scholarly journals Examination of parameterizations for CCN number concentrations based on in-situ aerosol activation property measurements in the North China Plain

2013 ◽  
Vol 13 (1) ◽  
pp. 145-176 ◽  
Author(s):  
Z. Z. Deng ◽  
C. S. Zhao ◽  
N. Ma ◽  
L. Ran ◽  
G. Q. Zhou ◽  
...  
Keyword(s):  
Size Distribution ◽  
Particle Number ◽  
Cloud Condensation Nuclei ◽  
Good Prediction ◽  
Number Size Distribution ◽  
The North ◽  
Precise Quantification ◽  
Particle Number Size Distribution ◽  
Aerosol Activation

Abstract. Precise quantification of cloud condensation nuclei (CCN) number concentrations is crucial for understanding aerosol indirect effect and characterizing this effect in models. An evaluation of various methods for CCN parameterization is carried out in this paper based on in-situ measurements of aerosol activation properties within HaChi (Haze in China) project. Comparisons are made by closure studies between methods using CCN spectra, bulk activation ratios, cut-off diameters and size-resolved activation ratios. The estimation of CCN number concentrations by the method using aerosol activation curves, either averaged over a day or with diurnal variation, is found to be most satisfying and straightforward. This could be well expected since size-resolved activation ratios include information regarding the effects of size-resolved chemical composition and mixing state on aerosol activation properties. The method using the averages of critical diameters, which are inferred from measured CCN number concentrations and particle number size distribution, also provides a good prediction of CCN number concentrations. Based on comparisons of all these methods in this paper, it is recommended that CCN number concentrations be predicted using particle number size distribution with inferred critical diameters or size-resolved activation ratios.

scholarly journals An examination of parameterizations for the CCN number concentration based on in situ measurements of aerosol activation properties in the North China Plain

2013 ◽  
Vol 13 (13) ◽  
pp. 6227-6237 ◽  
Author(s):  
Z. Z. Deng ◽  
C. S. Zhao ◽  
N. Ma ◽  
L. Ran ◽  
G. Q. Zhou ◽  
...  
Keyword(s):  
Particle Number ◽  
Cloud Condensation Nuclei ◽  
Number Concentration ◽  
In Situ Measurements ◽  
Chemical Compositions ◽  
Good Prediction ◽  
Size Distributions ◽  
The North ◽  
Aerosol Activation

Abstract. Precise quantification of the cloud condensation nuclei (CCN) number concentration is crucial for understanding aerosol indirect effects and characterizing these effects in models. An evaluation of various methods for CCN parameterization was carried out in this paper based on in situ measurements of aerosol activation properties within HaChi (Haze in China) project. Comparisons were made by closure studies between methods using CCN spectra, bulk activation ratios, cut-off diameters and size-resolved activation ratios. The estimation of CCN number concentrations by the method using aerosol size-resolved activation ratios, either averaged over a day or with diurnal variation, was found to be most satisfying and straightforward. This could be well expected since size-resolved activation ratios include information regarding the effects of size-resolved chemical compositions and mixing states on aerosol activation properties. The method using the averages of critical diameters, which were inferred from measured CCN number concentrations and particle number size distributions, also provided a good prediction of the CCN number concentration. Based on comparisons of all these methods in this paper, it was recommended that the CCN number concentration be predicted using particle number size distributions with inferred critical diameters or size-resolved activation ratios.

scholarly journals Long-term cloud condensation nuclei number concentration, particle number size distribution and chemical composition measurements at regionally representative observatories

2018 ◽  
Vol 18 (4) ◽  
pp. 2853-2881 ◽  
Author(s):  
Julia Schmale ◽  
Silvia Henning ◽  
Stefano Decesari ◽  
Bas Henzing ◽  
Helmi Keskinen ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Size Distribution ◽  
Radiative Forcing ◽  
Particle Number ◽  
Cloud Condensation Nuclei ◽  
Number Concentration ◽  
Size Distributions ◽  
Number Size Distribution ◽  
Particle Number Size Distribution

Abstract. Aerosol–cloud interactions (ACI) constitute the single largest uncertainty in anthropogenic radiative forcing. To reduce the uncertainties and gain more confidence in the simulation of ACI, models need to be evaluated against observations, in particular against measurements of cloud condensation nuclei (CCN). Here we present a data set – ready to be used for model validation – of long-term observations of CCN number concentrations, particle number size distributions and chemical composition from 12 sites on 3 continents. Studied environments include coastal background, rural background, alpine sites, remote forests and an urban surrounding. Expectedly, CCN characteristics are highly variable across site categories. However, they also vary within them, most strongly in the coastal background group, where CCN number concentrations can vary by up to a factor of 30 within one season. In terms of particle activation behaviour, most continental stations exhibit very similar activation ratios (relative to particles > 20 nm) across the range of 0.1 to 1.0 % supersaturation. At the coastal sites the transition from particles being CCN inactive to becoming CCN active occurs over a wider range of the supersaturation spectrum. Several stations show strong seasonal cycles of CCN number concentrations and particle number size distributions, e.g. at Barrow (Arctic haze in spring), at the alpine stations (stronger influence of polluted boundary layer air masses in summer), the rain forest (wet and dry season) or Finokalia (wildfire influence in autumn). The rural background and urban sites exhibit relatively little variability throughout the year, while short-term variability can be high especially at the urban site. The average hygroscopicity parameter, κ, calculated from the chemical composition of submicron particles was highest at the coastal site of Mace Head (0.6) and lowest at the rain forest station ATTO (0.2–0.3). We performed closure studies based on κ–Köhler theory to predict CCN number concentrations. The ratio of predicted to measured CCN concentrations is between 0.87 and 1.4 for five different types of κ. The temporal variability is also well captured, with Pearson correlation coefficients exceeding 0.87. Information on CCN number concentrations at many locations is important to better characterise ACI and their radiative forcing. But long-term comprehensive aerosol particle characterisations are labour intensive and costly. Hence, we recommend operating “migrating-CCNCs” to conduct collocated CCN number concentration and particle number size distribution measurements at individual locations throughout one year at least to derive a seasonally resolved hygroscopicity parameter. This way, CCN number concentrations can only be calculated based on continued particle number size distribution information and greater spatial coverage of long-term measurements can be achieved.

scholarly journals Size-resolved and bulk activation properties of aerosols in the North China Plain

2011 ◽  
Vol 11 (8) ◽  
pp. 3835-3846 ◽  
Author(s):  
Z. Z. Deng ◽  
C. S. Zhao ◽  
N. Ma ◽  
P. F. Liu ◽  
L. Ran ◽  
...  
Keyword(s):  
Size Distribution ◽  
North China Plain ◽  
North China ◽  
Cloud Condensation Nuclei ◽  
Number Concentration ◽  
Anthropogenic Aerosol ◽  
Number Size Distribution ◽  
The North ◽  
The North China Plain ◽  
Activation Ratio

Abstract. Size-resolved and bulk activation properties of aerosols were measured at a regional/suburban site in the North China Plain (NCP), which is occasionally heavily polluted by anthropogenic aerosol particles and gases. A Cloud Condensation Nuclei (CCN) closure study is conducted with bulk CCN number concentration (NCCN) and calculated CCN number concentration based on the aerosol number size distribution and size-resolved activation properties. The observed CCN number concentration (NCCN-obs) are higher than those observed in other locations than China, with average NCCN-obs of roughly 2000, 3000, 6000, 10 000 and 13 000 cm−3 at supersaturations of 0.056, 0.083, 0.17, 0.35 and 0.70%, respectively. An inferred critical dry diameter (Dm) is calculated based on the NCCN-obs and aerosol number size distribution assuming homogeneous chemical composition. The inferred cut-off diameters are in the ranges of 190–280, 160–260, 95–180, 65–120 and 50–100 nm at supersaturations of 0.056, 0.083, 0.17, 0.35 and 0.7%, with their mean values 230.1, 198.4, 128.4, 86.4 and 69.2 nm, respectively. Size-resolved activation measurements show that most of the 300 nm particles are activated at the investigated supersaturations, while almost no particles of 30 nm are activated even at the highest supersaturation of 0.72%. The activation ratio increases with increasing supersaturation and particle size. The slopes of the activation curves for ambient aerosols are not as steep as those observed in calibrations with ammonium sulfate suggesting that the observed aerosols is an external mixture of more hygroscopic and hydrophobic particles. The calculated CCN number concentrations (NCCN-calc) based on the size-resolved activation ratio and aerosol number size distribution correlate well with the NCCN-obs, and show an average overestimation of 19%. Sensitivity studies of the CCN closure show that the NCCN at each supersaturation is well predicted with the campaign average of size-resolved activation curves. These results indicate that the aerosol number size distribution is critical in the prediction of possible CCN. The CCN number concentration can be reliably estimated using time-averaged, size-resolved activation efficiencies without accounting for the temporal variations.

scholarly journals The effect of local sources on aerosol particle number size distribution, concentrations and fluxes in Helsinki, Finland

Tellus B ◽  
2013 ◽  
Vol 65 (1) ◽  
pp. 19786 ◽  
Author(s):  
Giovanna Ripamonti ◽  
Leena Järvi ◽  
Bjarke Mølgaard ◽  
Tareq Hussein ◽  
Annika Nordbo ◽  
...  
Keyword(s):  
Size Distribution ◽  
Aerosol Particle ◽  
Particle Number ◽  
Number Size Distribution ◽  
Local Sources ◽  
Particle Number Size Distribution
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