Export efficiency of black carbon aerosol in continental outflow: Global implications

[1] We use aircraft observations of Asian outflow from the NASATransport and Chemical Evolution over the Pacific (TRACE-P) mission over the NW Pacific in March–April 2001 to estimate the export efficiency of black carbon (BC) aerosol during lifting to the free troposphere, as limited by scavenging f...

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Bibliographic Details
Main Authors: Rokjin J. Park, Daniel J. Jacob, Paul I. Palmer, Antony D. Clarke, Rodney J. Weber, Mark A. Zondlo, Fred L. Eisele, Alan R. B, Donald C. Thornton, Glen W. Sachse, Tami C. Bond
Other Authors: The Pennsylvania State University CiteSeerX Archives
Format: Text
Language:English
Published: 2005
Subjects:
Arctic
Pacific
albedo
black carbon
Online Access:http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.62.2708
http://www-as.harvard.edu/chemistry/trop/publications/ParkRJEA_jgr_2005.pdf
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Summary:[1] We use aircraft observations of Asian outflow from the NASATransport and Chemical Evolution over the Pacific (TRACE-P) mission over the NW Pacific in March–April 2001 to estimate the export efficiency of black carbon (BC) aerosol during lifting to the free troposphere, as limited by scavenging from the wet processes (warm conveyor belts and convection) associated with this lifting. Our estimate is based on the enhancement ratio of BC relative to CO in Asian outflow observed at different altitudes and is normalized to the enhancement ratio observed in boundary layer outflow (0–1 km). We 2 similarly estimate export efficiencies of sulfur oxides (SOx =SO2(g) + fine SO4) and total inorganic nitrate (HNO3 T = HNO3(g) + fine NO3) for comparison to BC. Normalized export efficiencies for BC are 0.63–0.74 at 2–4 km altitude and 0.27–0.38 at 4–6 km. Values at 2–4 km altitude are higher than for SOx (0.48–0.66) and HNO3 T (0.29–0.62), implying that BC is scavenged in wet updrafts but not as efficiently as sulfate or nitrate. Simulation of the TRACE-P period with a global three-dimensional model (GEOS-CHEM) indicates that a model timescale of 1 ± 1 days for conversion of fresh hydrophobic to hydrophilic BC provides a successful fit to the export efficiencies observed in TRACE-P. The resulting mean atmospheric lifetime of BC is 5.8 ± 1.8 days, the global burden is 0.11 ± 0.03 Tg C, and the decrease in Arctic snow albedo due to BC deposition is 3.1 ± 2.5%. Citation: Park, R. J., et al. (2005), Export efficiency of black carbon aerosol in continental outflow: Global implications, J. Geophys.

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