scholarly journals Cloud processing of mineral dust: direct comparison of cloud residual and clear sky particles during AMMA aircraft campaign in summer 2006

2010 ◽  
Vol 10 (3) ◽  
pp. 1057-1069 ◽  
Author(s):  
A. Matsuki ◽  
A. Schwarzenboeck ◽  
H. Venzac ◽  
P. Laj ◽  
S. Crumeyrolle ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Mineral Dust ◽  
Large Fraction ◽  
Dust Particles ◽  
Cloud Droplets ◽  
Secondary Species ◽  
Cloud Processing ◽  
Clear Sky ◽  
Multidisciplinary Analysis ◽  
Dust Component

Abstract. In order to gain insights into the characteristics of the mineral dust particles incorporated in the actual cloud droplets and the related cloud processing, the French ATR-42 research aircraft equipped both with a counterflow virtual impactor (CVI) and community aerosol inlet was deployed in Niamey, Niger (13°30' N, 02°05' E) in August 2006 within the framework of the African Monsoon Multidisciplinary Analysis (AMMA) project. Cloud residual and clear-sky particles were collected separately and analyzed individually using a transmission electron microscope (TEM) and a scanning electron microscope coupled with an energy dispersive X-ray spectroscopy (SEM-EDX). The analysis revealed interesting characteristics on the coarse dust particles (Dp>1μm), particularly those which likely had acted as CCN. Traces of heterogeneously formed secondary sulfate, chloride and nitrate were found on many dust particles (though fraction of sulfate may be present in the form of gypsum as primary dust component). These secondary species were particularly enhanced in clouds (i.e. cloud processing). The study illustrates that calcium-rich particles assumed to be carbonates (Calcite, Dolomite) contained the secondary species in significantly larger frequency and amount than the silicates (Quartz, Feldspar, Mica, Clay), suggesting that they represent the most reactive fraction of the mineral dust. A surprisingly large fraction of the Ca-rich particles were already found in deliquesced form even in clear-sky conditions, most probably reflecting their extreme hygroscopicity, resulting from their reaction with HNO3 gas. Both silicate and Ca-rich particles were found dominant among the supermicron cloud residues, and they were supposed to be those previously activated as CCN. It is highly probable that the observed formation of soluble materials enhanced their cloud nucleating abilities.

scholarly journals Effect of surface reaction on the cloud nucleating properties of mineral dust: AMMA aircraft campaign in summer 2006

2009 ◽  
Vol 9 (1) ◽  
pp. 1797-1830 ◽  
Author(s):  
A. Matsuki ◽  
A. Schwarzenboeck ◽  
H. Venzac ◽  
P. Laj ◽  
S. Crumeyrolle ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Mineral Dust ◽  
Cloud Condensation Nuclei ◽  
Large Fraction ◽  
Dust Particles ◽  
Secondary Species ◽  
Cloud Processing ◽  
Clear Sky ◽  
Multidisciplinary Analysis ◽  
Dust Fraction

Abstract. In order to gain insights into the characteristics of the mineral dust fraction which actually serves as cloud condensation nuclei (CCN) including the related cloud processing, this study proceeded to directly collect CCN and compare their mixing states with that of the clear-sky aerosol particles. To pursue this goal, the French ATR-42 research aircraft equipped both with a counterflow virtual impactor (CVI) and community aerosol inlet was deployed in Niamey, Niger (13°30´ N, 02°30´ E) in August 2006 during one of the special observation periods (SOP) of the African Monsoon Multidisciplinary Analysis (AMMA) project. Both cloud residual and clear-sky particles were collected separately and later analyzed individually using transmission electron microscope (TEM) and scanning electron microscope coupled with energy dispersive X-ray spectroscopy (SEM-EDX). The analysis revealed interesting characteristics on the coarse dust particles (Dp>1 μm), particularly those which likely had acted as CCN. Traces of heterogeneously formed secondary sulfate, chloride and nitrate were found on many dust particles. These secondary species were particularly enhanced in clouds (i.e. cloud processing). The study illustrates that carbonates (Calcite, Dolomite) contained the secondary species in significantly larger frequency and amount than the silicates (Quartz, Feldspar, Mica, Clay), confirming that carbonates represent the most reactive fraction of the mineral dust. Surprisingly large fraction of the carbonate particles were already found in deliquesced form even in clear-sky conditions, most probably reflecting their extreme hygroscopicity following the reaction with HNO3 gas. There were also some indications that the large carbonate particles may be acting primarily as CCN under very low supersaturations, unless there is sufficient hygroscopic coatings on the silicates particles.

scholarly journals In-cloud formation of secondary species in iron-containing particles

2019 ◽  
Vol 19 (2) ◽  
pp. 1195-1206 ◽  
Author(s):  
Qinhao Lin ◽  
Xinhui Bi ◽  
Guohua Zhang ◽  
Yuxiang Yang ◽  
Long Peng ◽  
...  
Keyword(s):  
Southern China ◽  
Formation Rate ◽  
Cloud Formation ◽  
Dust Particles ◽  
Cloud Droplets ◽  
Aerosol Mass Spectrometer ◽  
Secondary Species ◽  
Cloud Processing ◽  
Aerosol Mass ◽  
Combustion Sources

Abstract. The increase in secondary species through cloud processing potentially increases aerosol iron (Fe) bioavailability. In this study, a ground-based counterflow virtual impactor coupled with a real-time single-particle aerosol mass spectrometer was used to characterize the formation of secondary species in Fe-containing cloud residues (dried cloud droplets) at a mountain site in southern China for nearly 1 month during the autumn of 2016. Fe-rich, Fe-dust, Fe-elemental carbon (Fe-EC), and Fe-vanadium (Fe-V) cloud residual types were obtained in this study. The Fe-rich particles, related to combustion sources, contributed 84 % (by number) to the Fe-containing cloud residues, and the Fe-dust particles represented 12 %. The remaining 4 % consisted of the Fe-EC and Fe-V particles. It was found that above 90 % (by number) of Fe-containing particles had already contained sulfate before cloud events, leading to no distinct change in number fraction (NF) of sulfate during cloud events. Cloud processing contributed to the enhanced NFs of nitrate, chloride, and oxalate in the Fe-containing cloud residues. However, the in-cloud formation of nitrate and chloride in the Fe-rich type was less obvious relative to the Fe-dust type. The increased NF of oxalate in the Fe-rich cloud residues was produced via aqueous oxidation of oxalate precursors (e.g., glyoxylate). Moreover, Fe-driven Fenton reactions likely increase the formation rate of aqueous-phase OH, improving the conversion of the precursors to oxalate in the Fe-rich cloud residues. During daytime, the decreased NF of oxalate in the Fe-rich cloud residues was supposed to be due to the photolysis of Fe-oxalate complexes. This work emphasizes the role of combustion Fe sources in participating in cloud processing and has important implications for evaluating Fe bioavailability from combustion sources during cloud processing.

scholarly journals In-cloud formation of secondary species in iron-containing particles

2018 ◽  
Author(s):  
Qinhao Lin ◽  
Xinhui Bi ◽  
Guohua Zhang ◽  
Yuxiang Yang ◽  
Long Peng ◽  
...  
Keyword(s):  
Southern China ◽  
Cloud Formation ◽  
Dust Particles ◽  
Cloud Droplets ◽  
Aerosol Mass Spectrometer ◽  
Secondary Species ◽  
Cloud Processing ◽  
Aerosol Mass ◽  
Combustion Sources

Abstract. The increase of secondary species through cloud processing potentially increases aerosol iron (Fe) bioavailability. In this study, a ground-based counterflow virtual impactor coupled with a real-time single-particle aerosol mass spectrometer was used to characterize the formation of secondary species in Fe-containing cloud residues (dried cloud droplets) at a mountain site in southern China for nearly one month during the autumn of 2016. Fe-rich, Fe-dust, Fe-elemental carbon (Fe-EC), and Fe-vanadium (Fe-V) cloud residual types were obtained in this study. The Fe-rich particles, related to combustion sources, contributed 84 % to the Fe-containing cloud residues, and the Fe-dust particles represented 12 %. The remaining 4 % consisted of the Fe-EC and Fe-V particles. It was found that extremely high amounts of sulfate had already accumulated on the Fe-containing particles before cloud events, leading to no distinct changes in sulfate during cloud events. Cloud processing contributed to the enhancement of nitrate, chloride, and oxalate in the Fe-containing cloud residues. However, the in-cloud formation of nitrate and chloride in the Fe-rich type was less obvious relative to the Fe-dust type. The enhancement of oxalate in the Fe-rich cloud residues was produced via aqueous oxidation of oxalate precursors (e.g., glyoxylate). Moreover, Fe chemistry involved in the Fenton reaction further promoted the conversion of the oxalate precursors to oxalate during cloud events, although the photolysis of Fe-oxalate complexes also existed in the Fe-rich cloud residues. This work emphasizes the role of combustion Fe sources in participating in cloud processing and has important implications for evaluating Fe bioavailability from combustion sources during cloud processing.

scholarly journals The potential influence of Asian and African mineral dust on ice, mixed-phase and liquid water clouds

2010 ◽  
Vol 10 (2) ◽  
pp. 4027-4077 ◽  
Author(s):  
A. Wiacek ◽  
T. Peter ◽  
U. Lohmann
Keyword(s):  
Liquid Water ◽  
Mineral Dust ◽  
Dust Emission ◽  
Ice Nucleation ◽  
Mixed Phase ◽  
Specific Humidity ◽  
Dust Particles ◽  
Ice Clouds ◽  
Cloud Processing ◽  
Mixed Phase Clouds

Abstract. This modelling study explores the availability of mineral dust particles as ice nuclei for interactions with ice, mixed-phase and liquid water clouds, also tracking the particles' history of cloud-processing. We performed 61 320 one-week forward trajectory calculations originating near the surface of major dust emitting regions in Africa and Asia using high-resolution meteorological analysis fields for the year 2007. Without explicitly modelling dust emission and deposition processes, dust-bearing trajectories were assumed to be those coinciding with known dust emission seasons. We found that dust emissions from Asian deserts lead to a higher potential for interactions with high clouds, despite being the climatologically much smaller dust emission source. This is due to Asian regions experiencing significantly more ascent than African regions, with strongest ascent in the Asian Taklimakan desert at ~25%, ~40% and 10% of trajectories ascending to 300 hPa in spring, summer and fall, respectively. The specific humidity at each trajectory's starting point was transported in a Lagrangian manner and relative humidities with respect to water and ice were calculated in 6-h steps downstream, allowing us to estimate the formation of liquid, mixed-phase and ice clouds. Practically none of the simulated air parcels reached regions where homogeneous ice nucleation can take place (T≲−40 °C) along trajectories that have not experienced water saturation first. By far the largest fraction of cloud forming trajectories entered conditions of mixed-phase clouds, where mineral dust will potentially exert the biggest influence. The majority of trajectories also passed through regions supersaturated with respect to ice but subsaturated with respect to water, where "warm" (T≳−40 °C) ice clouds may form prior to supercooled water or mixed-phase clouds. The importance of "warm" ice clouds and the general influence of dust in the mixed-phase cloud region are highly uncertain due to considerable scatter in recent laboratory data from ice nucleation experiments, which we briefly review in this work. For "classical" cirrus-forming temperatures, our results show that only mineral dust IN that underwent mixed-phase cloud-processing previously are likely to be relevant, and, therefore, we recommend further systematic studies of immersion mode ice nucleation on mineral dust suspended in atmospherically relevant coatings.

scholarly journals Atmospheric dissolved iron deposition to the global oceans: effects of oxalate-promoted Fe dissolution, photochemical redox cycling, and dust mineralogy

2013 ◽  
Vol 6 (1) ◽  
pp. 1901-1947 ◽  
Author(s):  
M. S. Johnson ◽  
N. Meskhidze
Keyword(s):  
Transport Model ◽  
Mineral Dust ◽  
Atmospheric Transport ◽  
Redox Cycling ◽  
Dust Particles ◽  
Dust Deposition ◽  
Chemical Transport Model ◽  
Cloud Processing ◽  
Form Model ◽  
Global Oceans

Abstract. Mineral dust deposition is suggested to be a significant atmospheric supply pathway of bioavailable iron (Fe) to Fe-depleted surface oceans. In this study, mineral dust and dissolved Fe (Fed) deposition rates are predicted for March 2009 to February 2010 using the 3-D chemical transport model GEOS-Chem implemented with a comprehensive dust-Fe dissolution scheme. The model simulates Fed production during the atmospheric transport of mineral dust taking into account inorganic and organic (oxalate)-promoted Fe dissolution processes, photochemical redox cycling between ferric (Fe(III)) and ferrous (Fe(II)) forms of Fe, dissolution of three different Fe-containing minerals (hematite, goethite, and aluminosilicates), and detailed mineralogy of wind-blown dust from the major desert regions. Our calculations suggest that during the yearlong simulation ~ 0.26 Tg (1 Tg = 1012 g) of Fed was deposited to global oceanic regions. Compared to simulations only taking into account proton-promoted Fe dissolution, the addition of oxalate to the dust-Fe mobilization scheme increased total annual model-predicted Fed deposition to global oceanic regions by ~ 75%. The implementation of Fe(II)/Fe(III) photochemical redox cycling in the model allows for the distinction between different oxidation states of deposited Fed. Our calculations suggest that during the daytime, large fractions of Fed deposited to the global oceans is likely to be in Fe(II) form, while nocturnal fluxes of Fed are largely in Fe(III) form. Model simulations also show that atmospheric fluxes of Fed can be strongly influenced by the mineralogy of Fe-containing compounds. This study indicates that Fed deposition to the oceans is controlled by total dust-Fe mass concentrations, mineralogy, the surface area of dust particles, atmospheric chemical composition, cloud processing, and meteorological parameters and exhibits complex and spatiotemporally variable patterns. Our study suggests that the explicit model representation of individual processes leading to Fed production within mineral dust are needed to improve the understanding of the atmospheric Fe cycle, and quantify the effect of dust-Fe on ocean biological productivity, carbon cycle, and climate.

scholarly journals The effects of mineral dust particles, aerosol regeneration and ice nucleation parameterizations on clouds and precipitation

2012 ◽  
Vol 12 (19) ◽  
pp. 9303-9320 ◽  
Author(s):  
A. Teller ◽  
L. Xue ◽  
Z. Levin
Keyword(s):  
Mineral Dust ◽  
Cloud Microphysics ◽  
Ice Nucleation ◽  
Aerosol Concentration ◽  
Ice Crystals ◽  
Dust Particles ◽  
Cloud Base ◽  
Minor Effect ◽  
Total Precipitation ◽  
Cloud Droplets

Abstract. This study focuses on the effects of aerosol particles on the formation of convective clouds and precipitation in the Eastern Mediterranean Sea, with a special emphasis on the role of mineral dust particles in these processes. We used a new detailed numerical cloud microphysics scheme that has been implemented in the Weather Research and Forecast (WRF) model in order to study aerosol–cloud interaction in 3-D configuration based on 1° × 1° resolution reanalysis meteorological data. Using a number of sensitivity studies, we tested the contribution of mineral dust particles and different ice nucleation parameterizations to precipitation development. In this study we also investigated the importance of recycled (regenerated) aerosols that had been released to the atmosphere following the evaporation of cloud droplets. The results showed that increased aerosol concentration due to the presence of mineral dust enhanced the formation of ice crystals. The dynamic evolution of the cloud system sets the time periods and regions in which heavy or light precipitation occurred in the domain. The precipitation rate, the time and duration of precipitation were affected by the aerosol properties only at small spatial scales (with areas of about 20 km2). Changes of the ice nucleation scheme from ice supersaturation-dependent parameterization to a recent approach of aerosol concentration and temperature-dependent parameterization modified the ice crystals concentrations but did not affect the total precipitation in the domain. Aerosol regeneration modified the concentration of cloud droplets at cloud base by dynamic recirculation of the aerosols but also had only a minor effect on precipitation. The major conclusion from this study is that the effect of mineral dust particles on clouds and total precipitation is limited by the properties of the atmospheric dynamics and the only effect of aerosol on precipitation may come from significant increase in the concentration of accumulation mode aerosols. In addition, the presence of mineral dust had a much smaller effect on the total precipitation than on its spatial distribution.

scholarly journals The effects of heating by transported dust layers on cloud and precipitation: a numerical study

2007 ◽  
Vol 7 (13) ◽  
pp. 3497-3505 ◽  
Author(s):  
Y. Yin ◽  
L. Chen
Keyword(s):  
Mineral Dust ◽  
Numerical Study ◽  
Cloud Model ◽  
Cloud Condensation Nuclei ◽  
Dust Particles ◽  
Cloud Base ◽  
Cloud Droplets ◽  
Cloud Optical Depth ◽  
Mineral Aerosols ◽  
Lower Cloud

Abstract. There have been numerous recent publications showing that mineral dust might be a good absorber for solar radiation in addition to its capability to act as cloud condensation nuclei (CCN) and ice forming nuclei (IFN), and could lead to reduced cloud cover and precipitation in the region where it is present. This effect is investigated using a dynamic cloud model with detailed microphysics of both warm and ice phase processes. The model is initialized using measured size distributions and concentrations of mineral dust particles. Our results show that when dust appears at the cloud-base height and below 3 km, where the temperature is warmer than −5°C, the heating induced by the presence of dust layers can inhibit the formation of cloud droplets and suppresses the development of precipitation, leading to lower cloud optical depth and albedo. On the other hand, when the dust layers are located at altitudes with temperature colder than −5°C, or above the −5°C level, mineral aerosols can act as effective ice nuclei, intensify the ice-forming processes, and may enhance the development of cloud and precipitation. It is also found that the heating effect is more pronounced in continental clouds than in maritime clouds.

scholarly journals Regional and global modeling of aerosol optical properties with a size, composition, and mixing state resolved particle microphysics model

2012 ◽  
Vol 12 (13) ◽  
pp. 5719-5736 ◽  
Author(s):  
F. Yu ◽  
G. Luo ◽  
X. Ma
Keyword(s):  
Optical Properties ◽  
Weather Forecasting ◽  
Transport Model ◽  
Large Fraction ◽  
Size Composition ◽  
Secondary Species ◽  
Carbon Particles ◽  
Clear Sky ◽  
Secondary Particles ◽  
Sky Conditions

Abstract. There exist large uncertainties in the present modeling of physical, chemical, and optical properties of atmospheric particles. We have recently incorporated an advanced particle microphysics (APM) model into a global chemistry transport model (GEOS-Chem) and a regional weather forecasting and chemistry model (WRF-Chem). Here we develop a scheme for calculating regional and global aerosol optical depth (AOD) from detailed aerosol information resolved by the APM model. According to GEOS-Chem-APM simulations, in most parts of the globe, the mass of secondary species resides mainly within secondary particles (60–90%), but in certain regions a large fraction (up to 50–80%) can become coated on various primary particles. Secondary species coated on black carbon and primary organic carbon particles significantly increase the size and hygroscopicity of these particles and thus impact their optical properties. The GEOS-Chem-APM model captures the global spatial distributions of AOD derived from AERONET, MODIS, and MISR measurements, generally within a factor of ~2. Our analysis indicates that modeled annual mean AODs at all sky and clear sky conditions differ by ~20% globally averaged and by >50% in some regions. The time series of WRF-Chem-APM predicted AOD over the northeastern United States in June 2008 have been compared to those from seven AERONET sites. Overall, the model mostly captures the absolute values as well as the variations of AOD at the AERONET sites (including dramatic changes associated with the crossing of high AOD plumes). Both GEOS-Chem and WRF-Chem simulations indicate that AOD over the northeastern US is dominated by secondary particles and have large spatiotemporal variations.

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