title: A potential large and persistent black carbon forcing over Northern Pacific inferred from satellite observations.
abstract: Black carbon (BC) aerosol strongly absorbs solar radiation, which warms climate. However, accurate estimation of BC's climate effect is limited by the uncertainties of its spatiotemporal distribution, especially over remote oceanic areas. The HIAPER Pole-to-Pole Observation (HIPPO) program from 2009 to 2011 intercepted multiple snapshots of BC profiles over Pacific in various seasons, and revealed a 2 to 5 times overestimate of BC by current global models. In this study, we compared the measurements from aircraft campaigns and satellites, and found a robust association between BC concentrations and satellite-retrieved CO, tropospheric NO2, and aerosol optical depth (AOD) (R2> 0.8). This establishes a basis to construct a satellite-based column BC approximation (sBC*) over remote oceans. The inferred sBC* shows that Asian outflows in spring bring much more BC aerosols to the mid-Pacific than those occurring in other seasons. In addition, inter-annual variability of sBC* is seen over the Northern Pacific, with abundances varying consistently with the springtime Pacific/North American (PNA) index. Our sBC* dataset infers a widespread overestimation of BC loadings and BC Direct Radiative Forcing by current models over North Pacific, which further suggests that large uncertainties exist on aerosol-climate interactions over other remote oceanic areas beyond Pacific.
authors.affiliation: Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing, China.|Woodrow Wilson School of Public and International Affairs, Princeton University, Princeton, NJ, USA.|College of Environmental Science and Engineering, Peking University, Beijing, China.
authors.forename: Zhongshu
authors.initials: Z
authors.lastname: Li
authors.affiliation: Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing, China.
authors.forename: Junfeng
authors.initials: J
authors.lastname: Liu
authors.affiliation: Woodrow Wilson School of Public and International Affairs, Princeton University, Princeton, NJ, USA.|Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ, USA.
authors.forename: Denise L
authors.initials: DL
authors.lastname: Mauzerall
authors.affiliation: Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ, USA.
authors.forename: Xiaoyuan
authors.initials: X
authors.lastname: Li
authors.affiliation: NOAA Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey, USA.
authors.forename: Songmiao
authors.initials: S
authors.lastname: Fan
authors.affiliation: NOAA Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey, USA.
authors.forename: Larry W
authors.initials: LW
authors.lastname: Horowitz
authors.affiliation: Department of Atmosphere and Oceanic Sciences, University of California at Los Angeles (UCLA), Los Angeles, CA, USA.
authors.forename: Cenlin
authors.initials: C
authors.lastname: He
authors.affiliation: Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing, China.
authors.forename: Kan
authors.initials: K
authors.lastname: Yi
authors.affiliation: Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing, China.
authors.forename: Shu
authors.initials: S
authors.lastname: Tao