Primary Ice Nucleation in Orographic Cirrus Clouds PDF Download
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Author: A. Spice
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Languages : en
Pages :
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Author: A. Spice
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Category :
Languages : en
Pages :
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Author: Benjamin Sherman
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Category :
Languages : en
Pages :
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In-situ measurements suggest that heterogeneous nucleation is the dominant ice formation mechanism in the upper atmosphere. Clouds formed heterogeneously typically contain lower ice concentrations and larger crystals than those formed homogeneously. Because heterogeneous ice formation occurs at lower ice supersaturations than homogeneous freezing of supercooled drops, sufficient heterogeneous freezing can suppress or eliminate the homogeneous freezing process. The difference in freezing process may significantly alter the radiative properties of and particle sedimentation rates from cirriform clouds. The underlying physical processes influencing the competition between heterogeneous and homogeneous nucleation remain poorly understood. One such process that may be of importance is surface kinetic resistance to ice vapor growth and its dependence on particle shape evolution, which is investigated in this thesis using the Kinetically Limited Adaptive Habit (KLAH) growth method in a Lagrangian parcel model framework.The KLAH model predicts axis-dependent growth efficiencies that allow for particle shape to evolve in time. After nucleation, ice particles become increasingly less isometric as they grow. This non-linearly increases the vapor flux to the semi-major axis, increasing the rate at which vapor is depleted from the ambient environment. We show that, in some cases, more surface resistance may in fact accelerate this increase in the growth rate. As a result, fewer heterogeneously-nucleated ice crystals are required to suppress homogeneous nucleation. This may help to explain the relative dominance of heterogeneous nucleation in the upper atmosphere. Furthermore, we show that simpler treatments of surface kinetics are unable to capture this effect, and may lead to both over- and under-predictions of ice concentration while also missing the evolution of ice particle shape that occurs above the cloud-base nucleation zone.
Author: Theodore William Wilson
Publisher:
ISBN:
Category :
Languages : en
Pages : 444
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Author: C. Guy Suits
Publisher: Elsevier
ISBN: 1483224112
Category : Science
Languages : en
Pages : 622
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The Collected Works of Irving Langmuir, Volume 11: Cloud Nucleation presents the papers written by Dr. Irving Langmuir on the study of artificial nucleation of clouds to produce precipitation. The compilation provides the study of every possible aspect of cloud and weather modification. This volume contains chapters that are devoted to the discussion of such subjects as the nucleation of clouds with dry ice; the analysis of photographic data showing the effects produced by supercooled clouds with ice nuclei; the production of rain by a chain reaction in cumulus clouds at temperatures above freezing; nucleation of clouds with silver iodide; and basic discoveries underlying weather modification. Meteorologists will find the book interesting and invaluable.
Author: Robert D. Kelly
Publisher:
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Category : Atmospheric nucleation
Languages : en
Pages : 176
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Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781722475284
Category :
Languages : en
Pages : 38
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Specific measurement of cirrus crystals by aircraft and temperature modified CN are used to specify measurements necessary to provide a basis for a conceptual model of cirrus particle formation. Key to this is the ability to measure the complete spectrum of particles at cirrus levels. The most difficult regions for such measurement is from a few to 100 microns, and uses a replicator. The details of the system to automate replicator data analysis are given, together with an example case study of the system provided from a cirrus cloud in FIRE 2, with particles detectable by replicator and FSSP, but not 2DC. Arnott, William P. and Hallett, John and Hudson, James G. Unspecified Center NAG1-1546...
Author: Ian D. Cohen
Publisher:
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Category : Cirrus clouds
Languages : en
Pages : 108
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Author:
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Category :
Languages : en
Pages : 19
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Author: David C. Rogers
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Category : Clouds
Languages : en
Pages : 322
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Author: Alessia Nicosia
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Heterogeneous ice nucleation is one element inside the overall complexity of the Earth's atmosphere, however, it has a profound impact on our representation of cloud properties: this process affects the optical thickness and lifetime of mixed-phase clouds and cirrus clouds, and it is responsible for a significant proportion of precipitations formed globally. Heterogeneous ice nucleation is related to the presence of specific aerosol particles, named ice nuclei particles (INP), with the unique ability of lowering the energy barrier required for the formation of ice crystals, especially where cloud's temperatures are >-38 °C. In the last decades, significant advancements have been made to the fundamental understanding of ice nucleation, however the lack of knowledge on the cloud ice phase still contributes to major uncertainties in climate model prediction of radiative forcing. This is partly due to limited observational data quantifying INP distributions and properties all over the world, especially in remote locations. In the first part of this thesis, field observations of ice nucleating particles have been performed at the Italian Climate Observatory “O. Vittori” on Mountain Cimone (2165 m above sea level), in the spring 2014 and autumn 2015, within the Bacchus and Air Sea Lab projects. For the first time we report the results of offline INP measurements, performed at a high altitude site within the Mediterranean basin. In the period 19-29 May 2014, a parallel campaign took place at the low-altitude station San Pietro Capofiume, a rural site in the Po Valley. The two campaigns were concerned, for a few days, by a Saharan Dust transport Event, which was recorded simultaneously at the high and the low-level station. We investigated the ambient number concentration of INP under condensation freezing activation mechanism (at -18 °C and above water saturation). In the second part of this thesis, we present the observations that were performed during the Arctic campaign Parcs-Maca, in the period of transition among the polar night and the polar day. We could characterise for the first time the ice nucleating and physical/chemical properties of the Arctic Primary Marine Aerosol, in a laboratory-controlled generation approach, that was combined to a mesocosm experiment. The aim of the mesocosm experiment was to adopt a multidisciplinary approach to study the effect of marine pollution on marine emissions. We found a moderate but significant decrease of the ice nuclei concentration in the polluted seawater (with respect to the control seawater) recorded in the freezing range between -8.5 and -19 °C and activated through immersion-freezing. Within the seaspray our measurements have indicated a relation among INP active at warm temperature (above -15 °C through immersion-freezing) and a calcium enrichment detected in PM1 filters (and followed by an apparent Chloride depletion). On the basis of our observations, and the results reported from other studies, a few suggestions on the nature of these marine ice nuclei have been suggested. In summary, the measurements made for this thesis provide new information on the concentrations of ice nuclei in ambient aerosol particles in remote regions (a high-altitude observatory in the central Mediterranean region) and in relation to a specific source (the Arctic sea spray).
