scholarly journals A Comparison of the Conservation of Number Concentration for the Continuous Collection and Vapor Diffusion Growth Equations Using One- and Two-Moment Schemes

2005 ◽  
Vol 44 (12) ◽  
pp. 1844-1849 ◽  
Author(s):  
Jerry M. Straka ◽  
Matthew S. Gilmore ◽  
Katharine M. Kanak ◽  
Erik N. Rasmussen
Keyword(s):  
Moment Method ◽  
Climate Models ◽  
Spectral Density Function ◽  
Number Concentration ◽  
Mixing Ratio ◽  
Vapor Diffusion ◽  
Moment Methods ◽  
Complex Models ◽  
Growth Equations ◽  
The One

Abstract One- and two-moment parameterizations are integrated over hydrometeor diameters D(0, ∞) for vapor diffusion and the continuous collection growth processes. For the conditions specified, the total number concentration of collector particles should be conserved. To address the problem, the gamma distribution function is used for the spectral density function. Predicted variables can include total mixing ratio q, total number concentration Nt, and characteristic diameter Dn (inverse of the distribution slope λ). In all of the cases, the slope intercept no is diagnosed or specified. The popular one- and two-moment methods that are explored include the one-moment method in which q is predicted, no is specified, and Nt and Dn are diagnosed; the one-moment method in which q is predicted, Dn is specified, and Nt and no are diagnosed; the two-moment method in which q and Dn are predicted and Nt and no are diagnosed; and the two-moment method in which q and Nt are predicted and no and Dn are diagnosed. It is demonstrated for the processes examined that all of the schemes 1) fail to conserve Nt for the collector particles when Nt should be conserved and 2) have other unphysical attributes, except for the two-moment method in which q and Nt are predicted. In recent years there has been a dramatic increase in the use of more-sophisticated microphysical parameterizations in cloud, mesoscale, and climate models, and it is increasingly important for a model user to be cognizant of the strengths and weaknesses of the parameterizations in complex models.

scholarly journals A New Double-Moment Microphysics Parameterization for Application in Cloud and Climate Models. Part II: Single-Column Modeling of Arctic Clouds

2005 ◽  
Vol 62 (6) ◽  
pp. 1678-1693 ◽  
Author(s):  
H. Morrison ◽  
J. A. Curry ◽  
M. D. Shupe ◽  
P. Zuidema
Keyword(s):  
Climate Models ◽  
Heat Budget ◽  
Number Concentration ◽  
The Arctic ◽  
Liquid Water Path ◽  
Microphysics Scheme ◽  
Radiative Fluxes ◽  
Arctic Clouds ◽  
Single Column ◽  
Double Moment

Abstract The new double-moment microphysics scheme described in Part I of this paper is implemented into a single-column model to simulate clouds and radiation observed during the period 1 April–15 May 1998 of the Surface Heat Budget of the Arctic (SHEBA) and First International Satellite Cloud Climatology Project (ISCCP) Regional Experiment–Arctic Clouds Experiment (FIRE–ACE) field projects. Mean predicted cloud boundaries and total cloud fraction compare reasonably well with observations. Cloud phase partitioning, which is crucial in determining the surface radiative fluxes, is fairly similar to ground-based retrievals. However, the fraction of time that liquid is present in the column is somewhat underpredicted, leading to small biases in the downwelling shortwave and longwave radiative fluxes at the surface. Results using the new scheme are compared to parallel simulations using other microphysics parameterizations of varying complexity. The predicted liquid water path and cloud phase is significantly improved using the new scheme relative to a single-moment parameterization predicting only the mixing ratio of the water species. Results indicate that a realistic treatment of cloud ice number concentration (prognosing rather than diagnosing) is needed to simulate arctic clouds. Sensitivity tests are also performed by varying the aerosol size, solubility, and number concentration to explore potential cloud–aerosol–radiation interactions in arctic stratus.

Control of flexible manipulators: A survey

Robotica ◽  
2004 ◽  
Vol 22 (5) ◽  
pp. 533-545 ◽  
Author(s):  
M. Benosman ◽  
G. Le Vey
Keyword(s):  
Linear Models ◽  
Control Strategies ◽  
Research Area ◽  
Future Research ◽  
Complex Nature ◽  
Open Problems ◽  
Complex Models ◽  
The Many ◽  
The One ◽  
Flexible Arms

A survey of the field of control for flexible multi-link robots is presented. This research area has drawn great attention during the last two decades, and seems to be somewhat less “attractive” now, due to the many satisfactory results already obtained, but also because of the complex nature of the remaining open problems. Thus it seems that the time has come to try to deliver a sort of “state of the art” on this subject, although an exhaustive one is out of scope here, because of the great amount of publications. Instead, we survey the most salient progresses – in our opinion – approximately during the last decade, that are representative of the essential different ideas in the field. We proceed along with the exposition of material coming from about 119 included references. We do not pretend to deeply present each of the methods quoted hereafter; however, our goal is to briefly introduce most of the existing methods and to refer the interested reader to more detailed presentations for each scheme. To begin with, a now well-established classification of the flexible arms control goals is given. It is followed by a presentation of different control strategies, indicating in each case whether the approach deals with the one-link case, which can be successfully treated via linear models, or with the multi-link case which necessitates nonlinear, more complex, models. Some possible issues for future research are given in conclusion.

A gradual desiccation method for improving the efficiency of protein crystallization screening

2012 ◽  
Vol 45 (4) ◽  
pp. 758-765 ◽  
Author(s):  
Qin-Qin Lu ◽  
Xu-Zhuo Xie ◽  
Rui-Qing Chen ◽  
Zi-Qing Wu ◽  
Qing-Di Cheng ◽  
...  
Keyword(s):  
Success Rate ◽  
Protein Crystallization ◽  
Diffusion Method ◽  
Powerful Method ◽  
Vapor Diffusion ◽  
Optimal Amount ◽  
Reservoir Solution ◽  
The One

In vapor diffusion protein crystallization screening, it has been reported that replacing the reservoir solution with desiccant can increase the crystallization success rate. Therefore, the desiccation method is a potentially powerful method in practical protein crystallization screening. However, this method is difficult to apply broadly because the optimal amount of desiccant for a specific screening task is unknown. Utilizing an unsuitable amount of desiccant can result in even worse screening results than would be obtained from the traditional vapor diffusion method. Here, it is shown that by employing a modified strategy, named the gradual desiccation method, the problem can be solved without knowing the optimal amount of desiccant, and the crystallization success rate can be further increased compared with the one-time desiccation method.

scholarly journals Statistical indicators of Arctic sea-ice stability – prospects and limitations

2016 ◽  
Vol 10 (4) ◽  
pp. 1631-1645 ◽  
Author(s):  
Sebastian Bathiany ◽  
Bregje van der Bolt ◽  
Mark S. Williamson ◽  
Timothy M. Lenton ◽  
Marten Scheffer ◽  
...  
Keyword(s):  
Sea Ice ◽  
Climate Models ◽  
Arctic Sea Ice ◽  
Ice Coverage ◽  
Arctic Sea ◽  
Complex Models ◽  
Large Heat ◽  
Annual Time Series ◽  
Arctic Sea Ice Loss ◽  
The Relationship

Abstract. We examine the relationship between the mean and the variability of Arctic sea-ice coverage and volume in a large range of climates from globally ice-covered to globally ice-free conditions. Using a hierarchy of two column models and several comprehensive Earth system models, we consolidate the results of earlier studies and show that mechanisms found in simple models also dominate the interannual variability of Arctic sea ice in complex models. In contrast to predictions based on very idealised dynamical systems, we find a consistent and robust decrease of variance and autocorrelation of sea-ice volume before summer sea ice is lost. We attribute this to the fact that thinner ice can adjust more quickly to perturbations. Thereafter, the autocorrelation increases, mainly because it becomes dominated by the ocean water's large heat capacity when the ice-free season becomes longer. We show that these changes are robust to the nature and origin of climate variability in the models and do not depend on whether Arctic sea-ice loss occurs abruptly or irreversibly. We also show that our climate is changing too rapidly to detect reliable changes in autocorrelation of annual time series. Based on these results, the prospects of detecting statistical early warning signals before an abrupt sea-ice loss at a "tipping point" seem very limited. However, the robust relation between state and variability can be useful to build simple stochastic climate models and to make inferences about past and future sea-ice variability from only short observations or reconstructions.

scholarly journals Ice Particle Production in Mid-level Stratiform Mixed-phase Clouds Observed with Collocated A-Train Measurements

2017 ◽  
Author(s):  
Damao Zhang ◽  
Zhien Wang ◽  
Pavlos Kollias ◽  
Andrew M. Vogelmann ◽  
Kang Yang ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Particle Production ◽  
Climate Models ◽  
Global Scale ◽  
Number Concentration ◽  
Mixed Phase ◽  
Liquid Water Path ◽  
Lidar Measurements ◽  
Dust Events ◽  
Mixed Phase Clouds

Abstract. Collocated CloudSat radar and CALIPSO lidar measurements between 2006 and 2010 are analyzed to study primary ice particle production characteristics in mid-level stratiform mixed-phase clouds on a global scale. For similar clouds in terms of cloud top temperature and liquid water path, Northern Hemisphere latitude bands have layer-maximum radar reflectivity (ZL) that is ~1 to 8 dBZ larger than their counterparts in the Southern Hemisphere. The systematically larger ZL under similar cloud conditions suggests larger ice number concentrations in mid-level stratiform mixed-phase clouds over the Northern Hemisphere, which is possibly related to higher background aerosol loadings. Furthermore, we show that northern mid- and high-latitude springtime has ZL that is larger by up to 8 dBZ (a factor of 6 higher ice number concentration) than other seasons, which might be related to more dust events that provide effective ice nucleating particles. Our study suggests that aerosol-dependent ice number concentration parameterizations are required in climate models to improve mixed-phase cloud simulations, especially over the Northern Hemisphere.

scholarly journals The Lognormal-Like Distributions in the Linear Growth Equations

2003 ◽  
Vol 17 (22n24) ◽  
pp. 4300-4307
Author(s):  
Ning-Ning Pang ◽  
Wen-Jer Tzeng
Keyword(s):  
Growth Process ◽  
Linear Growth ◽  
Growth Equation ◽  
Two Dimensional ◽  
Exponential Distributions ◽  
One Dimensional ◽  
The Social ◽  
Exponential Random Variables ◽  
Growth Equations ◽  
The One

The distributions of the global interfacial widths, correlation functions, and the local interfacial widths of the growth process described by the one-dimensional Edward-Wilkinson equation are shown to be denumerable convolutions of exponential distributions. The same conclusions can also be extended to the distributions of the global interfacial widths for another linear growth equation, describing some super-rough growth processes, in both one- and two-dimensional cases. Most of these distributions display the lognormal-like behavior. We propose that the mechanism provided by the accumulation of exponential random variables may contribute to a lot of the lognormal-like behavior observed in the social and natural sciences.

On Sedimentation and Advection in Multimoment Bulk Microphysics

2010 ◽  
Vol 67 (9) ◽  
pp. 3084-3094 ◽  
Author(s):  
Edward R. Mansell
Keyword(s):  
Turbulent Mixing ◽  
Particle Number ◽  
Ad Hoc ◽  
Leading Edge ◽  
Number Concentration ◽  
Advection Equation ◽  
Particle Number Concentration ◽  
Mixing Ratio ◽  
Conserve Particle Number ◽  
Size Sorting

Abstract In two-moment bulk microphysics schemes, the practice of using different weighted fall velocities for the various moments is known to lead to artificial growth in reflectivity values for fast-falling particles, particularly at the downward leading edge of a precipitation column. Two simple correction schemes that prevent these artifacts while still allowing some effects of size sorting are presented. The corrections are obtained by comparing particle number concentrations that result from two or three different sedimentation calculations. The corrections do not conserve particle number concentrations but do prevent spurious reflectivity growth automatically without the need to place ad hoc limits on mean particle size. Multimoment bulk microphysics schemes often have used inconsistent variables in terms of the appropriate advection equation (e.g., mass mixing ratio and particle number concentration). A brief review of consistent advection and turbulent mixing for such variables is presented to provide clarification.

Reliability of Approach Slabs and Modelling of Transition Zones of Bridges

2016 ◽  
Vol 821 ◽  
pp. 741-746 ◽  
Author(s):  
Kamil Laco ◽  
Viktor Borzovič
Keyword(s):  
Reinforced Concrete ◽  
Concrete Slab ◽  
Structural Models ◽  
Reinforced Concrete Slab ◽  
Transition Zones ◽  
Approach Slabs ◽  
Approach Slab ◽  
Complex Models ◽  
The One ◽  
Civil Engineers

The approach slab is the structural member of transition zones, which compensates a different settlement of bridge abutment and a road embankment. The main reason of different settlement is the consolidation of soil under the slab and the abutment. The geometry of approach slab, its length and the thickness is defined on the basis of differential settlement of embankment and the abutment. The static behaviour of slab is defined as a slab on elastic soil. The reinforced concrete slab is supported with the line rigid support on the one edge, and the rest of slab area interacts with the soil. The civil engineers design the reinforcement in those slabs based on the simplified structural scheme, without considering the elastic area support. This scheme is the simple supported slab on the both ends. The paper is dealing with the comparing of different structural models of the reinforced concrete approach slabs. The complex models of transition zones with the brick elements of the soil and the interaction with the reinforced concrete slab with the soil embankment are compared with the simplified models used by civil engineers. The analysis was performed on the transition zone of highway bridge from Slovakia based on its geometry and the subsoil consistence. In the parametric study was compared 8 soil stiffness’s on 10 structural models.

scholarly journals Aerosol hygroscopicity parameter derived from the light scattering enhancement factor measurements in the North China Plain

2014 ◽  
Vol 14 (3) ◽  
pp. 3459-3497 ◽  
Author(s):  
J. Chen ◽  
C. S. Zhao ◽  
N. Ma ◽  
P. Yan
Keyword(s):  
Light Scattering ◽  
Radiative Forcing ◽  
Enhancement Factor ◽  
Climate Models ◽  
Sensitivity Study ◽  
Number Concentration ◽  
Accurate Estimation ◽  
Hygroscopic Growth ◽  
Calculation Algorithm ◽  
Aerosol Hygroscopicity

Abstract. The relative humidity (RH) dependence of aerosol light scattering is an essential parameter for accurate estimation of the direct radiative forcing induced by aerosol particles. On account of the insufficient information of aerosol hygroscopicity in climate models, more details of the parameterized hygroscopic growth factors are urgently required. In this paper, a retrieval method to calculate the aerosol hygroscopicity parameter, κ, is proposed based on the in situ measured aerosol light scattering enhancement factor, namely f(RH), and particle number size distribution (PNSD) obtained from the HaChi (Haze in China) campaign. Measurements show that f(RH) sharply increases with the ascending RH, and the variation range of f(RH) is much wider at higher RH. Sensitivity study reveals that the f(RH) is more sensitive to the aerosol hygroscopicity than PNSD. f(RH) for polluted cases is distinctly higher than that for clean periods at a specific RH. The derived equivalent κ, combining with the PNSD measurements, is applied in the prediction of the CCN number concentration. Comparison between the predicted CCN number concentration with the derived equivalent κ and the measured ones agrees well, especially at high supersaturations. The proposed calculation algorithm of κ with the f(RH) measurements is demonstrated to be reasonable and can be widely used.

scholarly journals FaIRv2.0.0: a generalized impulse response model for climate uncertainty and future scenario exploration

2021 ◽  
Vol 14 (5) ◽  
pp. 3007-3036
Author(s):  
Nicholas J. Leach ◽  
Stuart Jenkins ◽  
Zebedee Nicholls ◽  
Christopher J. Smith ◽  
John Lynch ◽  
...  
Keyword(s):  
Greenhouse Gas ◽  
Impulse Response ◽  
Climate Models ◽  
Global Climate ◽  
Climate System ◽  
System Response ◽  
Common Denominator ◽  
Response Model ◽  
Wide Range ◽  
Complex Models

Abstract. Here we present an update to the FaIR model for use in probabilistic future climate and scenario exploration, integrated assessment, policy analysis, and education. In this update we have focussed on identifying a minimum level of structural complexity in the model. The result is a set of six equations, five of which correspond to the standard impulse response model used for greenhouse gas (GHG) metric calculations in the IPCC's Fifth Assessment Report, plus one additional physically motivated equation to represent state-dependent feedbacks on the response timescales of each greenhouse gas cycle. This additional equation is necessary to reproduce non-linearities in the carbon cycle apparent in both Earth system models and observations. These six equations are transparent and sufficiently simple that the model is able to be ported into standard tabular data analysis packages, such as Excel, increasing the potential user base considerably. However, we demonstrate that the equations are flexible enough to be tuned to emulate the behaviour of several key processes within more complex models from CMIP6. The model is exceptionally quick to run, making it ideal for integrating large probabilistic ensembles. We apply a constraint based on the current estimates of the global warming trend to a million-member ensemble, using the constrained ensemble to make scenario-dependent projections and infer ranges for properties of the climate system. Through these analyses, we reaffirm that simple climate models (unlike more complex models) are not themselves intrinsically biased “hot” or “cold”: it is the choice of parameters and how those are selected that determines the model response, something that appears to have been misunderstood in the past. This updated FaIR model is able to reproduce the global climate system response to GHG and aerosol emissions with sufficient accuracy to be useful in a wide range of applications and therefore could be used as a lowest-common-denominator model to provide consistency in different contexts. The fact that FaIR can be written down in just six equations greatly aids transparency in such contexts.

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