Urban wind speeds drop across cities as taller buildings block natural airflow and worsen heat

UPDATE - follow-up to Letting the wind flow freely is the secret to cooling our cities: Urban wind speeds near the ground have been dropping worldwide in a phenomenon known as terrestrial stilling since the 1980s, trapping heat and humidity in growing Indian cities.

Urban Design Factors

Amruthraj M.N., a consultant with the Sustainable Energy Lab at the Indian Institute for Human Settlements in Bengaluru, points out that surface-level wind speeds are typically reduced around 10 meters from the floor where pedestrians walk. Dense infrastructure, high-rise buildings, high compound walls, and podiums disrupt natural wind flow and block pre-defined wind corridors. Aaron Serre, a meteorologist from the University of Alabama in Huntsville, adds that replacing vegetation with asphalt and concrete cuts down evapotranspiration and worsens the urban heat island effect.

Physical Effects

When tall buildings interrupt wind, it can create the Venturi effect by funnelling through narrow spaces into fast gusts, or cause the downdraught effect by pushing winds downwards along structures. Prasad Vaidya, a senior adviser at IIHS, notes that unplanned building forms contribute to lower wind speeds and extra heat stress. Yugank Goyal from IIM Ahmedabad suggests using satellite imagery to build city ventilation maps and connect them to master plans.

Context

Urban planning experts emphasize that computational fluid dynamics simulations can help analyze how building shapes and open spaces affect wind movement. Cities like Stuttgart, Seoul, and Hong Kong have used similar assessments to improve city-wide ventilation, offering a model that growing Indian metropolitan areas could potentially follow.