Köppen’s Climate Classification
A Climates
Af - Tropical Rain Forest (Tropical Wet) - Wet all seasons
Controlling Factors: High year-round insolation and precipitation of doldrums (ITC); rising air along
trade wind coasts
Characteristics: Constant high temperatures
Equal day and night length
Low annual temperature range (3°F - 5°F)
Even distribution of precipitation
High cloud cover and humidity
Vegetation: Rain forest vegetation. (selva)
Jungle where light penetrates
Am - Tropical Monsoon - Excessively wet during high sun season
Controlling Factors: Summer onshore, winter offshore air movement related to shifting of ITC and
changing pressure over large land masses.
Transition between Af and Aw
Characteristics: Heavy high-sun rainfall (esp. w/ orographic lifting)
Short low-sun drought
Small temperature range (3°F - 10°F)
High temperature just prior to rainy season
Vegetation: Forest vegetation with fewer species than tropical rainforest grading to jungle and
thorn forest in drier margins
Aw - Tropical Savanna - (Tropical Wet & Dry) Wet during high sun season, dry during low sun
Controlling Factors: Alternation between high sun doldrums (ITC) and low-sun subtropical highs and
trades caused by shifting winds and pressure belts.
Characteristics: Distinct high-sun wet and low-sun dry seasons
Highest temperature ranges for A climates
Vegetation: Grasslands with scattered drought-resistant trees, scrub, thorn bushes
B Climates
BW - Desert (Arid)
Controlling Factors: Descending, diverging circulation of subtropical highs;
Continentality often linked with rainshadow location
Characteristics: Aridity, low RH, irregular and unreliable rainfall
Highest diurnal temperature range and highest percentage of sunshine
Highest daytime temperatures and windy conditions
Vegetation: Xerophytic veg., often barren, rocky or sandy surfaces
