Assessing the spatio-temporal dynamics of Ventilation Coefficient for Air Quality Management: A study of Ahmedabad city, India using WRF model

Urban air pollution is a growing public health challenge, with meteorology playing a crucial role in determining pollutant dispersion. In India, stagnant atmospheric conditions—characterized by weak winds and a shallow planetary boundary layer (PBL)—intensify pollution episodes, increasing health risks. The Ventilation Coefficient (VC), defined as the product of PBL height and mean wind speed within the PBL, serves as a key indicator of the atmosphere’s ability to disperse pollutants. This study examines the spatio-temporal variability of VC in Ahmedabad, India, using high-resolution Weather Research and Forecasting (WRF) model simulations for two contrasting meteorological periods: winter (13–19 January 2024) and summer (18–24 May 2024). By analysing these extreme regimes, the study provides insights into how seasonal and diurnal variations in VC impact the city’s air quality dynamics.

Results indicate a significant seasonal contrast in VC, with values ranging from 185 to 30,268 m²/s in winter and 322 to 44,316 m²/s in summer. The average VC during the 6.30 pm to 8.30 am (nighttime) during winter ranges between 899 – 2390 m²/s while that in summer ranges between 2678 – 4216 m²/s while that during 9.30 am – 5.30 pm (daytime) it varies between 12951 – 22782 m²/s in winter and 8,455 – 12,364 m²/s in summer. The observed variations highlight that atmospheric ventilation capacity fluctuates not only seasonally but also on hourly and daily timescales, influencing pollution dispersion patterns.

The findings underscore the potential of VC as a guiding parameter for air quality management, particularly in scheduling industrial emissions and optimizing mitigation strategies. A real-time forecast of VC could strengthen air pollution action plans by helping regulators anticipate periods of poor dispersion and implement timely interventions. By integrating VC into urban air quality policies, cities like Ahmedabad can develop more adaptive and effective approaches to reducing pollution exposure and safeguarding public health.