Tropical Forest Climate: Hot, Humid, and Relentlessly Wet

Tropical rainforests (Af, Am, Aw Köppen) maintain remarkably stable, energy-rich conditions year-round—no seasons, only intensity variations.

Core Parameters

• Temperature: 25–27°C (77–81°F) mean annual. Diurnal range (5–10°C) > annual range (<2°C). No frost.
• Rainfall: 2,000–10,000+ mm/yr (80–400+ in). No dry month (Af) or short dry season (Am). Convective storms daily.
• Humidity: 77–88% avg. Vapor pressure deficit near zero — limits transpiration cooling.
• Insolation: High but canopy intercepts 95%+. Forest floor: 1–2% PAR.
• Soil: Oxisols/Ultisols — deeply weathered, nutrient-poor, aluminum-toxic. Nutrients in biomass, not soil.

Ecological Consequences

Productivity: Highest terrestrial NPP (2,200 g C/m²/yr). Diversity: 50%+ Earth's species on 6% land. Stratification: Emergent, canopy, understory, forest floor — distinct microclimates. Decomposition: Rapid (weeks) — nutrient cycling tight.

Climate Change Vulnerability

Warming >2°C risks: increased tree mortality, drought-induced dieback, savannization (Amazon tipping point ~20–25% deforestation + warming), carbon feedback. Forests becoming carbon sources, not sinks.

Tropical forest climate isn't "weather"—it's a planetary life-support system operating at thermal and hydrological limits.