Urban planning must factor in wind flow to reduce city heat stress

UPDATE - follow-up to Letting the wind flow freely is the secret to cooling our cities: City planners need to include wind movement in urban design to help counter severe heat stress and air pollution. Near-surface wind speeds have dropped globally since the 1980s in a trend known as terrestrial stilling.

Urban Design Factors

Amruthraj M.N. from the Indian Institute for Human Settlements notes that wind speeds often drop around ten metres from the ground where pedestrians walk. Dense buildings, high compound walls, and podiums block natural wind corridors. Meteorologist Aaron Serre explains that concrete and asphalt replace plants, which lowers evapotranspiration and worsens the urban heat island effect. When wind hits tall buildings, it can cause the downdraught effect or the Venturi effect in narrow spaces.

Solutions and Challenges

Prasad Vaidya from IIHS suggests using computer simulations like computational fluid dynamics to study city ventilation, similar to work done in Stuttgart, Seoul, and Hong Kong. However, these models remain expensive and need high computing power. Yugank Goyal from IIM Ahmedabad recommends using satellite images to map city ventilation and build consistent wind records.

Context

Terrestrial stilling reduces near-ground air movement worldwide, making cities feel much hotter and trapping pollution longer. Urban planners can improve natural ventilation by spacing buildings properly and protecting open wind corridors.