Tropical Climates and Drainage Basins Notes

Key Question: What are similarities and differences in the temperature and rainfall patterns in the tropics?

Classification of locations in the tropics into climate zones according to their temperature and rainfall characteristics: Humid tropics (Af, Am, Aw); Arid tropics (BSh, BWh).
High temperatures are the key distinguishing characteristics of the tropics.
Variations in the amount of rainfall between the humid and arid tropics.
Seasonal variations in rainfall patterns in the different parts of the tropics.

The tropics are generally located between the latitudes 30° N and 30° S.
More strictly, they lie between the Tropic of Cancer (23.5° N) and the Tropic of Capricorn (23.5° S).
The locations of tropical regions can vary according to the Koppen-Geiger climate classification based on rainfall seasonality, duration of dry periods, annual rainfall totals, and temperature seasonality.

A Climates (Humid):
- Warm, wet places that lack temperature-defined winters but may have a distinctive dry season. Includes subtypes Af (tropical rainforest), Am (tropical monsoon), Aw (tropical savanna).
B Climates (Arid/Semi-arid):
- Characterized by a shortage of precipitation. Subtypes include BSh (sub-tropical steppe) and BWh (tropical desert).
Summary: The tropics comprises five main climate types as shown in the climate classification tables and figures.

A climograph is a graphical representation of the average precipitation and temperature for an area, used for comparing climates of different regions.
Rainfall is represented by vertical bars, while temperature is represented by a line graph. Data is typically derived from at least 30 years of climate records.

Temperature tends to be higher in the tropics compared to higher latitudes. Mean annual temperatures range from 18°C to 45°C.
Isotherms indicate areas of equal temperature during different seasons. During the northern hemisphere winter, the highest temperatures are in the southern hemisphere.

Latitudinal location & angle of incidence of overhead sun: High angles of incidence lead to concentrated solar energy and higher temperatures.
Differential heating of land and sea: Land heats quickly resulting in variable temperatures between terrestrial and maritime environments.
Topography: Elevation affects temperatures, with temperatures decreasing as altitude increases due to the environmental lapse rate (ELR).

Highest rainfall is found in the tropical rainforest (Af) and monsoonal (Am) climates, and rainfall decreases with distance from the equator and coast.
The rain shadow effect results in low rainfall on the leeward side of mountain ranges while high rainfall is found on the windward side.
Annual rainfall distribution varies greatly and can be influenced by high-pressure systems like the subtropical high pressure belt and ITCZ migration.

Relationship between temperature and rainfall indicates that wetter periods often coincide with higher temperatures due to the migration of the ITCZ.
Seasonal variations in temperature and rainfall patterns can differ between the northern and southern hemispheres.

Hadley Cells: Convection currents in the atmosphere driven by surplus heat in the tropics lead to pressure changes and influence rainfall patterns.
The movement of air associated with the Hadley Cells affects the distribution of rainfall across the tropics.
Seasonal shifts in wind patterns: Seasonal changes in the ITCZ and wind directions influence local rainfall dynamics, affecting arid and humid climates differently.

ENSO phases: Describe variations in ocean temperatures and atmospheric pressure in the tropical Pacific, influencing global climates.

El Niño (warm): Tends to increase rainfall in some areas but create droughts in others.
La Niña (cold): Often results in increased rainfall in regions like Southeast Asia while leading to drier conditions in places like South America.

Definition: A large rotating storm system fed by warm, moist air over warm ocean waters, with wind speeds exceeding 119 km/h.
Develop from larger atmospheric disturbances within the ITCZ or tropical easterly waves and are fueled by ocean heat through latent heat release.

Tropical cyclones can drastically alter rainfall patterns across affected regions, often causing significant flooding.
Areas near the coast, particularly those with low elevation and in close proximity to warm ocean waters, are most vulnerable to cyclonic impacts on climate due to their susceptibility to intense rainfall and storm surges.

Understanding tropical climates involves exploring the interplay between temperature, rainfall, atmospheric circulation, and even phenomena like tropical cyclones, which together shape the diverse environments found in tropical regions worldwide.

Include diagrams and climographs that illustrate various climate types, the circulation of the Hadley Cells, the seasonal patterns of the ITCZ, and data comparisons from affected areas during ENSO events.

Please refer back to original diagrams and figures in the course materials for visual aids as they correlate directly with the described texts.