Aerosol black carbon radiative forcing at an industrial city in northern India

During a comprehensive aerosol field campaign as part of ISRO‐GBP, extensive measurements of aerosol black carbon were made during December 2004, for the first time, at Kanpur, an urban continental location in northern India. BC diurnal variation is associated with changes in boundary layer mixing and anthropogenic activities. BC concentration in Kanpur is comparable to those measured in other mega cities of India but much higher than in similar locations of Europe, USA and Asia. High BC concentration is found both in absolute terms (6–20 μg m −3 ) and mass fraction (∼10%) yielding very low single scattering albedo (0.76). The estimated surface forcing is as high as −62 ± 23 W m −2 and top of the atmosphere (TOA) forcing is +9 ± 3 W m −2 , which means the atmospheric absorption is +71 W m −2 . The short wave atmospheric absorption translates to a lower atmospheric heating of ∼1.8°K/day. Large surface cooling and lower atmospheric heating may have impacts to regional climate.