Factors Influencing World Distribution of Plants and Animals

1. Climate

a) Temperature

• Controls metabolic rates, reproduction, and survival
• Temperature decreases with increasing latitude (equator to poles) and altitude (base to summit)
• Tropical regions near the equator support the highest biodiversity (tropical rainforests)
• Polar and high-altitude regions support only cold-adapted specialists (tundra, alpine plants)

b) Precipitation / Rainfall

• Plants and animals require water for survival; its availability determines biome type
• High rainfall + high temperature = tropical forests
• Low rainfall = deserts
• Seasonal rainfall = savannas and grasslands

c) Seasonality

• The predictability and extremity of seasons influences which organisms can complete their life cycles
• Species must time reproduction, migration, and dormancy with seasonal patterns

d) Sunlight (Insolation)

• Controls plant photosynthesis and hence primary productivity
• Determines what plant communities can establish, which in turn determines what animals can survive

2. Physical and Geographic Barriers

a) Oceans and Water Bodies

• The most effective barriers for terrestrial species
• Australia, Madagascar, and oceanic islands like Hawaii became isolated, producing high numbers of endemic species (found nowhere else)
• Australia has an estimated 600,000-700,000 species, with ~75% of its plants and mammals endemic

b) Mountain Ranges

• Act as climatic and physical barriers
• The Himalayas, Andes, and Rockies block moisture and create rain shadows
• They also isolate populations, promoting speciation on either side

c) Deserts

• Act as barriers to moisture-dependent species
• The Sahara separates North African and Sub-Saharan faunas

d) Continental Position (Latitude)

• Determines sun angle, daylength, and temperature range - foundational to all climate-based distributions

3. Soil Type and Topography (Edaphic Factors)

• Soil chemistry (pH, mineral content, organic matter) directly limits plant growth
• Calcareous (limestone) soils support different vegetation than acidic peat or sandy soils
• Drainage affects whether wetland, meadow, or forest plants can establish
• Topography creates microclimates - slopes, valleys, and aspect (N vs. S facing) alter local temperature and moisture

4. Ocean Currents and Atmospheric Circulation

• Ocean currents (e.g., the Gulf Stream) moderate coastal climates, allowing species to live further poleward than latitude alone would predict (e.g., temperate forests in northwest Europe)
• Jet streams influence rainfall patterns over large continental areas
• These modify the expected latitudinal distribution of biomes

5. Geological History and Continental Drift

• Plate tectonics has moved continents over millions of years, joining and separating landmasses
• When continents were connected (Pangaea), organisms spread freely; when they split, populations diverged into new species
• This explains why South America and Africa share some ancient related lineages (e.g., flightless birds - rhea vs. ostrich), yet differ in most modern fauna
• The Wallace Line in Southeast Asia marks a sharp faunal boundary between Asian and Australasian species, reflecting ancient oceanic separation

6. Species Interactions (Biotic Factors)

a) Competition

• Species exclude each other from habitats through competitive exclusion
• A species may be absent from a habitat it could physically tolerate because a competitor dominates it there

b) Predation and Herbivory

• Prey species avoid habitats where predators are abundant
• Plants are limited by the distribution of herbivores and vice versa (co-evolutionary constraint)

c) Mutualism and Symbiosis

• Many plants depend on specific pollinators (bees, birds, bats) - if the pollinator is absent, the plant cannot reproduce and establish
• Mycorrhizal fungi are essential for many trees to absorb nutrients; their absence from a region can exclude tree species

d) Disease and Parasites

• Pathogens and parasites can eliminate species from otherwise suitable habitats
• The tsetse fly (carrying trypanosomes) excludes large mammals, including livestock and humans, from large areas of sub-Saharan Africa

7. Dispersal and Colonization Ability

• Species differ enormously in how far they can travel
• Wind-dispersed seeds (dandelions, ferns) spread widely; large-seeded plants are more limited
• Flying animals (birds, bats, insects) have large ranges; non-flying animals are more constrained
• Long-distance dispersal events (seeds carried by ocean currents or birds) explain the presence of plants on remote islands
• The theory of island biogeography (MacArthur & Wilson) shows that species richness on islands reflects a balance between immigration rate and extinction rate

8. Evolutionary and Speciation History

• Species can only live where their evolutionary lineage originated or colonized
• Endemic species arise when populations become isolated and evolve independently over long periods
• Relict species (survivors of once-wider distributions) occur in isolated refugia after climate change reduced their range (e.g., the giant panda restricted to bamboo forests in China)

9. Niche Concept

• Every species has a fundamental niche - the full range of conditions it could theoretically survive in
• Its realized niche is smaller - where it actually lives, limited by competition, predation, and other biotic pressures
• Species' distributions map closely to their realized niches in nature

10. Human Activity (Anthropogenic Factors)

Summary Table

The Hydrological Cycle

Water Reservoirs

Key Processes of the Hydrological Cycle

1. Evaporation

• Solar energy heats surface water (oceans, lakes, rivers, soil), converting liquid water to water vapor
• Water vapor rises into the atmosphere
• Influenced by temperature, wind speed, humidity, and surface area
• Evaporation always exceeds precipitation over the oceans - this net transfer drives water onto land

2. Transpiration

• Plants absorb groundwater through roots and release water vapor through tiny pores (stomata) in their leaves
• Controlled by sunlight, temperature, and humidity
• Tropical forests are massive contributors - the Amazon rainforest recycles an enormous amount of water locally through transpiration

3. Evapotranspiration (ET)

• The combined loss of water from soil evaporation + plant transpiration
• Used as a single measure of water loss from land surfaces
• Represents the return pathway of soil and plant water to the atmosphere

4. Condensation

• As water vapor rises, it cools with altitude
• Cooling causes vapor to condense around tiny dust and aerosol particles, forming clouds and fog
• Dew and frost form when air near the ground cools below the dew point

5. Precipitation

• When water droplets in clouds collide, grow large, and become heavy enough, they fall as precipitation
• Forms: rain, snow, sleet, hail (depends on atmospheric temperature)
• Precipitation can fall on land or directly back into the ocean

6. Interception

• Vegetation canopy intercepts precipitation before it reaches the ground
• Intercepted water may evaporate directly back to the atmosphere or drip to the soil
• Forests intercept significant amounts, moderating runoff

7. Surface Runoff

• Water that falls on land and flows overland into streams, rivers, and ultimately back to the ocean
• Rate depends on slope, vegetation cover, soil permeability, and rainfall intensity
• Heavy runoff causes flooding; low runoff means more infiltration

8. Infiltration

• Water soaks into the soil from the surface
• Rate depends on soil type (sandy soils absorb fast; clay soils absorb slowly), vegetation, and saturation
• Infiltrated water recharges soil moisture

9. Percolation

• Water moves downward through soil and rock layers under gravity
• Eventually reaches the water table (the upper surface of the saturated zone)
• Replenishes groundwater aquifers

10. Groundwater Flow

• Water stored in underground aquifers moves slowly through permeable rock
• Discharges into rivers, lakes, wetlands, and the ocean as baseflow or springs
• Groundwater sustains river flow during dry seasons

11. Sublimation

• Water moves directly from solid ice/snow to vapor without passing through liquid phase
• Common on glaciers, snowfields, and in cold dry climates
• Contributes to atmospheric moisture in high-altitude and polar regions

12. Snowmelt and Glacial Runoff

• Seasonal melting of snow and glaciers releases large volumes of freshwater into rivers
• Critical water source for millions of people in Asia and the Americas
• Threatened by accelerating glacial retreat due to climate change

The Cycle as a Flow Diagram

         ATMOSPHERE
              ↑  Evaporation / Transpiration / Sublimation
              |
        [Clouds form via Condensation]
              |
              ↓  Precipitation (rain, snow, hail)
         LAND SURFACE
        /       |       \
  Interception  |     Surface Runoff → Rivers → Ocean
                |
          Infiltration
                |
         Soil Moisture
                |
          Percolation
                |
          GROUNDWATER
                |
        Baseflow / Springs → Rivers → OCEAN
                                         ↑
                              (Cycle restarts)

Energy and the Hydrological Cycle

• Evaporation absorbs latent heat from the surface, cooling it
• Condensation releases latent heat in the atmosphere, warming it and driving atmospheric circulation
• This latent heat transfer is a primary mechanism by which the tropics export heat to higher latitudes, moderating global climate

Importance of the Hydrological Cycle

Human Impacts on the Hydrological Cycle

• Deforestation - reduces transpiration and interception, increases runoff and flooding
• Urbanization - impervious surfaces (concrete, tarmac) prevent infiltration, increasing flash flooding
• Irrigation and agriculture - extracts groundwater faster than it recharges; alters ET rates
• Dams and reservoirs - alter timing and distribution of river flow
• Climate change - warmer temperatures increase evaporation rates, intensify precipitation events, accelerate glacier melt, and shift precipitation patterns globally. About 85% of studied species have already shifted their distributions in response

Summary

Evaporation/Transpiration → Condensation → Precipitation → Runoff/Infiltration → Groundwater → Back to Ocean

Types and Distribution of Precipitation

Part I: Types of Precipitation

A. By Physical Form

B. By Producing Mechanism (Most Important Classification)

1. Convective Precipitation

• Cause: Surface heating causes moist air to rise rapidly; strong vertical updrafts lift air to great heights
• Characteristics: Intense, short-duration, localized (small area)
• Weather pattern: Thunderstorms, tropical downpours
• Where: Tropics and mid-latitude summers; equatorial belt
• Example: Afternoon thunderstorms in the Congo Basin, Florida, or the Amazon

2. Cyclonic (Frontal) Precipitation

• Cause: Warm, moist air is drawn into a low-pressure system and rises over cooler, denser air at a front
• Two subtypes:
  • Frontal precipitation - occurs at warm or cold fronts where air masses meet
  • Non-frontal cyclonic - convergence in a low-pressure center without a distinct front
• Characteristics: Large-area, long-duration, moderate to light intensity
• Where: Mid-latitudes (30°-60° N and S), associated with travelling depressions
• Example: Rainfall over Western Europe, the British Isles, and eastern North America from passing mid-latitude cyclones

3. Orographic (Relief) Precipitation

• Cause: Moist air is forced to rise over a mountain range or elevated terrain
• As air rises, it cools adiabatically, condenses, and precipitates on the windward (facing the wind) slope
• On the leeward (sheltered) side, air descends, warms, and dries - creating a rain shadow
• Characteristics: Heavy rainfall on windward slopes; aridity in the rain shadow
• Where: Wherever mountains intercept prevailing moisture-laden winds
• Examples:
  • Western Ghats, India (southwest monsoon winds hit the ghats)
  • Western slopes of the Andes vs. Atacama Desert (rain shadow)
  • Himalayas creating the Tibetan Plateau rain shadow
  • Cherrapunji, India (one of the wettest places on Earth due to orographic lifting)
  • The western Cascades and Olympics in North America

4. Monsoon Precipitation (sometimes listed separately)

• Cause: Seasonal reversal of winds driven by differential heating of land and ocean
• In summer, continents heat faster than oceans; moist onshore winds bring heavy rainfall
• In winter, winds reverse and flow offshore - dry season
• Where: South Asia (Indian subcontinent), West Africa, Southeast Asia, northern Australia
• Example: Indian Summer Monsoon delivers ~80% of India's annual rainfall between June and September

Part II: World Distribution of Precipitation

Global Circulation and Precipitation Zones

Zone 1: Equatorial High-Rainfall Belt (0° - 10° N/S)

• Mechanism: The Intertropical Convergence Zone (ITCZ) - where trade winds from both hemispheres meet - forces massive convective uplift
• Result: Heavy, year-round convective rainfall (1,500 - 3,000+ mm/year)
• Regions: Amazon Basin, Congo Basin, Indonesian Archipelago, equatorial West Africa
• Some equatorial mountain areas (Colombia) receive over 10,000 mm/year - among the wettest on Earth

Zone 2: Subtropical Arid Zones (20° - 35° N/S)

• Mechanism: The descending limb of the Hadley Cell brings dry, subsiding air that suppresses precipitation
• Result: Hot deserts with very low rainfall (< 250 mm/year)
• Regions: Sahara, Arabian Desert, Sonoran Desert, Atacama Desert, Kalahari, Australian interior
• This accounts for most of the world's major deserts

Zone 3: Mid-Latitude Moderate-to-High Rainfall (40° - 65° N/S)

• Mechanism: Travelling depressions (mid-latitude cyclones) bring frontal precipitation; westerly winds carry moisture from oceans
• Windward (western) coasts of continents receive much more than interior or eastern coasts
• Regions: Western Europe (500-1,500 mm/year), Pacific Northwest USA, southern Chile
• Continental interiors become progressively drier (the "continental interior aridity" effect)

Zone 4: Polar Low-Precipitation Zones (> 65° N/S)

• Mechanism: Cold air holds very little moisture; descending air in polar high-pressure zones
• Result: Very low precipitation (< 200-300 mm/year) - polar deserts
• Regions: Antarctica, Greenland, Arctic tundra
• Antarctica receives so little precipitation it qualifies as the world's largest cold desert

Factors Controlling Regional Distribution

Regional Precipitation Highlights

World Precipitation Pattern Summary

Latitude Zone        Precipitation   Reason
------------------------------------------------------
0°-10° (Equatorial)  Very High       ITCZ convective uplift
10°-20° (Tropics)    Seasonal        ITCZ seasonal migration / monsoons
20°-35° (Subtropics) Very Low        Hadley Cell subsidence (deserts)
35°-60° (Temperate)  Moderate-High   Cyclonic / frontal + westerlies
60°-90° (Polar)      Very Low        Cold air, polar subsidence

Measurement of Precipitation

• Rain gauge - simplest, most direct measurement (mm or inches)
• Weather radar (RADAR) - maps areal distribution of rainfall in real time
• Satellite remote sensing - global coverage using microwave and infrared sensors (e.g. NASA TRMM, GPM missions)
• Results expressed as: point rainfall, areal rainfall, or isohyetal maps (lines of equal rainfall)

Key Takeaways

1. Three mechanisms produce precipitation: convective, cyclonic/frontal, and orographic - often working in combination
2. Latitude is the primary control of global distribution via atmospheric circulation (ITCZ, Hadley Cells, polar fronts)
3. Mountains create sharp local contrasts between windward (wet) and leeward (dry) sides
4. Ocean currents and distance from the sea modify the latitudinal pattern regionally
5. Globally, 59% of areas are showing an increasing precipitation trend, while 41% are showing a decrease, with the most notable changes linked to Hadley Cell expansion and shifts in monsoon patterns per recent research from Nature Scientific Reports

Global Ecological Imbalances

1. Pollution

A. Air Pollution

• Sources: Burning fossil fuels (power plants, vehicles), industrial emissions, agricultural burning, construction
• Major pollutants: CO₂, SO₂, NOₓ, particulate matter (PM2.5), ground-level ozone, methane
• Effects:
  • Respiratory and cardiovascular disease in humans (7 million deaths/year, WHO)
  • Acid rain - SO₂ and NOₓ react with water to form sulfuric and nitric acids, damaging forests, lakes, and soil
  • Smog formation over cities; reduced visibility and UV-B alteration
  • Stratospheric ozone depletion (from CFCs/HFCs) - increased UV-B radiation reaching Earth
• Geographic hotspots: South and East Asia (India, China), sub-Saharan Africa, industrial Eastern Europe

B. Water Pollution

• Sources: Industrial effluents, agricultural runoff (fertilizers, pesticides), sewage, oil spills, mining waste
• Major pollutants: Nitrates/phosphates (causing eutrophication), heavy metals (mercury, lead, arsenic), plastics, pathogens
• Effects:
  • Eutrophication - excess nutrients trigger algal blooms, deplete oxygen, create dead zones (e.g., Gulf of Mexico dead zone covers ~22,000 km²)
  • Contamination of drinking water for over 2 billion people
  • Disruption of aquatic ecosystems and food chains
  • Bioaccumulation of toxins (e.g., mercury) up food chains to humans

C. Soil (Land) Pollution

• Sources: Pesticides, herbicides, heavy metals from mining, industrial waste, landfills
• Effects: Loss of soil fertility, contamination of crops, groundwater pollution, reduced microbial biodiversity in soil

D. Plastic Pollution

• In 1950, world plastic production was ~2 million tons/year; by 2015 it reached 419 million tons/year
• An estimated 8 million tons enter the oceans annually
• Microplastics (< 5 mm) are now found in the deepest ocean trenches, polar ice, human blood, and breast milk
• Kills marine wildlife through ingestion and entanglement
• A UN treaty to curb plastic pollution, initiated in 2022, failed to produce an agreement in both 2024 (Busan) and 2025 (Geneva) meetings

E. Noise and Light Pollution

• Disrupt animal communication, breeding, navigation, and migration patterns
• Artificial light at night disorients sea turtles, migratory birds, and insects

2. Global Warming (Climate Change)

What Is It?

The Greenhouse Effect

• Solar radiation passes through the atmosphere and warms Earth's surface
• Earth radiates infrared (heat) energy back upward
• Greenhouse gases (CO₂, CH₄, N₂O, water vapor, CFCs) absorb and re-radiate this heat, trapping it in the lower atmosphere
• Human emissions have enhanced this natural effect to dangerous levels

Key GHGs and Sources

Current Status

• Each of the past 11 years (2015-2025) has been one of the 10 warmest on record
• 2024 is the single warmest year in recorded history, followed by 2023
• Global average temperature has risen approximately 1.2-1.3°C above pre-industrial levels
• The Paris Agreement (2015) set a target of limiting warming to 1.5°C - current trajectories put us on course for 2.5-3°C+ by 2100

Consequences of Global Warming

3. Reduction in Biodiversity

What Is Biodiversity?

• Genetic diversity - variation within species
• Species diversity - the variety of species in an area
• Ecosystem diversity - the range of habitats and ecological communities

The Biodiversity Crisis - Scale

• Approximately 1 million species are currently at risk of extinction (IPBES, 2019)
• Current species extinction rates are 10 to 100 times higher than the natural background rate
• The world has entered what scientists call the Sixth Mass Extinction - the first driven by a single species (humans)
• Wetland coverage has declined by 35% since 1970, directly affecting freshwater species
• Over 75% of the Earth's ice-free land has been significantly altered by human activity

Major Causes of Biodiversity Loss

Why Biodiversity Matters

• Food security: Over 75% of global food crops depend on pollinators, contributing US$235-577 billion annually to agricultural output
• Medicine: Over 50% of modern medicines are derived from natural sources
• Climate regulation: Forests absorb 2.6 billion tonnes of CO₂ annually
• Water purification: Ecosystems filter freshwater for billions of people
• Ecosystem services: Soil formation, flood control, disease regulation, nutrient cycling

Hotspots of Biodiversity Loss

• Tropical forests (Amazon, Congo, Southeast Asia)
• Coral reefs (25% of all marine species depend on them)
• Freshwater ecosystems (most threatened biome proportionally)
• Mediterranean-climate shrublands (California, Cape Region, Mediterranean Basin)

4. Depletion of Forests

Global Forest Cover

• Forests cover approximately 31% of Earth's land area (~4.06 billion hectares)
• They store 80% of terrestrial biodiversity
• Host over half the world's species
• Act as the world's largest terrestrial carbon sinks

Current Rate of Loss

• 8.1 million hectares of forest were lost in 2024 alone
• This is 63% higher than the trajectory needed to halt deforestation by 2030
• 8.8 million hectares experienced forest degradation in 2024
• Loss of humid primary tropical forests (the most irreplaceable) spiked in 2024 due to climate-driven fires
• At the halfway point to 2030, "the global deforestation curve has not begun to bend"

Leading Causes of Deforestation

Consequences of Deforestation

• Climate change acceleration: Forest loss converts carbon sinks to carbon sources; the Amazon now emits more CO₂ than it absorbs in degraded areas
• Biodiversity loss: Habitat destruction is the #1 driver of species extinction
• Disruption of water cycle: Forests recycle moisture through transpiration; deforestation reduces regional rainfall and increases flooding
• Soil degradation: Tree roots hold soil; removal leads to erosion, landslides, and desertification
• Loss of indigenous peoples' lands and cultures
• Reduced ecosystem services: Loss of watershed protection, flood buffering, pollination corridors

Interconnections - The Vicious Cycle

Deforestation
     ↓
Less carbon absorption → Global Warming intensifies
     ↓
Fires increase → More deforestation + More CO₂
     ↓
Habitat destruction → Biodiversity Loss
     ↓
Weakened ecosystems → Less pollution filtration
     ↓
More pollution → More warming + More biodiversity loss

Solutions and International Responses

Summary Table

Temperate and Tropical Cyclones

Part I: Temperate Cyclones (Extratropical Cyclones)

Definition

Formation (Norwegian Model - 5 Stages)

Stage 1: Stationary Front

• Cold polar air and warm tropical air lie side by side
• The boundary between them is the polar front
• No significant vertical motion yet

Stage 2: Wave Development (Incipient Stage)

• A disturbance causes a wave or kink along the polar front
• A small low-pressure centre develops at the wave crest
• Warm air begins to push northward (warm sector) and cold air pushes southward

Stage 3: Young Cyclone (Adult Stage)

• Two distinct fronts develop:
  • Warm Front (leading edge) - warm air gently rises over cold air ahead; gradual, widespread precipitation
  • Cold Front (trailing edge) - cold air actively undercuts warm air; intense, narrow precipitation band
• The warm sector (wedge of warm air) lies between the two fronts
• Pressure falls at the centre; winds intensify

Stage 4: Mature Cyclone / Occlusion

• Cold front moves faster than warm front and catches up with it
• Warm sector is lifted off the ground entirely - an occluded front forms
• Maximum intensity reached at this stage
• Centre pressure at its lowest; strongest winds

Stage 5: Dissipation

• Warm sector is completely occluded
• Temperature contrast disappears - the energy source is removed
• Low fills in and cyclone dies out

Characteristics of Temperate Cyclones

Weather Sequence with a Passing Temperate Cyclone

AHEAD OF WARM FRONT:
- Cirrus clouds (high) → cirrostratus → altostratus → nimbostratus
- Steady, prolonged rain or snow
- Temperature cool, pressure falling

IN THE WARM SECTOR:
- Stratus clouds, drizzle or no rain
- Temperature rises, wind shifts to SW
- Pressure steadier

COLD FRONT PASSAGE:
- Towering cumulonimbus clouds
- Heavy, intense but brief rain; thunderstorms possible
- Sharp temperature drop, wind veers to NW
- Pressure rises rapidly

AFTER COLD FRONT:
- Clear skies, cold temperatures
- Good visibility

Path and Tracks of Temperate Cyclones

• Generally move from west to east steered by the jet stream
• In winter, they adopt a more southerly track (e.g., crossing the Mediterranean)
• In summer, they shift northward, leaving the Mediterranean dry
• Most active cyclone tracks:
  • North Atlantic (Iceland Low region)
  • North Pacific (Aleutian Low region)
  • Southern Ocean (continuous belt of cyclones)

Significance

• Responsible for most of the rainfall in temperate regions (Europe, North America, southern South America)
• Bring welcome, gentle rains beneficial to agriculture
• Occasionally cause destructive windstorms and flooding

Part II: Tropical Cyclones

Definition

Conditions Needed for Formation

1. Warm ocean surface temperature - at least 26.5-27°C to a depth of ~50 m (provides heat and moisture energy)
2. Location at least 5° from the equator - so the Coriolis force is strong enough to initiate rotation (not possible at the equator)
3. High atmospheric humidity - especially in the mid-troposphere (fuel for latent heat release)
4. Atmospheric instability - rapid cooling with altitude to sustain vigorous convection (deep cumulonimbus clouds)
5. Low vertical wind shear - wind speed should not change much with altitude; high shear disrupts the developing warm core
6. Pre-existing disturbance - e.g., easterly wave, ITCZ convergence, or abandoned upper trough to provide initial rotation

Formation Process

1. Warm, moist ocean air rises vigorously (convection)
2. As air rises and cools, vast amounts of latent heat are released through condensation - this warms the column, lowering surface pressure
3. More air rushes in at the surface to fill the low, spiraling inward due to Coriolis
4. A self-sustaining circulation develops: rising air, outflow aloft, inflow below
5. A clear, calm eye forms at the centre as air subsides

Structure of a Tropical Cyclone

The Eye

• Diameter: 20-65 km
• Calm, clear, virtually no wind
• Formed by subsiding air at the centre
• Lowest pressure and highest temperature in the system

The Eye Wall

• Ring of intense cumulonimbus clouds surrounding the eye
• Strongest winds and heaviest rainfall occur here
• Winds can exceed 250-300 km/h in intense storms
• The most dangerous part of the cyclone

Rain Bands

• Spiral bands of clouds and rain extending outward from the eye wall
• Can extend 500-1,000 km from the centre
• Bring heavy rain and gusty winds

Vertical Structure

Characteristics of Tropical Cyclones

Path of Tropical Cyclones

1. Move westward initially (driven by tropical easterlies)
2. Curve northward (or southward in SH) around 20° latitude
3. Recurve north-eastward around 25-30° latitude (picked up by westerlies)
4. Dissipate after 30° latitude as ocean temperatures cool below 26°C

• Bay of Bengal - strikes Bangladesh, Myanmar, India
• Arabian Sea - strikes Oman, India, Pakistan
• Caribbean / Gulf of Mexico - Atlantic hurricanes strike USA, Central America
• Western Pacific - most active basin globally; typhoons strike Philippines, Japan, China
• South Indian Ocean - strikes Madagascar, Mozambique

Dissipation of Tropical Cyclones

• They move over cool ocean water (energy source cut off)
• They make landfall (moisture supply cut off, friction increases)
• They move into regions of high vertical wind shear
• They encounter a stable atmosphere that suppresses convection

Part III: Key Differences - Side by Side Comparison

Naming and Classification of Tropical Cyclones

Hazards of Tropical Cyclones

1. High winds - structural damage, uprooted trees
2. Storm surge - the most deadly hazard; ocean water pushed inland by winds, can reach 5-9 m above normal sea level
3. Extreme rainfall - inland flooding, landslides, river flooding
4. Tornadoes - spawned in rain bands
5. Coastal erosion - beach and cliff destruction