Homogenous and Heterogeneous Ice Nucleation from Biomass Burning Aerosol PDF Download
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Author: Yannick J. Rigg
Publisher:
ISBN:
Category : Environmental sciences
Languages : en
Pages :
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Author: Yannick J. Rigg
Publisher:
ISBN:
Category : Environmental sciences
Languages : en
Pages :
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Author: Sarah Sihvonen
Publisher:
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Category :
Languages : en
Pages :
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Aerosol particles impact the climate by serving as the seeds to form water droplets and ice to form clouds. However, these aerosol-cloud interactions are the least understood aspect of our understanding of the climate system. Mineral dust aerosol is the largest global source of ice nucleating particles. During atmospheric transport, mineral dust can be exposed to sulfuric acid, which has been shown to decrease the ice nucleation activity of these particles. Many explanations for this observation, such as chemical changes to the surface or product formation that blocks active sites, have been suggested. Our research focused on building a molecular picture of these surfaces to understand why sulfuric acid exposure reduces the ice nucleation activity of clay minerals such as kaolinite. We performed studies using X-ray diffraction and solid state NMR that investigate the changes that clay minerals undergo as a result of acid exposure. We are the first to show that the formation of a product on the surface of kaolinite was responsible for the decreased ice nucleation activity, not surface changes to the mineral itself. We continued to study aerosol-cloud interactions by using parcel models that explore the impact of ice growth surface kinetics on the competition between heterogeneous and homogeneous ice nucleation in clouds. We found that impaired growth of ice favors homogeneous freezing. The parcel models will be expanded to include our work on clay minerals to explore the impact of chemical aging of ice nuclei on overall cloud properties. We also studied the effect of acidic-processing on coal fly ash samples. Coal fly ash has been found to have a similar atmospheric impact as mineral dust, but is studied to a lesser extent. Like mineral dust, coal fly ash can serve as a source of bioavailable iron to phytoplankton in nutrient limited regions of the ocean. Fly ash has also been found to serve as an ice nucleating material. We performed aqueous sulfuric acid-treatment on fly ash samples representative of the types produced in the United States. We found that a soluble salt, gypsum (hydrated calcium sulfate), formed on three out of four samples. The most iron rich sample did not react with sulfuric acid. However, acidic-processing was shown to increase the amount of soluble iron which has implications for the biogeochemical cycle. These results also demonstrate that further work investigating these fly ash systems is warranted. In addition to our work on ice nucleation, we constructed a photoacoustic spectrometer to measure the absorbance of aerosol particles to study the optical properties of atmospheric aerosol. These measurements will aid in understanding the interactions of aerosol particles with light and the radiative balance of the planet.
Author: Bingbing Wang
Publisher:
ISBN:
Category : Aerosols
Languages : en
Pages : 320
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Author: Zaminhussein Abdulali Kanji
Publisher:
ISBN: 9780494609897
Category :
Languages : en
Pages : 490
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The indirect aerosol effect contributes to major uncertainties in determining the radiation budget of the earth. A large uncertainty is due to the formation of ice clouds onto natural or anthropogenic aerosols. Field studies have shown that mineral type particles are often associated with ice crystals in the mid-upper troposphere and given the long residence time in the atmosphere of dust particles (∼2 weeks in the absence of precipitation), their contribution to ice formation processes is not fully defined.It was concluded that there is no single value for the onset of ice formation in the atmosphere via deposition freezing. The associated contact angles show that there is a distribution of active sites on IN and that not all active sites have the same affinity for initiation of ice formation even within the same aerosol type. This work provides evidence that deposition mode nucleation can be an alternate pathway to homogeneous nucleation when mineral aerosols are present in the troposphere since the high T-low RH conditions required for deposition mode nucleation are more easily encountered in the atmosphere than the low T-high RH required for homogeneous nucleation.In order to probe ice formation onto natural mineral dust in a setting where it could be suspended as aerosol, a new continuous flow diffusion chamber (CFDC) was built. This allowed investigations of the effects of total aerosol surface area and particle size. The CFDC was also used in an international inter-comparison of ice nucleation instrumentation to compare efficiencies of soot, biological aerosol (bacteria) and samples of natural desert dusts from different regions of the world. The laboratory observations were parameterized using nucleation rates (Jhet) and contact angles (theta) as described by classical nucleation theory.For both this experimental technique and a static one developed during the candidate's Masters degree, mineral dust particulate proved to be the most efficient ice nuclei (IN) activating at RH with respect to ice (RH i) as low as 105% at T=233 K. The efficiency varied with particle size and aerosol surface area (SA). Large particles or higher SA activated at lower RHi than small particles or lower SA. The static chamber was sensitive to the first ice event out of a large SA and therefore gave true onset RHi, which was lower than the onset defined by the CFDC studies, which was not sensitive to a single ice event. In addition the static chamber used a broader size range of particulate matter, including super micron particles while the CFDC particles sizes were restricted to below 0.5 microm. Soot and organic coated dust particles were inefficient IN compared to pure dust. Soot aerosols showed some efficiency at T
Author: Constantin Andronache
Publisher: Elsevier
ISBN: 012810550X
Category : Science
Languages : en
Pages : 302
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Mixed-Phase Clouds: Observations and Modeling presents advanced research topics on mixed-phase clouds. As the societal impacts of extreme weather and its forecasting grow, there is a continuous need to refine atmospheric observations, techniques and numerical models. Understanding the role of clouds in the atmosphere is increasingly vital for current applications, such as prediction and prevention of aircraft icing, weather modification, and the assessment of the effects of cloud phase partition in climate models. This book provides the essential information needed to address these problems with a focus on current observations, simulations and applications. Provides in-depth knowledge and simulation of mixed-phase clouds over many regions of Earth, explaining their role in weather and climate Features current research examples and case studies, including those on advanced research methods from authors with experience in both academia and the industry Discusses the latest advances in this subject area, providing the reader with access to best practices for remote sensing and numerical modeling
Author: Anatoli Bogdan
Publisher:
ISBN:
Category :
Languages : en
Pages : 79
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 998
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In this study, an aerosol-dependent ice nucleation scheme [Liu and Penner, 2005] has been implemented in an aerosol-enabled multi-scale modeling framework (PNNL MMF) to study ice formation in upper troposphere cirrus clouds through both homogeneous and heterogeneous nucleation. The MMF model represents cloud scale processes by embedding a cloud-resolving model (CRM) within each vertical column of a GCM grid. By explicitly linking ice nucleation to aerosol number concentration, CRM-scale temperature, relative humidity and vertical velocity, the new MMF model simulates the persistent high ice supersaturation and low ice number concentration (10 to 100/L) at cirrus temperatures. The low ice number is attributed to the dominance of heterogeneous nucleation in ice formation. The new model simulates the observed shift of the ice supersaturation PDF towards higher values at low temperatures following homogeneous nucleation threshold. The MMF models predict a higher frequency of midlatitude supersaturation in the Southern hemisphere and winter hemisphere, which is consistent with previous satellite and in-situ observations. It is shown that compared to a conventional GCM, the MMF is a more powerful model to emulate parameters that evolve over short time scales such as supersaturation. Sensitivity tests suggest that the simulated global distribution of ice clouds is sensitive to the ice nucleation schemes and the distribution of sulfate and dust aerosols. Simulations are also performed to test empirical parameters related to auto-conversion of ice crystals to snow. Results show that with a value of 250 [mu]m for the critical diameter, Dcs, that distinguishes ice crystals from snow, the model can produce good agreement to the satellite retrieved products in terms of cloud ice water path and ice water content, while the total ice water is not sensitive to the specification of Dcs value.
Author: Bernhard Zobrist
Publisher:
ISBN:
Category :
Languages : en
Pages : 133
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Author: Thibault Hiron
Publisher:
ISBN:
Category : Impact
Languages : en
Pages :
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Author: Ari Laaksonen
Publisher: Elsevier
ISBN: 0128143223
Category : Science
Languages : en
Pages : 296
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Nucleation of Water: From Fundamental Science to Atmospheric and Additional Applications provides a comprehensive accounting of the current state-of-the-art regarding the nucleation of water. It covers vapor-liquid, liquid-vapor, liquid-ice and vapor-ice transitions and describes basic kinetic and thermodynamic concepts in a manner understandable to researchers working on specific applications. The main focus of the book lies in atmospheric phenomena, but it also describes engineering and biological applications. Bubble nucleation, although not of major atmospheric relevance, is included for completeness. This book presents a single, go-to resource that will help readers understand the breadth and depth of nucleation, both in theory and in real-world examples. Offers a single, comprehensive work on water nucleation, including cutting- edge research on ice, cloud and bubble nucleation Written primarily for atmospheric scientists, but it also presents the theories in such a way that researchers in other disciplines will find it useful Written by one of the world’s foremost experts on ice nucleation
