Impact of new particle formation on the concentrations of aerosols and cloud condensation nuclei around Beijing

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2 ! JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 116, D19208, doi: /2011jd016025, 2011!! Impact of new particle formation on the concentrations of aerosols and cloud condensation nuclei around Beijing H. Matsui, 1 M. Koike, 1 Y. Kondo, 1 N. Takegawa, 2 A. Wiedensohler, 3 J. D. Fast, 4 and R. A. Zaveri 4 Received 28 March 2011; revised 14 July 2011; accepted 19 July 2011; published 13 October New particle formation (NPF) is one of the most important processes in controlling the! D19208 MATSUI ET AL.: NPF CALCULATION AROUND BEIJING D19208 Figure 1. Diagram for nucleation and new particle formation processes and their impact on condensation nuclei (CN) and cloud condensation nuclei (CCN) concentrations and aerosol indirect effects. The red, blue, and green arrows show the competing processes of condensable gases between preexisting particles and nucleated secondary particles. J* denotes the formation rate of clusters and is defined by equations (1) and (2) in this study.!

3 Classification of Particles Based on the Size distribution

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6 M. Kulmala et al. / Aerosol Science 35 (2004) Fig. 2. Typical particle formation event in Hyyti.al.a boreal forest site on 13th March 1996: particle size distribution data as a surface plot (a), and total particle number concentration versus time (b).

7 Fig. 6. Time series plot of sulphuric acid vapour and nm particles during a nucleation event at Idaho Hill, CO on 21 September, 1993 (Weber et al., 1997).

8 CLARKE ET AL.: PARTICLE PRODUCTION IN THE REMOTE MARINE ATMOSPHERE 16,407 S. Mid Latitudes (Tasmania) 8 ACE-1 Cloud Outflow---Nucleation... Equatorial (Christmas I.) H2SO4, nucleation 6 Mid Day /(.'-i:'."/ H2SO 4, nucleation /.._.'.: [ I '"... '- "".?"' ' '"':.'1 cøagulatiøn... O '",.;...-..:.'.'¾ ; ;::..': I subsidence,,..,. En..tr_ain. me_nt... IN:ERSlOI o o 5000 Particles (#/crn 3) 60øS EQUATOR Particles (#/cm 3) Figure 14. A cartoon of the nucleation and cycling of particles in the remote marine troposphere as evidence from the observations made on ACE 1. Clouds both scavenge MBL aerosol and source new particles aloft with meteorology and subsidence linking these mechanisms over large spatial scales (see text). surface areas are below about 5 gm 2 cm -3. Separatevidence for new particle formation in the 3-4 nm range was also directly that growth to detectable sizes of gm appeared to be rapid at perhaps a few tens of minutes to hours. Sulfuric acid observed in these regions (P. H. McMurry, personal concentrations also appeared moderately enhanced in these correspondence, 1997). The fact that the larger UCN have regions with typical concentrations of the order of 107 molecules concentrations higher than the UF in most of these regions cm -3. Both particle production and sulfuric acid were found to be suggests that growth of nuclei up to 10 gm diameter or larger must occur in a relatively short period (tens of minutes to hours) as the cloud outflow mixes with dry clean air. We note that for these regions of FSSP surface area that are near or below this value, an appreciable contribution to total surface area exists for more enhanced in cloud outflow regions in noon to early afternoon, apparently as a result of more active photochemistry. Highest new particle concentrations were generally associated with regions of lowest surface areas and water vapor mixing ratios intermediate between moist surface layers and dry regions particle sizes below our "FSSP" lower threshold. Examination of aloft and above cloud. These observations are in general typical RDMA data under these conditions suggest that an additional % of the FSSP surface area may be present below our FSSP detection limit. During these periods of recent "nucleation events" some of this is new surface area, at times 30%, that results from the nucleation itself. At the same time some of the surface area must be a result of mixing with the agreement with previous observations [Perry and Hobbs, 1994] and support their description of cloud processing, although we note that our midlatitude observations occurred at significantly lower altitudes and warmer temperatures(i.e.,-2 ø to-15øc). Growth and evolution of these particles aloft was evident in the data over periods estimated to be hours to a day or so during environmental air after the onset of nucleation. Hence, we which time the smaller nuclei appeared to merge with an Aitken estimate the actual surface area at time of nucleation lies mode usually centered near pm depending upon somewhere between the FSSP value and about twice that value. location and altitude. Flights in postfrontal subsidence revealed smaller nuclei in the MBL both aboard the C-130 and the R/V Discoverer [Bates et al., this issue], indicating that these were 7. Conclusions likely to have been mixed into the MBL as particles formed aloft Several flights have been described from the ACE 1 by previous convective clouds. experimenthat were focused on aerosol nucleation in the free Observations in the tropical free troposphere near Christmas troposphere. All of these observations were found to be linked Island supported earlier data that suggested convective cloud directly or by inference to the air that had been recently processed processes near the ITCZ resulted in new particle production aloft. by clouds. The process of nucleation appeared to be active in the Vertical profiles in this region revealed that smallest region of detrainment and mixing described as cloud outflow and monomodal nuclei were present aloft that gradually increased in

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