[1] Altitude profiles of aerosol black carbon (BC) in the atmospheric boundary layer and above it were measured for the first time in India, over the urban location Hyderabad, onboard an aircraft during two consecutive days of February 2004. The profiles on both the days were consistent, and showed a rapid decrease in BC concentration within the boundary up to $550 m AGL (where convective activity prevailed). Sodar measurements from the nearby location revealed the mean boundary layer height to be $600 m during the flight period. The decrease in BC above the boundary layer was quite weak up to $2.2 km AGL.
Simultaneous measurements of aerosol black carbon (BC) mass concentration using an Aethalometer Model AE-42 and mixing layer height (MLH) using a monostatic sonic detection and ranging (SODAR) system were carried out from January 2006 to January 2007 at the mega-city Delhi. The BC concentration generally had a typical diurnal variation with morning and late-afternoon/night peaks. The average BC concentration during the whole period of observation was fairly high at 14.75 µg m −3 . The BC concentration nearly doubled during cloudy-sky conditions compared to that during clear-sky conditions. The seasonal variation showed a maximum average concentration during the winter (25.5 µg m −3 ) and a minimum during the monsoon season (7.7 µg m −3 ), with post-and pre-monsoon values at 13.7 and 9.4 µg m −3 , respectively. The average BC concentrations were strongly affected by the ventilation coefficient, a product of average wind speed (WS) and average MLH, and were found to be strongly anticorrelated. A simple model of BC concentration along with the MLH and WS was applied to estimate the average BC emission, which was found to vary in the range 11 000-17 000 kg of BC per day. The maximum emission during the day averaged every hour for different months lay in the range 1000-2100 kg h −1 . The mean monthly emission varied in the range 0.35-0.52 Gg per month, giving rise to an annual estimated emission of 4.86 Gg in the year 2006 over Delhi.
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