Efficient vertical transport of black carbon in the planetary boundary layer

Abstract:

Vertical distribution of black carbon (BC) determines the layer where its heating impacts exert. This study presents continuous and simultaneous measurements at surface, and on a mountain site above the wintertime planetary boundary layer influenced by uplifted surface anthropogenic emissions. BC was observed efficiently transported upwards by daytime convective mixing. However, this vertical transport was less for other particulate masses. An about two-folds higher BC mass fraction was thus present at mountain than surface, hereby a lowered single-scattering albedo (SSA) by 0.06. This may be caused by the evaporative loss of condensed semi-volatile materials, prevailing the secondary particulate formation, in a cleaner environment containing less precursors. The elevated BC mass corresponded with the most intensive solar radiation at midday, wielding more heating impacts over the PBL. This phenomenon may apply to other remote regions where a reduced SSA will introduce more positive radiative effects.