Climate Studies
Difference between climate and weather
Weather
Climate
• Describes the atmospheric conditions at a specific place
and time
• Describes the average atmospheric conditions of a place
over a specific period of time
• Weather is defined as the day to day state of the
atmosphere, and it is short-term (minutes to weeks)
variation
• Climate is defined as statistical weather information that
describes the variation of weather at a given place for a
specified time interval
• Weather conditions are measured over a short period e.g. a
few hours or days
• Climate conditions are measured over many years, e.g.,
30 years
• Determined by real time measurements of
atmospheric pressure, wind speed and direction,
humidity, precipitation cloud cover, and other variables
• Determined by averaging weather data over periods of 30
years.
• Weather changes abruptly within a short period.
• Weather varies from one place to another within a region
• Most weather elements are measured by weather
instruments
• Climate changes slowly and gradually over many years
• Climate remains uniform over a large area
• Climatic elements are not measured but calculated from
the recorded weather data.
Factors influencing climate
• Usually, the elements of weather (which make up climate) vary from
place to place.
• Because climate is influenced by weather, the elements of weather
are the same as the elements of climate.
Latitude
• Latitude is distance away from the equator
• This factor influences temperature and rainfall. Areas around and
close to the equator experience higher temperature and receive
higher rainfall than those farther away.
• So the rainfall and temperature decreases as one moves away
from the equator.
• The equator and places near the equator are hotter while places in or
near the south and north poles are colder.
Altitude:
• Altitude: is height above sea level
• This influences temperature and atmospheric pressure of an area.
• Temperature decreases with increasing altitude at the rate of 6.5°C
for every 1 kilometre rise in altitude. This concept is called the
Environmental Lapse Rate (ELR)
• Therefore, low altitude areas are warmer than high altitude areas.
• Atmospheric pressure decreases with increasing altitude. Pressure
at sea level is higher than pressure at the summit of a high mountain
Ocean currents
• The nature of the ocean current influences the temperature of
the wind blowing over it and transfers this influence to the land
adjacent to the ocean.
• This will either lead to reduction or increase in the temperature of
the land depending on the type of the ocean current.
• The wind blowing over warm ocean currents will pick moisture
from the ocean and often causes heavy rainfall over the land
while the wind blowing over the cold ocean current brings little
or no rainfall to the land.
Distance from the sea
• This influences temperature and rainfall.
• Places located near the sea experience high temperature and
receive high rainfall than those located farther away.
• This is because of high rates of evaporation from the water
surface, which eventually causes heavy rainfall along the coastal
areas.
• For this reason, coastal regions often experience higher
temperatures and rainfall than inland areas
Aspect
• Aspect: This term refers to the direction in which a slope faces. It
influences temperature and rainfall.
• For example, the south facing slopes in the northern hemisphere are
always warmer than the north-facing slopes.
• Also the windward side of the mountain receives heavier rainfall
than the leeward side
Wind and airmasses
• Wind carries moisture with it as it flows. Warm wind blowing over a
cold region warms the cold region over which it flows.
• However, if the wind is cold, it cools the region. Warm, moist wind
blowing towards a cold, dry region may lead to formation of
rainfall in the destination region.
• Cold, dry wind blowing over a dry region brings no rainfall and if the
blowing is repeated over several years, it may cause aridity in that
region
ITCZ
• Intertropical Convergence Zone(ITCZ):
• This is a low-pressure area around the equator. The moist trade winds
meet within this region.
• The ITCZ moves up in the northern hemisphere during the winter season
and the people in the northern hemisphere will receive rainfall.
• In summer the ITCZ will come down to the southern and countries in the
southern will receive rainfall.
• Places farther away from this zone experience only one rainy season while
places close to the zone experience two seasons of heavy rainfall.
This is because the winds converge around this region twice a year
Africa’s Climatic Regions
Savannah Climate
• Savannah Climate is described as hot wet summers cool dry winters
• Rainfall
• Mean annual rainfall ranges from (800mm- 1600mm) per year[Rainfall decreases with distance
from equator].
• In the northern hemisphere, the rainy season begins in May and lasts till September.
• In the southern hemisphere, the rainy season is from October to March.
• Temperature
• Mean annual temperature is greater than 18° C.
• The monthly temperature hovers between 20° C and 32° C for lowland stations.
• Highest temperatures do not coincide with the period of the highest sun (e.g. June in the
northern hemisphere) but occur just before the onset of the rainy season, i.e. April in Northern
Hemisphere and October in Southern Hemisphere.
• Days are hot and nights are cold. This extreme diurnal range of temperature is another
characteristic feature of the Sudan type of climate.
• Winds
• The prevailing winds of the region are the Trade Winds, which bring rain to
the coastal districts.
• They are strongest in the summer [favorable position of ITCZ] but are
relatively dry by the time they reach the continental interiors or the western
coasts [Trade winds are easterlies – flow from east to west. So rainfall
decreases from east to west here].
• In West Africa, the North-East Trades, in fact, blow off-shore [continent to
sea] from the Sahara Desert and reach the Guinea coast as a dry, dustladen winds.
• What is the reason for alternating wet and dry seasons in Savanna
type climate?
• On shore winds in summer bring rains.
• Off-shore winds in winter keep the climate dry.
Natural Vegetation of Savanna Climate
• The savanna landscape is typified by scattered tall grass and short trees.
• The grasslands are also called ‘bush-veld’.
• The trees are deciduous, shedding their leaves in the cool, dry season to
prevent excessive loss of water through transpiration, e.g. acacias.
• Trees usually have broad trunks, with water-storing devices to survive through
the prolonged drought.
• Many trees are umbrella shaped, exposing only a narrow edge to the strong
winds.
• In true savanna lands, the grass is tall and coarse, growing 25m high.
The elephant grass may attain a height of even 10m.
• Grasses appear greenish and well-nourished in the rainy season but turns yellow
and dies down in the dry season that follows.
• As the rainfall diminishes towards the deserts the savanna merges into thorny
scrub.
• Animal Life of the Savanna
• The savanna is known as the ‘big game country’ as thousands of
animals are trapped or killed each year by people from all over the
world.
• There are two main groups of animals in the savanna, the grasseating herbivorous animals and the fleshing-eating carnivorous
animals.
• The herbivorous include the zebra, antelope, giraffe, deer, gazelle,
elephant etc. [most of the National geographic and Animal Planet
documentaries on wild animals are shot in savanna regions] and
carnivorous animals include the lion, tiger, leopard, hyena, panther,
jaguar, jackal etc..
• Species of reptiles and mammals including crocodiles, alligators,
giant lizards live together with the larger rhinoceros and
hippopotamus in rivers and marshy lakes.
Equatorial/Tropical Rainforest Climate
• Tropical rainforests are located between 10°N and 10°S of the Equator
where temperatures stay near 28°C throughout the year. Rainforests
typically receive over 2000mm of rain each year.
• Usually dominated by the Intertropical Convergence Zone (ITCZ).
• The type of rainfall they normally receive is the convectional rainfall
usually after the hottest afternoon.
• This type rainfall is accompanied by thunder and lightning
• They receive rainfall on daily basis
• The largest rainforests are in the Amazon in Brazil (South America),
Democratic Republic of Congo (Africa) and Indonesia (South East Asia).
Tropical rainforests are also found in Hawaii and the islands of the Pacific &
Caribbean.
Why trees are cut in the Tropical rainforest
• Most of the tropical rainforests of Africa exist in the Congo
• West Africa has suffered heavy deforestation from logging and agriculture and
only a small portion of the original cover remains.
• Mining
• Settlement eg rural settlements and urban growth
• Making roads and railway lines
• Agriculture
• Since the 1990s, timber from Central Africa, especially Gabon, Cameroon, and
the Congo, is increasingly used to fill the void created by the departure from the
market of West African timber exporters.
• deforestation is accelerating in Central Africa.
• Large areas of forest are also being concessions for industrial-scale agriculture,
like oil palm plantations.
Rainforest vegetation levels
• Tropical rainforests have dense vegetation. From ground level up these levels of vegetation are:
• The shrub layer. It is dark and gloomy with very little vegetation between the trees. During heavy
rainfalls this area can flood.
• The under canopy. It is the second level up. There is limited sunlight. Saplings wait here for larger
plants and trees to die, leaving a gap in the canopy which they can grow into.
• Woody climbers called lianas avoid having to wait for gaps by rooting in the ground and climbing
up trees to get to the sunlight.
• The canopy. This is where the upper parts of most of the trees are found. The canopy is typically
about 20 to 40 metres tall. This leafy environment is home to insects, arachnids, birds and some
mammals.
• Emergents. These are the tops of the tallest trees in the rainforest. These are much higher, and so
are able to get more light than the average trees in the forest canopy.
Buttress roots
Adaptations
• Plants and animals living in the Tropical Rainforest must be able to
adapt to the year round humidity and constant warm, humid and wet
weather. The tropical rainforest contains the most species of plant
and animal life, therefore there is immense competition for food and
sunlight.
Plant Adaptations in the Tropical Rainforest
• The bark on the rainforest trees is thin which prevents other plants from growing on
them and supports evaporation from the excess humidity.
• The leaves on most of the plants have what is called drip tips which help plants shed the
excess moisture from the rainfall.
• The trees have long, very straight trunks and don’t branch out until they reach the
canopy where sunlight can be found.
• Leaves of plants and trees are very large to help them absorb as much of the sunlight as
is possible.
• They have an opening filled with nectar that will attract insects, such as ants and flies.
Many flowering plants will grow on to trees in able to get sunshine (epiphytes).
Examples of Plants found in the Tropical Rainforest:
• The tropical rainforest contains more species of plants .Orchids, Philodendrons, Ferns,
Kapok Trees, Banana Trees, Rubber Trees, Bamboo, Trees, Cassava Trees, Avocado Trees.
(Teak) Giant Red Cedar , Ebony, Mahogany trees
Animal Adaptations in the Tropical Rainforest
• Animals come in various colors which act as a camouflage to protect them from their predators.
• Many of the animals are able to move freely among the many trees which act as both food and
shelter for them.
• Quite a few of the tropical rainforest animals are able to swim and cope with a wet and swamp
like environment.
• Some animals (bats) are nocturnal which help them avoid the warmer daytime temperatures.
• Many of the birds have larger and stronger beaks. Some animals are poisonous which protect
them from their predators.
• Due to the competition for food with so many animals, some animals are very specialized and
only eat one type of plant or insect.
Examples of Animals found in the Tropical Rainforest:
• The tropical rainforest contains more species of animals and insects make up the largest group of
animals. Anacondas, Monkeys, Toucans, Macaws, Herens, Cougars, Pumas, Orangutans, Gorrilas,
Sloths, Parrots and Frogs.
DESERT CLIMATE
• A desert is a region that receives less than 250mm of rain per year.
About one-third of Earth’s land surface is desert.
• Deserts may be hot or cold, with great expanses of barren sand or
snow or sandy gravel with hardy vegetation.
• In hot deserts precipitation falls as rain; in cold deserts, it falls as
snow. Both types of deserts have very little precipitation and very low
humidity.
• Deserts have extreme temperatures. During the day the temperature
may reach 50°C, when at night it may fall to below 0°C. Deserts have
less than 250 mm of rainfall per year. The rain can be unreliable. Most
deserts are found between 20° and 35° north and south of the
equator.
• Desert Landscapes
- Sandy desert is called – reg desert
- Rocky/stony desert is called – erg desert
- Smooth rock desert – hamada desert
Causes of deserts
• There are five factors which form desert areas:
• the presence of high pressure, creating cloud-free conditions
• cold ocean currents : when they meet the westerlies wind they
produce fog and no rainfall
• mountain ranges to create rain shadows: Rain shadow areas will not
receive rainfall so the area turns into a desert
• Offshore winds: Winds blowing from the land towards the sea so its
dry and does not produce rainfall
• Distance away from the sea results in the formation of a desert
Adaptations of plants
• a degree of ephemeralism ( plants can survive for a short after the rains
and they die), remaining dormant in the soil as fruits or seeds
• unique dispersal systems, i.e. barbs and bristles
• xerophytic,- water-seeking, they can survive in dry conditions
• root adaptations, tap roots or heavy lateral branching
• small leaves, with sunken or restricted openings
• pale, reflective, leaves
• hairs, spines or thick waxy–walled leaves, evolved to replace what might
nominally exist
• Halophytic plants- plants that can survive in salty conditions
• Plants with adaptations which allow them to live in hot and dry conditions are called xerophytic.
The following adaptations allow plants to survive in the hot desert environment:
• Small leaves - these ensure that less water is lost from the plant by transpiration because the leaf
has a smaller surface area.
• Tap roots - these are long roots (7-10 metres long) that reach deep under the ground to access
water supplies. The tap roots are much longer and bigger than the plant which is visible at the
surface.
• Spines - some plants have spines instead of leaves, eg cactuses. Spines lose less water than leaves
so are very efficient in a hot climate. Spines also prevent animals from eating the plant.
• Waxy skin - some leaves have a thick, waxy skin on their surface. This reduces water loss by
transpiration. A leathery or waxy coating on the leaves and stems reduces evaporation
• Water storage - some plants, known as succulents, store water in their stems, leaves, roots or
even fruits. Plants which store water in their leaves and stems also have a thick waxy skin so that
they lose less water by transpiration. Thick stems or other plant parts provide water storage
space.
Pancake Prickly Pear Cactus.
Barrel Cactus.
Saguaro Cactus.
Lace or Hedgehog Cactus.
Organ Pipe Cactus.
Brittlebush.
Creosote Bush.
Desert Ironwood Plant.
How have animals adapted to the desert?
• Few animals have adapted to survive the hottest desert regions
besides scorpions and small reptiles.
• In areas with a greater supply of water, the level of biodiversity
increases as vegetation such as shrubs, cacti and hardy trees form the
foundation of a more extensive food web.
HOW HAVE CAMELS ADAPTED TO THE
DESERT?
• Camels have been domesticated for at least 3500 years and have long been valued as
pack animals. Camels have adapted to survive hot deserts because they:
• have humps to store fat which a camel can break down into water and energy when
nourishment is not available;
• rarely sweat, even in hot temperatures so when they do take in fluids they can conserve
them for long periods of time;
• have large, tough lips enable them to pick at dry and thorny desert vegetation;
• have broad, flat, leathery feet to spread their weight and provide protection from hot
sand;
• lose little water through urination and perspiration; and
• have slit-like nostril and two rows of eyelashes to protect themselves from the sand.
• They can go for weeks without water
HOW HAVE FENNEC FOXES ADAPTED TO THE
DESERT?
• The fennec fox is the smallest of all fox species. They are found in the
Sahara Desert and elsewhere in North Africa. They are nocturnal which
helps them deal with the heat of the desert environment. They have also
made some physical adaptations help as well. For example, they:
• have thick fur on feet protecting them from the hot ground;
• have large, bat-like ears radiate body heat and help keep them cool;
• have long, thick hair that insulates them during cold nights and protects
them from the hot sun during the day;
• have light coloured fur to reflect sunlight and keep their bodies cools.
HOW HAVE KANGAROO RATS ADAPTED TO
THE DESERT?
• A kangaroo rat is a rodent that is found in desert areas in southwestern North America. Desert kangaroo rats live in areas with loose
sand, often dune terrain. Kangaroo rats have made a number of
adaptations to enable them to survive in the desert, including:
• getting moisture from their seed diet;
• living in burrows during the day to avoid extreme heat;
• having large back legs that allow them to jump almost 3m to avoid
predators;
• having large ears, which enables them to hear approaching predators.
•
Camels are herbivores; they eat desert vegetation, such as grasses, herbs, and leaves.
How do camels adapt to their environment?
•
Camels have many adaptations that allow them to live successfully in desert conditions. Deserts are hot and dry.
•
Winds blow sand all around, so a camel has long eyelashes. It has nostrils that can open and close.
Why do camels have long eyelashes?
•
The long eyelashes keep sand out of the camel's eyes.
•
Thick eyebrows shield the eyes from the desert sun.
•
Why does a camel have nostrils which can close?
•
A camel’s nostrils can close so it doesn't get sand up its nose.
Other Adaptations:
1.
A camel can go a week or more without water, and they can last for several months without food.
They can drink up to 32 gallons (46 litres) of water at one drinking session!
2. Camels store fat in the hump, not water. The fat can be metabolised for energy.
3. Unlike most mammals, a healthy camel's body temperature fluctuates (changes) throughout the day from 34°C to 41.7°C (93°F-107°F.)
This allows the camel to conserve water by not sweating as the environmental temperature rises.
4. Camels feet are wide so they can walk on sand more easily. Their huge feet help them to walk on sand without sinking into it.
5. Camels have thick lips so they can eat the prickly desert plants with out feeling pain.
6. The colour of their bodies helps them to blend into their environment.
7. Camel's ears are covered with hair, even on the inside. The hair helps keep out sand or dust that might blow into the animal's ears
•
Desert creatures derive water directly from plants, particularly succulent ones, such as cactus.
•
Many species of insects thrive in the deserts this way. Some insects tap plant fluids such as nectar
or sap from stems, while others extract water from the plant parts they eat, such as leaves and fruit.
•
The abundance of insect life permits insectivorous birds, bats and lizards to thrive in the desert.
•
Some desert creatures utilize all of these physical and behavioural mechanism to survive the extremes of heat and dryness.
•
Certain desert mammals, such as kangaroo rats, live in underground dens which they seal off to block out midday heat and to recycle the moisture
from their own breathing.
•
These ingenious rodents (there are a number of species) also have specialized kidneys with extra microscopic tubules
to extract most of the water from their urine and return it to the blood stream. And much of the moisture that would be exhaled
in breathing is recaptured in the nasal cavities by specialized organs.
•
If that weren't enough, kangaroo rats, and some other desert rodents, actually manufacture their water metabolically
from the digestion of dry seeds.
•
These highly specialized desert mammals will not drink water even when it is given to them in captivity!
•
These are just a few examples of the ingenious variety of adaptations animals use to survey in the desert, overcoming the extremes of heat and the
paucity of water.
How human beings live in deserts
(Adaptation)
• by moving from place to place in search for food and water with their animals . This lifestyle is called
pastoral nomadism
• Drilling of boreholes and construction of dams for practice irrigation
• Get money from tourism when visitors come to see their tourist attractions eg the Egyptian Pyramids
• Dew harvesting so that they can get water to throughout the day
• They practice cloud seeding ie a way to produce more rainfall
• Trading with other countries especially with oil, diamonds, uranium, gold to get other products which want.
• They use camels for transporting their products for long distance.
• They use long robes to protect themselves from dust particles and strong winds in deserts
• They also get water from roots which squeeze to get water
• They also survive from milk , meat and blood from their animals
• Some are practising afforestation and reforestation