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 mineral dust particles, aerosol regeneration and ice nucleation parameterizations on clouds and precipitation

2012 ◽  
Vol 12 (3) ◽  
pp. 8225-8267
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 realistic meteorological data. Using a number of case 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 area 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 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 Integrating laboratory and field data to quantify the immersion freezing ice nucleation activity of mineral dust particles

2015 ◽  
Vol 15 (1) ◽  
pp. 393-409 ◽  
Author(s):  
P. J. DeMott ◽  
A. J. Prenni ◽  
G. R. McMeeking ◽  
R. C. Sullivan ◽  
M. D. Petters ◽  
...  
Keyword(s):  
Mineral Dust ◽  
Order Approximation ◽  
Ice Nucleation ◽  
Calibration Factor ◽  
Dust Particles ◽  
Single Type ◽  
Aerosol Layer ◽  
Atmospheric Measurements ◽  
Immersion Freezing ◽  
Nucleation Activity

Abstract. Data from both laboratory studies and atmospheric measurements are used to develop an empirical parameterization for the immersion freezing activity of natural mineral dust particles. Measurements made with the Colorado State University (CSU) continuous flow diffusion chamber (CFDC) when processing mineral dust aerosols at a nominal 105% relative humidity with respect to water (RHw) are taken as a measure of the immersion freezing nucleation activity of particles. Ice active frozen fractions vs. temperature for dusts representative of Saharan and Asian desert sources were consistent with similar measurements in atmospheric dust plumes for a limited set of comparisons available. The parameterization developed follows the form of one suggested previously for atmospheric particles of non-specific composition in quantifying ice nucleating particle concentrations as functions of temperature and the total number concentration of particles larger than 0.5 μm diameter. Such an approach does not explicitly account for surface area and time dependencies for ice nucleation, but sufficiently encapsulates the activation properties for potential use in regional and global modeling simulations, and possible application in developing remote sensing retrievals for ice nucleating particles. A calibration factor is introduced to account for the apparent underestimate (by approximately 3, on average) of the immersion freezing fraction of mineral dust particles for CSU CFDC data processed at an RHw of 105% vs. maximum fractions active at higher RHw. Instrumental factors that affect activation behavior vs. RHw in CFDC instruments remain to be fully explored in future studies. Nevertheless, the use of this calibration factor is supported by comparison to ice activation data obtained for the same aerosols from Aerosol Interactions and Dynamics of the Atmosphere (AIDA) expansion chamber cloud parcel experiments. Further comparison of the new parameterization, including calibration correction, to predictions of the immersion freezing surface active site density parameterization for mineral dust particles, developed separately from AIDA experimental data alone, shows excellent agreement for data collected in a descent through a Saharan aerosol layer. These studies support the utility of laboratory measurements to obtain atmospherically relevant data on the ice nucleation properties of dust and other particle types, and suggest the suitability of considering all mineral dust as a single type of ice nucleating particle as a useful first-order approximation in numerical modeling investigations.

scholarly journals Heterogeneous ice nucleation on dust particles sourced from nine deserts worldwide – Part 2: Deposition nucleation and condensation freezing

2019 ◽  
Vol 19 (2) ◽  
pp. 1059-1076 ◽  
Author(s):  
Yvonne Boose ◽  
Philipp Baloh ◽  
Michael Plötze ◽  
Johannes Ofner ◽  
Hinrich Grothe ◽  
...  
Keyword(s):  
Active Sites ◽  
Mineral Dust ◽  
Atmospheric Transport ◽  
Chemical Imaging ◽  
Ice Nucleation ◽  
Dust Particles ◽  
Full Potential ◽  
Nucleation Behavior ◽  
Crystal Water ◽  
Desert Dust

Abstract. Mineral dust particles from deserts are amongst the most common ice nucleating particles in the atmosphere. The mineralogy of desert dust differs depending on the source region and can further fractionate during the dust emission processes. Mineralogy to a large extent explains the ice nucleation behavior of desert aerosol, but not entirely. Apart from pure mineral dust, desert aerosol particles often exhibit a coating or are mixed with small amounts of biological material. Aging on the ground or during atmospheric transport can deactivate nucleation sites, thus strong ice nucleating minerals may not exhibit their full potential. In the partner paper of this work, it was shown that mineralogy determines most but not all of the ice nucleation behavior in the immersion mode found for desert dust. In this study, the influence of semi-volatile organic compounds and the presence of crystal water on the ice nucleation behavior of desert aerosol is investigated. This work focuses on the deposition and condensation ice nucleation modes at temperatures between 238 and 242 K of 18 dust samples sourced from nine deserts worldwide. Chemical imaging of the particles' surface is used to determine the cause of the observed differences in ice nucleation. It is found that, while the ice nucleation ability of the majority of the dust samples is dominated by their quartz and feldspar content, in one carbonaceous sample it is mostly caused by organic matter, potentially cellulose and/or proteins. In contrast, the ice nucleation ability of an airborne Saharan sample is found to be diminished, likely by semi-volatile species covering ice nucleation active sites of the minerals. This study shows that in addition to mineralogy, other factors such as organics and crystal water content can alter the ice nucleation behavior of desert aerosol during atmospheric transport in various ways.

scholarly journals Photomineralization mechanism changes the ability of dissolved organic matter to activate cloud droplets and to nucleate ice crystals

2019 ◽  
Vol 19 (19) ◽  
pp. 12397-12412 ◽  
Author(s):  
Nadine Borduas-Dedekind ◽  
Rachele Ossola ◽  
Robert O. David ◽  
Lin S. Boynton ◽  
Vera Weichlinger ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
Organic Acids ◽  
Liquid Water ◽  
Supercooled Liquid ◽  
Ice Nucleation ◽  
Ice Crystals ◽  
Cloud Droplets ◽  
Photochemical Processing

Abstract. An organic aerosol particle has a lifetime of approximately 1 week in the atmosphere during which it will be exposed to sunlight. However, the effect of photochemistry on the propensity of organic matter to participate in the initial cloud-forming steps is difficult to predict. In this study, we quantify on a molecular scale the effect of photochemical exposure of naturally occurring dissolved organic matter (DOM) and of a fulvic acid standard on its cloud condensation nuclei (CCN) and ice nucleation (IN) activity. We find that photochemical processing, equivalent to 4.6 d in the atmosphere, of DOM increases its ability to form cloud droplets by up to a factor of 2.5 but decreases its ability to form ice crystals at a loss rate of −0.04 ∘CT50 h−1 of sunlight at ground level. In other words, the ice nucleation activity of photooxidized DOM can require up to 4 ∘C colder temperatures for 50 % of the droplets to activate as ice crystals under immersion freezing conditions. This temperature change could impact the ratio of ice to water droplets within a mixed-phase cloud by delaying the onset of glaciation and by increasing the supercooled liquid fraction of the cloud, thereby modifying the radiative properties and the lifetime of the cloud. Concurrently, a photomineralization mechanism was quantified by monitoring the loss of organic carbon and the simultaneous production of organic acids, such as formic, acetic, oxalic and pyruvic acids, CO and CO2. This mechanism explains and predicts the observed increase in CCN and decrease in IN efficiencies. Indeed, we show that photochemical processing can be a dominant atmospheric ageing process, impacting CCN and IN efficiencies and concentrations. Photomineralization can thus alter the aerosol–cloud radiative effects of organic matter by modifying the supercooled-liquid-water-to-ice-crystal ratio in mixed-phase clouds with implications for cloud lifetime, precipitation patterns and the hydrological cycle.Highlights. During atmospheric transport, dissolved organic matter (DOM) within aqueous aerosols undergoes photochemistry. We find that photochemical processing of DOM increases its ability to form cloud droplets but decreases its ability to form ice crystals over a simulated 4.6 d in the atmosphere. A photomineralization mechanism involving the loss of organic carbon and the production of organic acids, CO and CO2 explains the observed changes and affects the liquid-water-to-ice ratio in clouds.

Influence of organic and biogenic substances on the ice nucleation properties of mineral dust particles

2020 ◽  
Author(s):  
Kristian Klumpp ◽  
Claudia Marcolli ◽  
Thomas Peter
Keyword(s):  
Amino Acids ◽  
Organic Acids ◽  
Mineral Dust ◽  
Particle Surface ◽  
Ice Nucleation ◽  
Dust Particles ◽  
Biogenic Substances ◽  
Immersion Freezing ◽  
Mixed Phase Clouds ◽  
Ice Nucleation Activity

<p>The formation of ice in mixed phase clouds occurs in the presence of aerosol particles with the ability to nucleate ice on their surface. These ice-nucleating particles (INPs) represent usually a small fraction of particles in an atmospheric aerosol. One of the main particle types which act as INPs are mineral dust particles. Among other factors, the accumulation of semivolatile substances on the particle surface can alter the ice nucleation properties of such particles.</p><p>In recent immersion freezing experiments, we investigated the influence of organic acids, amino acids and polyols on the highly ice nucleation active K-feldspar microcline. Microcline dust was suspended in solutions of the above-mentioned substances and frozen in a differential scanning calorimeter (DSC). These experiments give us insight into the ice nucleation characteristics of the particles in the presence of the tested organic and biogenic substances. Our measurements show an overall decrease in ice nucleation activity of microcline in the presence of organic acids and amino acids. <br><br></p>

scholarly journals Chemical processing does not always impair heterogeneous ice nucleation of mineral dust particles

2010 ◽  
Vol 37 (24) ◽  
pp. n/a-n/a ◽  
Author(s):  
Ryan C. Sullivan ◽  
Lorena Miñambres ◽  
Paul J. DeMott ◽  
Anthony J. Prenni ◽  
Christian M. Carrico ◽  
...  
Keyword(s):  
Mineral Dust ◽  
Ice Nucleation ◽  
Dust Particles ◽  
Chemical Processing ◽  
Heterogeneous Ice Nucleation

scholarly journals On the limits of Köhler activation theory: how do collision and coalescence affect the activation of aerosols?

2017 ◽  
Vol 17 (13) ◽  
pp. 8343-8356 ◽  
Author(s):  
Fabian Hoffmann
Keyword(s):  
Critical Radius ◽  
Cloud Model ◽  
Cloud Droplet ◽  
Aerosol Concentration ◽  
Cloud Base ◽  
Cloud Droplets ◽  
Activation Theory ◽  
Large Eddy ◽  
Kohler Theory ◽  
Additional Process

Abstract. Activation is necessary to form a cloud droplet from an aerosol, and it is widely accepted that it occurs as soon as a wetted aerosol grows beyond its critical radius. Traditional Köhler theory assumes that this growth is driven by the diffusion of water vapor. However, if the wetted aerosols are large enough, the coalescence of two or more particles is an additional process for accumulating sufficient water for activation. This transition from diffusional to collectional growth marks the limit of traditional Köhler theory and it is studied using a Lagrangian cloud model in which aerosols and cloud droplets are represented by individually simulated particles within large-eddy simulations of shallow cumuli. It is shown that the activation of aerosols larger than 0. 1 µm in dry radius can be affected by collision and coalescence, and its contribution increases with a power-law relation toward larger radii and becomes the only process for the activation of aerosols larger than 0. 4–0. 8 µm depending on aerosol concentration. Due to the natural scarcity of the affected aerosols, the amount of aerosols that are activated by collection is small, with a maximum of 1 in 10 000 activations. The fraction increases as the aerosol concentration increases, but decreases again as the number of aerosols becomes too high and the particles too small to cause collections. Moreover, activation by collection is found to affect primarily aerosols that have been entrained above the cloud base.

scholarly journals Influence of particle size on the ice nucleating ability of mineral dusts

2009 ◽  
Vol 9 (18) ◽  
pp. 6705-6715 ◽  
Author(s):  
A. Welti ◽  
F. Lüönd ◽  
O. Stetzer ◽  
U. Lohmann
Keyword(s):  
Particle Size ◽  
Size Dependence ◽  
Water Saturation ◽  
Mineral Dust ◽  
Ice Nucleation ◽  
Dust Particles ◽  
Ice Nuclei ◽  
Mineral Dusts ◽  
Measured Activation ◽  
Formation Efficiency

Abstract. The recently developed Zurich Ice Nucleation Chamber (ZINC) was used to explore ice nucleation of size-selected mineral dust particles at temperatures between −20°C and −55°C. Four different mineral dust species have been tested: montmorillonite, kaolinite, illite and Arizona test dust (ATD). The selected particle diameters are 100 nm, 200 nm, 400 nm and 800 nm. Relative humidities with respect to ice (RHi) required to activate 1% of the dust particles as ice nuclei (IN) are reported as a function of temperature. An explicit size dependence of the ice formation efficiency has been observed for all dust types. 800 nm particles required the lowest RHi to activate. Deposition nucleation below water saturation was found only below −30°C or −35°C dependent on particle size. Minimum RHi for 1% activation were 105% for illite, kaolinite and montmorillonite at −40°C, respectively 110% for ATD at −45°C. In addition, a possible parameterisation for the measured activation spectra is proposed, which could be used in modeling studies.

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