TOPIC 2.5 CLIMATE AND NATURAL VEGETATION
FACTORS INFLUENCING CLIMATE
• Latitude: closer to the equator = higher temperature
• Distance from the sea: coastal area = warmer winters
• and cooler summers
• Prevailing winds: seasonal difference in heating
• between land and sea affects temperature of prevailing
• wind. Warm prevailing wind = rise in temperature
• Ocean currents: warm currents raise winter
• temperatures in coastal areas; cold currents cool them
• down in summer
• Altitude: higher altitude = lower temperature (1° per
• 100m)
EQUATORIAL CLIMATE
MAIN CHARACTERISTICS
• Low pressure all year long (doldrums)
• Midday sun on vertical angle, giving maximum insolation
• Average temperature around 30ºC
• Small temperature range
• Heavy convectional rainfall
• Average annual rainfall of over 2000 mm
• High relative humidity (75%)
HOW DOES EQUATORIAL CLIMATE FORM? (HADLEY CELLS)
• Definition: Hadley cells are large-scale atmospheric circulation systems that help transfer heat
from the equator to higher latitudes.
• Formation:
o Sun heats the equator intensely, causing air to rise because warm air is less dense.
o The rising air cools as it moves away from the equator at high altitudes.
• Sinking Air:
, o At around 30° north and south of the equator, the cooler air sinks, creating high-
pressure zones.
o These high-pressure areas often lead to dry climates and deserts.
• Surface Flow:
o The sinking air flows back toward the equator at the surface, completing the cycle.
• Impact:
o Drives global wind patterns, such as trade winds.
o Influences the climate in tropical and subtropical regions.
• Relationship with equatorial climate:
o Rising Warm Air: The intense heating at the equator causes warm, moist air to rise.
o Consistent Rainfall: As the air rises, it cools, and water vapor condenses, leading to
frequent and heavy rainfall typical of the equatorial climate.
o Stable Temperatures: The consistent solar energy and Hadley circulation maintain warm
temperatures year-round.
o High Humidity: The constant moisture from rainfall and evaporation creates high
humidity levels.
, RAINFALL IN EQUATORIAL CLIMATE
• Convectional rain:
o 1. The sun's rays heat the ground.
o 2. This heats the air above it so it rises.
o 3. As the air rises it cools.
o 4. Condensation point is reached & cloud forms
producing thunder storms.
• Frontal rain:
o This happens mostly at mid-latitudes where
warm tropical air meets cold polar air.
o 1. Warm air moves towards the cold air.
o 2. Being less dense the warm air rises over the
cold air.
o 3. The air cools as it rises.
o 4. Condensation occurs & clouds form to
produce rain.
• Relief rain:
o 1. When warm, moist air hits mountains it is forced to rise,
o 2. As it rises it cools. Condensation occurs producing clouds & rain or snow.
o 3. On the leeward side the cool air sinks getting warmer.
o 4. The air behind the mountains is warmer & dryer so there's less rain. The rain
shadow area.
FACTORS INFLUENCING CLIMATE
• Latitude: closer to the equator = higher temperature
• Distance from the sea: coastal area = warmer winters
• and cooler summers
• Prevailing winds: seasonal difference in heating
• between land and sea affects temperature of prevailing
• wind. Warm prevailing wind = rise in temperature
• Ocean currents: warm currents raise winter
• temperatures in coastal areas; cold currents cool them
• down in summer
• Altitude: higher altitude = lower temperature (1° per
• 100m)
EQUATORIAL CLIMATE
MAIN CHARACTERISTICS
• Low pressure all year long (doldrums)
• Midday sun on vertical angle, giving maximum insolation
• Average temperature around 30ºC
• Small temperature range
• Heavy convectional rainfall
• Average annual rainfall of over 2000 mm
• High relative humidity (75%)
HOW DOES EQUATORIAL CLIMATE FORM? (HADLEY CELLS)
• Definition: Hadley cells are large-scale atmospheric circulation systems that help transfer heat
from the equator to higher latitudes.
• Formation:
o Sun heats the equator intensely, causing air to rise because warm air is less dense.
o The rising air cools as it moves away from the equator at high altitudes.
• Sinking Air:
, o At around 30° north and south of the equator, the cooler air sinks, creating high-
pressure zones.
o These high-pressure areas often lead to dry climates and deserts.
• Surface Flow:
o The sinking air flows back toward the equator at the surface, completing the cycle.
• Impact:
o Drives global wind patterns, such as trade winds.
o Influences the climate in tropical and subtropical regions.
• Relationship with equatorial climate:
o Rising Warm Air: The intense heating at the equator causes warm, moist air to rise.
o Consistent Rainfall: As the air rises, it cools, and water vapor condenses, leading to
frequent and heavy rainfall typical of the equatorial climate.
o Stable Temperatures: The consistent solar energy and Hadley circulation maintain warm
temperatures year-round.
o High Humidity: The constant moisture from rainfall and evaporation creates high
humidity levels.
, RAINFALL IN EQUATORIAL CLIMATE
• Convectional rain:
o 1. The sun's rays heat the ground.
o 2. This heats the air above it so it rises.
o 3. As the air rises it cools.
o 4. Condensation point is reached & cloud forms
producing thunder storms.
• Frontal rain:
o This happens mostly at mid-latitudes where
warm tropical air meets cold polar air.
o 1. Warm air moves towards the cold air.
o 2. Being less dense the warm air rises over the
cold air.
o 3. The air cools as it rises.
o 4. Condensation occurs & clouds form to
produce rain.
• Relief rain:
o 1. When warm, moist air hits mountains it is forced to rise,
o 2. As it rises it cools. Condensation occurs producing clouds & rain or snow.
o 3. On the leeward side the cool air sinks getting warmer.
o 4. The air behind the mountains is warmer & dryer so there's less rain. The rain
shadow area.
