Urban planning must factor in wind flow to combat city heat

UPDATE - follow-up to Letting the wind flow freely is the secret to cooling our cities: Urban planners and experts warn that dense construction and slower near-ground winds continue to worsen heat stress in Indian cities. Terrestrial stilling, a global drop in wind speed near the ground, has been taking place since the 1980s. Amruthraj M.N., a consultant at the Sustainable Energy Lab at the Indian Institute for Human Settlements in Bengaluru, notes that reduced wind speed typically occurs around 10 meters from the floor where pedestrians move. Aaron Serre, a meteorologist from the University of Alabama, explains that dense infrastructure creates turbulence and surface friction.

Urban Design Factors

High compound walls, podiums, and closely clumped high-rise buildings restrict wind corridors and slow down wind speeds. When winds hit tall buildings, they can create the Venturi effect by funnelling through narrow spaces into strong gusts, or cause the downdraught effect by pushing downwards. Prasad Vaidya, a senior adviser at IIHS, points out that unplanned higher building forms contribute to lower wind speeds and extra heat stress. Experts suggest using computational fluid dynamics simulations and satellite imagery to build city ventilation maps, though these tools remain costly and underused.

Context

Urban microclimates are heavily shaped by physical structures, vegetation cover, and surface materials like concrete. Understanding these wind patterns helps city planners design better layouts to improve air movement and public health.