Global-scale seasonally resolved black carbon vertical profiles over the Pacific

Black carbon (BC) aerosol loadings were measured during the High-performance Instrumented Airborne Platform for Environmental Research Pole-to-Pole Observations (HIPPO) campaign above the remote Pacific from 85 degrees N to 67 degrees S. Over 700 vertical profiles extending from near the surface to max similar to 14 km altitude were obtained with a single-particle soot photometer between early 2009 and mid-2011. The data provides a climatology of BC in the remote regions that reveals gradients of BC concentration reflecting global-scale transport and removal of pollution. BC is identified as a sensitive tracer of extratropical mixing into the lower tropical tropopause layer and trends toward surprisingly uniform loadings in the lower stratosphere of similar to 1 ng/kg. The climatology is compared to predictions from the AeroCom global model intercomparison initiative. The AeroCom model suite overestimates loads in the upper troposphere/lower stratosphere (similar to 10x) more severely than at lower altitudes (similar to 3x), with bias roughly independent of season or geographic location; these results indicate that it overestimates BC lifetime.