Module 1

Question 1

Weather vs Climate

Answer 1

Weather relates to hourly, daily atmospheric conditions such as precipitation, hours of sunshine, cloud cover, temperature and humidity. The most important fact is that it is short-term.

The climate of a place is based on the average weather conditions for a particular place taken over a minimum of a 30-year period. It is a general
picture and the weather received for a place can be vastly different from its usual climate.

Question 2

What is the Atmosphere

Answer 2

The Earth’s atmosphere consists of air-a mixture of various gases surrounding the Earth to a height of many kilometres.

There are four vertical layers within the atmosphere:
1) Troposphere
2) Stratosphere
3) Mesosphere
4) Thermosphere

The outer limit of the atmosphere is set at 1000km, but the vast majority of our weather and climate is found within the lower 12km.

Question 3

Radiation

Answer 3

Insolation is solar radiation received in the Earth’s atmosphere or at its surface, in the form of short-wave solar energy.

Only approximately 52% of this insolation reaches the earth’s surface.

The rest is absorbed by water vapour, dust and clouds or is reflected by the Earth’s surface and scattered by particles in the air.

This reflection is called the albedo. The albedo of an object is the extent to which it diffusely reflects light from the Sun.

Reflected heat, in the form of long-wave radiation, is trapped in our atmosphere and keeps our planet warm (this is known as the natural greenhouse effect).

Question 4

Albedo

Answer 4

Albedo refers to the reflectivity of a surface and is the fraction of solar energy (shortwave radiation) reflected from the Earth back into space.

For example
Ice, especially with snow on top of it, has a HIGH albedo whereas water is much more absorbent and less reflective (LOW albedo). So, if there is a lot of water, more solar radiation is absorbed by the ocean than when ice dominates.

This becomes important in spring and summer when the radiation entering through can greatly increase the melt rate of the sea ice.

Question 5

Temperature

Answer 5

Air Temperature refers to the temperature of the air as observed at 1.2 m (4ft) above the ground surface.

The temperature of the Earth’s surface is the outcome of two processes:
i. The inward receipt of solar energy or insolation
ii. The outward loss of heat by radiation or exsolation

The volume or level of each process decreases from the Equator to the poles and so does the resulting energy budget.

Since the trend in insolation receipts being more than that of exsolation, the energy balance changes at around latitude 35° from surplus to deficit.

This spatial variation in the global energy budget is the principal factor determining the spatial pattern of temperatures over the Earth’s surface.

Question 6

Factors affecting temperature

Answer 6

1) Latitude:
Latitude is the distance (measured in degrees) to the north and south of the Equator. The further away the location is from the equator, the smaller the angle
at which the sun’s rays strike the earth.

The smaller the angle of incidence of the sun’s rays, the greater the distance through the atmosphere the rays have to pass. Therefore, away from the equator, where the angle of incidence of the sun’s ray is less
than 90°, the solar radiation is spread over a larger area. Therefore, less intense heating takes place, causing temperature to become lower.

2) Altitude:
Altitude is the height of a point above the sea level.
Temperature decreases by 6.5°C for every increase in 1,000m increase in altitude.

The air at high altitudes is thin. Thin air is unable to absorb heat as effectively as the dense air at sea
level because it has a smaller concentration of gases to trap heat. Thus places at higher altitudes have a lower temperature.

3) Cloud Cover
When there is high humidity, the cloud cover is greater. In equatorial regions with thick cloud cover, incoming solar radiation will be absorbed, reflected and scattered. Thus keeping the land cool and the heating effect is less intense. At night clouds reflect heat radiated by the ground back to the earth’s surface, preventing heat from escaping into outer space. This keeps the temperature of the ground high at night. As such there is a smaller difference in day and night temperatures.

However, in areas such as deserts, there is less cloud cover so there is more insolation reaching the surface resulting in intense heating with temperatures easily reaching 40 degrees Celsius. At night, the absence of cloud cover causes the rapid escape of heat resulting in very low temperatures of 15 degrees Celsius. Thus there is a greater diurnal range

Question 7

Global Heat Budget & Energy Balance

Answer 7

The global heat budget is the balance between incoming and outgoing solar radiation.

At the Equator, there is an energy surplus (net gain), whereas at the poles there is an energy deficit. To keep energy balanced at the Earth’s surface, excess energy is transferred from lower latitude energy surplus areas to higher latitude energy deficit areas by atmospheric circulation.

If there was no atmospheric circulation, lower latitudes would get hotter and hotter and higher latitudes colder and colder.

Question 8

Heat Transfers

Answer 8

Horizontal heat transfers:
The transfer of heat from the equator to the poles occurs via winds - 80% (large scale to small scale) and ocean currents (20%).

Vertical heat transfers:
Exist to stop the atmosphere from cooling and the Earth’s surface from overheating. They include:
1) Conduction: The process through which the air receives heat from contact with the ground. Requires a medium

2) Radiation: The process by which heat energy is transferred without requiring a medium

3) Convection: Hot air, being lighter than cold air raises as convection currents. It requires a medium

4) Latent Heat: It is the quantity of heat energy needed to change. When solar radiation changes liquid water to water vapour, latent heat is absorbed but the atmosphere’s temperature does not change.
convection, latent heat transfers and radiation.

Question 9

Factors affecting Wind Speed & Direction

Answer 9

1. Pressure-Gradient
   Differences in air temperature, due to the unequal heating of the atmosphere, cause differences in air pressure.
   A frequent cause of a horizontal difference in air pressure is a difference in air temperature and resulting difference in air density. When air
   warms, it tends to rise and expand. This causes low pressure. When cooling occurs, the air tends to sink and contract, causing high pressure.
   When there is pressure gradient, it produces a force that causes air to move from the place of higher pressure to a place of lower pressure.
   This force is known as the pressure-gradient force and it increases as the difference in air pressure across a specified distance increases.
   The direction of the pressure-gradient force is ALWAYS oriented from high to low pressure at a 90° angle to isobars (isobars that are close together indicate a larger force  faster/stronger winds).
2. Coriolis Effect
   Due to the Earth’s rotation, winds are deflected by the Coriolis effect (force). In the Northern Hemisphere the Coriolis effect deflects movement to the right and in the Southern Hemisphere it deflects movement to the left.
   The magnitude of the Coriolis force varies directly with the wind speed and the rate of the Earth’s rotation.
   The force also varies with the latitude and it is a maximum at the poles and minimum (zero) at the equator (no deflection at the equator).

Eventually, the pressure-gradient force and the Coriolis force acting on the wind balance each other out.
This results in a wind known as a geostrophic wind. It has a constant speed and follows a relatively straight path that minimizes deflection.
Geostrophic winds occur in the upper atmosphere, above the surface layer

3.Friction (frictional drag)
This affects air flows in the atmosphere, near the
Earth’s surface. The closer individual air molecules are to the surface, the more they are slowed by surface drag, creating a frictional force.
The direction of the frictional force is always OPPOSITE to the direction of air movement.
The magnitude of the frictional force depends primarily on the “roughness” of the surface (there is less frictional force with movement across a smooth snow or water surface than across a mountainous
terrain, forested area)
Friction affects wind direction (surface winds vs. upper winds) as well as modifies the Coriolis force.

Question 10

Tricellular Model- Surface Circulation

Answer 10

On a rotating Earth’s surface, the driving force of the global circulation is again the intense heating received at equatorial areas. This produces deep convection with the rising air carried up to the tropopause by the
release of latent heat.
The tropopause (and its associated inversion) force
the rising air to spread out horizontally towards the poles. The Coriolis force results in this air being deflected to become part of the global flow of upper-air westerlies.
The system is caused by UNEQUAL heating of the Earth’s atmosphere at different latitudes.

The Hadley Cell:
This cell exist on either side of the Equator. Hot air at the Equator rises as the north-easterly and south easterly trade winds meet to the form the Intertropical Convergence Zone (ITCZ). The convergence of these two air masses of warm moist air results in large cumulus and cumulonimbus clouds as the air rises and cools rapidly. This produces afternoon thunderstorms. (LOW PRESSURE ZONE) Near the equator, at the ITCZ, winds tend to be light and the air is very stable in the known as the doldrums. The rising air eventually moves away from the equator and flow to towards the poles and with increasing density it subsides to form the descending limb of the Hadley cell.
The air subsides and diverges at about 30 degrees north and south of the Equator creating subtropical high pressure belts resulting in dry stable conditions with clear skies. The air currents return to the Equator as the north-easterly and south-easterly trade winds

Ferrel Cell:
This cell stretches between 30 and 60 degrees north and south of the Equator. Here, the air flows poleward. The relatively warm, sub-tropical air flows at low altitudes towards the poles in the Ferrel Cell until it meets cooler polar air, at which point it rises.
This is an area of low pressure, known as the Polar Front (depressions are formed along the Polar Front). The resultant unstable conditions produce the heavy cyclonic rainfall associated with mid-latitude depressions. The air then returns to 30 degrees north and south of the Equator where it descends to form an area of high pressure.

Polar Cell:
Air from the cell rises at 60 degrees north and south of the Equator, at the polar front and then flows to the north and south poles. Dry air sinking at the poles then blows along the surface toward 60 degrees north and south where the cycle is repeated.

Question 11

Jet Streams

Answer 11

Jet streams are narrow bands of strong wind or air currents that generally move eastward in the
mid to upper troposphere tropopause). Jet streams are some of the strongest winds in the atmosphere, with speeds usually ranging from 129 to 225 kilometers per hour

Jet streams form when warm air masses meet cold air masses in the atmosphere. They exist largely because of a difference in heat. Dramatic temperature differences between the warm and cool air masses can cause jet streams to move at much higher speeds.

The fast-moving air currents in a jet stream can transport weather systems across countries in the northern hemisphere, affecting temperature and precipitation.

Question 12

Rossby Waves

Answer 12

Rossby waves are large horizontal atmospheric undulation that is associated with the polar-front jet stream and separates cold polar air from warm tropical air.

Rossby waves form as a result of one, the uneven/differential heating of the Earth’s surface due to the different sizes and shapes the land masses
and two, the inability of air to travel through a mountain, causing it to rise up, go over or go around it.

They are created when air masses move northward or southward, causing variations in atmospheric pressure and creating areas of high and low pressure. These pressure variations in turn cause the jet stream to meander in a wave-like pattern, with troughs and ridges forming along its path.

The existence of these waves explains the low-pressure cells (cyclones) and high-pressure cells (anticyclones) that are important in producing
the weather of the middle and higher latitudes.

Sometimes, the waves can also stall and can lead to heatwaves, droughts and floods as the regions of hot and cold air hover over the same regions
for days, or even weeks.

Question 13

What causes local winds?

Answer 13

Local winds are caused by small scale temperature and pressure differences.

They affect a much smaller geographical area compared to large scale systems such as depressions and tropical cyclones.

Two examples of local winds are land and sea breezes and valley winds.

Question 14

Land & Sea Breezes

Answer 14

This is a wind system that develops over coastal areas.
It is caused by the different specific heat capacities of water and land to absorb and retain heat from the Sun.

During the day, if the weather is sunny and calm, the land quickly absorbs shortwave solar radiation and starts to warm. Some of this heat is transferred to the air above, which starts to rise.

By contrast, over the sea, the temperature does not rise so much because water warms relatively slowly.

The temperature difference between sea and lad sets up a pressure gradient, with relatively low pressure over the land and relatively high pressure over the sea.

This causes air to blow inland as a SEA BREEZE. Typically, the breeze starts in the mid-morning and strengthen during the afternoon, subsiding in the evening when the Sun’s rays are weaker.

Overnight, the land cools more quickly than the sea.
This causes a reversal in the temperature and pressure gradient and a breeze develops from the land onto the sea, known as a LAND BREEZE.

Question 15

Valley Winds

Answer 15

At night, the ground surface cools. This is particularly marked when the sky is clear because cloud cover
acts as a ‘blanket’ and reduces the heat loss from radiation cooling.
In mountain regions, the ground and air is coldest over snow and ice fields. The cold air is relatively dense and it starts to sink. If this flow continues, a cold wind, known as a KATABATIC WIND, develops down the valley.
During the day, the wind flow is reversed. The sun’s rays heat the valley floor and slopes, causing relatively warm air to rise. If the flow develops up the valley, it is known as an ANABATIC WIND.

Question 16

Microclimates

Answer 16

A microclimate is the climate in the lower few metres of the atmosphere, over a relatively small area, for example on a valley slope, in an urban
area or within a woodland area.

Local factors such as:
- slope angle
- quantity and type of vegetation cover
- building material
- heat conductivity
are all important influences.

Question 17

Valley Microclimates

Answer 17

It is dependent on aspect, slope angle and altitude.

Relatively cool air tends to sink downwards at night, valley bottoms are often cooler than higher slopes. Night time radiation from the Earth’s surface escapes upwards and there are no turbulent winds to cause air at different levels to mix.

Frost hollow (low lying areas in which frost is most likely) can form on the valley floor. The effect of frost hollows on farming is important. Plants that are
sensitive to frost have to be grown on valley slopes rather than on the valley bottom.

Within hilly and mountainous regions, the different angle and aspect of slope creates different microclimates on opposite sides of valleys. This is especially true for valleys that trend east-west because there is a marked difference in intensity of solar radiation that the north and south facing slopes receive.

Question 18

Woodland Microclimates

Answer 18

On hot days, it is often cooler in woodland or forests.
This is because there is a distinct microclimate under the trees.

Typically, between 5 and 15% of incoming solar radiation is reflected by leaves and much of the rest is absorbed by the tree canopy.

It is not only the temperature that is affected. Trees provide shelter from winds so air is often still in a woodland. Because air movement is weak, moisture from transpiration is not quickly dispersed and humidity tends to be high.

At night, the effect of a tree canopy is to retain heat, causing the range of temperature inside the
woodland to be less than elsewhere.

The exact microclimate within woodland depends upon the type of tree and season. Trees that provide a very dense canopy cut out most of the light, while deciduous trees in winter provide very little cover and a high proportion of light reaches the ground.

In general, the darker the conditions, the fewer plants will grow (therefore there is little vegetation on the floor of trees with a dense canopy cover).

Under deciduous trees there are often very dense vegetation in spring and then the vegetation tends to die in high summer, when the tree canopy is left.

Question 19

What is absolute humidity?

Answer 19

It is the mass of water vapour in a given volume of air(g/m^3)

Question 20

What is adiabatic cooling/warming?

Answer 20

This is an internal change in the pressure and temperature of a gas whereby no heat is gained or lost to an external source. There is a decrease in pressure accompanied by an associated increase in volume and a decrease in temperature as a parcel of air rises. Conversely, descending air experiences a rise in pressure and a decrease in volume resulting in a rise in temperature.

Question 21

What is advection cooling?

Answer 21

This refers to the drop in temperature resulting from warm moist air moving over a cooler land or sea surface.

Question 22

What is the carbon cycle?

Answer 22

This is a circulation revolving around the storage of carbon dioxide in the atmosphere. It involves the movement of carbon through the atmosphere, rivers, oceans, sedimentary rocks, and living organisms. The amount of atmospheric carbon can be increased by such activities as the burning of forest and fossil fuels and reduced by photosynthesis.

Question 23

What is conditional instability?

Answer 23

When such conditions are prevalent, the ELR is lower than the DALR but higher than the SALR. Rising air that might otherwise sink continues to rise as the release of latent heat resulting from condensation keeps the parcel of air warmer than the surrounding air.

Question 24

What is dew?

Answer 24

It is the condensation of water directly onto ground surfaces, vegetation or objects. Rapid heat loss at night causes the air closest to the surface to reach its dew point.

Question 25

What is the dew point?

Answer 25

This is the temperature at which air becomes saturated. Once the dew point has been reached, the process of condensation will commence forming dew, fog and cloud. (Relative humidity of 100%)

Question 26

What is the dry adiabatic lapse rate (DALR) ?

Answer 26

The rate at which an unsaturated parce of air cools as it rises, or warms as it descends. As a bubble of air forms and rises from the ground (example over a small island), it becomes warmer than the surrounding sea. As the bubble of air rises, it EXPANDS because atmospheric pressure is LOWER. This causes it to cool. (9.8 C per 1000m)

Question 27

What is the environmental lapse rate (ELR) ?

Answer 27

The environmental lapse rate refers to the actual rate at which the temperature of the surrounding air changes with respect to altitude in the atmosphere. It is measured or observed in the atmosphere and can vary depending on various factors such as time of day, season, weather patterns, and location. The environmental lapse rate can be either positive (temperature decreases with altitude) or negative (temperature increases with altitude), and it can vary significantly from the adiabatic lapse rates.

Question 28

What is instability?

Answer 28

The continued rising of an air mass that is warmer than the surrounding - environmental air. It results in large storm clouds.

Question 29

What is relative humidity?

Answer 29

The ratio of water vapour that is actually present in air to the amount of moisture that the air can hold when saturated

Question 30

What is the saturated adiabatic lapse rate (SALR) ?

Answer 30

The rate of fall in air temperature by adiabatic change as saturated air gains altitude (5.4 C per 1000m). It is less than DALR as latent heat is released as a result of condensation. If a rising air bubble falls in temperature below its dew point, condensation occurs and this reduces the lapse rate. This is because water vapour releases latent heat when it changes to a liquid. The heat has the effect of slowing the rate at which the rising air cools.

Question 31

What is an urban heat island?

Answer 31

An effect in which temperatures within an urban area are often significantly higher than those of surrounding rural areas.

Question 32

Stability (Stable Air)

Answer 32

This is where a parcel of air rises and cools at a faster rate than the air surrounding it. The parcel of air is colder and denser than its surroundings so cannot rise further and sinks. Condensation and then subsequent rainfall does not occur. Stability is most commonly associated with high pressure and anticyclones.

Question 33

Instability (Unstable Air)

Answer 33

If a parcel of air is then heated (by conduction, etc.) it leads to a high lapse rate and the air rises and cools less quickly than its surroundings. If it remains warmer than its surroundings, the air parcel will continue to rise. If dew point is reached, clouds and thunderstorms may result.

Question 34

Conditional Instability

Answer 34

This means that the parcel of air is stable as long as it DOES NOT fall in temperature to its dew point. Above the height where condensation occurs (i.e., the condensation level), the air starts to cool more slowly (at the SALR). It may reach a point where it becomes warmer than surrounding air and is then unstable. This situation can arise if air is forced upwards over high ground or over a cooler mass of air. It occurs if the ELR is between the DALR and SALR.

Question 35

What is advection fog?

Answer 35

This is caused when relatively warm, moist air passes over a colder surface. The lower layers of air are cooled and, if they go below the dew point, condensation occurs. This can happen on coastlines where a cold ocean current cools the air above. An onshore breeze can then blow the fog inland where it can persist for several kilometres. Eventually, the warmer land heats the air and the water droplets evaporate.

Question 36

What is radiation fog?

Answer 36

This occurs when the Earth’s surface cools at night, particularly in cloudless conditions. The cold ground cause the temperature of overlying air to fall below its dew point. The resulting condensation creates fog. It does not form in windy conditions because turbulent air does not stay in contact with the ground long enough for sufficient cooling to occur. In hilly or mountainous regions, cold air tends to flow downhill at night thereby causing the temperature to be lower in valleys than on higher slopes. This is why fog forms in hollows and valleys. Fog can persist all day if the cold air is trapped beneath warmer air in a temperature inversion. Under normal daytime conditions, the ground warms causing air to rise. But if it is foggy, the sunlight might not penetrate to the ground and there is no uplift of warm air to break the inversion. When this happens in urban areas, the combination of fog, smoke and vehicle exhausts can create SMOG. Only wind that is strong enough to mix the air can clear the fog under these circumstances.

Question 37

Collision and Coalescence Theory

Answer 37

In this theory, raindrops form from cloud droplets as a result of the two processes of collision and coalescence, causing droplets to merge into each other. This theory is associated with warm clouds, where the temperatures are still high enough for no ice to be present (water is in it liquid state). However, it also works in combination with the ice-crystal process in cool and cold clouds if a part of the temperature profile is above freezing. According to this theory, precipitation forms when small water droplets in a cloud collide and merge with each other, eventually growing large enough to fall to the ground as raindrops. The process of collision and coalescence begins when tiny water droplets in a warm cloud collide with each other, sticking together and forming larger droplets. As these larger droplets fall through the cloud, they continue to collide and merge with smaller droplets, growing in size and eventually becoming large enough to overcome the upward air currents that keep them suspended in the atmosphere. Once the droplets become heavy enough, they fall to the ground as precipitation.

Question 38

Ice-Crystal Theory

Answer 38

This process is associated with clouds where at least some of the water present exists in its solid state (requires both liquid droplets and ice particles in the cloud). As a result, it occurs in cold clouds (clouds whose tops rise above the freezing level). Most cold clouds have a mixed composition; with water droplets in the lower layers and supercooled water and ice above. In clouds like these, the rainfall can be intense. According to this theory, precipitation forms when ice crystals in the upper atmosphere grow in size through the process of deposition, in which water vapor freezes onto the surface of the crystals. As the ice crystals become heavier, they fall through the atmosphere, and if they encounter a layer of air with a temperature above freezing, they will begin to melt, forming raindrops.

Question 39

Short term variations in the global heat budget

Answer 39

Weather Systems: For example, during a high-pressure system (anticyclone), air descends, resulting in clear skies and dry weather, which allows more solar radiation to reach the Earth's surface, increasing the heat budget. In contrast, during a low-pressure system (cyclone), air ascends, leading to cloud formation and precipitation, which can reflect or absorb incoming solar radiation, reducing the heat budget. Atmospheric Aerosols: Atmospheric aerosols are tiny particles suspended in the atmosphere. Aerosols can originate from natural sources like volcanic eruptions, forest fires, or human activities such as burning fossil fuels and industrial processes. Aerosols can reflect and scatter incoming solar radiation, reducing the amount of solar radiation reaching the Earth's surface, and hence decreasing the heat budget. They can also absorb and re-emit outgoing longwave radiation from the Earth's surface, affecting the radiative balance. Aspect

Question 40

Convectional Rainfall

Answer 40

Very common in areas where the ground is heated by the hot sun, such as the Tropics. This is why those areas experience heavy rainfalls most afternoons. Convectional rainfall occurs when: - The surface of the earth is heated by the sun. - The warm surface heats the air above it. Hot air always rises so this newly heated air does so. - As it rises the air-cools and begins to condensate. - Further rising and cooling causes a large amount of condensation to occur and rain is formed. Convection tends to produce towering cumulonimbus clouds, which produce heavy rain and possible thunder and lightning.

Question 41

Frontal Rainfall

Answer 41

Frontal rainfall occurs when: - This is associated with the movement of depressions over the country - Two air masses meet, one a warm air mass and one a cold air mass. - The lighter, less dense, warm air is forced to rise over the denser, cold air. - This causes the warm air to cool and begin to condense. - As the warm air is forced to rise further condensation occurs and rain is formed. Frontal rain produces a variety of clouds, which bring moderate to heavy rainfall.

Question 42

Relief/Orographic Rainfall

Answer 42

Relief Rainfall occurs when: - The prevailing winds pick up moisture from the sea as they travel across it, making the air moist. - The moist air reaches the coast and is forced to rise over mountains and hills. - This forces the air to cool and condense, forming clouds. - The air continues to be forced over the mountains and so it drops its moisture as relief rain. - Once over the top of the mountain the air will usually drop down the other side, warming as it does so. This means it has a greater ability to carry water moisture and so there is little rain on the far side of the mountain. This area is called the rain shadow.

Question 43

Weather conditions associated with depressions

Answer 43

Clouds: Depressions are often associated with extensive cloud cover, as rising air cools and condenses, forming clouds. (stratus, nimbostratus, or cumulonimbus) Precipitation: Precipitation is often widespread and can be heavy, especially near the center of the depression. Wind: Low-pressure systems are characterized by cyclonic or counterclockwise rotation of winds in the Northern Hemisphere (clockwise in the Southern Hemisphere). Winds blow towards the center of the depression, which is known as the eye or the center of the cyclone, and can be strong, especially near the center. Instability: Depressions are often associated with unstable weather conditions, including rapidly changing weather patterns, thunderstorms, and sometimes severe weather events such as tornadoes or waterspouts.

Question 44

Weather conditions associated with anticyclones

Answer 44

Clear skies: Anticyclones are generally associated with clear skies and minimal cloud cover. As air descends and compresses in a high-pressure system, it becomes more stable, inhibiting the formation of clouds and promoting clear weather. Dry weather: Anticyclones tend to bring dry weather, as the descending air in high-pressure systems inhibits the formation of clouds and precipitation. This can result in prolonged periods of dry weather and low relative humidity. Light winds: Anticyclones are typically characterized by calm or light winds. The descending air in a high-pressure system tends to suppress the formation of strong winds, resulting in generally light and variable winds.

Question 45

How are Inter-Tropical Convergence Zones(ITCZ) formed?

Answer 45

The ITCZ is an area of low pressure that forms due to the action of the Hadley Cell, where the Northeast Trade Winds meet the Southeast Trade Winds near the Earth’s equator. Northeast and Southeast Trade Winds converge along the equatorial trough of low pressure. The rising air that results is responsible for the cloudiness and precipitation that mark the ITCZ.

Question 46

Weather conditions associated with ITCZs

Answer 46

Convectional rainfall: The ITCZ is known for its abundant rainfall due to the convergence of trade winds and the resulting uplift of warm, moist air. As the warm air rises, it cools and condenses, leading to convectional rainfall. This can result in heavy rainfall and thunderstorms, especially during the peak of the rainy season. Clouds: The ITCZ is often characterized by extensive cloud cover. The rising warm air leads to the formation of cumulus and cumulonimbus clouds, which can contribute to the rainy and sometimes stormy conditions associated with the ITCZ. Intense solar heating: The ITCZ is located near the equator, where the sun's rays are most direct and intense. This can result in strong solar heating of the surface, leading to high temperatures and high humidity.

Question 47

How are hurricanes formed?

Answer 47

Stage 1 - Trade winds become unstable because of northward movement of the ITCZ Stage 2 - Warm, moist air is forced upwards and cools rapidly Stage 3 - The Earth rotation causes spiral motion Stage 4 - Lower-level winds spiral inwards towards the eye

Question 48

Weather conditions associated with hurricanes

Answer 48

1) Strong Winds: Hurricanes are characterized by powerful winds that can reach sustained speeds of over 74 miles per hour (119 kilometers per hour) or more. 2) Heavy Rainfall: Hurricanes are also known for their heavy rainfall, which can result in widespread and prolonged precipitation. 3) Thunderstorms and Lightning: Along with strong winds and heavy rainfall, hurricanes often generate numerous thunderstorms and lightning. 4) Storm Surges: They are large and powerful oceanic waves that are driven by the strong winds and low atmospheric pressure associated with hurricanes.

Question 49

Warm fronts

Answer 49

Warm fronts are formed when warm air rises over a mass of cold air. As the air lifts into regions of lower pressure, it expands, cools and condenses the water vapour as wide, flat sheets of cloud. Warm fronts are shown on synoptic charts by a solid line with semicircles pointing towards the colder air and in the direction of movement. On coloured weather maps, a warm front is drawn with a solid red line with red semicircles.

Question 50

Cold Fronts

Answer 50

Cold fronts are usually associated with depressions. A cold front is the transition zone where a cold air mass is replacing the warmer air mass. The cold air is following the warm air and gradually moves underneath the warmer air. When the warm air is pushed upwards it will rain heavily. Often more rain will fall in the few minutes the cold front passes than it will during the whole passage of a warm front. As the cold front passes, the clouds roll by and the air temperature is cooler. Cold fronts are shown on synoptic charts by a solid line with triangles along the front pointing towards the warmer air and in the direction of movement. On coloured weather maps, a cold front is drawn with a solid blue line with blue triangles.

Question 51

Occluded Fronts

Answer 51

Occluded fronts occur at the point where a cold front takes over a warm front or the other way around. If a cold front undercuts a warm front it is known as a cold occlusion and if the cold front rises over the warm front it is called a warm occlusion. Occluded fronts bring changeable weather conditions. On a synoptic chart occluded fronts are represented by semicircles and triangles positioned next to each other. The triangles are in blue and the semicircles are in red, or both are purple (mixing both red and blue colours together).

Question 52

Tropical disturbance - Tropical Cyclone

Answer 52

If tropical disturbances intensity and develop a greater structure and cyclonic rotation, they can become tropical depressions. In turn, if a tropical depression intensifies and the sustained wind speeds surpass 62 km per hour, it becomes a tropical storm. In turn, if further development occurs and the fully formed tropical storm exhibits sustained winds in excess of 119 km per hour, a tropical cyclone is formed.

Question 53

Conditions for hurricane formation

Answer 53

1) Ocean Temperatures: Ocean waters must have warm sea-surface temperatures above 26°C. Below this threshold temperature, hurricanes will not form or they will weaken rapidly once they move over water below this threshold. 2) Distance form Equator/Latitude: Hurricanes generally originate between 5-25° latitude in tropical waters. Without the spin of the earth and the resulting Coriolis force, hurricanes would not form. Since the Coriolis force is at a maximum at the poles and a minimum at the equator, hurricanes cannot form within 5° latitude of the equator. The Coriolis force generates a counter clockwise spin to low pressure in the Northern Hemisphere and a clockwise spin to low pressure in the Southern Hemisphere. 3) Vertical Wind Shear: Hurricanes need a low vertical wind shear (change in wind speed with height), especially in the upper level of the atmosphere. Strong upper level winds destroy the storms structure by displacing the warm temperatures above the eye and limiting the vertical accent of air parcels. 4) Humidity: Hurricanes need high relative humidity values from the surface to the mid-levels of the atmosphere. Dry air in the mid-levels of the atmosphere impedes hurricane development. Dry air causes evaporation of liquid water. Since evaporation is a cooling process, it reduces the warm core structure of the hurricane and limits vertical development of convection.

Question 54

Air Masses

Answer 54

An air mass is a large volume of air which travels from one area (source region) to another. An air mass exhibits a uniformity of temperature, humidity and vertical structure within the lower atmosphere. The weather an air mass brings is determined by the region it has come from and the type of surface it has moved over. In large, relatively uniform expanses of the world, masses of air in contact with the surface may remain stationary for several days (often beneath a high-pressure system having calm/light winds)

Question 55

Types of Air Masses

Answer 55

Pc - Polar Continental (affects the northern Caribbean) Em - Equatorial Marine Tm - Tropical Marine

Question 56

Urban vs Rural Microclimates

Answer 56

Temperature: Urban- Higher temperatures in the day and night. Buildings and roads absorb and trap more heat. Heat is also generated by people, buildings, cars and factories Rural- Areas with trees are cool since the canopy intercepts most of the sunlight resulting in small diurnal range due its moderating effect. Grasslands hotter but moderated by strong breeze Interception and Infiltration: Urban- Interception is less with limited infiltration and aggressive run-off. Flash flooding can be a major problem Rural- Most rain is intercepted and infiltration rates are very high as the forest floor acts like a sponge Wind: Urban- Tall building acts as windbreakers but they often produce eddies. High winds may be funneled in between buildings causing turbulence Rural- Trees reduce wind speed and are planted as windbreakers Precipitation: Urban- Greater frequency, duration and thickness of fog. Thunder and lightning are more frequent due to strong thermals Rural- Rainfall intense and in large amounts distributed throughout the year in tropical rainforest, facilitated by the high evapotranspiration rates.

Question 57

Causes of climate change

Answer 57

1) Volcanic eruptions: They result in large quantities of dust being thrown high into the atmosphere. This can lower the temperature of the Earth's atmosphere. Dust particles are also act as hygroscopic nuclei that facilitate condensation and lead to cloud formation and rainfall 2)Plate Tectonics: After the separation of Pangaea, the continents moved away from the Equator and the temperature over them decreased. Long periods of uplift in the geological past have produced mountains that acts as barriers to the circulation of air and cause the climate to change 3) Global Warming & Human Influence: An increase in greenhouse gases is leading to an increase in temperature worldwide, which in turn can result in various climate changes. It is already causing ice at the polar ice caps to melt. Use of internal combustion engines. Methane produced in the rearing of farm animals. Burning of fossil fuels.

Question 58

The greenhouse effect

Answer 58

When sunlight reaches Earth’s surface, it can either be reflected back into space or absorbed by Earth. Once absorbed, the planet releases some of the energy back into the atmosphere as heat (also called infrared radiation). Greenhouse gases (GHGs) like water vapour (H2O), carbon dioxide (CO2), and methane (CH4) absorb energy, slowing or preventing the loss of heat to space. In this way, GHGs act like a blanket, making Earth warmer than it would otherwise be. These greenhouse gas emissions have increased the greenhouse effect and caused Earth’s surface temperature to rise.

Question 59

Evidence of rapid climate change

Answer 59

1) Sea level rise: Global sea level has risen about 17cm in the last century. The rate in the last decade, however, is nearly double that of the last century. 2) Global temperature rise: All three major global surface temperature reconstructions show that Earth has warmed since 1880. Most of this warming has occurred since the 1970s, with the 20 warmest years having occurred since 1981 and with all 10 of the warmest years occurring in the past 12 years. 3) Declining Arctic sea ice: Both the extent and thickness of Arctic sea ice has declined rapidly over the last several decades. 4) Extreme events The number of record high temperature events in the United States, for example, has been increasing, while the number of record low temperature events has been decreasing, since 1950. The U.S. has also witnessed increasing numbers of intense rainfall events.

Question 60

Impact of Climate Change

Answer 60

Climate change affects our environment and natural resources, and impacts our way of life in many ways. For example: 1) Warmer temperatures increase the frequency, intensity, and duration of heat waves, which can pose health risks, particularly for young children and the elderly. 2) Rising sea levels threaten coastal communities and ecosystems. (Maldives and Mauritius) 3) Changes in the patterns and amount of rainfall, as well as changes in the timing and amount of stream flow, can affect water supplies and water quality and the production of hydroelectricity. 4) Changing ecosystems influence geographic ranges of many plant and animal species and the timing of their lifecycle events, such as migration and reproduction. 5) Increases in the frequency and intensity of extreme weather events, such as heat waves, droughts, and floods, can increase losses to property, cause costly disruptions to society, and reduce the availability and affordability of insurance.

Question 61

Strategies for reducing global warming

Answer 61

1) Impose special taxes on carbon dioxide emissions to encourage energy conservation 2)Organize tree planting programmes 3) Increase funding for research into alternative renewable sources of energy 4) Provide financial aid to developing countries to help reduce environmental degradation especially deforestation 5) Develop techniques for recovering methane that is given off by landfills and cattle farms (methanes traps 20 times as much heat as CO2

Question 62

Consequences of Global Warming

Answer 62

1) Shortage of fresh water 2) More powerful hurricanes 3) Extensive bleaching of coral reefs 4) Large-scale beach erosion 5) Decline in fishing industry

Question 63

Long term variations in the global heat budget

Answer 63

1) Changes in Surface Features: Alterations in the Earth's surface features, such as land use changes and modifications to Earth's surface albedo (reflectivity), can also impact the heat budget. For example, deforestation, urbanization, and changes in agricultural practices. These changes can lead to alterations in local and regional heat budgets, and consequently impact climate patterns over longer periods. 2) Changes in Atmospheric Composition: Changes in the composition of the Earth's atmosphere can also influence the heat budget. For instance, increases in greenhouse gases. Human activities, such as burning fossil fuels, deforestation, and industrial processes, have contributed to the increase in greenhouse gases in the atmosphere, leading to long-term changes in Earth's heat budget and influencing global climate. 3) Changes in Solar Radiation: Variations in solar radiation reaching the Earth's surface can have long-term effects on Earth's heat budget. Factors such as changes in solar activity, such as solar cycles or variations in solar output, can impact the amount of solar radiation received by the Earth.

Question 64

Adiabatic Lapse Rate (ALR)

Answer 64

It describes what happens when a parcel of air rises and the decrease in pressure is accompanied by an associated increase in volume and a decrease in temperature. Conversely, descending air will be subject to an increase in pressure causing a rise in temperature

Question 65

What are depressions?

Answer 65

Depressions, sometimes called mid-latitude cyclones or wave cyclones, are areas of low pressure located between 30° and 60° latitude. Depressions are characterized by their circular wind-flow, low pressure field and sharply contrasting air mass properties. Depressions develop when warm air from the sub-tropics meets cold air from the polar regions.

Question 66

What are anticylcones?

Answer 66

Anticyclones are the opposite of depressions - they are an area of high atmospheric pressure (typically above 1020mb) where the air is sinking. In contrast to depressions, anticyclones only involve one type of air mass which usually cover large areas and do not have any fronts. They are high pressure systems in which the air moves downwards towards the earth's surface. As the air descends, the molecules become compressed, the pressure increases and it warms. When air is warming, any moisture in the atmosphere is evaporated so no clouds can form.

Question 67

Where are Tropical Rainforest located?

Answer 67

Tropical rainforests are generally found between 30°N and 30°S latitudes, covering 6 - 7% of the Earth’s land surface. Tropical rainforests can be found around the world: In Central and South America; in Western Africa, eastern Madagascar, and the Zaire basin; and in Indo-Malaysia along the west coast of India,

Question 68

What are the climatic conditions associated with tropical rainforest?

Answer 68

- Equatorial climate zones - Temperatures are consistently high throughout the year - The diurnal and annual temperature ranges are small - The environment is pretty wet in tropical rainforests, maintaining a high humidity of 77% to 88% year-round. - The yearly rainfall ranges from 80 to 400 inches (2000 to 10 000 mm) and it can rain very heavy.

Question 69

What are the flora and fauna associated with tropical rainforest?

Answer 69

There four principal layers of vegetation: 1) Emergent - Wide crowns, 50m 2) Canopy - Their branches form a canopy, like a big beach umbrella that shades the forest floor. Thick, woody vines are found in the canopy. 3) Understory - dark, cool area below the canopy, but above the ground. The understory is shaded from much of the sunlight by the canopy. 4) Shrub - This is the area where fallen, decomposing plants and trees lay on the ground. Epiphytes: Epiphytes are plants that grow on the surfaces of other plants, such as trees, without harming or taking nutrients from the host plant. In tropical rainforests, epiphytes form unique plant communities that thrive in the canopy layer of the forest. Orchids, bromeliads, ferns, and mosses are some of the common types of epiphytes found in tropical rainforests. These plants have adapted to living in the canopy by using specialized mechanisms to capture and store water and nutrients from the air and rain. Lianas: Lianas are woody vines that grow vertically from the forest floor to the canopy, often wrapping around trees for support. In tropical rainforests, lianas form dense, tangled networks that create a unique plant community. They compete with trees for sunlight and other resources, and can sometimes outcompete the trees, leading to changes in forest structure and composition. Lianas often have specialized adaptations, such as thick stems for support and large leaves to capture sunlight in the understory, which allow them to thrive in the competitive environment of the rainforest. Buttress roots: These are the upper part of the roots large trees that add considerably to the mechanical strength of the base of the trunk. Eg the silk cotton tree Drip tip: A sometimes funnel-shaped part of leaves on plants found in tropical rainforests that allow water to easily drip off the leaf during rainfall

Question 70

The importance of trees and forest

Answer 70

- More food and medicine - More timber - Higher water table (increased infiltration-increased percolation-increased groundwater storage) - Reduced soil erosion - Home for flora and fauna - Increased evapotranspiration, more rain

Question 71

Challenges with the development of tropical rainforest

Answer 71

- The soil is usually not very fertile as nutrient supply is dependent on the maintenance of a thick forest cover - Discomfort due to the high humidity and temperatures which at times can be unbearable at well over 30 degrees C - Developing countries need to exploit as many of their resources as possible in order to foster development. However at the same time they are being urged by developed countries to conserve forest for the greater good of the Earth's climate - Diseases such as yellow fever, malaria and dengue are carried by mosquitoes which thrive in the wet environment.

Question 72

Opportunities with the development of tropical rainforest

Answer 72

- land for agriculture, houses and roads - jobs for local workers in road building, logging, agriculture, mining and construction - the generation of income (often in valuable foreign currency) for the LDC when wood, minerals, and other resources are sold - scientific investigation into rainforest plants may provide new food sources and medicines

Question 73

Sustainable management of the forest

Answer 73

- Agro-forestry - growing trees and crops at the same time. This lets farmers take advantage of shelter from the canopy of trees. It prevents soil erosion and the crops benefit from the nutrients from the dead organic matter. - Selective logging - trees are only felled when they reach a particular height. This allows young trees a guaranteed life span and the forest will regain full maturity after around 30-50 years. - Education - ensuring those involved in exploitation and management of the forest understand the consequences behind their actions. - Afforestation - the opposite of deforestation. If trees are cut down, they are replaced to maintain the canopy. - Forest reserves - areas protected from exploitation. - Monitoring - use of satellite technology and photography to check that any activities taking place are legal and follow guidelines for sustainability.

Question 74

Sustainable management of the forest

Answer 74

- Agro-forestry - growing trees and crops at the same time. This lets farmers take advantage of shelter from the canopy of trees. It prevents soil erosion and the crops benefit from the nutrients from the dead organic matter. - Selective logging - trees are only felled when they reach a particular height. This allows young trees a guaranteed life span and the forest will regain full maturity after around 30-50 years. - Education - ensuring those involved in exploitation and management of the forest understand the consequences behind their actions. - Afforestation - the opposite of deforestation. If trees are cut down, they are replaced to maintain the canopy. - Forest reserves - areas protected from exploitation. - Monitoring - use of satellite technology and photography to check that any activities taking place are legal and follow guidelines for sustainability.

Question 75

What are the climatic conditions associated with tropical grasslands (savannahs)?

Answer 75

The tropical grasslands (savanna) biome is located mainly between latitudes 5 degrees and 15 degrees North and South of the equator Savanna regions have two distinct seasons - a wet season and a dry season. There is very little rain in the dry season. In the wet season vegetation grows, including lush green grasses and wooded areas. The largest expanses of savanna are in Africa for example Kenya and Tanzania. Savanna grasslands can also be found in Brazil in South America, Trinidad (Aripo Savannah) and Guyana (Rupununi Savannahs)

Question 76

What are the flora and fauna associated with tropical grasslands?

Answer 76

Plants have to adapt to the long dry periods. Many plants are xerophytic - for example, the acacia tree with its small, waxy leaves and thorns. Plants may also have long roots that reach down to the water table. Baobab Tree- Swollen trunk with water, leaves shed Pyrophyte- A plant that is adapted to withstand seasonal fires

Question 77

Challenges with the development of tropical grasslands

Answer 77

- Much of the area is unsuitable for certain types of land use like cultivating agricultural crops due to poor soil quality and low rainfall - The tsetse fly which carries sleeping sickness in some parts of Africa is a deterrent to the successful rearing of cattle -Human activity often results in fires that can burn very large areas

Question 78

Opportunities with the development of tropical rainforest

Answer 78

- Quarrying to remove sand and gravel - Wild animals in grasslands areas of Africa are used as a tourist attraction - Ranching - Storage of carbon in the soil which remains undisturbed

Question 79

What are the climatic conditions associated with temperate grasslands?

Answer 79

- Cool temperate continental - Large seasonal range of temperatures - The cloudless skies also result in a large diurnal range of temperature. - Winters are very cold with some months having temperatures below freezing

Question 80

Where are temperate grasslands located?

Answer 80

- They occur in the northern hemisphere in the center of continents between the latitudes of 40 and 60 degrees North. The best examples exist in the North American Prairies and the Russian steppes

Question 81

What are the flora and fauna associated with temperate grasslands?

Answer 81

The grasses do not grow as tall or as rapidly as those of tropical grasslands. Buffalo and grama grasses are dominant. Also oats, wheat, barley. With growth buds at or just below the surface, the grasses are able to survive cold, drought and fire. The grasses provide food for herbivores such as bison, antelopes, kangaroos and rabbits

Question 82

Challenges with the development of temperate grasslands

Answer 82

- Climate extremes with heat waves in summer and harsh winters - Environmental degradation - Extinction of fauna and flora

Question 83

Opportunities with the development of temperate grasslands

Answer 83

- Bread basket of the world's cereal food production wheat, rye, oats, barley - Large cattle ranches

Question 84

Where are Northern coniferous forest located?

Answer 84

They occur north of 60 degrees North in North America and Eurasia as well as at high altitudes in some mountains in temperate latitudes The largest areas of this type of vegetation are in Canada and Russia

Question 85

What are the climatic conditions associated with Northern coniferous forest ?

Answer 85

- They thrive in cold continental climates with long winters - Snowstorms are common - Several months have temperatures below freezing

Question 86

What are the flora and fauna associated with Northern coniferous forest?

Answer 86

- Coniferous trees have thick bark to protect against the cold. - They are cone-shaped, with flexible branches which help them to cope with heavy snow fall. - Pine cones protect the seeds during the harsh winter. - The thin waxy needles reduce water loss. - Their evergreen nature means that the needles can photosynthesize whenever there is sufficient sunlight. - The dense forest creates warmth during the harsh winter. black spruce, larch or tamarack and white spruce the most common species. Coniferous forest exist as one layer of vegetation. The undergrowth is limited due mainly to the thick, spongy layer of acidic, slowly decomposing neddles

Question 87

Challenges with the development of Northern coniferous forest

Answer 87

- Harsh winters, blizzards and snowstorms - Water exists in the form of ice during winter and little rainfall occurs during summer so water conservation is important

Question 88

Opportunities with the development of Northern coniferous forest

Answer 88

- Strands of softwood trees that are used in the pulp and paper industry - Many countries in the Caribbean have used Caribbean pine to stabilize the soil in steep mountainous terrain that is subject to fires during the dry season. - Establishing parks for recreational. Hiking, kayaking and 'white-water' rafting

Question 89

What are the four main components of soil?

Answer 89

1) Minerals: these are naturally occurring chemical elements or compounds that possess a crystalline structure and are the constituents of rocks. When rocks break down into soils, some of the mineral components become available to plants as nutrients. 2) Organic Matter: this is the material that forms from living matter. There is an accumulation of decaying remains of the leaves, stems and the roots of the plants in the upper layers of the soil. In addition, there is also waste matter from worms, insects and other animals. The decay processes are carried out by a number of microorganisms (bacteria, fungi, etc.). 3) Water: there is an electrical attraction between the mineral particles and the water molecules (from rainfall) surrounding them. In a moist soil, water fills much of the space between the mineral particles. Even in dry soils, the attraction of the water molecules around the mineral particles can still be present, with a thin film of water around the particles. The water is a weak solution of the various chemicals found in the soil. Without the water, many chemical changes cannot occur within the soil. 4) Air: the air in soils contains more carbon dioxide and less oxygen and nitrogen than atmospheric air. The air fills the spaces among the mineral particles, organic matter and water.

Question 90

What are the horizons of the soil profile?

Answer 90

The O Horizon is where leaves and other decaying vegetation lie on the surface. This mainly organic layer is sometimes subdivided into: - L: Litter (leaves and other organic debris) - F: Fermentation layer of partly decomposed organic matter - H: Humus (fully decomposed organic matter) Some of the material in the O Horizon is carried downwards into the A Horizon by insects and other small organisms. The A Horizon is where most of the organic material accumulates and humus content is high. Soluble minerals and clay particles are washed down or ELUVIATED from the A into the B Horizon. The B Horizon consists of weathered parent material and redeposited minerals and clay particles. It is sometimes called the ZONE OF ILLUVIATION. The C Horizon is made up of weathered and disintegration bed rock and other parent material.

Question 91

Soil Texture

Answer 91

Soil texture is the degree of coarseness or fineness of a soil (size of the particles in the soil) and is determined by the proportions of sand, silt and clay. The texture of a soil can be determined by feel. A sandy soil is light. It feels gritty and does not stick together when squeezed. It warms and cools quickly. It also allows water to soak through relatively quickly (it is porous, as the sand particle form irregular shapes that leave gaps in between, even when they are packed together). A clay soil is heavy and sticky when wet and can be rolled and moulded. It does not let water soak through as quickly as a sandy soil. This is because the fine texture allows the particles to pack close together. Although this makes the soil less porous, it allows more water to be retained in the soil. A silty soil feels smooth, almost ‘soapy’ and will form a ball. It qualities lie in between those of sand and clay. A soil that is a mix of clay, sand and/or silt is called a ‘loam’.

Question 92

What does soil texture affect?

Answer 92

1) the moisture content and aeration 2) retention of nutrients 3) ease of cultivation and root penetration

Question 93

What are the types of soil structures?

Answer 93

Crumb -the peds form irregular shapes approximately 2-4mm in diameter. Air and water can pass through this type of soil, between the peds and also through the peds themselves which are porous. Excellent productivity Granular - the peds are usually small and are often nearly round in shape. Soils with these structures are highly porous and have high permeability if the peds remain intact. Platy - Flat overlapping plates with horizontal axes. Low porosity and drainage restricts root growth. Low productivity Blocky - Irregular shape close fitting rounded or angular edges. Porous and permeable with good drainage. Productive Prismatic - Vertical columns with angular edges. Porous and permeable with good drainage and root development. Very good productivity Columnar - Vertical columns with rounded edges. Porous and permeable with good drainage and root development. Very good productivity

Question 94

Soil Fertility

Answer 94

Soil fertility is the ability of soil to provide water, air, and nutrients for plant growth. Soil texture and structure influence fertility by affecting water retention and aeration. Soil moisture is crucial for supplying water and nutrients to plants, while air in the soil contains oxygen needed by living organisms. Soil organisms break down organic matter, and humus, formed from decomposition, provides nutrients and improves soil structure. In sandy soils, humus retains moisture, while in clay soils, it improves drainage and aeration. Warm, airy soils support faster decomposition, and microorganisms like bacteria and fungi play a crucial role. Larger organisms like worms and ants create passageways for air and warmth in the soil. Nutrients, including carbon, hydrogen, and oxygen from rainwater and air, are essential for plant growth. Other nutrients come from sources like humus, rock minerals, fertilizers, and manure. Major nutrients like nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur, as well as minor nutrients like iron, manganese, copper, and zinc, are vital for plant growth. Nitrogen is the most important nutrient required in significant quantities after carbon, hydrogen, and oxygen.

Question 95

What is soil acidity?

Answer 95

This is a measure of the concentration of hydrogen cations with greater acidity indicating a higher concentration. Soils that are either slightly acidic or basic are best for farming. Too much acidity however releases iron and aluminium which can be toxic to plants and other organisms in excessive amounts

Question 96

What is soil colour?

Answer 96

In some cases soil colour may reflect soil formation or parent material. Blacks soils indicate the presence of humus and red soils indicate iron. A white crust in a semi-arid area indicates a saline crust, while a white layer in a humid environment indicates heavy leaching. Grey-blue speckling indicates reduced iron compounds, poor drainage and therefore gleying.

Question 97

Factors affecting soil formation

Answer 97

1) Climate: including temperature and precipitation, influences soil properties such as weathering, organic matter decomposition, and vegetation. In humid tropical regions, climate promotes high humus content and deep weathered layers in soils, while in Arctic areas, soils are thin and slow to decompose due to cold and waterlogged conditions. 2) Parent material: such as bedrock and unconsolidated materials, impacts soil formation by influencing soil texture, mineral nutrient content, depth, drainage, and color. Different rock types weather at varying rates, releasing minerals differently. Parent material undergoes mechanical and chemical weathering processes. 3) Plants: They utilize carbon, hydrogen, and nutrients from air, water, and soil for growth. When plants die, these elements are recycled and returned to the soil. Different types of plant material decompose at varying rates, with soft tissues decaying rapidly and woody material and coniferous needles decomposing slowly. The rate of decomposition affects the acidity and fertility of the resulting soil, with slower decomposition resulting in more acidic and less fertile soil. Soil pH can vary depending on the type of vegetation, with coniferous trees typically resulting in more acidic soil compared to deciduous trees. Decomposition is carried out by micro-organisms, including bacteria and fungi, as well as other organisms like mites, worms, insects, and mammals. Organic matter undergoes mineralization and humification stages during decomposition. 4) Relief: It causes different drainage conditions and by determining the aspect of soils (the way they face, affecting how much sunlight or shade they receive). Soils formed on slopes are generally well drained, but are often thin because material is washed downslope. On flat land, soils can sometimes be waterlogged but they usually have a greater depth than on slopes. A sequence of soil types down a slope is known as a CATENA. 5) Time: Soils develop slowly and show distinct characteristics based on their age and formation. Tropical soils are typically older and deeper compared to soils in temperate regions. Recently deposited materials, such as volcanic ash or sand dunes, may have very young soils with no recognizable horizons and little mixing of organic matter.

Question 98

Soil classification - Zonal Soils

Answer 98

Mature soils developed over a long time under the influences of a particular climate. Examples include podzols, chernozems, latosols and laterites Temperature and precipitation have a great influence on natural vegetation. The vegetation provides the organic matter that decomposes into soil and, in turn, is recycled in plant nutrients. Climate also affects the rate of weathering of the underlying parent material. For example, in hot humid climates where chemical weathering is rapid, a deep soil layer is typical.

Question 99

Soil classification - Intrazonal Soils

Answer 99

Typres of soil whose formation is related to particular conditions of rock type or ground water. Examples include rendzina and terra rossa derived from limestone and gley soils

Question 100

Soil classification - Azonal Soils

Answer 100

Immature soils that have undergone limited development and are characterized by an absence of well-developed soil horizons. these include alluvial and scree soils

Question 101

Soil types - Lateritic Soils (Latosols)

Answer 101

They are found in humid tropical and equatorial zones They are characterized as follows: 1) Chemical and mechanical decomposition of the parent rock is complete, owing to the favourable conditions of moisture and heat. 2) Silica has been almost entirely leached from the soil. 3) Sesquioxides of iron and aluminium have accumulated in the soil as abundant and permanent residual materials. 4) Humus is almost or entirely lacking because of the rapidity of bacterial action in the prevailingly warm temperatures. 5) The soil is distinctively reddish because of the presence of sesquioxides of iron. The silicate clay minerals render the latosols relatively low in plasticity (stickiness) and remarkably porous. Consequently rainfall sinks readily into these soils. True latosols are found only in warm, humid regions and, hence, correspond closely with the wet equatorial climate and the tropical wet-dry climate (though the red-yellow podzolic soils show the effects of laterization, they are not to be classified as true latosols). Latosols quickly lose their fertility under crop cultivation because excessive leaching has removed the plant nutrients in all but a thin surface layer. However, the soil is favourable for the growth of broadleaf evergreen rainforest. An interesting feature of latosols is the local development of accumulations of iron and aluminium sesquioxides into layers that can be cut out as building bricks. The material is termed laterite. On exposure to the drying effects of the air, these blocks become very hard. Valuable mineral deposits occur as laterites. These are thick layers of such minerals as bauxite, limonite and manganite. Variations of the latosols have been described as yellowish-brown lateriatic and reddish-brown lateriatic soils. Large upland areas of Africa and India within the tropical wet-dry climate regime have black and dark gray tropical soils. These dark soils may be related to special conditions of underlying bedrock.

Question 102

Soil types - Chernozems

Answer 102

They are black soils and are found in temperate grasslands such as the prairies of North America and the steppes of Europe. They are deep, fertile soils that retain water well. The tall grasses dry down to produce a thick sod cover. Grasses extract many bases from the soil but soon return when they die The extensive root systems keep the soil well aerated, producing a fine crumb structure rich in humus. Where ploughing takes place, it mixes the soil which results in good yields for extended periods There is a predominant upward movement of water caused by high summer temperatures and drying winds. Calcium carbonated accumulates as nodules that are mostly concentrated about 1m below the surface. Slight leaching occurs during snow melt and rainfall. A dark homogeneous A1 layer forms that is usually more than 1 m thick. Beneath this is a brownish A2 layer containing calcium carbonate and this merges with an distinct B horizon.

Question 103

Soil Erosion

Answer 103

Soil erosion is a natural process. It becomes a problem when human activity causes it to occur much faster than under natural conditions. Soil erosion by water, wind and tillage affects both agriculture and the natural environment. However it has been accelerated as a result of mankind's unwise actions, such as overgrazing or unsuitable cultivation practices. These leave the land unprotected and vulnerable. Then, during times of erosive rainfall or windstorms, soil may be detached, transported and deposited.

Question 104

The effects of soil erosion

Answer 104

1) Desertification Desertification can be characterized by the droughts and arid conditions the landscape endures as a result of human exploitation of fragile ecosystems. Effects include land degradation, soil erosion and sterility, and a loss of biodiversity, with huge economic costs for nations where deserts are growing. 2) Loss of arable land Arable land is any land that can be used to grow crops. Many of the practices used in growing those crops can lead to the loss of topsoil and destruction of soil characteristics that make agriculture possible. 3) Clogged and polluted waterways Soil eroded from the land, along with pesticides and fertilizers applied to fields, washes into streams and waterways. This sedimentation and pollution can damage freshwater and marine habitats and the local communities that depend on them. 4) Increased flooding Land is often transformed from a forest or other natural landscape, such as floodplains and wetlands, into a crop field or pasture. The converted land is less able to soak up water, making flooding more common. There are methods to improve soil water holding capacity as well as restoration and maintenance of wetlands.

Question 105

Soil Conservation

Answer 105

Soil conservation is a "combination" of practices used to protect the soil from degradation. First and foremost, soil conservation involves treating the soil as a living ecosystem and recognizing that all the organisms that make the soil their home, play important roles in producing a fertile healthy environment. In addition to preserving soil life and organic matter, the other principles of soil conservation are to: - manage surface runoff, - protect bare exposed soil surfaces, and highly susceptible sites (e.g. steep slopes), and -protect downstream watercourses from sedimentation and pollution.

Question 106

Soil Conservation methods

Answer 106

1) Contour Farming Contour farming involves tilling and planting along the contour, rather than up and down the slope. The furrows and rows of plants act as dams which slow down the flow of water moving down the slope. Unless some type of contour farming is used, particularly on long slopes, serious field erosion can result. 2) Windbreaks A windbreak or shelterbelt is a vegetation barrier designed to reduce or eliminate the velocity of the wind and hence reduce wind erosion. Windbreaks consist of one to five rows of trees or shrubs; shelter belts are six or more rows wide. 3) Crop Rotation Crop Rotation is an alternative to planting a field in the same crop year after year Instead, the main crop is rotated. Crop rotation provides several benefits. Rotation reduces the risk of insect and disease problems, thus decreasing a pesticide dependency. Legumes have the special ability to take in atmospheric nitrogen and convert it to forms usable by other plants (nitrogen fixing plants). When used as a green fertilizer, legumes return a significant amount of organic matter to the soil. Their deep roots create tunnels for air and water to enter the soil. 4) Afforestation - deep rooted trees and other types of vegetation are planted in areas where vegetation was removed. Fast growing trees are usually used. The aim is to produce a dense network of roots to bind the soil together

Question 107

Catena

Answer 107

A sequence of soil types down a slope owing to variations of weathering, transportation processes and soil moisture conditions

Question 108

Capillary action

Answer 108

The upward movement of water through the soil. It is caused by the attraction of water molecules to the particles of soil. In dry climates, salts are drawn upward and may result in a crust of salt forming on the surface

Question 109

Mor

Answer 109

Undecomposed leaf litter. In areas that are cold and wet, plant matter is slow to decompose since the actions of soil organisms are inhibited. This results in an acidic, nutrient deficient surface horizon

Question 110

Mull

Answer 110

Humus incorporated within the soil to give a crumbly, black, nutrient rich layer. In moist well aerated soils it favours plant growth

Question 111

Illuviation

Answer 111

The deposition in the B horizon of soil matter removed from the A horizon. Concentration of iron and clay particles may result in the formation of iron and clay pans (impermeable layers)

Question 112

Eluviation

Answer 112

The washing down of soil constituents through a soil profile by the process of leching (involving the dissolving of minerals) and the mechanical downwash (involving solids such as humus and clay)

Question 113

Regolith

Answer 113

A layer of decomposed or disintegrated rock debris overlying un-weathered bedrock. It differs from a mature soil in that it is deficient in organic matter

Question 114

Field Capacity

Answer 114

The maximum amount of water that a soil can hold before it is drawn away by gravity

Question 115

Identification of soil horizons

Answer 115

1) Obtain permission from the owner of the land before digging the pit. 2) If the area is vegetated, cut the turf and place it to one side. 3) Place the dug soil onto a plastic sheet. Replace the soil into the hole when completed with the study. 4) Try not to disturb the leaf litter layer around the hole when digging, since its depth will need to be recorded. 5) Dig the pit either 1 metres deep or down to the regolith, whichever is less. Use a measuring tape. 6) As best as possible, dig the hole so that it is straight down (vertical). Slice one face clean. 7) Sketch each horizon, ensuring to include the roots, what the leaf litter looks like, any worm holes or other signs of soil creatures. Colour pencils are essential. 8) Measure, in cm, the depth of each soil layer from the top of each soil horizon to where approximately the soil horizon changes. Record the depth on your sketch 9)Record all measurements/features on record sheet/notebook

Question 116

Leaching

Answer 116

It is the rapid removal of water-soluble bases from the upper horizons of the soil profile. Some leached material may be redeposited in the lower horizons while some is completely lost as it reaches the water or is transported laterally by throughflow This results in the proportion of hydrogen ions in the soil rising as such, the soil becomes more acidic and less fertile.

Question 117

Podzolization

Answer 117

It leads to the formation of podsols (acidic soils). Podzolization involves the removal of soluble bases such as iron and aluminum leaving behind a white or grey A horizon consisting largely of silica sand. The process is most commonly associated with soils that develop in the humid mid-latitudes under coniferous forests The result of these processes is that the A Horizon is a pale, ash colour. By contrast, the B Horizon contains illuviated (washed in) material that is darker in colour. Sometimes iron oxide is redeposited as a distinct layer that becomes very hard, known as an ‘iron pad’.

Question 118

Calcification

Answer 118

In humid conditions (relatively wet climates), leaching removes soluble calcium salts from the soil. However, in arid and semi-arid regions, these salts may not be entirely removed but are redeposited in the B Horizon. The result can be light coloured patches of calcium carbonate and calcium sulphate (gypsum) in the lower soils levels. This process is most common in prairie grasslands of North America and the steppes of Ukraine and Russia. In these regions, black chernozem soils tend to form. The A Horizon is dark coloured because it is very rich in humus.

Question 119

Gleying

Answer 119

This process occurs in waterlogged soils, either in low lying river valleys or in areas where the underlying rock is impermeable. It also occurs in tundra regions where permafrost remains frozen underneath a thawed surface layer. The pore spaces in the soil fill with water and produce anaerobic conditions (no oxygen). Iron oxide within the soil is ‘reduced’ (chemically changed by the removal of oxygen). This causes the reddish coloured ferric oxide to turn into blue/grey ferrous oxide. Where soil is waterlogged for only part of the year, it might contain reddish patches or ‘mottles’ in a grey/blue background.

Question 120

Laterization

Answer 120

In humid tropical areas, the vegetation and leaf litter are quickly decomposed by micro-organisms. Chemical weathering of the parent material is also rapid. This produces clays that contain soluble compounds of calcium, iron and aluminium oxides. Under these conditions, leaching removes the soluble material but leaves oxides in the A Horizon. The resulting soils are called latosols (ferrallitic soils) and are typically found in tropical rainforests . Iron oxide gives them a characteristic red colour. In tropical areas where there is a wet and dry season, there is leaching followed by an upwards capillary action. In these conditions, the accumulation of iron and aluminium oxide can form a distinct layer. If this layer becomes hard and cemented, it is known as a LATERITE.

Question 121

Salinization

Answer 121

It typically occurs in arid and semi-arid regions with high daytime temperatures. The heat causes an upward movement of water through the soil. Dissolved salts in the water, such as sodium and potassium, are left as a crust of salt crystals when water evaporates from the ground surface. This can happen when the water table is near the surface and also in irrigated areas, particularly when too much water is applied or when there is poor drainage.

Question 122

Causes of Flooding

Answer 122

1) Deforestation Without plant cover, erosion can occur and sweep the land into rivers. The agricultural plants that often replace the trees cannot hold onto the soil and many of these plants can actually worsen soil erosion. And as land loses its fertile soil, agricultural producers move on, clear more forest and continue the cycle of soil loss. 2) Overgrazing The conversion of natural ecosystems to pasture land doesn’t damage the land initially as much as crop production, but this change in usage can lead to high rates of erosion and loss of topsoil and nutrients. Overgrazing can reduce ground cover, enabling erosion and compaction of the land by wind and rain. This reduces the ability for plants to grow and water to penetrate, which harms soil microbes and results in serious erosion of the land. 3) Use of agrochemicals Pesticides and other chemicals used on crop plants have helped farmers to increase yields. Scientists have found that overuse of some of these chemicals changes soil composition and disrupts the balance of microorganisms in the soil. This stimulates the growth of harmful bacteria at the expense of beneficial kinds.