Urban Heat Refugia: Thermal Tolerance & Microclimate Survival

Diurnal Cycle

Time of day 12:00

Auto-advance day (~40s/cycle)

City Design

Tree canopy / park cover 28%

Cool-roof & pavement adoption 0%

Species

Thermal tolerance limit 29°C

Readouts

Mean city temp

—

Rural baseline

20.0°C

Population alive

—

In refugia now

—

Elapsed simulated time

0.0 days

Cool tile (near rural baseline) Moderate heat Severe heat-island tile Agent in cool refugia Agent under heat stress

How it works

Each tile's surface temperature is driven by a thermal-inertia (heat-storage) model, the standard first-order explanation for why the urban heat island often peaks after dark: paved and built surfaces absorb far more heat during the day than they can radiate away by night.

solar(t)   = ΔT_max · max(0, sin(π·(t−6)/13))   for 6h ≤ t ≤ 19h
dH/dt      = (solar(t) − H) / τ                  (Newtonian relaxation)
T(tile)    = T_rural + H

ΔT_max and the thermal time-constant τ depend on land cover: asphalt/roof tiles have high ΔT_max (≈6–7 °C) and long τ (≈5.5 simulated hours), so they keep releasing stored heat well into the night; tree-canopy/park tiles have low ΔT_max (≈1.5 °C, shading + evapotranspiration) and short τ (≈1.4 h), tracking the sun closely and cooling fast at dusk. Cool-roof/pavement adoption scales ΔT_max down directly (higher albedo → less absorbed radiation).

The pollinator population performs negative thermotaxis — a documented insect behavior — by sampling the temperature gradient at its own tile and stepping down-gradient toward cooler neighbors, biased by random wander:

stress(t)  = stress(t−dt) + max(0, T − T_tolerance)·dt   (heat accumulates)
recovery   = stress − 0.5·dt      if T ≤ T_tolerance
death      when stress exceeds a fixed lethal dose

Tree canopy and cool-roof sliders let you test the two real mitigation levers cities actually use — more green cover creates more low-τ, low-ΔT refugia tiles; higher albedo lowers the ceiling temperature everywhere. Watch how population survival depends on refugia density as much as on how hot the hottest tile gets.

12:00 · Day 0

Sun: overhead

⚠ Couldn't load the 3D engineThree.js failed to load from the CDN. Check your connection and reload.