Understanding the responses of precipitation extremes to global climate change remains limited owing to their poor representations in models and complicated interactions with multi-scale *** we take the record-breakin...
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Understanding the responses of precipitation extremes to global climate change remains limited owing to their poor representations in models and complicated interactions with multi-scale *** we take the record-breaking precipitation over China in 2021 as an example,and study its changes under three different climate scenarios through a developed pseudo-global-warming(PGW)experimental framework with 60-3 km variable-resolution global ensemble *** to the present climate,the precipitation extreme under a warmer(cooler)climate increased(decreased)in intensity,coverage,and total amount at a range of 24.3%-37.8%(18.7%-56.1%).With the help of the proposed PGW experimental framework,we further reveal the impacts of the multi-scale system interactions in climate change on the precipitation *** the warmer climate,large-scale water vapor transport converged from double typhoons and the subtropical high marched into central China,enhancing the convective energy and instability on the leading edge of the transport *** a result,the mesoscale convective system(Mcs)that directly contributed to the precipitation extreme became stronger than that in the present *** the contrary,the cooler climate displayed opposite changing characteristics relative to the warmer climate,ranging from the large-scale systems to local environments and to the *** summary,our study provides a promising approach to scientifically assess the response of precipitation extremes to climate change,making it feasible to perform ensemble simulations while investigating the multi-scale system interactions over the globe.
A double-plume convective parameterization scheme is revised to improve the precipitation simulation of a global model(Global-to-Regional Integrated Forecast System;GRIST).The improvement is achieved by considering th...
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A double-plume convective parameterization scheme is revised to improve the precipitation simulation of a global model(Global-to-Regional Integrated Forecast System;GRIST).The improvement is achieved by considering the effects of large-scale dynamic processes on the trigger of deep *** closure,based on dynamic CAPE,is improved accordingly to allow other processes to consume CAPE under the more restricted convective trigger *** revised convective parameterization is evaluated with a variable-resolution model setup(110–35 km,refined over East Asia).The Atmospheric Model Intercomparison Project(AMIP)simulations demonstrate that the revised convective parameterization substantially delays the daytime precipitation peaks over most land areas,leading to an improved simulated diurnal cycle,evidenced by delayed and less frequent afternoon ***,changes to the threshold of the trigger function yield a small impact on the diurnal amplitude of precipitation because of the consistent setting of dCAPE-based trigger and *** simulated mean precipitation remains reasonable,with some improvements evident along the southern slopes of the Tibetan *** revised scheme increases convective precipitation at the lower levels of the windward slope and reduces the large-scale precipitation over the upper slope,ultimately shifting the rainfall peak southward,which is in better agreement with the observations.
Accurately simulating mesoscale convective systems (MCSs) is essential for predicting global precipitation patterns and extreme weather events. Despite the ability of advanced models to reproduce MCS climate statistic...
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Accurately simulating mesoscale convective systems (MCSs) is essential for predicting global precipitation patterns and extreme weather events. Despite the ability of advanced models to reproduce MCS climate statistics, capturing extreme storm cases over complex terrain remains challenging. This study utilizes the Global-Regional Integrated Forecast System (GRIST) with variableresolution to simulate an eastward-propagating MCS event. The impact of three microphysics schemes, including two single-moment schemes (WSM6, Lin) and one double-moment scheme (Morrison), on the model sensitivity of MCS precipitation simulations is investigated. The results demonstrate that while all the schemes capture the spatial distribution and temporal variation of MCS precipitation, the Morrison scheme alleviates overestimated precipitation compared to the Lin and WSM6 schemes. The ascending motion gradually becomes weaker in the Morrison scheme during the MCS movement process. Compared to the runs with convection parameterization, the explicit-convection setup at 3.5-km resolution reduces disparities in atmospheric dynamics due to microphysics sensitivity in terms of vertical motions and horizontal kinetic energy at the high-wavenumber regimes. The explicit-convection setup more accurately captures the propagation of both main and secondary precipitation centers during the MCS development, diminishing the differences in both precipitation intensity and propagation features between the Morrison and two single-moment schemes. These findings underscore the importance of microphysics schemes for global nonhydrostatic modeling at the kilometer scale. The role of explicit convection for reducing model uncertainty is also outlined.
The paper presents a computationally efficient surrogate-based optimization algorithm for the inverse design of transonic airfoils. Our approach replaces the direct optimization of an accurate, but computationally exp...
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The paper presents a computationally efficient surrogate-based optimization algorithm for the inverse design of transonic airfoils. Our approach replaces the direct optimization of an accurate, but computationally expensive, high-fidelity airfoil model by an iterative re-optimization of two different surrogate models. Initially, for a few design iterations, a corrected physics-based low-fidelity model is employed, which is subsequently replaced by a response surface approximation model. The low-fidelity model is based on the same governing fluid flow equations as the high-fidelity one, but uses coarser mesh resolution and relaxed convergence criteria. The shape-preserving response prediction (SPRP) technique is utilized to predict the high-fidelity model response, here, the airfoil pressure distribution. In this prediction process, SPRP employs the actual changes of the low-fidelity model response (or the surface approximation model) due to the design variable adjustments. The SPRP algorithm is embedded into the trust region framework to ensure good convergence properties of the optimization procedure. Our algorithm is applied to constrained inverse airfoil design in inviscid transonic flow. A comparison with the basic version of the optimization algorithm, exploiting only a physics-based low-fidelity model, is carried out. While the performance of both versions is similar with respect to their ability to match the target pressure distribution, the improved algorithm offers substantial design cost savings, from 25 to 72 percent, depending on the test case. (C) 2014 Elsevier Masson SAS. All rights reserved.
This paper proposes a framework for designing an agent based simulation to allow for easy aggregation and/or disaggregation of agent characteristics, behaviors, and interactions using a supply chain modeling context. ...
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ISBN:
(纸本)9781457721090
This paper proposes a framework for designing an agent based simulation to allow for easy aggregation and/or disaggregation of agent characteristics, behaviors, and interactions using a supply chain modeling context. Guidelines are provided for designing agent structure to demonstrate scalability in terms of fidelity to fit the needs of the analysis. The design methodology is based on combining hierarchical modeling with data-driven modeling. Related work done in variable-resolution modeling is a generalization for any modeling technique, while our proposed guidelines are specific for development of agent based models.
This paper describes mission-system planning (MSP) and mission-system analysis (MSA), It relate their needs to two frontier subjects: multi resolution, multi perspective modeling (MRMPM) and exploratory analysis. Afte...
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ISBN:
(纸本)0819440620
This paper describes mission-system planning (MSP) and mission-system analysis (MSA), It relate their needs to two frontier subjects: multi resolution, multi perspective modeling (MRMPM) and exploratory analysis. After a brief explanation of mission-system planning, I describe an application: the mission of halting a mechanized invasion force with long-range fires such as fighter and bomber aircraft. The application involves defining the relevant system, decomposing it analytically, and assessing overall system effectiveness over a relevant scenario space. The appropriate decomposition depends on one's point of view and responsibilities, and may have both hierarchical and network aspects. The result is a need for multiple levels of resolution in each of several perspectives. Evaluation of system capabilities then requires models. Strategically useful mission-system evaluation requires low-resolution (highly abstracted models), but the validity and credibility of those evaluations depends on deeper work and is enhanced by the ability to zoom in on components of the system problem-to explore underlying mechanisms and related capabilities in more detail. Given success in such matters, the remaining challenge is to find reductionist ways in which to display and explain analysis conclusions and motivate decisions. This also requires abstraction, the soundness of which can be enhanced with appropriate tools for data analysis of results from the exploratory work across scenario space.
In this paper we review motivations for multi-level resolutionmodeling (MRM) (also called variable-resolution modeling) within a single model an integrated hierarchical family of models, or both. We then present a ne...
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ISBN:
(纸本)0819428183
In this paper we review motivations for multi-level resolutionmodeling (MRM) (also called variable-resolution modeling) within a single model an integrated hierarchical family of models, or both. We then present a new depiction of consistency criteria for models at different levels. After describing our hypotheses for studying the process of MRM with examples, we define a simple but policy-relevant problem involving the use of precision fires to halt an invading army. We then illustrate MRM with a sequence of abstractions suggested by formal theory, visual representation, and approximation. We milk the example for insights about why MRM is different and often difficult, and how it might be accomplished more routinely. It should be feasible even in complex systems such as JWARS and JSIMS, but it is by no means easy. Comprehensive MRM designs are unlikely. It is useful to take the view that some MRM is a great deal better than none and that approximate MRM relationships are often quite adequate. Overall, we conclude that high-quality MRM requires new theory, design practices, modeling tools, and software tools, all of which will take some years to develop. Current object-oriented programming practices may actually be a hindrance.
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