Vertical transport and removal of black carbon over East Asia in spring during the A-FORCE aircraft campaign

Monday, 15 December 2014
Naga Oshima1, Makoto Koike2, Yutaka Kondo2, Hisashi Nakamura2, Nobuhiro Moteki2, Hitoshi Matsui3, Nobuyuki Takegawa4 and Kazuyuki Kita5, (1)Meteorological Research Institute, Ibaraki, Japan, (2)University of Tokyo, Tokyo, Japan, (3)JAMSTEC Japan Agency for Marine-Earth Science and Technology, Research Institute for Global Change, Kanagawa, Japan, (4)Tokyo Metropolitan University, Tokyo, Japan, (5)Ibaraki University, Mito, Japan
The Aerosol Radiative Forcing in East Asia (A-FORCE) aircraft campaign was conducted at 0-9 km in altitude over East Asia in March-April 2009 to investigate transport and removal processes of aerosols, their physical and chemical properties, and cloud microphysical properties in Asian outflow. In this study, mechanisms of vertical transport of black carbon (BC) aerosols and their three-dimensional transport pathways over East Asia in spring were examined through numerical simulations for the A-FORCE campaign using a modified version of the Community Multiscale Air Quality (CMAQ) modeling system. The simulations reproduced the spatial distributions of mass concentration of BC and its transport efficiency observed by the A-FORCE campaign reasonably well, including its vertical and latitudinal gradients and dependency on precipitation amount that air parcels experienced during the transport. During the A-FORCE period, two types of pronounced upward BC mass fluxes from the planetary boundary layer (PBL) to the free troposphere (FT) were found over northeastern and inland-southern China. Over northeastern China, cyclones with modest precipitation were the primary uplifting mechanism of BC. Over inland-southern China, both cumulus convection and orographic uplifting along the slopes of the Tibetan Plateau played important roles in the upward transport of BC, despite its efficient wet deposition due to a large amount of precipitation supported by an abundant moisture supply by the low-level southerlies. In addition to the midlatitude (35–45°N) eastward outflow within the PBL (21% BC removal by precipitation during transport), the uplifting of BC over northeastern and inland-southern China and the subsequent BC transport by the midlatitude lower tropospheric (50% BC removal) and subtropical (25–35°N) midtropospheric westerlies (67% BC removal), respectively, provided the major transport pathways for BC export from continental East Asia to the Pacific.