Impact of aerosol composition on cloud condensation nuclei activity 1Beijing Weather Modification Office, Beijing, China
25 Apr 2012
2Institude of Urban Meteorology, CMA, Beijing, China
Received: 24 Oct 2011 – Published in Atmos. Chem. Phys. Discuss.: 17 Jan 2012Abstract. The impact of aerosol composition on cloud condensation nuclei (CCN)
activity were analyzed in this study based on field experiments carried out
at downtown Tianjin, China in September 2010. In the experiments, the CCN
measurements were performed at supersaturation (SS) of 0.1%, 0.2% and
0.4% using a thermal-gradient diffusion chamber (DMT CCNC), whereas the
aerosol size distribution and composition were simultaneously measured with
a TSI SMPS and an Aerodyne Aerosol Mass Spectrometer (AMS), respectively.
The results show that the influence of aerosol composition on CCN activity
is notable under low SS (0.1%), and their influence decreased with
increasing SS. For example, under SS of 0.1%, the CCN activity increases
from 4.5±2.6% to 12.8±6.1% when organics fraction decrease
from 30–40% to 10–20%. The rate of increase reached up to 184%.
While under SS of 0.4%, the CCN activity increases only from 35.7±19.0%
to 46.5±12.3% correspondingly. The calculated NCCN
based on the size-resolved activation ratio and aerosol number size
distribution correlated well with observed NCCN
at high SS (0.4%), but this consistence decreased with the falling of SS. The slopes of linear
fitted lines between calculated and observed NCCN are 0.708, 0.947, and
0.995 at SS of 0.1%, 0.2% and 0.4% respectively. Moreover, the
stand deviation (SD) of calculated NCCN increased with the decreasing
of SS. A case study of CCN closure analyses indicated that the calculated
error of NCCN could reach up to 34% at SS of 0.1% if aerosol
composition were not included, and the calculated error decreased with the
raising of SS. It is decreased to 9% at SS of 0.2%, and further
decreased to 4% at SS of 0.4%.
Revised: 23 Mar 2012 – Accepted: 02 Apr 2012 – Published: 25 Apr 2012
Citation: Zhang, Q., Meng, J., Quan, J., Gao, Y., Zhao, D., Chen, P., and He, H.: Impact of aerosol composition on cloud condensation nuclei activity, Atmos. Chem. Phys., 12, 3783-3790, doi:10.5194/acp-12-3783-2012, 2012.