Number concentration and size distribution of soot aerosols of heptane fire at low pressures

2021 ◽  
Author(s):  
Shenlin Yang ◽  
Fang Pu ◽  
Zhen Wang ◽  
Zhaoqi Liu ◽  
Manhou Li
Keyword(s):  
Size Distribution ◽  
Number Concentration ◽  
Low Pressures

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 Improved rain-rate and drop-size retrievals from airborne and spaceborne Doppler radar

2017 ◽  
Author(s):  
Shannon L. Mason ◽  
J. Christine Chiu ◽  
Robin J. Hogan ◽  
Lin Tian
Keyword(s):  
Size Distribution ◽  
Drop Size ◽  
Rain Rate ◽  
Doppler Radar ◽  
Number Concentration ◽  
Doppler Velocity ◽  
Light Rain ◽  
Warm Rain ◽  
Rain Drop ◽  
Drop Number

Abstract. Satellite radar remote-sensing of rain is important for quantifying of the global hydrological cycle, atmospheric energy budget, and many microphysical cloud and precipitation processes; however, radar estimates of rain rate are sensitive to assumptions about the raindrop size distribution. The upcoming EarthCARE satellite will feature a 94-GHz Doppler radar alongside lidar and radiometer instruments, presenting opportunities for enhanced global retrievals of the rain drop size distribution. In this paper we demonstrate the capability to retrieve both rain rate and a parameter of the rain drop size distribution from an airborne 94-GHz Doppler radar using CAPTIVATE, the variational retrieval algorithm developed for EarthCARE radar–lidar synergy. For a range of rain regimes observed during the Tropical Composition, Cloud and Climate Coupling (TC4) field campaign in the eastern Pacific in 2007, we explore the contributions of Doppler velocity and path-integrated attenuation (PIA) to the retrievals, and evaluate the retrievals against independent measurements from a second, less attenuated, Doppler radar aboard the same aircraft. Retrieved drop number concentration varied over five orders of magnitude between light rain from melting ice, and warm rain from liquid clouds. Doppler velocity can be used to estimate rain rate over land, and retrievals of rain rate and drop number concentration are possible in profiles of light rain over land; in moderate warm rain, drop number concentration can be retrieved without Doppler velocity. These results suggest that EarthCARE rain retrievals facilitated by Doppler radar will make substantial improvements to the global understanding of the interaction of clouds and precipitation.

scholarly journals Modeling particle nucleation and growth over northern California during the 2010 CARES campaign

2015 ◽  
Vol 15 (21) ◽  
pp. 12283-12313 ◽  
Author(s):  
A. Lupascu ◽  
R. Easter ◽  
R. Zaveri ◽  
M. Shrivastava ◽  
M. Pekour ◽  
...  
Keyword(s):  
Size Distribution ◽  
Particle Number ◽  
Particle Formation ◽  
Number Concentration ◽  
Aerosol Size Distribution ◽  
Particle Nucleation ◽  
Particle Number Concentration ◽  
New Particle Formation ◽  
Organic Vapors ◽  
Diurnal Variability

Abstract. Accurate representation of the aerosol lifecycle requires adequate modeling of the particle number concentration and size distribution in addition to their mass, which is often the focus of aerosol modeling studies. This paper compares particle number concentrations and size distributions as predicted by three empirical nucleation parameterizations in the Weather Research and Forecast coupled with chemistry (WRF-Chem) regional model using 20 discrete size bins ranging from 1 nm to 10 μm. Two of the parameterizations are based on H2SO4, while one is based on both H2SO4 and organic vapors. Budget diagnostic terms for transport, dry deposition, emissions, condensational growth, nucleation, and coagulation of aerosol particles have been added to the model and are used to analyze the differences in how the new particle formation parameterizations influence the evolving aerosol size distribution. The simulations are evaluated using measurements collected at surface sites and from a research aircraft during the Carbonaceous Aerosol and Radiative Effects Study (CARES) conducted in the vicinity of Sacramento, California. While all three parameterizations captured the temporal variation of the size distribution during observed nucleation events as well as the spatial variability in aerosol number, all overestimated by up to a factor of 2.5 the total particle number concentration for particle diameters greater than 10 nm. Using the budget diagnostic terms, we demonstrate that the combined H2SO4 and low-volatility organic vapor parameterization leads to a different diurnal variability of new particle formation and growth to larger sizes compared to the parameterizations based on only H2SO4. At the CARES urban ground site, peak nucleation rates are predicted to occur around 12:00 Pacific (local) standard time (PST) for the H2SO4 parameterizations, whereas the highest rates were predicted at 08:00 and 16:00 PST when low-volatility organic gases are included in the parameterization. This can be explained by higher anthropogenic emissions of organic vapors at these times as well as lower boundary-layer heights that reduce vertical mixing. The higher nucleation rates in the H2SO4-organic parameterization at these times were largely offset by losses due to coagulation. Despite the different budget terms for ultrafine particles, the 10–40 nm diameter particle number concentrations from all three parameterizations increased from 10:00 to 14:00 PST and then decreased later in the afternoon, consistent with changes in the observed size and number distribution. We found that newly formed particles could explain up to 20–30 % of predicted cloud condensation nuclei at 0.5 % supersaturation, depending on location and the specific nucleation parameterization. A sensitivity simulation using 12 discrete size bins ranging from 1 nm to 10 μm diameter gave a reasonable estimate of particle number and size distribution compared to the 20 size bin simulation, while reducing the associated computational cost by ~ 36 %.

scholarly journals Measurement of nonvolatile particle number size distribution

2016 ◽  
Vol 9 (1) ◽  
pp. 103-114 ◽  
Author(s):  
G. I. Gkatzelis ◽  
D. K. Papanastasiou ◽  
K. Florou ◽  
C. Kaltsonoudis ◽  
E. Louvaris ◽  
...  
Keyword(s):  
Size Distribution ◽  
Black Carbon ◽  
Biomass Burning ◽  
Particle Number ◽  
Number Concentration ◽  
Experimental Methodology ◽  
Particle Number Concentration ◽  
Scanning Mobility Particle Sizer ◽  
Number Size Distribution ◽  
Particle Sizer

Abstract. An experimental methodology was developed to measure the nonvolatile particle number concentration using a thermodenuder (TD). The TD was coupled with a high-resolution time-of-flight aerosol mass spectrometer, measuring the chemical composition and mass size distribution of the submicrometer aerosol and a scanning mobility particle sizer (SMPS) that provided the number size distribution of the aerosol in the range from 10 to 500 nm. The method was evaluated with a set of smog chamber experiments and achieved almost complete evaporation (> 98 %) of secondary organic as well as freshly nucleated particles, using a TD temperature of 400 °C and a centerline residence time of 15 s. This experimental approach was applied in a winter field campaign in Athens and provided a direct measurement of number concentration and size distribution for particles emitted from major pollution sources. During periods in which the contribution of biomass burning sources was dominant, more than 80 % of particle number concentration remained after passing through the thermodenuder, suggesting that nearly all biomass burning particles had a nonvolatile core. These remaining particles consisted mostly of black carbon (60 % mass contribution) and organic aerosol (OA; 40 %). Organics that had not evaporated through the TD were mostly biomass burning OA (BBOA) and oxygenated OA (OOA) as determined from AMS source apportionment analysis. For periods during which traffic contribution was dominant 50–60 % of the particles had a nonvolatile core while the rest evaporated at 400 °C. The remaining particle mass consisted mostly of black carbon with an 80 % contribution, while OA was responsible for another 15–20 %. Organics were mostly hydrocarbon-like OA (HOA) and OOA. These results suggest that even at 400 °C some fraction of the OA does not evaporate from particles emitted from common combustion processes, such as biomass burning and car engines, indicating that a fraction of this type of OA is of extremely low volatility.

scholarly journals Nucleation-mode particle pool and large increases in <i>N</i><sub>cn</sub> and <i>N</i><sub>ccn</sub> observed over the northwestern Pacific Ocean in the spring of 2014

2019 ◽  
Vol 19 (13) ◽  
pp. 8845-8861 ◽  
Author(s):  
Juntao Wang ◽  
Yanjie Shen ◽  
Kai Li ◽  
Yang Gao ◽  
Huiwang Gao ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Size Distribution ◽  
Cloud Condensation Nuclei ◽  
Number Concentration ◽  
Atmospheric Particles ◽  
Northwestern Pacific ◽  
Condensation Nuclei ◽  
Northwestern Pacific Ocean ◽  
Mean Values ◽  
Nucleation Mode

Abstract. Determination of the updated concentrations of atmospheric particles (Ncn) and the concentrations of cloud condensation nuclei (Nccn) over the northwestern Pacific Ocean (NWPO) are important to accurately evaluate the influence of aerosol outflow from the Asian continent on the climate by considering the rapid changes in emissions of air pollutants therein. However, field observations in the last two decades are scarce. We conducted a cruise campaign over the NWPO to simultaneously measure Ncn, Nccn and the size distribution of aerosol particles from day of year (DOY) 81 to DOY 108 of 2014. The mean values of Nccn at supersaturation (SS) of levels 0.2 % and 0.4 % were 0.68±0.38×103 and 1.1±0.67×103 cm−3, respectively, with an average of 2.8±1.0×103 cm−3 for Ncn during the cruise over the NWPO. All are approximately 1 order of magnitude larger than spring observations made during the preceding two decades in the remote marine atmosphere. The larger values, against the marine natural background reported in the literature, imply an overwhelming contribution from continental inputs. The calculated activity ratios (ARs) of the cloud condensation nuclei (CCN) were 0.30±0.11 and 0.46±0.19 at SS levels of 0.2 % and 0.4 %, respectively, which are almost the same as those of upwind semi-urban sites. High Nccn and CCN activities were observed from DOY 98 to DOY 102, when the oceanic zone received even stronger continental input. Excluding biomass burning (BB) and dust aerosols, good correlation between Nccn at 0.4 % SS and the number concentrations of > 60 nm particles (N>60 nm) was obtained during the entire cruise period, with a slope of 0.98 and R2=0.94, and the corresponding effective hygroscopicity parameter (κ) was estimated to be 0.40. A bimodal size distribution pattern of the particle number concentration was generally observed during the entire campaign when the N>90 nm varied largely. However, the N<30 nm, accounting for approximately one-third of the total number concentration, varied narrowly, and two NPF events associated with vertical transport were observed. This implies that a pool of nucleation-mode atmospheric particles is aloft. BB and dust events were observed over the NWPO, but their aerosol contributions to Ncn and Nccn were minor (i.e., 10 % or less) on a monthly timescale.

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