We have:
Notes A and Notes B
Notes A
PHYSICAL GEOGRAPHY
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1. EVOLUTION, COMPOSITION AND STRUCTURE OF THE EARTH
2. ENDOGENIC PROCESSES OF THE EARTH
3. EXOGENIC PROCESSES OF THE EARTH
PRACTICAL GEOGRAPHY
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1. APPLICATION OF STATISTICS IN GEOGRAPHY
4. MAPS AND MAP INTERPRETATION
THE LONGEST RIVERS IN AFRICA
1. Nile River – 6,650 Km
The Nile River is
not only the longest river in Africa but also in the world. It flows South to
North, beginning near Lake Victoria and
emptying into the Mediterranean Sea –
crossing eleven East
African countries en route (Burundi, Tanzania, Rwanda, the Democratic
Republic of the Congo, Kenya, Uganda, Sudan, Ethiopia, South Sudan, and Egypt) and discharging an
average of 99,941 cubic feet of water per second.
It’s
difficult to overestimate the importance of this river in the history and
development of the region. It was along the banks of the Nile that the Ancient
Egyptians flourished and, in the view of the Greek historian Herodotus, their
land was a gift from the river. They named it “Black” or “Ar”, a reference to
the colour of its waters or Aur, and relied on it for a myriad of functions,
from agricultural irrigation and fishing to transportation and trade. Even
today, it’s said that 95% of Egyptians still live within a few miles of the
river.
2. Congo River
The
Congo River (formerly known as the Zaire River) is the second-longest river in
Africa, the ninth-longest in the world, and the deepest
river on the planet, both in terms of maximum and average depth. Its point
of origin can be considered to be in the highlands of North eastern Zambia and/or the
Katanga Plateau in the Southeastern corner of the Democratic
Republic of the Congo. In either case, the river flows in a counter-clockwise
arc, twice crossing the equator, and discharging 1,454,964 cubic feet of water
per second on its way to the Atlantic Ocean at
a seaport called Banana (or Banane) in the Democratic Republic of the Congo.
3. Niger River – 4,180 Km
Draining
an area encompassing nine countries over roughly 730,000 square miles, the
Niger River is an arc of some 2,600 miles through western Africa. Along the
way, it’s known by various names, including Kwarra, Isa Eghirren and Joliba.
One of the longest rivers in Africa, it’s home to almost 250 species of
freshwater fish, many of them endemic to the river. They are joined by three
types of crocodile – among them the Nile crocodile – lizards and a variety of
birds, including geese, herons, pelicans, and even flamingos.
4. River Zambezi – 2,574 Km
Its
name means “great river” and the Zambezi certainly lives up to it. Not only is
it the fourth longest of the rivers Africa has to offer, but it’s the longest
east-flowing river on the continent and the largest that flows from Africa into
the Indian Ocean. Sometimes spelled “Zambesi”, it drains 540,000 square miles
of south-central Africa, and flows through or along the boundaries of six
countries. Amongst these are Angola, Botswana, Mozambique, Namibia, Zambia, and
Zimbabwe.
5. River Ubangi – 2,270 km
Ubangi
River is the fifth longest river in Africa with length of 2,270 km (1,410) and
is a major tributary of the Congo River in equatorial Africa. The Ubangi is
formed at the junction of the Uele and Bomu rivers. It then flows westward and
southward through Central African Republic, Democratic Republic of the Congo
and Republic of Congo.
6. The Orange River
With a
length of 2160 kilometers, the Orange River flows mainly in South Africa.
The area of the basin of this river is 973 000 km². The average flow rate at
its mouth is about 370 cubic meters per second.
The
Orange River originates in the Drakensberg Mountains at an altitude of 3150 meters
(Lesotho). Part of its course serves as the land border between South Africa
and Namibia. Then the Orange River ends its course in the Atlantic Ocean. This
river is very important for South Africa because the water of the Orange River
is used to irrigate crops as well as to produce electricity.
IMPORTANCE
OF RIVERS
1. We all
need water to survive
It
goes without saying, but fresh, clean water is essential for humans and nature
to survive. Rivers are precious sources of fresh drinking water for
people across the world. And when rivers are so
badly polluted by industry or unevenly
distributed by poor water management practices, it can
be a case of life-or-death. This unfortunately happens across the
world.
2. Biodiversity
River ecosystems provide diverse habitats,
supporting a variety of plant and animal species. It also contributes to
the intricate
web of biodiversity and contributes to ecological balance.
Consider the Mississippi
River Delta as shown in this map. Marshes, swamps, and waterways create a
rich ecosystem. This supports a wide range of plant and animal species, from
migratory birds to various fish.
3. Habitats
Rivers
provide excellent habitat and food for many of the earth’s organisms. Many rare
plants and trees grow by rivers. Ducks, voles, otters and beavers make their
homes on the river banks. Reeds and other plants like bulrushes grow along the
river banks.
Other
animals use the river for food and drink. Birds such as kingfishers eat small
fish from the river. In Africa, animals such as antelopes, lions and elephants
go to rivers for water to drink. Other animals such as bears catch fish from
rivers.
River
deltas have many different species of wildlife. Insects, mammals and birds use
the delta for their homes and for food.
…….
Weather
Weather is defined as conditions of the atmosphere which occur at a place at specific time periods, that is, from hour to hour or day to day. It changes from time to time and from place to place. For example, it may be raining in the morning and Sunny in the afternoon.
Weather may also be defined as the day-to-day state of the atmosphere, and its short-term variation ranges from minutes to several weeks. Weather is an important aspect of our lives. The weather often determines how and where we live, what we do, what we wear and what we eat. The scientific study of weather is called meteorology, and a person who studies weather is called meteorologist.
Describe the importance of weather.
Weather is an important because it affects human activities. The following are some of the reasons why weather is important;
- Weather is one of the fundamental processes that shape the Earth. The process of weathering breaks down the rocks into smaller fragments which later turn into soil. Also, weather plays a major role in erosion of the surface soil.
- The weather of any given region is important because it affects water, sunlight and temperature of an area. Variation in long-term weather patterns and tendencies can result in certain regions getting more or less water, Sunlight and temperature than other areas. These factors therefore play an important role by influencing the type of plants and animals that can survive in the area
- Certain weather patterns can also cause natural disasters. For example, strong winds, hail, floods, sleet, ice and frost.
- Studying weather characteristics of a given place over a long period of time enables the climatic conditions of that place to be established. Therefore, weather can be used as a basis for determining the climate of a given place.
- The knowledge of weather enables people to carry out their economic activities depending on the weather and climatic conditions of their localities. For example, people living in areas which receive high rainfall can engage in dairy farming and the growing crops such as tea, coffee, banana, etc.
Show the relationship between weather and human occupations
Weather condition is a great determinant of timing of doing various human activities. For example, during the morning people can actively work in agricultural fields but as the weather gets hotter, people cannot engage in production so actively due to an excessive atmospheric temperature which could lead to sweating and discomfort.
Weather change can also influence other human activities as well. For example, on a rainy day, very few people can participate in outdoor activities. Farmers may not go to the farms. Likewise, people may fear to travel because sometimes the rain may cause floods, demolish bridges or erode the roads.
Therefore, there is a need to adjust human activities according to change in the weather so as to avoid adverse weather conditions. For example, working during rainy or very Sunny days may affect our health. Therefore, weather affects the efficiency of our daily
………
Elements of weather
Weather elements refer to a combination of natural phenomena that make up the weather. There are several elements that make the weather. The weather elements are temperature, pressure, precipitation, wind, humidity, clouds and Sunshine
The study of these elements can provide the basis for forecasting weather and defining the climate. The following sub sections present detailed information about each element of weather
Names of elements of weather.
- Temperature
The temperature is the state of hotness or coldness of the atmosphere. It is usually measured by an instrument called thermometer and expressed in degrees on a Celsius or Fahrenheit scale.
- Precipitation
This refers to the deposition of moisture on the Earth’s surface from the atmosphere. This moisture includes rain, snow, ice, hail, mist and sleet.
Example: Demonstrating the rainfall formation
Boil some water in a pot. Wait for some minutes until the water starts boiling, and then hold a container filled with cold water over the pot. As the steam comes in contact with the container, it condenses to form droplets which will then fall down. This is a simple demonstration on how rain is formed.
Rainfall formation
The Sun’s heat causes water to evaporate from the surface of the oceans, lakes, rivers and other water bodies. This vapour rises into the atmosphere where it condenses to form clouds. Because the air is cooler at higher altitudes, the vapour is cooled to form small droplets that join together to form larger drops which are then too heavy to remain in the air, so it falls as rain. The figure 4.5 shows the water cycle, also called the hydrologic cycle.
Types of rainfall
(i). Convectional rainfall This is formed through the rising of the moist air currents, which condenses at higher altitudes to form clouds that result in rainfall
(ii). Orographic rainfall Sometimes moist winds are forced by a high mountain to rise and the moisture in it condenses to form rainfall. The rain formed in this manner is called orographic rainfall. The side of the mountain facing away from the direction of wind gets little or no rainfall. This phenomenon is called the rain shadow effect
An example of the rain shadow effect in Tanzania is found on the western side of Mount Kilimanjaro. Winds blow from the Indian Ocean in the east and are forced by this mountain to rise up and drop moisture on the eastern and south western slopes. When these winds blow over to the western side of the mountain, they are already relatively dry. As a result, they bring very little rainfall to the Masai steppe. Other examples are the Rocky Mountains which affect the rain-bearing winds from the Pacific; and the Andes in Chile which affect the rain-bearing winds from the Pacific on the Patagonia plateau
iii. Cyclonic rainfall This occurs when large masses of air with different characteristics of temperature and moisture meet. As the warmer and moist air is forced up over the cooler and dry air, it expands, cools and water vapour condenses to form clouds and rainfall
On the other hand, tropical cyclones are formed over oceans in the tropics between latitude 8°N and 8°S. They usually bring very heavy rainfall and are associated with thunderstorms and very fast-moving winds which often cause destructions along coastal settlements. In the Caribbean and USA, tropical cyclones are called hurricanes. In Africa they are known as cyclones, while in China and Japan they are called typhoons but in North Australia, they are known as Willy–Willies.
- Humidity
Humidity is the state of the atmosphere in relation to the amount of water vapour it contains. Humidity indicates the degree of dampness of the air and it is one of the main influences on weather. It is expressed in either absolute or relative terms. Absolute humidity is the actual amount of water vapour present in a certain volume of air at a given temperature, expressed in grams per cubic meter. Relative humidity is the amount of water vapour present in a mass of air, expressed as a percentage of the total amount of water vapour that would be present when that air is saturated at that temperature. Air is saturated when the atmosphere cannot hold any more water vapour. This condition depends on the temperature and pressure of the air.
- Atmospheric pressure
The air around us has weight. Atmospheric pressure (or air pressure) is the weight of the air resting on the Earth’s surface. It is the weight exerted by air on the Earth’s surface
The force with which air presses down on a unit area is called atmospheric pressure. But this pressure is exerted equally in all directions. Atmospheric pressure can be demonstrated by the following experiment
Take a glass full of water, cover the top of the glass with a piece of thin paper, and then hold the glass upside down. The water in the glass will not spill out because pressure of the air is pressing the paper so that it does not fall out.
- Wind
Wind is air in motion, from high pressure areas to low pressure area. It is a moving air mass, especially on the Earth’s surface. Usually, there is a movement of air from high pressure to low pressure areas, which is caused by differences in heating of air over different parts of the Earth’s surface. The air that moves from a region of high pressure to that of low pressure is called wind. Heated air expands, becomes less dense and rises up. Cooled air contracts, becomes denser and sinks down. When air sinks, its pressure increases because it is compressed, but when air rises, its pressure decreases because its molecules are spread over a large area. Areas from where heated air is rising are called areas of low pressure, while areas in which cool air is sinking are called areas of high pressure.
During the day the land is usually warmer than the sea, and the air pressure on the land is lower than that over the sea. Therefore, air blows from sea to land. This kind of air movement (wind) is known as sea breeze. But during the night the land is cooler than the sea and there is low pressure on the sea. Therefore, winds blow from the land to the sea. This air movement is called land breeze.
On the Earth’s surface, the regions of the north and south poles are very cold and have high pressure while the belt along the equator is very hot and has low pressure. This makes air move from the poles towards the equator. In the equatorial belt, rising air is replaced by air moving in from the north and south of the equator. We should then expect two belts of wind blowing towards the equator. But this is not exactly so because the earth rotates from west to east. According to Ferrel’s law air or water moving freely in any direction over the Earth’s surface is turned (deflected) to the right of its course in the northern hemisphere and to the left in the southern hemisphere. Therefore, wind blowing from the north towards the equator in the northern hemisphere will blow from the northeast and not from the north, and any winds blowing from the south towards the equator in the southern hemisphere will blow from the southeast and not from due south.
In the equatorial belt of low pressure, between 5oN and 5oS latitudes, intense solar heating causes the moist air to raise in great convection columns. This belt is called the doldrums or low pressure belt. The rising air spreads out and moves towards the poles. In so doing, it cools and thus contracts, and develops high pressure. This occurs around 30°N and 30°S. Thus, the air sinks and builds up high pressure at these latitudes. These latitudes are called horse latitudes or subtropical high-pressure cells
In latitudes 30°N and 30°S some of the high pressure air moves over the surface towards the equator as the north east and south east trade winds. Some moves over the surface towards the poles as westerlies
In each hemisphere, there are three wind systems which operate between the indicated latitudes namely
- The Polar wind system (between the North Pole and 60°N; and between the South Pole and 60°S)
- The tropical wind system (between 30°N and 60°N; and 30°S and 60°S)
- The equatorial wind system (between 30°N and 30°S)
Occasionally in the westerly wind system, depressions and anticyclones develop. A depression is an area of low pressure in which winds blow inwards in a circular motion. This motion is anti-clockwise in the northern hemisphere and clockwise in the southern hemisphere. A depression develops when cold heavy air comes in contact with warm most air. Depressions are usually associated with cyclonic rains. Anti-cyclones are areas of high pressure in which winds blow in a clockwise, circular motion in the northern hemisphere. They are associated with cool fine weather with no rain and they normally follow a depression.
- Cloud cover
Cloud cover refer to the fraction of the sky obscured by clouds when observed from a particular location. It is also known as cloudiness, cloud age or cloud amount. The cloud cover is observed by using eyes. However, Ceilometer is an instrument used to measure cloud height and cover. Ceilometer works day or night by shining an intense beam of light which is modulated at the audio frequency, at overhead cloud.
- Sunshine
The amount of Sunshine depends on latitude and amount of cloud in the sky. In some of the world’s deserts, the number of Sunshine hours is very high, more than 3,600 hours each year. In the Eastern Sahara Desert, the Sun is covered by clouds for less than 100 hours a year. Hours of Sunshine are usually recorded on a simple machine called Campbell-Stokes recorder.
The importance of each element
Importance of temperature
- Temperature is an important factor in rain formation. Temperature causes the evaporation of water vapour from water bodies, land and plants. The resulting water vapour then condenses to make clouds that form rain
- Temperature is the main factor in the blowing of wind. When the Sun heats the Earth’s surface unevenly, the resulting changes in temperature create changes in pressure and density. The ultimate result of these changes is the movement of air from a region of high pressure (cold area) to an area of low pressure (heated area). This movement of air is called wind
- Plant growth is also highly influenced by temperature. It affects transpiration, seed germination and the rate of photosynthesis in different ways, For example, temperature controls planting dates and the growth of plants
Importance of precipitation
- Precipitation especially rainfall, plays an important role in weathering of rocks. It dissolves the chemicals in rocks, thus helping to peel them apart. This action is called weathering, The weathered rocks, in turn, form the soil. Weathering is particularly influenced by temperature and rainfall
- Some sports such as skiing, skating, etc. take place on frozen snow. Therefore, snow as a form of precipitation acts as a playground on which numerous games and sports can take place
- Rainfall provides us with the water we need for various uses such as irrigation, drinking, washing, cleaning, etc. When it rains, water collects into streams and rivers from where it is collected, purified and supplied to homes for various purposes. Rainfall can be harvested directly as it falls from the sky. It is then stored in tanks for different uses. Rain water is natural, pure and can be used without any further purification
- Rain is an important component of the water cycle and is responsible for depositing most of the fresh water on the earth. It provides suitable conditions for many types of ecosystems, as well as water for hydropower plants.
Importance of Sunshine
- The energy from the Sun can be trapped, harnessed and put into various uses including cooking, heating, lighting and generating power for operating machines. It also affects the amount of heat received on the earth. When the Sun shines for many hours, the temperature of the earth rises and when there is no Sunshine the temperature drops down
- The Sun’s energy is used by green plants to make their own food through the process of photosynthesis. Solar energy is also used to dry crops, clothes, etc. Our skins are also capable of converting the solar energy into vitamin D
……..
Concept of weather
Define Weather
Weather is defined as conditions of the atmosphere which occur at a place at specific time periods, that is, from hour to hour or day to day. It changes from time to time and from place to place. For example, it may be raining in the morning and Sunny in the afternoon.
Weather may also be defined as the day-to-day state of the atmosphere, and its short-term variation ranges from minutes to several weeks. Weather is an important aspect of our lives. The weather often determines how and where we live, what we do, what we wear and what we eat. The scientific study of weather is called meteorology, and a person who studies weather is called meteorologist.
Describe the importance of weather.
Weather is an important because it affects human activities. The following are some of the reasons why weather is important;
- Weather is one of the fundamental processes that shape the Earth. The process of weathering breaks down the rocks into smaller fragments which later turn into soil. Also, weather plays a major role in erosion of the surface soil.
- The weather of any given region is important because it affects water, sunlight and temperature of an area. Variation in long-term weather patterns and tendencies can result in certain regions getting more or less water, Sunlight and temperature than other areas. These factors therefore play an important role by influencing the type of plants and animals that can survive in the area
- Certain weather patterns can also cause natural disasters. For example, strong winds, hail, floods, sleet, ice and frost.
- Studying weather characteristics of a given place over a long period of time enables the climatic conditions of that place to be established. Therefore, weather can be used as a basis for determining the climate of a given place.
- The knowledge of weather enables people to carry out their economic activities depending on the weather and climatic conditions of their localities. For example, people living in areas which receive high rainfall can engage in dairy farming and the growing crops such as tea, coffee, banana, etc.
Show the relationship between weather and human occupations
Weather condition is a great determinant of timing of doing various human activities. For example, during the morning people can actively work in agricultural fields but as the weather gets hotter, people cannot engage in production so actively due to an excessive atmospheric temperature which could lead to sweating and discomfort.
Weather change can also influence other human activities as well. For example, on a rainy day, very few people can participate in outdoor activities. Farmers may not go to the farms. Likewise, people may fear to travel because sometimes the rain may cause floods, demolish bridges or erode the roads.
Therefore, there is a need to adjust human activities according to change in the weather so as to avoid adverse weather conditions. For example, working during rainy or very Sunny days may affect our health. Therefore, weather affects the efficiency of our daily
………
Elements of weather
Weather elements refer to a combination of natural phenomena that make up the weather. There are several elements that make the weather. The weather elements are temperature, pressure, precipitation, wind, humidity, clouds and Sunshine
The study of these elements can provide the basis for forecasting weather and defining the climate. The following sub sections present detailed information about each element of weather
Names of elements of weather.
- Temperature
The temperature is the state of hotness or coldness of the atmosphere. It is usually measured by an instrument called thermometer and expressed in degrees on a Celsius or Fahrenheit scale.
- Precipitation
This refers to the deposition of moisture on the Earth’s surface from the atmosphere. This moisture includes rain, snow, ice, hail, mist and sleet.
Example: Demonstrating the rainfall formation
Boil some water in a pot. Wait for some minutes until the water starts boiling, and then hold a container filled with cold water over the pot. As the steam comes in contact with the container, it condenses to form droplets which will then fall down. This is a simple demonstration on how rain is formed.
Rainfall formation
The Sun’s heat causes water to evaporate from the surface of the oceans, lakes, rivers and other water bodies. This vapour rises into the atmosphere where it condenses to form clouds. Because the air is cooler at higher altitudes, the vapour is cooled to form small droplets that join together to form larger drops which are then too heavy to remain in the air, so it falls as rain. The figure 4.5 shows the water cycle, also called the hydrologic cycle.
Types of rainfall
(i). Convectional rainfall This is formed through the rising of the moist air currents, which condenses at higher altitudes to form clouds that result in rainfall
(ii). Orographic rainfall Sometimes moist winds are forced by a high mountain to rise and the moisture in it condenses to form rainfall. The rain formed in this manner is called orographic rainfall. The side of the mountain facing away from the direction of wind gets little or no rainfall. This phenomenon is called the rain shadow effect
An example of the rain shadow effect in Tanzania is found on the western side of Mount Kilimanjaro. Winds blow from the Indian Ocean in the east and are forced by this mountain to rise up and drop moisture on the eastern and south western slopes. When these winds blow over to the western side of the mountain, they are already relatively dry. As a result, they bring very little rainfall to the Masai steppe. Other examples are the Rocky Mountains which affect the rain-bearing winds from the Pacific; and the Andes in Chile which affect the rain-bearing winds from the Pacific on the Patagonia plateau
iii. Cyclonic rainfall This occurs when large masses of air with different characteristics of temperature and moisture meet. As the warmer and moist air is forced up over the cooler and dry air, it expands, cools and water vapour condenses to form clouds and rainfall
On the other hand, tropical cyclones are formed over oceans in the tropics between latitude 8°N and 8°S. They usually bring very heavy rainfall and are associated with thunderstorms and very fast-moving winds which often cause destructions along coastal settlements. In the Caribbean and USA, tropical cyclones are called hurricanes. In Africa they are known as cyclones, while in China and Japan they are called typhoons but in North Australia, they are known as Willy–Willies.
- Humidity
Humidity is the state of the atmosphere in relation to the amount of water vapour it contains. Humidity indicates the degree of dampness of the air and it is one of the main influences on weather. It is expressed in either absolute or relative terms. Absolute humidity is the actual amount of water vapour present in a certain volume of air at a given temperature, expressed in grams per cubic meter. Relative humidity is the amount of water vapour present in a mass of air, expressed as a percentage of the total amount of water vapour that would be present when that air is saturated at that temperature. Air is saturated when the atmosphere cannot hold any more water vapour. This condition depends on the temperature and pressure of the air.
- Atmospheric pressure
The air around us has weight. Atmospheric pressure (or air pressure) is the weight of the air resting on the Earth’s surface. It is the weight exerted by air on the Earth’s surface
The force with which air presses down on a unit area is called atmospheric pressure. But this pressure is exerted equally in all directions. Atmospheric pressure can be demonstrated by the following experiment
Take a glass full of water, cover the top of the glass with a piece of thin paper, and then hold the glass upside down. The water in the glass will not spill out because pressure of the air is pressing the paper so that it does not fall out.
- Wind
Wind is air in motion, from high pressure areas to low pressure area. It is a moving air mass, especially on the Earth’s surface. Usually, there is a movement of air from high pressure to low pressure areas, which is caused by differences in heating of air over different parts of the Earth’s surface. The air that moves from a region of high pressure to that of low pressure is called wind. Heated air expands, becomes less dense and rises up. Cooled air contracts, becomes denser and sinks down. When air sinks, its pressure increases because it is compressed, but when air rises, its pressure decreases because its molecules are spread over a large area. Areas from where heated air is rising are called areas of low pressure, while areas in which cool air is sinking are called areas of high pressure.
During the day the land is usually warmer than the sea, and the air pressure on the land is lower than that over the sea. Therefore, air blows from sea to land. This kind of air movement (wind) is known as sea breeze. But during the night the land is cooler than the sea and there is low pressure on the sea. Therefore, winds blow from the land to the sea. This air movement is called land breeze.
On the Earth’s surface, the regions of the north and south poles are very cold and have high pressure while the belt along the equator is very hot and has low pressure. This makes air move from the poles towards the equator. In the equatorial belt, rising air is replaced by air moving in from the north and south of the equator. We should then expect two belts of wind blowing towards the equator. But this is not exactly so because the earth rotates from west to east. According to Ferrel’s law air or water moving freely in any direction over the Earth’s surface is turned (deflected) to the right of its course in the northern hemisphere and to the left in the southern hemisphere. Therefore, wind blowing from the north towards the equator in the northern hemisphere will blow from the northeast and not from the north, and any winds blowing from the south towards the equator in the southern hemisphere will blow from the southeast and not from due south.
In the equatorial belt of low pressure, between 5oN and 5oS latitudes, intense solar heating causes the moist air to raise in great convection columns. This belt is called the doldrums or low pressure belt. The rising air spreads out and moves towards the poles. In so doing, it cools and thus contracts, and develops high pressure. This occurs around 30°N and 30°S. Thus, the air sinks and builds up high pressure at these latitudes. These latitudes are called horse latitudes or subtropical high-pressure cells
In latitudes 30°N and 30°S some of the high pressure air moves over the surface towards the equator as the north east and south east trade winds. Some moves over the surface towards the poles as westerlies
In each hemisphere, there are three wind systems which operate between the indicated latitudes namely
- The Polar wind system (between the North Pole and 60°N; and between the South Pole and 60°S)
- The tropical wind system (between 30°N and 60°N; and 30°S and 60°S)
- The equatorial wind system (between 30°N and 30°S)
Occasionally in the westerly wind system, depressions and anticyclones develop. A depression is an area of low pressure in which winds blow inwards in a circular motion. This motion is anti-clockwise in the northern hemisphere and clockwise in the southern hemisphere. A depression develops when cold heavy air comes in contact with warm most air. Depressions are usually associated with cyclonic rains. Anti-cyclones are areas of high pressure in which winds blow in a clockwise, circular motion in the northern hemisphere. They are associated with cool fine weather with no rain and they normally follow a depression.
- Cloud cover
Cloud cover refer to the fraction of the sky obscured by clouds when observed from a particular location. It is also known as cloudiness, cloud age or cloud amount. The cloud cover is observed by using eyes. However, Ceilometer is an instrument used to measure cloud height and cover. Ceilometer works day or night by shining an intense beam of light which is modulated at the audio frequency, at overhead cloud.
- Sunshine
The amount of Sunshine depends on latitude and amount of cloud in the sky. In some of the world’s deserts, the number of Sunshine hours is very high, more than 3,600 hours each year. In the Eastern Sahara Desert, the Sun is covered by clouds for less than 100 hours a year. Hours of Sunshine are usually recorded on a simple machine called Campbell-Stokes recorder.
The importance of each element
Importance of temperature
- Temperature is an important factor in rain formation. Temperature causes the evaporation of water vapour from water bodies, land and plants. The resulting water vapour then condenses to make clouds that form rain
- Temperature is the main factor in the blowing of wind. When the Sun heats the Earth’s surface unevenly, the resulting changes in temperature create changes in pressure and density. The ultimate result of these changes is the movement of air from a region of high pressure (cold area) to an area of low pressure (heated area). This movement of air is called wind
- Plant growth is also highly influenced by temperature. It affects transpiration, seed germination and the rate of photosynthesis in different ways, For example, temperature controls planting dates and the growth of plants
Importance of precipitation
- Precipitation especially rainfall, plays an important role in weathering of rocks. It dissolves the chemicals in rocks, thus helping to peel them apart. This action is called weathering, The weathered rocks, in turn, form the soil. Weathering is particularly influenced by temperature and rainfall
- Some sports such as skiing, skating, etc. take place on frozen snow. Therefore, snow as a form of precipitation acts as a playground on which numerous games and sports can take place
- Rainfall provides us with the water we need for various uses such as irrigation, drinking, washing, cleaning, etc. When it rains, water collects into streams and rivers from where it is collected, purified and supplied to homes for various purposes. Rainfall can be harvested directly as it falls from the sky. It is then stored in tanks for different uses. Rain water is natural, pure and can be used without any further purification
- Rain is an important component of the water cycle and is responsible for depositing most of the fresh water on the earth. It provides suitable conditions for many types of ecosystems, as well as water for hydropower plants.
Importance of Sunshine
- The energy from the Sun can be trapped, harnessed and put into various uses including cooking, heating, lighting and generating power for operating machines. It also affects the amount of heat received on the earth. When the Sun shines for many hours, the temperature of the earth rises and when there is no Sunshine the temperature drops down
- The Sun’s energy is used by green plants to make their own food through the process of photosynthesis. Solar energy is also used to dry crops, clothes, etc. Our skins are also capable of converting the solar energy into vitamin D
3 Comments
se4nd me data
Sijaziona notes za geography paper two, human and economic geography. Msaada plz
Good try