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Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781721290482
Category :
Languages : en
Pages : 36
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Book Description
The research objective of this NASA grant-funded project was to determine in detail how large-scale processes. in combination with cloud-scale radiative, microphysical, and dynamical processes, govern the formation and multi-layered structure of Arctic stratus clouds. This information will be useful for developing and improving 1D (one dimensional) boundary layer models for the Arctic. Also, to quantitatively determine the effects of leads on the large-scale budgets of sensible heat, water vapor, and condensate in a variety of Arctic winter conditions. This information will be used to identify the most important lead-flux processes that require parameterization in climate models. Our approach was to use a high-resolution numerical model, the 2D (two dimensional) University of Utah Cloud Resolving Model (UU CRM), and its 1D version, the University of Utah Turbulence Closure Model (UU TCM), a boundary layer model based on third-moment turbulence closure, as well as a large-eddy simulation (LES) model originally developed by C.H. Moeng. Kruegen, Steven K. and Delnore, Victor E. (Technical Monitor) Langley Research Center
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781721290482
Category :
Languages : en
Pages : 36
Get Book Here
Book Description
The research objective of this NASA grant-funded project was to determine in detail how large-scale processes. in combination with cloud-scale radiative, microphysical, and dynamical processes, govern the formation and multi-layered structure of Arctic stratus clouds. This information will be useful for developing and improving 1D (one dimensional) boundary layer models for the Arctic. Also, to quantitatively determine the effects of leads on the large-scale budgets of sensible heat, water vapor, and condensate in a variety of Arctic winter conditions. This information will be used to identify the most important lead-flux processes that require parameterization in climate models. Our approach was to use a high-resolution numerical model, the 2D (two dimensional) University of Utah Cloud Resolving Model (UU CRM), and its 1D version, the University of Utah Turbulence Closure Model (UU TCM), a boundary layer model based on third-moment turbulence closure, as well as a large-eddy simulation (LES) model originally developed by C.H. Moeng. Kruegen, Steven K. and Delnore, Victor E. (Technical Monitor) Langley Research Center
Author: Loewe, Katharina
Publisher: KIT Scientific Publishing
ISBN: 3731506866
Category : Physics
Languages : en
Pages : 174
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Book Description
This work provides new insights into macro- and microphysical properties of Arctic mixed-phase clouds: first, by comparing semi-idealized large eddy simulations with observations; second, by dissecting the influences of different surface types and boundary layer structures on Arctic mixed- phase clouds; third, by elucidating the dissipation process; and finally by analyzing the main microphysical processes inside Arctic mixed-phase clouds.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 3
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Book Description
During the recent 3 month Arctic Ocean Expedition (AOE-96) to the North Pole during the summer of 1996 an enormous amount of data collected on the Arctic planetary boundary layer. In preparation for the expedition, the authors have developed an expanded and quite flexible 1-D computer code based on the successful work of ReVelle and of ReVelle and Coulter on modeling of boundary layer ''bursting''. This new code, BLMARC (Boundary Layer, Mixing, Aerosols, Radiation and Clouds), explicitly includes the physical and chemical effects due to the presence of clouds, aerosols and associated air chemistry. Using data from AOE-96 and the model BLMARC, the authors have begun a systematic effort to compare observations of the high Arctic boundary layer against numerical modeling results. The preliminary results for case963 and case964 are quite promising. The second period exhibits what appears to be bursting effects in the temperature, the winds and in the aerosol concentration and the modeling efforts have shown a similar set of features as well. Current work also includes model experiments with BLMARC on the aerosol nucleation and growth in the Arctic PBL and cloud and fog formation.
Author: Yaosheng Chen
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Arctic mixed-phase clouds are often multi-layered. Different cloud layers interact through radiation as well as ice precipitation falling from upper layer clouds into the lower layer clouds. The evolution of an Arctic mixed-phase stratiform cloud under prescribed perturbations from an overlaying cloud in the form of downwelling longwave radiation and ice precipitation was simulated and documented. The perturbations created regions with heterogeneous properties in the horizontal direction within the lower level cloud, the consequence of which was the development of a mesoscale circulation that propagated the perturbations well beyond the location of the initial perturbed region.In a separate study, we forward modeled radar Doppler spectra based on a large-eddy simulation (LES) model simulation of a single layer Arctic mixed-phase cloud and compared the modeled quantities with those retrieved from the observations. We show that there was a significant contribution from the microphysical broadening to the cloud radar Doppler spectral width in Arctic mixed-phase clouds. LES simulations configured with different ice particle characteristics captured different aspects of the observations in the simulated case, where a mixture of ice particles of different properties were likely present. The dynamics of the LES simulations, characterized with the total turbulent kinetic energy dissipation rate, agreed fairly well with the values retrieved from the observations. Due to significant numerical dissipation in the model for the case evaluated here, the TKE dissipation rate from the subgrid-scale model did not represent the dissipation rate in the model.
Author: Katharina Loewe
Publisher:
ISBN: 9781013281204
Category : Science
Languages : en
Pages : 160
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Book Description
This work provides new insights into macro- and microphysical properties of Arctic mixed-phase clouds: first, by comparing semi-idealized large eddy simulations with observations; second, by dissecting the influences of different surface types and boundary layer structures on Arctic mixed- phase clouds; third, by elucidating the dissipation process; and finally by analyzing the main microphysical processes inside Arctic mixed-phase clouds. This work was published by Saint Philip Street Press pursuant to a Creative Commons license permitting commercial use. All rights not granted by the work's license are retained by the author or authors.
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:
Publisher:
ISBN:
Category :
Languages : en
Pages : 6
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Book Description
My goals are to investigate and understand the turbulent transfer of momentum, heat, salt, and other scalar contaminants in naturally occurring boundary layers of the ocean, and to apply this knowledge to understanding air-ice-ocean interaction in polar regions. Objectives of the project include (i) gathering and analyzing turbulence data from the ocean boundary layer (OBL) under sea ice; (ii) developing techniques, including both new instrumentation and analysis methods, for determining turbulent fluxes in the boundary layer; (iii) combining measurements and theory (including numerical modeling) for concise descriptions of turbulent boundary layer scales; and (iv) using the results to develop parameterizations of important boundary layer processes for large scale numerical models of the sea ice/upper ocean system.
Author: Chʻiu-chʻing Chang
Publisher:
ISBN:
Category : Climatic changes
Languages : en
Pages : 396
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Book Description
"The formation of Arctic stratus clouds (ASC) and the maintenance of the cloudy Arctic boundary layer are studied with two models: a one-dimensional radiative-convective model and a three-dimensional large eddy simulation (LES) model. The one-dimensional radiative-convective model consists of a comprehensive radiative module, a cloud parameterization with detailed microphysics and a convective adjustment scheme. The model is designed specifically for studying ASC formation. With this model, the roles of radiation and cloud microphysics in the formation of ASCs and multiple cloud layers are investigated. The simulations reproduce both single and multiple cloud layers that were observed with inversions of temperature and humidity occurring near the cloud top. The detailed cloud microstructure produced by the model also compares well with the observations. The physics of the formation of both single and multiple cloud layers is investigated. Radiative cooling plays a key role during the initial stage of cloud formation in a atmosphere. It leads to a continual temperature decrease promoting water vapor condensation on available cloud condensation nuclei. The vertical distribution of humidity and temperature determines the radiative cooling and eventually where and when the cloud forms. The observed temperature inversion may also be explained by radiative cooling. The three-dimensional LES model is adopted to evaluate the one-dimensional model, especially the convective adjustment scheme. The advantages and limitations of the one-dimensional model are discussed. The LES results suggest that the convective adjustment scheme is capable of capturing the main features of the vertical heat and moisture fluxes in the cloudy Arctic boundary layer. The LES model is also used to investigate the maintenance of the cloudy Arctic boundary layer. The turbulence in the cloudy Arctic boundary layer is primarily maintained by the bouyancy effect due to the cloud top cooling. It is found that weak large scale downward motion aids in cloud development and maintenance"--3.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 45
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Book Description
[1] Simulations of mixed-phase clouds in forecasts with the NCAR Atmosphere Model version 3 (CAM3) and the GFDL Atmospheric Model version 2 (AM2) for the Mixed-Phase Arctic Cloud Experiment (M-PACE) are performed using analysis data from numerical weather prediction centers. CAM3 significantly underestimates the observed boundary layer mixed-phase cloud fraction and cannot realistically simulate the variations of liquid water fraction with temperature and cloud height due to its oversimplified cloud microphysical scheme. In contrast, AM2 reasonably reproduces the observed boundary layer cloud fraction while its clouds contain much less cloud condensate than CAM3 and the observations. The simulation of the boundary layer mixed-phase clouds and their microphysical properties is considerably improved in CAM3 when a new physically based cloud microphysical scheme is used (CAM3LIU). The new scheme also leads to an improved simulation of the surface and top of the atmosphere longwave radiative fluxes. Sensitivity tests show that these results are not sensitive to the analysis data used for model initialization. Increasing model horizontal resolution helps capture the subgrid-scale features in Arctic frontal clouds but does not help improve the simulation of the single-layer boundary layer clouds. AM2 simulated cloud fraction and LWP are sensitive to the change in cloud ice number concentrations used in the Wegener-Bergeron-Findeisen process while CAM3LIU only shows moderate sensitivity in its cloud fields to this change. Furthermore, this paper shows that the Wegener-Bergeron-Findeisen process is important for these models to correctly simulate the observed features of mixed-phase clouds.
Author: Arctic System Science Ocean-Atmosphere-Ice Interactions (Program)
Publisher:
ISBN:
Category : Arctic regions
Languages : en
Pages : 102
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Book Description
