Japan Geoscience Union Meeting 2014

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Symbol A (Atmospheric, Ocean, and Environmental Sciences) » A-AS Atmospheric Sciences, Meteorology & Atmospheric Environment

[A-AS22_1AM1] Atmospheric Chemistry

Thu. May 1, 2014 9:00 AM - 10:45 AM 511 (5F)

Convener:*Nobuyuki Takegawa(Research Center for Advanced Science and Technology, University of Tokyo), Yousuke Sawa(Geochemical Research Department, Meteorological Research Institute), Yugo Kanaya(Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology), Kenshi Takahashi(Research Institute for Sustainable Humanosphere, Kyoto University), Hiroshi Tanimoto(National Institute for Environmental Studies), Chair:Takuma Miyakawa(Japan Agency for Marine-Earth Science and Technology)

9:15 AM - 9:30 AM

[AAS22-09] The main controlling factor of black carbon mass concentration in rainwater during 2010-2013 summer in East Asia

*Tatsuhiro MORI1, Sho OHATA1, Yutaka KONDO1, Nobuhiro MOTEKI1, Hitoshi MATSUI2, Aya IWASAKI3, Nobutaka TOMOYOSE3, Hisashi KADENA3 (1.Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo, Japan, 2.Japan Agency for Marine-Earth Science and Technology, Tokyo, Japan, 3.Okinawa Prefectural Institute of Health and Environment)

Keywords:Black Carbon, wet deposition

Black carbon (BC) particles are emitted into the atmosphere by incomplete combustion processes, and removed by precipitation. The measurements of BC mass concentration in rainwater improve the quantitative understanding of BC loss because wet deposition is the major sink of BC. We measured BC mass concentration in the air (MBC) and in rainwater (CBC) simultaneously at Cape Hedo on Okinawa Island, Japan, in the East China Sea, from April 2010 to March 2013 in order to understand CBC in each rain event during 2010-2013 summer. The rainwater is collected by an automated wet-only sampler during a 24 period. Photo-absorption photometer with heated inlet (COSMOS) is used to measure MBC. CBC was measured by a system consisting of an ultrasonic nebulizer and a Single Soot Photometer (SP2). It is often heavy rain by cumulonimbus cloud during summer in East Asia, so that MBC an hour before raining is expected to be related to CBC. However, the correlation between MBC and CBC in all rain events during 2010-2013 summer is not agreed (r2 = 0.12). Then, we extracted the heavy rain events, which had positive convective available potential energy (CAPE). These extraction was performed with the National Centers for Environmental Prediction (NCEP) Final (FNL) Operational Global Analysis data every 6 hours. This result was that CBC was correlated with MBC (r2 = 0.47). In order to investigate if CBC (Estimated CBC) is explained with MBC and the liquid water content, Estimated CBC is verified by comparing the observed CBC. The liquid water content is maximum at the equilibrium level (EL) by the condensation process theoretically if the total water mixing ratio is conserved in the air parcel. If BC in the parcel is active as cloud condensation nuclei (CCN) at lifted condensation level and removed by precipitation at EL, the equation of Estimated CBC at EL is represented as Estimated CBC=MBC/(mv*WCR). mv is the water vapor content an hour before raining at the ground level. Water condensation ratio (WCR) is the mass ratio of liquid water content to water vapor content, which is calculated with the NCEP reanalysis data. Compared with the observed CBC, Estimated CBC is correlated with the observed CBC well (r2 = 0.68). It suggests that Estimated CBC is correctly represented as CBC with MBC and the most liquid water content at EL. The observed CBC is three times higher than Estimated CBC because the cloud droplets including BC particles might be collected during falling down.