Analytic Closed-Form Solution of a Mixed Layer Model for Stratocumulus Clouds PDF Download
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Author: Bengu Ozge Akyurek
Publisher:
ISBN:
Category :
Languages : en
Pages : 119
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Book Description
Stratocumulus clouds play an important role in climate cooling and are hard to predict using global climate and weather forecast models. Thus, previous studies in the literature use observations and numerical simulation tools, such as large-eddy simulation (LES), to solve the governing equations for the evolution of stratocumulus clouds. In contrast to the previous works, this work provides an analytic closed-form solution to the cloud thickness evolution of stratocumulus clouds in a mixed-layer model framework. With a focus on application over coastal lands, the diurnal cycle of cloud thickness and whether or not clouds dissipate are of particular interest. An analytic solution enables the sensitivity analysis of implicitly interdependent variables and extrema analysis of cloud variables that are hard to achieve using numerical solutions. In this work, the sensitivity of inversion height, cloud-base height, and cloud thickness with respect to initial and boundary conditions, such as Bowen ratio, subsidence, surface temperature, and initial inversion height, are studied. A critical initial cloud thickness value that can be dissipated pre- and post-sunrise is provided. Furthermore, an extrema analysis is provided to obtain the minima and maxima of the inversion height and cloud thickness within 24 h. The proposed solution is validated against LES results under the same initial and boundary conditions. Then, the proposed analytic framework is extended to incorporate multiple vertical columns that are coupled by advection through wind flow. This enables a bridge between the micro-scale and the mesoscale relations. The effect of advection on cloud evolution is studied and a sensitivity analysis is provided.
Author: Bengu Ozge Akyurek
Publisher:
ISBN:
Category :
Languages : en
Pages : 119
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Book Description
Stratocumulus clouds play an important role in climate cooling and are hard to predict using global climate and weather forecast models. Thus, previous studies in the literature use observations and numerical simulation tools, such as large-eddy simulation (LES), to solve the governing equations for the evolution of stratocumulus clouds. In contrast to the previous works, this work provides an analytic closed-form solution to the cloud thickness evolution of stratocumulus clouds in a mixed-layer model framework. With a focus on application over coastal lands, the diurnal cycle of cloud thickness and whether or not clouds dissipate are of particular interest. An analytic solution enables the sensitivity analysis of implicitly interdependent variables and extrema analysis of cloud variables that are hard to achieve using numerical solutions. In this work, the sensitivity of inversion height, cloud-base height, and cloud thickness with respect to initial and boundary conditions, such as Bowen ratio, subsidence, surface temperature, and initial inversion height, are studied. A critical initial cloud thickness value that can be dissipated pre- and post-sunrise is provided. Furthermore, an extrema analysis is provided to obtain the minima and maxima of the inversion height and cloud thickness within 24 h. The proposed solution is validated against LES results under the same initial and boundary conditions. Then, the proposed analytic framework is extended to incorporate multiple vertical columns that are coupled by advection through wind flow. This enables a bridge between the micro-scale and the mesoscale relations. The effect of advection on cloud evolution is studied and a sensitivity analysis is provided.
Author: Christopher R. Jones
Publisher:
ISBN:
Category : Climatic changes
Languages : en
Pages : 142
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Book Description
Subtropical stratocumulus clouds are important part of the Earth's energy budget. The response of low clouds to Earth's changing climate is one of the dominant uncertainties in global warming projections, due primarily to unresolved parameterized cloud processes in global climate models (GCMs). Improving our understanding of the role stratocumulus clouds play in response to climate change requires both a better understanding of the underlying physical mechanisms that govern stratocumulus clouds, and also better representing these processes in GCMs. This work addresses both aspects, using a range of models, from an idealized mixed-layer model (MLM) to a high-resolution large eddy simulation (LES). The aerosol indirect effect (AIE) for nondrizzling stratocumulus clouds is strongly dependent on an entrainment-sedimentation feedback that increases the entrainment efficiency for higher droplet concentrations, thereby decreasing the cloud amount. However, a single column model (SCM) derived from the CAM5 GCM exhibits the opposite sign of this response mechanism. Using an SCM we find that a combination of issues contribute to this, but the primary cause is due to a representation of cloud condensate within the PBL parameterization that is inconsistentwith other microphysical parameterizations that affect the cloud liquid water, rendering the entrainment efficiency insensitive to droplet concentration. The response of a representative stratocumulus to a variety of idealized climate-change perturbations is used in conjunction with an identically-forced LES to interpret the underlying mechanisms behind the observed sensitivity. The MLM and LES agree remarkably well for all cases where the boundary layer doesn't decouple in the LES. For doubling CO2 forcing perturbations estimated from the CMIP3 multimodel mean, the MLM predicts a positive shortwave cloud feedback, like most CMIP3 global climate models. The cloud remains overcast but thins in the warmer, moister, CO2-enhanced climate, due to the combined effects of an increased lower-tropospheric vertical humidity gradient and an enhanced free tropospheric greenhouse effect that reduces the radiative driving of turbulence. Reduced subsidence due to weakening of tropical overturning circulations and a strengthening of the capping inversion partly counteract these two factors by raising the inversion and allowing the cloud layer to deepen. These compensating mechanisms may explain the large scatter in low cloud feedbacks predicted by climate models. The rapidity with which a stratocumulus cloud can respond to perturbations is important for understanding its response to perturbations that occur across a range of characteristic time scales. Using a MLM and LES, I show that there are three separate timescales: a slow adjustment timescale associated with boundary layer deepening (several days), an intermediate thermodynamic timescale (approximately 1 day), and a hitherto unidentified fast timescale (6-12 hours) for cloud water path adjustment associated with internal entrainment rate feedbacks. The fast timescale response is elicited by perturbations to overlying humidity and surface and atmosphere temperature, whereas purely radiative perturbations do not elicit an entrainment-liquid water path feedback. A range of MLM entrainment closures are shown to support a fast timescale, provided the entrainment rate is sensitive to the integrated buoyancy flux. The underlying entrainment-liquid flux adjustment mechanism suggests a cloud-thinning response to a uniformly warmed climate perturbation.
Author:
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ISBN:
Category : Aeronautics
Languages : en
Pages : 940
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Author: J. R. Garratt
Publisher: Cambridge University Press
ISBN: 9780521467452
Category : Mathematics
Languages : en
Pages : 340
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Book Description
The book gives a comprehensive and lucid account of the science of the atmospheric boundary layer (ABL). There is an emphasis on the application of the ABL to numerical modelling of the climate. The book comprises nine chapters, several appendices (data tables, information sources, physical constants) and an extensive reference list. Chapter 1 serves as an introduction, with chapters 2 and 3 dealing with the development of mean and turbulence equations, and the many scaling laws and theories that are the cornerstone of any serious ABL treatment. Modelling of the ABL is crucially dependent for its realism on the surface boundary conditions, and chapters 4 and 5 deal with aerodynamic and energy considerations, with attention to both dry and wet land surfaces and sea. The structure of the clear-sky, thermally stratified ABL is treated in chapter 6, including the convective and stable cases over homogeneous land, the marine ABL and the internal boundary layer at the coastline. Chapter 7 then extends the discussion to the cloudy ABL. This is seen as particularly relevant, since the extensive stratocumulus regions over the subtropical oceans and stratus regions over the Arctic are now identified as key players in the climate system. Finally, chapters 8 and 9 bring much of the book's material together in a discussion of appropriate ABL and surface parameterization schemes in general circulation models of the atmosphere that are being used for climate simulation.
Author: Chao Jih-Ping
Publisher:
ISBN:
Category : Cloud physics
Languages : en
Pages : 152
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Book Description
Author: Robert Pincus
Publisher: Springer
ISBN: 3319772732
Category : Science
Languages : en
Pages : 396
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Book Description
This volume presents a series of overview articles arising from a workshop exploring the links among shallow clouds, water vapor, circulation, and climate sensitivity. It provides a state-of-the art synthesis of understanding about the coupling of clouds and water vapor to the large-scale circulation. The emphasis is on two phenomena, namely the self-aggregation of deep convection and interactions between low clouds and the large-scale environment, with direct links to the sensitivity of climate to radiative perturbations. Each subject is approached using simulations, observations, and synthesizing theory; particular attention is paid to opportunities offered by new remote-sensing technologies, some still prospective. The collection provides a thorough grounding in topics representing one of the World Climate Research Program’s Grand Challenges. Previously published in Surveys in Geophysics, Volume 38, Issue 6, 2017 The aritcles “Observing Convective Aggregation”, “An Observational View of Relationships Between Moisture Aggregation, Cloud, and Radiative Heating Profiles”, “Implications of Warm Rain in Shallow Cumulus and Congestus Clouds for Large-Scale Circulations”, “A Survey of Precipitation-Induced Atmospheric Cold Pools over Oceans and Their Interactions with the Larger-Scale Environment”, “Low-Cloud Feedbacks from Cloud-Controlling Factors: A Review”, “Mechanisms and Model Diversity of Trade-Wind Shallow Cumulus Cloud Feedbacks: A Review”, “Structure and Dynamical Influence of Water Vapor in the Lower Tropical Troposphere”, “Emerging Technologies and Synergies for Airborne and Space-Based Measurements of Water Vapor Profiles”, “Observational Constraints on Cloud Feedbacks: The Role of Active Satellite Sensors”, and “EUREC4A: A Field Campaign to Elucidate the Couplings Between Clouds, Convection and Circulation” are available as open access articles under a CC BY 4.0 license at link.springer.com.
Author: Alexander P. Khain
Publisher: Cambridge University Press
ISBN: 0521767431
Category : Nature
Languages : en
Pages : 643
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Book Description
Provides a comprehensive analysis of modern theories of cloud microphysical processes and their representation in numerical cloud models.
Author:
Publisher:
ISBN:
Category : Physics
Languages : en
Pages : 998
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Author:
Publisher:
ISBN:
Category : Mechanics, Applied
Languages : en
Pages : 620
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Author: Advisory Committee on Technology and Society
Publisher: National Academies Press
ISBN: 9780309037860
Category : Social Science
Languages : en
Pages : 1298
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Book Description
Cities and Their Vital Systems asks basic questions about the longevity, utility, and nature of urban infrastructures; analyzes how they grow, interact, and change; and asks how, when, and at what cost they should be replaced. Among the topics discussed are problems arising from increasing air travel and airport congestion; the adequacy of water supplies and waste treatment; the impact of new technologies on construction; urban real estate values; and the field of "telematics," the combination of computers and telecommunications that makes money machines and national newspapers possible.
