm and moist air from the Indian Ocean, influencing South Africa's eastern weather.

The intertropical convergence zone (ITCZ) affects the movement of anticyclones and other weather systems, following the summer hemisphere.

Line thunderstorms occur only in summer due to the interaction between the South Atlantic High and the South Indian High.

Coastal lows are low-pressure systems that develop year-round and move along the coastline from west to east.

Berg winds are hot and dry winds that form during winter as a result of the interaction between the Kalahari High and a coastal low.

The inversion layer, formed by the meeting of warm moist air and cold air, plays a critical role in South Africa's weather, particularly in the impact of the Kalahari High.

During summer, the Kalahari High's position above the escarpment allows warm moist air to penetrate the interior, leading to rainfall and thunderstorms.

The impact of line thunderstorms includes both positive aspects, such as water restoration and nitrogen fixing, and negative aspects, like flooding and property damage.

Strategies to combat the impact of Berg winds include wetting the soil, evacuating people and livestock, and ensuring emergency services are well-equipped and efficient.

The video emphasizes the importance of understanding the foundational principles of meteorology to grasp the concepts of subtropical anticyclones and their weather impacts.

Transcripts

hi again then welcome back to our grade

12 Geographic cap series I'd like to

thank you for tuning in and I hope this

video will make things as simple as

possible for you in the previous video

guys we went through tropical Cyclones

we covered the general characteristics

areas where tropical Cyclones form

factors necessary for their formation

everything okay so every single detail

or concept that you have to master you

have to know under tropical Cyclone so

if you haven't watched that video or

those videos because they actually

videos please do so they are in the

playlist of the geography caps Series so

for this video guys we are going to

cover the subtropical anticyclones and

the associated weather conditions so

we'll look at every concept that is

under subtropical anticyclones that is

also including the traveling

disturbances which are your line

thunderstorms Coastal low pressure cells

and the South African back WIS okay

their impacts their strategies we'll

also take a look at how you identify

these on a synoptic and satellite image

the most important thing is the

foundation right so we have to start

with the factors that affect South

Africa's weather and there are three of

those which is the ocean currents the

Topography of the country and also the

latitudinal position of the country so

let's start with currents there are two

different currents that we have and that

is the warm mozic current and the cold

bangua current okay so some of you may

ask what are currents so simply guys

current actually describes the movement

of an ocean or you may say that a

current is actually a fluid within a

fluid or a moving or the movement of a

fluid within another fluid or within the

same fluid okay a simple example guys

when you have a kettle H let's say your

Kettle is transparent you can see

through everything so you can see the

water movement and so on and so on so

when you switch on your Kettle and and

when the water is about to Bow you'd

find out that there are shooting

currents so currents that actually water

that is moving uh shooting upwards like

that okay those uh movements of water

within this volume of water that is what

we call currents okay we see that on a

bigger scale so you have the war mozic

current that is on the Eastern side of

the country that is in the Indian Ocean

okay this current is responsible

for the high temperatures of the Indian

Ocean it is responsible for the

production of warm moist air after

evaporation of the Indian Ocean so after

evaporation the Indian Ocean produces

warm and moist air okay remember it's an

ocean so it has to be moist and it's

warm okay so the warm mozic current is

the reason why we have warm moist air

that is produced on the the Eastern

ocean of the country and then on the

western side we have the cold benguela

current and it is of course on the

Atlantic Ocean this results in the

production of cold dry air okay let me

use blue you have cold dry air moving

Inland and this of course these uh two

ms's affect the South African weather as

we will explore and discuss that so we

have cold dry air from the Atlantic

Ocean and warm moist air from the Indian

Ocean due to these two different

currents so let's keep that in mind okay

the second factor that affects South

Africa's weather is the Topography of

the country so that means we are

referring to the shape of the land this

is to say if I were to draw a

crosssection across the country so I'm

drawing it from X here all the way to Y

there okay so I draw a cross-section I

want to figure out how does the land

change how is it shaped well the result

I'm going to get looks something like

this so i' find that as I'm moving

towards Inland the interior of the

country I'm actually going up in height

and when I get to the interior I am on

top of this High Ling flat mountain

which we call the plateau okay so this

is the plate and on the sides of the

plate okay so you see these big bumps on

the side of on either side of the

plateau those big bumps is what we call

escapements so there we go so we have

those escapements on either side of the

plateau as you can see and as you move

away from the interior towards the coast

of course the altitude drops okay so

this is critical guys because as you

will see this influences South Africa's

weather and winter and and in summer

okay as we will explore and then the

third factor that affects South Africa's

weather is the latitudinal position of

the country where is the country

situated or located in terms of of of

its latitude so the country is actually

situated over the

30° latitude 30° South so that is the

subtropical high pressure belt uh so if

you remember your geography well guys

from um grade 10 and 11 you should be

able to understand that okay and this

results in the formation of three

anticyclones that we are going to

discuss in this video so because of the

latitudinal position of sa which means

that it is situated along the which is

situated along the subtropical high

pressure belt this results in the

formation of three anticyclones the

three anticyclones and before we

actually get into that let's first

discuss because let's remind ourselves

of an anticyclone guys what did we say

are the characteristics of an anti

Cyclone okay so an anticyclone forms as

a result of sinking air so you have air

that is

sinking and it is putting pressure of

course against the ground and hence you

form an area of high pressure so

anticyclones and High Press cell those

are the same things okay and so as of

course we discussed in the very first

video of this geography series we found

that um there's

anticyclonic movement of air okay um

inside this anticyclone so as it is uh

sinking down is actually rotating

anticlockwise okay and as it sinks down

guys we said that it actually gets

warmer and warmer okay so we start to

see

warm air As you move towards the surface

which is what we call adiabatic warming

and we said that there's no condensation

that occurs in high pressure cells and

hence we see a calm weather we see a

sunny weather no cloud formation so

there's zero cloud cover and of course

as I said guys we see um anticlockwise

movement of air okay and we also see the

surface uh Divergence okay so if you

haven't watched that video guys please

do it's the very first video of this

series okay so let's get into it then so

these are the three anticyclones that we

are referring to okay so we'll start

with this one that is on the western

side of the country this anticyclone is

situated on the namibian coast and U you

can also say it is situated on the

Atlantic Ocean and this anticyclone is

the South Atlantic anticyclone okay it's

very important guys that you remember

the name of the anticyclone okay so that

you can be able to identify it they do

ask you to name it okay so it's very

critical that you understand the

position of each one of them the

location of them and of course they

names okay so that means within this we

see anticlockwise movement of air okay

so we have air uh moving away from these

high pressure cells okay so it can also

move inwards okay so air that is moving

from the ocean towards the land we call

it onshore winds and remember air from

the South Atlantic anticyclone is cold

and it's dry okay has little moisture

cold air tends to retain very little

moisture guys okay we also see that

South Atlantic anticyclone can sometimes

move okay um all of them actually can

move um we'll talk talk about that but

when it actually does move southwards

okay which usually happens during the

summer you'd find that it can actually

block the mid latitude cyclone from from

affecting the country right so it can

actually block this mid latitude cyclone

from entering Inland and so when it

blocks the mid latitude cyclone we say

that it reaches okay so we call it ring

okay that's it moving further southwards

and hence blocking the mid latitude

cyclone from entering into Inland okay

okay so we also have another type of

anticyclone that is situated on the

interior of the country okay and by the

way the South Atlantic anticyclone is

the strongest of the three okay because

it has cold air okay because it's

associated with cold air cold air that

is used by the Atlantic Ocean presses so

cold air presses or puts a higher

pressure on the ground than relatively

warmer air okay and so because this is

the South Atlantic anticyclone is

associated with cold air and hence it is

the strongest of the three now in the

interior we have another anticyclone

which we call the

Kari anticyclone okay so this is in the

interior it's actually on the

plate situated on the plate so the plate

that we referring to there so you

actually have the Kalahari that is

present over the plateau during a

particular season that we will discuss

so the Kalahari anticyclone okay so you

can say anticyclone or high pressure so

it really has multiple terms okay so

this is on the interior of the country

and it's weak during the summer very

weak because there's weak subsidence and

during the the winter is actually strong

because there's strong subsidence and

for those of you who don't know

subsidence guys we're actually referring

to a sinking down okay so if it is

strong subsidence that means you have

cold air that actually pushes against

the ground cold air creates a strong

subsidence a strong uh sinks strongly

and presses against the ground puts a

lot of pressure against the ground okay

so this happens during the winter when

you have cold air during the summer

there's weak subst okay we'll discuss

this don't worry about that now and then

on the Eastern side you actually have

the South Indian anticyclone as you can

see guys situated on the Indian Ocean

and of course it brings because it is in

the Indian Ocean C this there will be

anticlockwise movement from this high

pressure okay which means that you are

going to have onshore winds but they

will be warm and moist so warm and moist

air will come from the north okay from

the Northeast and cold and dry air gets

in from the southwest okay so okay I

need you to note that right so these are

the three anticyclones and their

locations and some of their

characteristics okay it's very important

that you understand this okay so um we

talked about the location uh we talked

about reaching okay and so when it comes

to migration guys we mean that all of

these um anticyclones are not stationary

they do move okay so due to the ITC that

migration northward migration so during

winter right so let me just

throw okay this so the itz which is the

intertropical convergence so I'm not

sure if I did uh talk about that uh

discussed that in the tropical cyclone

and mid Cyclone videos but if did not I

apologize for that and so the

intertropical convergence so moves um

northwards and southwards depending on

the season of that particular hemisphere

the itcz follows summer so it follows

the hemisphere that has sum okay or in

which there is sum so if there is sum in

the Northern Hemisphere and there is

winter in the southern hemisphere that

means the intertropical Convergence Zone

will move towards the north okay so if

it moves towards the north it drags

along with it all of the um of the

weather systems so your Cyclones okay

your M latitud Cyclones your tropical

Cyclones your

anticyclones um all of them move towards

the North and of course when it is

summer in the southern hemisphere the

intertropical conversion Zone moves

further south okay so if it moves

further South that means all of those

weather systems also move further south

okay so they follow the intertropical

converence so so of course as you might

imagine these become closer during

winter because during winter that would

mean it is summer in the northern

hemisphere and hence the itcz will move

to the north dragging along with it

these anticyclones and hence if they

were here okay at the beginning um then

they will move further north to this

current position that they are in now

okay so this makes them closer to the

land and hence they are able to affect

South Africa during the winter okay so

very prominent during the winter okay

this is not to say they do not affect

the country during summer okay but we do

see a lot of interaction during winter

Okay so we've covered that and so we

also covered this Kalahari strength

which changes of course as I said weak

in summer strong in Winter okay so those

are the three anticyclones guys okay so

let's move on then to the Kalahari High

pressures impact on South Africa's

weather and before we actually get into

that here I think it's critical that we

first discuss this phenomenon which we

call the inversion layer what happens is

that okay I think I did explain this in

one of the past videos okay but I don't

mind doing that again so the Indian

Ocean of course so this is a

cross-section from this area to there

okay so it's a cross-section it views

the side view um of this area okay or

the the cross-section of this area so we

know that there is a plateau in the

interior and there is an escapement

there and so we know that there is also

warm moist air that is coming in Inland

from the Indian Ocean so what happens is

that when you have this warm moist air

this warm moist air tends to rise up

okay so it rises along the escarment so

you'll have warm moist air Rising along

the escarment like that okay there we go

and so as it rises we know that air

cools down guys right so as this warm

air rises it actually cools down so it

becomes cooler and cooler

right

okay and we also have because of the

Kalahari High we also have cold air okay

we also have sinking air okay sinking

air as we said and as sinking air sinks

or descends what happens to it

guys okay so as air sinks we said that

it actually warms up okay so you have

warm you have cold air becoming warmer

and warmer duee to a diabatic warming

and so now this air warms up okay warms

up as it is sinking down it warms up

becomes warmer and warmer as you can see

right and so now looking at this section

okay if we can just observe this

particular section here okay so in this

section you actually find out

that as you are let's say this was you

rising up the mountain so maybe you were

mountain climbing so as you are rising

up you're actually going to find out

okay that the

temperature actually Rises as the height

Rises up okay normally we know that as

you are rising up a mountain the

temperature drops okay it gets colder

and colder okay that's the normal um

condition right so when then you have

this phenomenon where you have Rising

temperature with Rising height this

layer right here this is the layer that

we call the inversion layer so the

inversion layer is

formed okay it's inverted okay um it's

not normal okay so that's what we call

the inversion layer it's the opposite of

the decreasing temperature with

increasing height but rather now it's um

increasing temperature with increasing

height okay so that's how we form the

inversion layer guys right so let's then

move on okay and discuss the Kalahari's

impact on South African weather okay and

again guys this inversion layer is

critical when you're explaining the

Kalahari High's impact on South African

we so we're saying that during winter

the Kalahari high is strong okay or has

a strong subsidence okay so as you would

see so as you would expect you have cold

air which will sink down okay creating

an area of high pressure so even in

synoptic weather maps you are going to

find there is a strong high pressure so

there will be an H okay so in a synoptic

weather

map okay in the interior of the C you'll

find there is a a high pressure there so

this would be an indication to you that

this is actually winter because that

means that this Kalahari high pressure

right here is strong okay and You' find

that during summer there's actually a

low pressure there okay because there's

Rising air right Rising air puts low

pressure on the ground and hence

creating a low pressure system on the

surface so this is what we call the

thermal Low by the way right and of

course this is the Kalahari being strong

um during winter okay

right so during winter we know that

there is a strong

subsidence of cold air so there's cold

air that is pushing against the ground

it creates an area of high pressure okay

pushing against the

ground right and so as it pushes against

the ground it actually

also results in the inversion layer

being pushed downwards okay so the

inversion layer is being pushed

downwards by this cold by this cold air

mass okay due to this strong subsidence

so it pushes down this inversion layer

below the

escapement okay so this is what happens

during winter those are your first um

points okay you start by uh the strong

subsidence during winter and then cold

air pushing down this inversion layer um

below the escarment

now this means that the warm moist air

that originates from the Indian Ocean

cannot enter through cannot penetrate

through cannot enter and hence affect

the

interior weather okay and hence um

result in um cloud formation and so that

will not happen because now you actually

have this inversion layer which acts as

um which acts as a barrier that prevents

this warm waste air from getting through

to the interior of the country okay so

due to this okay so if of course if the

warm air would be able to get through it

would cause it would rise up it it would

rise up cool down condense form clouds

and result in rainfall but because this

does not happen actually is prevented to

go from going through and hence this

results in a sunny so we we so during

winter we get stable sunny weather okay

remember this cold a is sinking down

it's not rising up and hence because it

is sinking down there is no condensation

that occurs there is no cloud formation

that occurs and hence we see no cloud

cover we see a

sunny weather okay so that's what we see

during winter okay in the interior of

the country right now let's talk about

during summer so in summer what happens

now so in summer you actually have weak

you actually have weak subsidence okay

remember it's summer and so there's more

air rising up than descending down okay

so because it is warm the land heats up

the air air rises up okay and so now

you'd find find out that the Kalahari

high is actually above way above the

escapement okay it has a weak subsidence

and you'll find it in higher altitudes H

because there's war there's more Rising

air than sinking air and hence now this

inversion layer is therefore lifted up

okay so it's therefore lifted up and it

is lifted up above the escapement so as

you can see this inversion layer is

above the escapement and hence the warm

moist air from the Indian Ocean is able

to get through to the interior of the

country okay gets through to the

interior of the country it rises up it

cools down it condenses forms clouds

right and hence this results in

rainfall okay and mind you this air is

actually coming from from the south um

Indian High moving towards the land why

is it going to move towards the land

well because there is an area of low

pressure in the interior there is the

low there is the thermal low in the

interior of course air will want to move

from the high pressure to the low

pressure so this results in an unstable

weather this results in heavy rainfall

this results in thunderstorms so as you

can see during summer that's why we have

a lot of uh

flooding okay on the Eastern side of the

country okay because there's a lot of

rain okay because of this influence of

the Kalahari right so it's very

important that you are able to put it in

words guys okay be able to put it in

words um and also be able to um draw it

okay but when you are drawing it make

sure that you annotate okay make sure

you're right down so warm air cannot

pass through inversion layer is lowered

so on and so on okay right so let's move

on then uh so we move on to the

traveling disturbances so traveling

disturbances there's actually three of

them there's the line thunderstorms

there's Coastal low and lastly there is

the B winds okay we are going to explain

their formation and their impact so

let's start with the line thunderstorms

Okay so the line thunderstorms first of

all develop only in summer so I've

underlined this because I know that we

can we can switch things up okay it's

very critical that you remember that

line thunderstorms only okay in summer

and um you should and it should make

sense okay and so we saying that so

let's start with the affirmation so

during summer a theral low is present in

the interior so during summer as we know

guys okay the the sun heats up the land

and that heat is transferred via

conduction um to the air and then air

rises up puts a a little pressure on the

ground and hence we create an area of

low pressure okay on the ground so this

is what you will find on any synoptic

weather map during the summer so there

is a thermal low during the summer okay

in the interior of the country and

because you have the South Atlantic High

and you have the South Indian high on

the Eastern side and we know that there

is anticlockwise movement of air okay

Within These so we say that so we're

saying that this creates a pressure

gradient okay so pressure gradient guys

really um so this speaks to the movement

or the attraction that air has uh

towards the low pressure okay from the

high pressure um we also talk about the

pressure gradiant force uh which is of

course the force that um is responsible

for the movement of air from in the area

of high pressure towards an area of low

pressure so this creates a pressure

gradient and leads to warm moist South

Indian high pressure

air

okay from the

Northeast and uh or converging with cold

dry South Atlantic High Press air from

the southwest okay I hope that doesn't

doesn't make things difficult for you so

we have the South Atlantic high pressure

right we're saying that it is invited or

it moves towards this

thalo and you have the South Indian high

pressure air okay which is warm and

moist okay it also moves towards this

low pressure this thermal low and they

they actually meet

up

at this line or this front that we call

the moisture front Okay so and it

stretches um from of course the North

West to the South East okay and so these

two ms's me up along this moisture front

Okay and the reason why we call it a

moisture front because that's because on

either side of it

you actually have different ms's of

moisture so we say that saying that

because we know that on the E side of

the moisture front you have

warm moist air okay that is coming in

from the

south um Indian high pressure cell and

then on the western side of this

moisture front you actually have

cold dry air that is coming in from the

South Atlantic High and and hence the

dry

air and moist air they are divided by

this front or this boundary that we call

the moisture front because these are two

ms's of different moisture contents this

one is moist this one is dry okay so

that's why we call it moisture front

Okay so you have this air coming from

the

Northeast okay this war moist air from

the south Indian high pressure and you

have the cold dry air from the South

Atlantic high pressure coming in from

the

southwest okay and they meet up along

that moisture front Okay so you have

warm air and cold air meeting up okay at

the center at the interior of the

country along the moisture front and so

what happens now when you have cold air

and uh warm air meeting up okay so we

know this from the mid latitude cyclone

we know that cold air will lift the warm

air okay and so this means that during

this

interaction cold air so warm air will

rise up and cold air will wge underneath

so this what so this cross-section will

look like this cold air will actually

rise

up and warm air will actually rise up

and cold air will wge underneath so of

course as cold as warm air rises up it

will cool down and it will

condense okay

and form

clouds in this case it will form huge

tall cumulon numus clouds okay so it

rises up cools down and condenses

forming tall cumulonimbus clouds okay so

we start to see clouds that will form

along this moisture front Okay and it

will rain on the Eastern side of the

moisture front so the result is your

thunderstorm s heavy rainfall hail that

is on the that will rain on the Eastern

side of this front Okay because there's

cold air here there's sinking air on

this side there's Rising air on that

side okay so this promotes um this

promotes this prep precipitation to ur

on the Eastern side of this

okay okay so I hope that made it easier

for you okay so it's very important that

you actually write each and every little

detail because this can have a lot of

marks okay and and so please be detail

uh please be specific and do not skip

points guys okay do not

rush and be precise okay so when it

comes to the impact that these line

thunderstorms have so we'll start with

the positives and then the negatives so

the positive impact that these have of

course this brings a lot of rain on the

Eastern side of the country and hence

when we talking about was water

restoration uh water storage that means

that we are going to restore water in

dams we are going to fill up our dams

which of course are responsible for

storing our water okay and the second

one is that lightning okay remember

lightning is one of the precipitation

that will occur after condensation after

cloud formation so lightning this is

what we call nitrogen fixing so you have

lightning so light due to its heat it

converts the nitrogen molecules that are

in the air converts them into nitrates

okay in the soil so You' have a

molecule okay so it actually because it

has a lot of heat it actually can break

up that molecule and this now you will

have atoms free atoms of nitrogen

nitrogen atoms uh they bond with oxygen

atoms and so and then during um

precipitation they fall into the soil

and so now the soil will have a lot of

nitrogen content and hence it's good um

it's fertiliz natural fertilizer guys

for the soil okay so that is good for

farmers and um natural plants wild

plants and so let's move on the negative

impact is that you have heavy rainfall

okay which will cause flooding okay

we've seen numerous incidents where you

have flooding especially last year and

this year flooding of course you cannot

forget that guys uh we also see hail

okay uh which are those um little ice

masses that actually destroy cars

destroy a lot of property so hail and

lightning actually can cause damage to

property and it can also injure or kill

people okay so those are the two

negative impacts of ler storms and two

positive impacts right okay so those are

line thunderstorms guys I hope I've made

it simple enough enough for you right so

we move on then to the coastal low so

Coastal low is another traveling

disturbance and it actually develops in

summer and winter so as the word suggest

it is a coastal low so it's a low

pressure so it's a cyclone and so we see

clockwise movement in the Southern

Hemisphere okay clockwise rotation of

air and it moves along the coastline

guys from west to east okay the usually

like asking the question of let's say

they would have this particular Coastal

low and let's say this is um Cape Town

and they would ask you if this Coastal

law has actually passed Cape Town or is

actually still approaching Cape Town

okay because you know the direction um

of the coastal load you would of course

say that it is still approaching Cape

Town because it is moving from where

West moving along the coast affecting

all these areas moving towards the east

right okay so be aware of those

questions okay expect them another thing

that we know that we see here is that

because of this clockwise rotation that

means that air so air from the Atlantic

Ocean will enter inlands okay that means

that that we call that means that will

be onshore winds okay and and we know

that that is cold dry air okay remember

this is the Atlantic Ocean which is

affected by the cold bangua current so

you have cold dry air moving in of

course they have small moisture or

limited moisture they move in inlands

okay so they bring cold dry conditions

in land okay and again because of the

continuous rotation of air inside this

Coastal low you also have air that is

moving outside the land okay moving

towards the ocean and that is called

offshore winds okay so offshore winds

because they are coming in from Inland

remember the land does not have a lot of

water surfaces and hence it is dry so

it's warm and it is dry with no moisture

so those conditions will be experienced

by people that are living on this side

of the coastal low okay and on this side

of the coastal low they will experience

these particular conditions okay so the

weather is different the weather

conditions are different from on either

side of the costal low okay and then on

the Eastern side uh we know that we have

the the Indian Ocean and hence the

Indian Ocean produces warm moist air

okay so warm moist air because of this

rotation again we will have warm waste

air coming Inland okay and because you

have warm was air warm waste

air and so it will rise up it will cool

down and it will form clouds and that

will result in rainfall on this side so

people on this side might experience

rainfall and people on this on this side

of the coastal low they will experience

warm dry conditions with limited

moisture because this is offshore winds

that are coming actually from the land

which is dry okay so that's what you

need to note guys when it comes to

Coastal lows

okay right and it's very critical that

you are able to identify them in

synoptic weather maps Okay so they will

look like something like that okay low

pressure something like that so that you

would know if it is along the coast then

that is a coastal low okay be able to

identify them and when it comes for and

for line thunderstorms you'd find out

there's a lot there's cloud formation

that is that actually stretches

diagonally like that okay then you would

know that those are your life

thunderstorms in your satellite images

let's get into the last concept we have

which is called the bag winds okay so B

winds are simply hot and dry winds okay

which develop in winter so they usually

affect settlements before mid latitude

Cyclones arrive uh let's discuss how

they form so beg winds are are a result

of an interaction between the strong

Kalahari High and a coastal low during

winter we know that there is a strong

Kal har high right so we know that in

our synoptic weather maps we will have H

there that represents our kalahar high

and because we said that a coastal low

actually develops in both winter and

summer we have a coastal low okay that

is on the coast and so because now you

have a high pressure and a low pressure

this will create a pressure gradient

such that now you will have air moving

in from the high pressure towards the

coast okay to that low low pressure okay

so that pressure gradient you say that

it is created because of the strongar

high and the coastal low in win okay and

then so air will flow from the Kalahari

High towards the coastal low but the

Kalahari high as we said that we said

that it is situated on the plate right

so it is actually on Higher Grounds or

um higher altitudes so you have this

Kalahari High here and and towards the

coast okay right over here you have that

Coastal low so now air will move from

the kalahar

high in the plateau and will actually

move down in altitude in height moving

towards the coast okay so it's critical

that you describe all of that so as it

is moving towards the coastal low it's

actually descending down the escarment

okay and as it descends down the

escarment guys so when air is descending

what happens it warms up okay so this

will actually warm up as it descend so

it will warm up adiabatically and of

course this removes moisture as we know

so when you warm up air more you get rid

of the moisture that it has and hence

that and hence we say that it is dry so

when it arrives in these settlements

right over here they will experience hot

air because of the ad diabatic warming

and they will experience dry air because

um you got rid of moisture as you were

warming that air up okay so by the time

it reaches these coastal areas it will

be hot and dry okay so that's how you

form back winds it's an interaction

between Kalahari High and the coastal

low okay so that's what we're saying

here so as this a subsides down the

escapement it warms up adiabatically

removing its moisture okay and so this

hence uh causes hot and dry conditions

okay these are actually uncomfortable

okay dry air is very

uncomfortable um and so of course these

will have an impact on people and the

environment and animals okay and plants

so the impact is that it will initiate

and encourage the spread of felt fires

okay so we seen a lot of fa fires um

during winter because of these uh back

winds okay so this spreads okay F fires

because in order to have a f fire you

have to have dry conditions and then up

the temperature okay because the and so

it's easy to for a fire to spread when

the environment is actually dry okay so

it can have fire spreading through out

uh and covering a lot of hectars because

it is because the soil is dry the

environment is dry okay so we see saying

that we see a spread of f fires we also

see that farmers have their properties

destroyed remember this is fire and so

fire destroys Burns fire destroys

shelters okay and so we will see

properties destroyed and Equipment as

well so there's loss of livestock

there's loss of equipment okay a lot of

farmers have lost a lot of livestock

they have lost a lot of equipment due to

fire due to these faires okay we also

see loss of lives people get injured

people um um lose their lives because of

these back winds okay and because these

occurs these

occurs in any type of environment

whether it's the the forest whether it's

open space um whether it's grassland so

on and so on so um animal habitats get

destroyed and people and animals suffer

from dehydration

okay right and so how can we combat this

impact how can we minimize it okay okay

so we have strategies here so what can

we do okay so we can first of all wet

the so oil okay in order to prevent

spread of fires okay remember we said

that fires spread if the environment is

dry okay so if you can actually wet the

soil um um then you would be actually

preventing the spread of fires okay

because wet soil

prevents um fires from spreading and

covering larger distances okay evacuate

people and livestock uh to safer areas

okay uh so this is to prevent the loss

of lives um the injuries on Livestock on

people and imer Emergency Services

should be well equipped and efficient

that means quick okay there should be a

quick response guys because these fires

can spread pretty quickly okay um we

also see that we have to provide

sufficient water okay uh to fight the

spreading uh fires and to hydrate

victims Okay so again that speaks to

your emergency services that speaks to

your firefighters they should have

sufficient water that will be able to

fight these um fires and also provide

people with drinking water okay so that

they can be able to hydrate okay so

these uh are the concepts that are under

the subtropical anticyclones and

Associated weather patterns guys so um

with this I've equipped you with the

necessary knowledge it's very important

that you are able to describe every

little detail it should make sense to

you okay and also always refer back to

the foundation principles that we

referred to in the first in the very

first video of this series okay I hope

this was as simple as possible okay so

I'll see you in the next video we'll be

doing Valley climates okay cheers is