Tropical climates Flashcards
(27 cards)
Types of tropical climate (A)
- Rainforest (Af)
- Monsoon (Am)
- Savanna (Aw)
Air masses
Large body of air in which the variation (horizontal gradients) of the main physical properties are low
Source region
Area where air mass develops its characteristic temperature and moisture conditions
2 main source regions
- Areas of relative calm - high pressure
- Where the surface is relatively uniform eg. deserts, oceans
Air masses classified by:
- Latitude of source area
- Continental (dry) vs maritime (moist)
- Stability of air mass
How can air masses be changed
(creating secondary air masses)
- Internal changes
- Effect of the surface
Intertropical convergence zone (ITCZ)
- Place where wind blows inwards and rises convectively
- Low pressure area - (clouds +rain)
- Found at 5*N
- Wanders seasonally (influenced by sun and heating of land)
Subtropical anticyclones
- Large, high-pressure area formed due to subsiding cold air
- Around 30-35* N/S at the tropopause (part of Hadley cell)
- Found over continents, in winter + oceans in summer
- Move towards poles in summer
- eg. in Australia, high-pressure belt is located over the continent in winter and shifts southward over the ocean in summer
The highs pass south of Sydney in summer and move further north in winter - Creates temperature inversions especially over cold continents
- Promote arid conditions
What is a gyre
- Large system of circular ocean currents formed by global wind patterns and Earth’s rotation
- Move warm water from the equator toward the poles and cold water from the poles toward the equator
Impact of gyres:
- East coasts in the SH and west coasts in the NH are warm and wet because warm poleward currents raise coastal air temperatures.
- Most west coasts tend to be cool and dry due to advection of cold water from the poles and the upwelling of deep, cold currents
How do ocean currents affect the climate?
- Ocean currents move warm or cold water around the globe.
- Warm currents (e.g. Gulf Stream) make nearby areas warmer.
- Cold currents (e.g. Peru Current) make nearby areas cooler.
- Also affect rainfall by changing air temperature and humidity.
Wind impacted by
- Temperature of the wind is determined by the area of origin and characteristics of the surface it blows over
- eg. wind blowing from the sea is cooler in summer than from the land
Monsoon
- Describes wind patterns that experience a seasonal reversal
What causes the monsoon in India?
The monsoon is caused by seasonal changes in pressure:
Summer: Land heats up, creating low pressure → moist air from the ocean is drawn in → heavy rain.
Winter: Land cools, creating high pressure → dry air flows out to sea.
NE monsoon (Oct-Jan)
- Winter season Jan-Feb
The Northeast Monsoon sets in after the Southwest monsoon withdraws, usually in mid-October
Winds shift from southwest to northeast, bringing moisture-laden air from the Bay of Bengal over southern India
- Cool, dry winds blow outwards from land to sea.
- Most of India is dry, but southern India and Sri Lanka get some rain.
- In spring, the high-pressure system over India is gradually replaced by a low-pressure system
SW monsoon (June-Sept)
- Occurs June–Sept.
- Hot dry season March-May
- Rainy season occurs as the low-pressure system intensifies due to warming of the land
- Once pressure is low enough, air from the equatorial low and the southern hemisphere is sucked in
- Warm, moist air blows from sea to land.
- Brings heavy rain to most of India—over 75% of annual rainfall.
- Starts in the south in June and moves northward
Impacts of monsoon
- Brings over 75% of India’s rainfall
- Support rice and tea farming
- Helps winter cropping
- Rainfall is uneven (north-west stays dry)
- Very hot and dry periods - 49*C in the north
- Dust storms and dry rivers
Pakistan floods
- August 2010
Causes:
- Record monsoon rainfall - (heaviest in 80 years)
-Deforestation increased runoff
- Old infrastructure eg. dams and embankments failed
Impacts:
- 1600 dead, 2 million+ homeless
- 20 million people affected
- Cholera spread
- $1 billion crop damage
- Destroyed infrastructure
- $9 billion needed for repairs + growth halved
- 69,000km2 of farmland destroyed
What is the Köppen climate classification system based on?
Two main factors:
- Temperature
- Seasonality of rainfall
Used worldwide to group climates into six main types
Six main Koppen climate types:
A – Tropical rainy (coldest month > 18 °C)
B – Dry (desert)
C – Warm temperate rainy (coldest month −3 °C to 18 °C; warmest > 10 °C)
D – Cold boreal (coldest ≤ −3 °C; warmest ≥ 10 °C)
E – Tundra (warmest 0–10 °C)
F – Perpetual frost (warmest < 0 °C)
What are the rainfall-based subdivisions in the Köppen system?
f – No dry season
m – Monsoonal (short dry season, heavy rain)
s – Dry summer
w – Dry winter
Features of tropical climate types (Group A)?
Af – Tropical humid (rainforest):
- High temps year-round (>20 °C)
- Rainfall > 50 mm every month (8–12 months)
- Found near the equator (5°–10°)
- Always humid with frequent rain and clouds
Aw – Tropical seasonal (savanna):
- Distinct dry season (1–7 wet months)
- Rainfall varies with latitude
- High temps with seasonal thundery storms
Am – Tropical monsoon:
- Dry winters, very wet summers
- Temp peak before monsoon, cooler during wet season
- Heavy rain from moist maritime air
Brunei
Climate Type:
- Equatorial tropical – hot, humid, and wet year-round.
Influences:
- Location near the Intertropical Convergence Zone (ITCZ).
- Two monsoon seasons:
- North-east monsoon (Dec–Mar): cooler, drier period.
- South-west monsoon (May–July): wetter period.
- El Nino Southern Oscillation (ENSO)
- El Niño → dry conditions.
- La Niña → wetter conditions.
Rainfall:
- Over 2300 mm/year; higher in hills (up to 4000 mm).
- Two rainfall peaks:
Dec (wettest) & May–July (smaller peak). - Thunderstorm peaks: Apr–May & Sept–Nov (late afternoon/evening).
- Short, intense storms common.
Temperature:
- Very uniform, high all year.
- Slightly cooler Dec–Mar due to cold surges from China.
What is El Nino
El Niño is an irregular warming of surface waters in the eastern Pacific Ocean near South America. It disrupts global wind and rainfall patterns and occurs every 3–7 years.
