Lidars support air quality management in Delhi

The 2010 Commonwealth Games (CWG) hold in Delhi in October 2010 provided an opportunity to pilot an innovative two-fold modeling project involving compact aerosol backscatter lidars. Our work presents how such lidars could improve the understanding of air pollution patterns in Delhi, and feed an air quality forecast model at both the regional and the urban scales.

In a first phase lasting for two months over the pre-monsoon period, two aerosol lidars continuously ran in the arid region of Rajasthan, 300-500 km West of Delhi, using a depolarization channel to discriminate between spherical and non-spherical particles. They provided aerosol profiles in real time in an attempt to support the boundary conditions analysis of the TM5/CHIMERE model used, as shown through a couple of case studies. We also took the opportunity to combine our lidars retrieved light extinction, and the AOD data obtained from the two Aeronet sunphotometers in the region, to further explore the characteristics of the monsoon failure zone in 2010 compared to 2009 according the available data.

In a second phase, lidars continuously ran four eight weeks at four locations within New Delhi metropolitan area, and an additional one was operated from a running vehicle all over the CWG period along New Delhi inner and outer ring roads and CWG special routes. That experimental set up allowed to picture in real time the influence of emissions in terms of aerosol density, and tentatively mass concentration, within the planetary boundary layer (PBL).

Both approaches provide a new potential in improving our knowledge about pollution processes, in modeling and forecasting pollution events, and in setting up decision making tools for emission reduction strategies.