Dust aerosol optical properties over North China

Abstract. Aerosol optical properties were obtained from ground-based sunphotometer data at nine observatories over North China during two periods of 1996–1998 and 2002–2003. The seasonal changes of aerosol optical depth (AOD) at five wavelengths were observed, with the highest value of AOD in spring, while the lowest in winter. Four patterns of AOD diurnal variation were obtained, of which the high value occurred in the morning, noon, evening and no remarkable change, respectively. Together with meteorological records, the characteristics of AOD during dust weather were analyzed, and the results show that it was more detailed and accurate to use AOD to depict the strength change of dust weather than to use surface visibility. Based on measurements by aerodynamic instrument for particle size distribution, a positive correlation between dust particle number concentration and Ångström turbidity coefficient β, and a negative correlation between aerosol geometric mean diameter (GMD) and wavelength exponent αwere revealed.

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Estimating CCN number concentrations using aerosol optical properties: Role of particle number size distribution and parameterization

10.5194/acp-2019-149 ◽

2019 ◽

Author(s):

Yicheng Shen ◽

Aki Virkkula ◽

Aijun Ding ◽

Krista Luoma ◽

Helmi Keskinen ◽

...

Keyword(s):

Optical Properties ◽

Size Distribution ◽

Particle Number ◽

Cloud Condensation Nuclei ◽

Geometric Mean ◽

Measurement Data ◽

Correlation Coefficients ◽

Size Distributions ◽

Aerosol Optical Properties ◽

Average Bias

Abstract. The concentration of cloud condensation nuclei (CCN) is an essential parameter affecting aerosol-cloud interactions within warm clouds. Long-term CCN number concentration (NCCN) data are scarce, there are a lot more data on aerosol optical properties (AOPs). It is therefore valuable to derive parameterizations for estimating NCCN from AOP measurements. Such parameterizatios have been made earlier, in the present work a new one is presented. The relationships between AOPs, NCCN and particle number size distributions were investigated based on in-situ measurement data from six stations in very different environments around the world. The parameterization derived here depends on the scattering Ångström exponent (SAE), backscatter fraction (BSF) and total scattering coefficient (σsp) of PM10 particles. The analysis showed that the dependence of NCCN on supersaturation SS% is logarithmic: NCCN ≈ ((287 ± 45)SAE10ln(SS%/(0.093 ± 0.006))(BSF − BSFmin) + (5.2 ± 3.3))σsp. At the lowest supersaturations of each site (SS% ≈ 0.1) the average bias, defined as the ratio of the AOP-derived and measured NCCN varied from ~ 0.7 to ~ 1.5 at most sites except at a Himalayan site where bias was > 4. At SS% > 0.3 the average bias ranged from ~ 0.7 to ~ 1.3 at all sites. In other words, at SS% > 0.3 NCCN was estimated with an average uncertainty of approximately 30 % by using nephelometer data. The squared correlation coefficients between the AOP-derived and measured NCCN varied from ~ 0.5 to ~ 0.8. The coefficients of the parameterization derived for the different sites were linearly related to each other. To study the explanation of this, lognormal unimodal particle size distributions were generated and NCCN and AOPs were calculated. The simulation yielded similar relationships between the coefficients as in the field data. It also showed that the relationships of the coefficients are affected by the geometric mean diameter and width of the size distribution and the activation diameter.

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The microphysical characters of wintertime mixed-phase clouds in North China.

10.5194/egusphere-egu21-3691 ◽

2021 ◽

Author(s):

Xuexu Wu ◽

Minghuai Wang ◽

Daniel Rosenfeld ◽

Delong Zhao ◽

Deping Ding

Keyword(s):

Water Content ◽

North China ◽

Particle Number ◽

Number Concentration ◽

Mixed Phase ◽

Ice Crystals ◽

Particle Number Concentration ◽

Aggregation Process ◽

Higher Temperature ◽

Mixed Phase Clouds

We use aircraft observation data to investigate the microphysical characters of wintertime mixed-phase clouds in North China, including the cloud particle number concentration (Nc), the liquid water content (LWC), the ice particle number concentration (Ni), the ice water content (IWC), the particle spectrum distributions (PSDs) and the effective diameter (De). For wintertime mixed-phase clouds, the average Nc and Ni were 170&#177;154 cm-3 and 26&#177;39 L-1, respectively; the average LWC and IWC were 0.05&#177;0.06 and 0.07&#177;0.09g/m3, respectively; the De for cloud particles was 10&#177;4 &#956;m. When compared to the results from other regions, including East Europe, North America, Southern Ocean and Tibetan Plateau, we found that the wintertime mixed-phase cloud in North China has larger Nc, smaller LWC, IWC and De, and narrower PSDs. The main reason might be the larger aerosol loading and smaller water content in the atmosphere in winter in North China. With increasing temperature, Nc and LWC increased, but Ni and De decreased. The dominate physical processes in wintertime mixed-phase cloud were aggregation process and riming process. As the temperature increased, the peak concentration of ice PSD decreased, but Ni increased and the ice PSD became wider, indicating more ice crystals and the ice crystals became larger at higher temperature. With temperature increasing, the ice habit also changed, and the amount of plates, irregular crystals and their aggregates increased. What&#8217;s more, with the existence of larger LWC at higher temperature, the ice crystals gradually tightened and their surface became more complicated as well. Therefore, both aggregation process and riming process were more active at higher temperature, but riming process changed much more. This work fills the gap in the observation of wintertime mixed-phase clouds in north China, and the results suggest that the wintertime mixed-phase clouds have some unique microphysical characters.<div>&#160;</div>

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Aerosol Optical Properties at SORPES in Nanjing, East China

10.5194/acp-2017-863 ◽

2017 ◽

Cited By ~ 1

Author(s):

Yicheng Shen ◽

Aki Virkkula ◽

Aijun Ding ◽

Jiaping Wang ◽

Xuguang Chi ◽

...

Keyword(s):

Optical Properties ◽

Growth Phase ◽

Radiative Forcing ◽

Mass Fraction ◽

Particle Number ◽

Eastern China ◽

Green Light ◽

Seasonal Cycles ◽

Aerosol Optical Properties ◽

Pollution Episodes

Abstract. Aerosol optical properties (AOPs) and supporting parameters – particle number size distributions, mass concentrations and trace gases (NOx and NOy) – were measured at SORPES, a regional background station in Nanjing, China from June 2013 to May 2015. The aerosol was highly scattering: the average scattering coefficient was σsp = 410 ± 320 Mm−1, the absorption coefficient σap = 26 ± 19 Mm−1 and the single-scattering albedo SSA = 0.93 ± 0.03 for the green light. The SSA in Nanjing appears to be slightly higher than published values from several other sites in China and elsewhere. The average Ångström exponent of absorption (AAE) for the wavelength range 370–950 nm was 1.04 and the AAE range 0.7–1.4. These AAE values can be explained with different amounts of non-absorbing coating on pure BC cores and different core sizes so the data does not suggest any significant contribution to absorption by brown carbon. The AOPs had typical seasonal cycles with high σsp and σap in winter and lower in summer: the averages were σsp = 545 ± 425 Mm−1 and σap = 36 ± 24 Mm−1 in winter and σsp = 364 ± 294 Mm−1 and σap = 20 ± 13 Mm−1 in summer. The intensive AOPs had no clear seasonal cycles, the variations of them were rather related to the evolution of pollution episodes. The diurnal cycles of the intensive AOPs were clear and in in agreement with the cycle of the particle number size distribution. The diurnal cycle of SSA was similar to that of the air photochemical age, suggesting that the darkest aerosol originated from fresh traffic emissions. A Lagrangian retroplume analysis showed that the sources of high σsp and σap are mainly in eastern China. Synoptic weather dominated the cycle of AOPs in a temporal scale of 2–7 days. During pollution episodes, modeled PBLH decreased, whereas PM2.5 concentrations, σsp and σap typically increased gradually and remained high during several days but decreased faster, sometimes by even more than an order of magnitude within some hours. During the growth phase of the pollution episodes the intensive AOPs evolved clearly. The mass scattering efficiency MSE of of PM2.5 grew during the extended pollution episodes from ~4 m2 g−1 to ~6 m2 g−1 and the mass fraction of BCe decreased from ~10 % to ~2 % during the growth phase of the episodes. Particle growth resulted in b decreasing from more than 0.16 to less than 0.10, SSA growing from less than 0.9 to more than 0.95 and radiative forcing efficiency RFE growing from less than −26 W m−2 τ−1 to more than −24 W m−2 τ−1. In other words, the darker aerosol – the aerosol that had a higher BC mass fraction – had a more negative radiative forcing efficiency, i.e., they have the property of cooling the atmosphere more efficiently per unit optical depth than the aerosol with the higher SSA and a lower BC mass fraction. This counterintuitive result is due to the size of the particles: the upscatter fraction of small particles is higher than that of the big ones which more than compensates the darkness of them. The RFE probability distribution at SORPES was clearly more narrow than at a clean background site which is in agreement with a published RFE climatology.

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Aerosol optical properties in the North China Plain during HaChi campaign: an in-situ optical closure study

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-5959-2011 ◽

2011 ◽

Vol 11 (12) ◽

pp. 5959-5973 ◽

Cited By ~ 106

Author(s):

N. Ma ◽

C. S. Zhao ◽

A. Nowak ◽

T. Müller ◽

S. Pfeifer ◽

...

Keyword(s):

Optical Properties ◽

North China Plain ◽

North China ◽

Scattering Coefficient ◽

Aerosol Optical Properties ◽

Mean Values ◽

The North ◽

The North China Plain ◽

The Mean

Abstract. The largest uncertainty in the estimation of climate forcing stems from atmospheric aerosols. In early spring and summer of 2009, two periods of in-situ measurements on aerosol physical and chemical properties were conducted within the HaChi (Haze in China) project at Wuqing, a town between Beijing and Tianjin in the North China Plain (NCP). Aerosol optical properties, including the scattering coefficient (σsp), the hemispheric back scattering coefficient (σbsp), the absorption coefficient (σap), as well as the single scattering albedo (ω), are presented. The diurnal and seasonal variations are analyzed together with meteorology and satellite data. The mean values of σsp, 550 nm of the dry aerosol in spring and summer are 280±253 and 379±251 Mm−1, respectively. The average σap for the two periods is respectively 47±38 and 43±27 Mm−1. The mean values of ω at the wavelength of 637 nm are 0.82±0.05 and 0.86±0.05 for spring and summer, respectively. The relative high levels of σsp and σbsp are representative of the regional aerosol pollution in the NCP. Pronounced diurnal cycle of $σsp, σap and ω are found, mainly influenced by the evolution of boundary layer and the accumulation of local emissions during nighttime. The pollutants transported from the southwest of the NCP are more significant than that from the two megacities, Beijing and Tianjin, in both spring and summer. An optical closure experiment is conducted to better understand the uncertainties of the measurements. Good correlations (R>0.98) are found between the values measured by the nephelometer and the values calculated with a modified Mie model. The Monte Carlo simulation shows an uncertainty of about 30 % for the calculations. Considering all possible uncertainties of measurements, calculated σsp and σbsp agree well with the measured values, indicating a stable performance of instruments and thus reliable aerosol optical data.

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Aerosol optical properties at SORPES in Nanjing, east China

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-5265-2018 ◽

2018 ◽

Vol 18 (8) ◽

pp. 5265-5292 ◽

Cited By ~ 12

Author(s):

Yicheng Shen ◽

Aki Virkkula ◽

Aijun Ding ◽

Jiaping Wang ◽

Xuguang Chi ◽

...

Keyword(s):

Optical Properties ◽

Growth Phase ◽

Radiative Forcing ◽

Particle Number ◽

Eastern China ◽

Green Light ◽

Particle Growth ◽

Seasonal Cycles ◽

Aerosol Optical Properties ◽

Pollution Episodes

Abstract. Aerosol optical properties (AOPs) and supporting parameters – particle number size distributions, PM2.5 mass concentrations, and the concentrations of trace gases (NOx and NOy) – were measured at SORPES, a regional background station in Nanjing, China from June 2013 to May 2015. The aerosol was highly scattering: the average scattering coefficient was σsp=403 ± 314 Mm−1, the absorption coefficient σap=26 ± 19 Mm−1, and the single-scattering albedo SSA = 0.93 ± 0.03 for green light. The SSA in Nanjing appears to be slightly higher than published values from several other sites in China and elsewhere. The average Ångström exponent of absorption (AAE) for the wavelength range 370–950 nm was 1.04 and the AAE range was 0.7–1.4. These AAE values can be explained with different amounts of non-absorbing coating on pure black carbon (BC) cores and different core sizes rather than contribution by brown carbon. The AOPs had typical seasonal cycles with high σsp and σap in winter and low ones in summer: the averages were σsp=544 ± 422 and σap=36 ± 24 Mm−1 in winter and σsp=342 ± 281 and σap=20 ± 13 Mm−1 in summer. The intensive AOPs had no clear seasonal cycles, the variations in them were rather related to the evolution of pollution episodes. The diurnal cycles of the intensive AOPs were clear and in agreement with the cycle of the particle number size distribution. The diurnal cycle of SSA was similar to that of the air photochemical age, suggesting that the darkest aerosol originated from fresh traffic emissions. A Lagrangian retroplume analysis showed that the potential source areas of high σsp and σap are mainly in eastern China. Synoptic weather phenomena dominated the cycle of AOPs on a temporal scale of 3–7 days. During pollution episodes, modeled boundary layer height decreased, whereas PM2.5 concentrations and σsp and σap typically increased gradually and remained high during several days but decreased faster, sometimes by even more than an order of magnitude within some hours. During the growth phase of the pollution episodes the intensive AOPs evolved clearly. The mass scattering efficiency MSE of PM2.5 grew during the extended pollution episodes from ∼ 4 to ∼ 6 m2 g−1 and the mass fraction of BCe decreased from ∼ 10 to ∼ 3 % during the growth phase of the episodes. Particle growth resulted in the backscatter fraction decreasing from more than 0.16 to less than 0.10, SSA growing from less than 0.9 to more than 0.95, and radiative forcing efficiency (RFE) changing from less than −26 W m−2 to more than −24 W m−2, which means that the magnitude of RFE decreased. The RFE probability distribution at SORPES was clearly narrower than at a clean background site which is in agreement with a published RFE climatology.

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Evolution of Aerosol Particles in the Rainfall Process via Method of Moments

Abstract and Applied Analysis ◽

10.1155/2013/709497 ◽

2013 ◽

Vol 2013 ◽

pp. 1-7 ◽

Cited By ~ 1

Author(s):

Fangyang Yuan ◽

Fujun Gan

Keyword(s):

Particle Size ◽

Particle Size Distribution ◽

Size Distribution ◽

Method Of Moments ◽

Particle Number ◽

Aerosol Particles ◽

Geometric Mean ◽

Number Concentration ◽

Brownian Diffusion ◽

Particle Number Concentration

The method of moments is employed to predict the evolution of aerosol particles in the rainfall process. To describe the dynamic properties of particle size distribution, the population balance equation is converted to moment equations by the method of moments and the converted equations are solved numerically. The variations of particle number concentration, geometric mean diameter, and geometric standard deviation are given in the cases that the Brownian diffusion and inertial impaction of particles dominate, respectively. The effects of raindrop size distribution on particle size distribution are analyzed in nine cases. The results show that the particle number concentration decreases as time goes by, and particles dominated by Brownian diffusion are removed more significantly. The particle number concentration decreases much more rapidly when particle geometric mean diameter is smaller, and the particle size distribution tends to be monodisperse. For the same water content, the raindrops with small geometric mean diameters can remove particles with much higher efficiency than those with large geometric mean diameters. Particles in the “Greenfield gap” are relatively difficult to scavenge, and a new method is needed to remove it from the air.

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Aerosol optical properties in the North China Plain during HaChi campaign: an in-situ optical closure study

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-9567-2011 ◽

2011 ◽

Vol 11 (3) ◽

pp. 9567-9605 ◽

Cited By ~ 4

Author(s):

N. Ma ◽

C. S. Zhao ◽

A. Nowak ◽

T. Müller ◽

S. Pfeifer ◽

...

Keyword(s):

Optical Properties ◽

North China Plain ◽

North China ◽

Aerosol Optical Properties ◽

Mean Values ◽

The North ◽

The North China Plain ◽

The Mean ◽

Local Emissions

Abstract. The largest uncertainty in the estimation of radiative forcings on climate stems from atmospheric aerosols. In winter and summer of 2009, two periods of in-situ measurements on aerosol physical and chemical properties were conducted within the HaChi project at Wuqing, a town between Beijing and Tianjin in the North China Plain (NCP). Aerosol optical properties including scattering coefficient (σsp), hemispheric back scattering coefficient (σbsp), absorption coefficient (σap, as well as single scattering albedo (ω) are presented. The characteristics of diurnal and seasonal variations are analyzed together with the meteorological and satellite data. The mean values of σsp, 550 nm of the dry aerosol in winter and summer are 280 ± 253 and 379 ± 251 Mm−1, respectively. The average σap for the two periods are respectively 47 ± 38 and 43 ± 27 Mm−1. The mean values of ω are 0.83 ± 0.05 and 0.87 ± 0.05 for winter and summer, respectively. The relative high levels of σsp and σbsp are representative of the regional polluted aerosol of the North China Plain. Pronounced diurnal cycle of σsp, σap and ω are found, mainly influenced by the evolution of boundary layer and accumulation of local emissions during night-time. Regional transport of pollutants from southwest in the NCP is significant both in winter and summer, while high values of σsp and σap correlate with calm winds in winter, which indicating the significant contribution of local emissions. An optical closure experiment is conducted to better understand uncertainties of the measurements. Good correlations (R>0.98) are found between values measured by nephelometer and values calculated with a modified Mie model. Monte Carlo simulations show an uncertainty of about 30% for the calculations. Considering all possible uncertainties of measurements, calculated σsp and σbsp agree well with measured values, indicating a stable performance of instruments and thus a reliable aerosol optical data.

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Supplementary material to "Estimating CCN number concentrations using aerosol optical properties: Role of particle number size distribution and parameterization"

10.5194/acp-2019-149-supplement ◽

2019 ◽

Author(s):

Yicheng Shen ◽

Aki Virkkula ◽

Aijun Ding ◽

Krista Luoma ◽

Helmi Keskinen ◽

...

Keyword(s):

Optical Properties ◽

Size Distribution ◽

Particle Number ◽

Aerosol Optical Properties ◽

Number Size Distribution ◽

Supplementary Material ◽

Particle Number Size Distribution

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Vertical distributions of aerosol optical properties during the spring 2016 ARIAs airborne campaign in the North China Plain

10.5194/acp-2017-1021 ◽

2018 ◽

Author(s):

Fei Wang ◽

Zhanqing Li ◽

Xinrong Ren ◽

Qi Jiang ◽

Hao He ◽

...

Keyword(s):

Optical Properties ◽

North China Plain ◽

North China ◽

Aerosol Optical Properties ◽

Air Masses ◽

Scattering Coefficients ◽

The North ◽

The North China Plain ◽

Aerosol Scattering ◽

Vertical Distributions

Abstract. Vertical distributions of aerosol optical properties derived from measurements made during 11 aircraft flights over the North China Plain (NCP) in May–June 2016 during the Air Chemistry Research In Asia (ARIAs) were analyzed. Aerosol optical data from in situ aircraft measurements shows good correlation with ground-based measurements. The regional variability of aerosol optical profiles such as aerosol scattering and backscattering, absorption, extinction, single scattering albedo (SSA), and the Ångström exponent (α) are for the first time thoroughly characterized over the NCP. The SSA at 550 nm showed a regional mean value of 0.85 ± 0.02 with moderate to strong absorption and the α ranged from 0.49 to 2.53 (median 1.53) indicating both mineral dust and accumulation mode aerosols. Most of the aerosol particles were located in the lowest 2 km of the atmosphere. We describe three typical planetary boundary layer (PBL) scenarios and associated transport pathways as well as the correlation between aerosol scattering coefficients and relative humidity (RH). Aerosol scattering coefficients decreased slowly with height in the clean PBL condition, but decreased sharply above the PBL under polluted conditions, which showed a strong correlation (R2 &geq; 0.78) with ambient RH. Back-trajectory analysis shows that clean air masses generally originated from the distant north-western part of China while most of the polluted air masses were from the heavily polluted interior and coastal areas near the campaign area.

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