Laboratory Studies of Water Ice Nucleation and Growth at Conditions Relevant to Martian Cloud Formation PDF Download
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Author: Brendan Douglas Mar
Publisher:
ISBN:
Category : Atmospheric nucleation
Languages : en
Pages : 76
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Author: Brendan Douglas Mar
Publisher:
ISBN:
Category : Atmospheric nucleation
Languages : en
Pages : 76
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Book Description
Author: Robert M. Haberle
Publisher: Cambridge University Press
ISBN: 110817938X
Category : Science
Languages : en
Pages : 613
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Book Description
Humanity has long been fascinated by the planet Mars. Was its climate ever conducive to life? What is the atmosphere like today and why did it change so dramatically over time? Eleven spacecraft have successfully flown to Mars since the Viking mission of the 1970s and early 1980s. These orbiters, landers and rovers have generated vast amounts of data that now span a Martian decade (roughly eighteen years). This new volume brings together the many new ideas about the atmosphere and climate system that have emerged, including the complex interplay of the volatile and dust cycles, the atmosphere-surface interactions that connect them over time, and the diversity of the planet's environment and its complex history. Including tutorials and explanations of complicated ideas, students, researchers and non-specialists alike are able to use this resource to gain a thorough and up-to-date understanding of this most Earth-like of planetary neighbours.
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781720413455
Category :
Languages : en
Pages : 54
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We use a time dependent, microphysical cloud model to study the formation of carbon dioxide clouds in the Martian atmosphere. Laboratory studies by Glandor et al. show that high critical supersaturations are required for cloud particle nucleation and that surface kinetic growth is not limited. These conditions, which are similar to those for cirrus clouds on Earth, lead to the formation of carbon dioxide ice particles with radii greater than 500 micrometers and concentrations of less than 0.1 cm(exp -3) for typical atmospheric conditions. Within the current Martian atmosphere, CO2 cloud formation is possible at the poles during winter and at high altitudes in the tropics during periods of increased atmospheric dust loading. In both cases, temperature perturbations of several degrees below the CO2 saturation temperature are required to nucleate new cloud particles suggesting that dynamical processes are the most common initiators of carbon dioxide clouds rather than diabatic cooling. The microphysical cloud model, coupled to a two-stream radiative transfer model, is used to reexamine the impact of CO2 clouds on the surface temperature within a dense CO2 atmosphere. The formation of carbon dioxide clouds leads to a warmer surface than what would be expected for clear sky conditions. The amount of warming is sensitive to the presence of dust and water vapor in the atmosphere, both of which act to dampen cloud effects. The radiative warming associated with cloud formation, as well as latent heating, work to dissipate the clouds when present. Thus, clouds never last for periods much longer than several days, limiting their overall effectiveness for warming the surface. The time average cloud optical depth is approximately unity leading to a 5-10 K warming, depending on the surface pressure. However, the surface temperature does not rise about the freezing point of liquid water even for pressures as high as 5 bars, at a solar luminosity of 75% the current value.Colaprete,
Author:
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ISBN:
Category :
Languages : en
Pages :
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Abstract : Ice particles in atmospheric clouds play an important role in determining cloud lifetime, precipitation and radiation. It is therefore important to understand the whole life cycle of ice particles in the atmosphere, e.g., where they come from (nucleation), how they evolve (growth), and where they go (precipitation). Ice nucleation is the crucial step for ice formation, and in this study, we will mainly focus on ice nucleation in the lab and its effect on mixed-phase stratiform clouds. In the first half of this study, we investigate the relevance of moving contact lines (i.e., the region where three or more phases meet) on the phenomenon of contact nucleation. High speed video is used to investigate heterogeneous ice nucleation in supercooled droplets resting on cold substrates under two different dynamic conditions: droplet electrowetting and droplet vibration. Results show that contact-line motion is not a sufficient condition to trigger ice nucleation, while locally curved contact lines that can result from contact-line motion are strongly related to ice nucleation. We propose that pressure perturbations due to locally curved contact lines can strongly enhance the ice nucleation rate, which gives another interpretation for the mechanism for contact nucleation. Corresponding theoretical results provide a quantitative connection between pressure perturbations and temperature, providing a useful tool for ice nucleation calculations in atmospheric models. In this second half of the study, we build a minimalist model for long lifetime mixed-phase stratiform clouds based on stochastic ice nucleation. Our result shows that there is a non-linear relationship between ice water contact and ice number concentration in the mixed-phase cloud, as long as the volume ice nucleation rate is constant. This statistical property may help identify the source of ice nuclei in mixed-phase clouds. In addition, results from Lagrangian ice particle tracking in time dependent fields show that long lifetime ice particles exist in mixed-phase stratiform clouds. We find that small ice particle can be trapped in eddy-like structures. Whether ice particles grow or sublimate depends on the thermodynamic field in the trapping region. This dynamic-thermodynamic coupling effect on the lifetime of ice particles might explain the fast phase-partition change observed in the mixed phase cloud.
Author:
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Category :
Languages : en
Pages :
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This study reports on heterogeneous ice nucleation activity of predominantly organic (or coated with organic material) anthropogenic particles sampled within and around the polluted environment of Mexico City. The onset of heterogeneous ice nucleation was observed as a function of particle temperature (Tp), relative humidity (RH), nucleation mode, and particle chemical composition which is influenced by photochemical atmospheric aging. Particle analyses included computer controlled scanning electron microscopy with energy dispersive analysis of X-rays (CCSEM/EDX) and scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). In contrast to most laboratory studies employing proxies of organic aerosol, we show that anthropogenic organic particles collected in Mexico City can potentially induce ice nucleation at experimental conditions relevant to cirrus formation. The results suggest a new precedent for the potential impact of organic particles on ice cloud formation and climate.
Author: Shaena Rochel Berlin
Publisher:
ISBN:
Category :
Languages : en
Pages : 78
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Book Description
Ice clouds scatter and absorb solar radiation, affecting atmospheric and surface temperatures (Gettelman et al., 2012). On Mars, where ice contained in clouds makes up a large portion of total atmospheric water vapor, ice clouds also alter the planetary water budget (Maltagliati et al., 2011; Rafkin et al., 2013). Thus, it is important for climate models to be able to accurately predict the conditions under which ice clouds can form. Typical Martian temperatures at cloud-formation height range from -150-200 K (Trainer, Toon, & Tolbert, 2009). Heterogeneous deposition nucleation is thought to be the dominant freezing mechanism on Mars due to the abundance of mineral dust to serve as ice nuclei (IN) (Mdittanen et al., 2005). The parameters for such nucleation are not well characterized at such low temperatures (Trainer et al., 2009). Previous experimental studies have investigated the relative humidity required for deposition nucleation within the Martian temperature range. However, most studies took place on bulk aerosol samples, did not use mineral dusts analogous to Martian dust, or were constrained by particle lifetime and temperature limits. In this project, we re-purpose a single-particle instrument and set it up to perform experiments for more precise ice nucleation data under Martian atmospheric conditions. We use an electrodynamic balance (EDB) to levitate individual particles with diameters around 10 pm. We calculate the size of the particle and changes in size based on the holding voltages. The system can be cooled to 200 K in its current configuration, and the relative humidity and atmospheric constituents can be controlled by adding gas. To test the EDB, we perform validation experiments. We investigate deliquescence and efflorescence on salts at room temperature and 0 'C. We modify the cooling system, thermocouples, and relative humidity sensors and begin freezing experiments with Arizona Test Dust (ATD) and with Mojave Mars Simulant (MMS) dust. We investigate water uptake on MMS particles and find it to be non-hygroscopic but wettable, uptaking monolayers of water between 65-95% relative humidity. From 200 K to 220 K, MMS does not nucleate up to 115% RHice, suggesting that higher supersaturations are needed for ice clouds to form; some Martian cloud modelers should revisit the critical supersaturation parameterization. Future work will improve the EDB and use it to examine phase functions and light scattering.
Author: Ari Laaksonen
Publisher: Elsevier
ISBN: 0128143215
Category : Science
Languages : en
Pages : 294
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Book Description
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
Author: Zaminhussein Abdulali Kanji
Publisher:
ISBN: 9780494609897
Category :
Languages : en
Pages : 490
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Book Description
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: David C. Rogers
Publisher:
ISBN:
Category : Clouds
Languages : en
Pages : 322
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Author: Zaminhussein Abdulali Kanji
Publisher:
ISBN: 9780494163191
Category :
Languages : en
Pages : 168
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Book Description
Laboratory studies are described whereby the heterogeneous ice nucleating ability of various dust samples was studied for particles mounted on a hydrophobic cold stage. Ice formation is observed using digital photography. The relative humidity with respect to ice (RHIce) and temperature conditions of the flow system are validated by observing (NH4)2SO 4 deliquescence. Four types of solid mineral samples, including authentic Saharan dust, and commercial samples of alumina, silica and montmorillonite, were investigated in the deposition freezing mode. The size of the dust particles ranged from 0.5 to 5 microns, and the temperature range was from 263 to 218 K. With roughly 104 particles present on the cold stage, the onset for ice formation was observed at low relative humidities, between 102 and 108% RHIce, for all samples and temperatures. This indicates that deposition mode nucleation is an efficient mode of ice formation, particularly under the cold temperatures prevalent in the cirrus regime. By contrast, ice deposition onto n-hexane soot particles was not nearly so efficient. Nucleation rates prevalent in the experiment are calculated as a function of relative humidity from a suite of experiments conducted with Saharan dust where the dependence of the onset RHIce as a function of the total dust surface area was measured.
