Urban morphology amplifies extreme winter PM2.5pollution through wind-driven ventilation suppression over Delhi

Authors:
Preprint
Publisher website
Google Scholar
Abstract
Severe wintertime PM₂.₅ episodes over the Delhi National Capital Region arise from interactions among emissions, regional transport, and urban-modified boundary-layer dynamics. Chemistry transport models frequently underestimate peak concentrations, partly due to simplified surface representation. This study quantifies how updated land-use/land-cover (LULC) and explicit urban morphology alter urban meteorology and regulate pollution buildup during the 13 November 2024 peak event over the northwestern Indo-Gangetic Plain. WRF-Chem simulations were conducted in three configurations: (i) default USGS LULC, (ii) updated LULC based on ESA WorldCover 2021, and (iii) updated LULC coupled with UT-GLOBUS urban morphology with identical emissions and chemistry across experiments.Updating LULC alone produced minimal changes in near-surface wind speed and PM₂.₅. Whereas, explicit urban morphology introduced building-resolved aerodynamic drag, reducing 10 m wind speeds from 1.21-1.51 m s⁻¹ to ~0.10 m s⁻¹ and decreasing the nocturnal ventilation coefficient by ~62%. Weakened dispersion increased simulated hourly PM₂.₅ peaks from ~100 µg m⁻³ to ~300 µg m⁻³, improved temporal correlation with observations (R = 0.77), and confined enhanced accumulation to the lowest 400-500 m. Elevated aerosol loading further suppressed early daytime boundary-layer growth through aerosol-radiation feedback, reinforcing pollutant persistence. These findings demonstrate that realistic urban morphology corrects wind biases, reduces excessive ventilation, and substantially improves simulation of pollution extremes, underscoring the need to integrate high-resolution urban structure into regional air-quality models globally.

This publication has 20 references indexed in Scilit: