scholarly journals Using Radar Reflectivity to Evaluate the Vertical Structure of Forecast Convection

2018 ◽  
Vol 57 (12) ◽  
pp. 2835-2849 ◽  
Author(s):  
Mariusz Starzec ◽  
Gretchen L. Mullendore ◽  
Paul A. Kucera
Keyword(s):  
Sensitivity Analysis ◽  
Vertical Structure ◽  
Three Dimensional ◽  
Radar Reflectivity ◽  
Convective Structure ◽  
Object Based ◽  
Convective Cells ◽  
The Impact

AbstractSeveral months of regional convection-permitting forecasts using two microphysical schemes (WSM6 and Thompson) are evaluated to determine the accuracy of the simulated convective structure and convective depth and the impact of microphysical scheme on simulated convective properties and biases. Forecasts are evaluated by using concepts from object-based approaches to compare the three-dimensional simulated reflectivity field with the reflectivity field as observed by radar. Results from analysis of both schemes reveals that forecasts generally perform well near the surface but differ considerably aloft both from observations and from each other. Forecasts are found to contain too many convective cores that are individually larger than in the observations, with at least double the number of observed convective cores reaching the midtroposphere (i.e., 4–8 km). Although the number of cores is overpredicted, WSM6 cores typically contain lower simulated reflectivity values than the observations, and the regions of highest reflectivity values do not extend far enough vertically. Conversely, Thompson cores are found to have significantly higher reflectivity values within cores, with the strongest intensities extending higher than in the observations and having magnitudes higher than any observed cores. Forecast reflectivity distributions within convective cells are found to contain more spread than in the observations. The study also assessed the uncertainty in simulated reflectivity calculations by using a second commonly utilized method to calculate simulated reflectivity. The sensitivity analysis reveals that the primary conclusions with each method are similar but the variability generated by using different simulated reflectivity calculations can be as pronounced as when using different microphysical schemes.

scholarly journals Three-Dimensional Evolution of Mesoscale Anticyclones in the Lee of Crete

2020 ◽  
Vol 7 ◽  
Author(s):  
Artemis Ioannou ◽  
Alexandre Stegner ◽  
Franck Dumas ◽  
Briac Le Vu
Keyword(s):  
Numerical Model ◽  
Vertical Structure ◽  
Three Dimensional ◽  
Wind Forcing ◽  
Water Model ◽  
Mountain Range ◽  
Dynamical Process ◽  
Ekman Pumping ◽  
Spatio Temporal ◽  
The Impact

Motivated by the recurrent formation of mesoscale anticyclones in the southeast of Crete, we investigated with a high resolution model the response of the ocean to orographic wind jets driven by the Cretean mountain range. As shown in the dynamical process study of Ioannou et al. (2020) which uses a simplified shallow-water model, we confirm here, using the CROCO (Coastal and Regional Ocean COmmunity) model, that the main oceanic response to the Etesian wind forcing is the formation of mesoscale anticyclones. Moreover, we found that the intensity of the wind-induced Ekman pumping acting on the eddies, once they are formed, modulates their intensity. Among the various coastal anticyclones formed during summer and fall 2015, only one of them will correspond to a long lived structure (M_IE15) which is similar to the Ierapetra Eddy detected in 2015 (O_IE15) on the AVISO/DUACS products. Thanks to the DYNED-Atlas data base, we were able to perform a quantitative comparison of the vertical structure of such long-lived anticyclone between the numerical model and the in-situ measurements of the various Argo profilers trapped inside the eddy core. Even without assimilation or any nudging, the numerical model was able to reproduce correctly the formation period, the seasonal evolution and the vertical structure of the O_IE15. The main discrepancy between the model and the altimetry observations is the dynamical intensity of the anticyclone. The characteristic eddy velocity derived from the AVISO/DUACS product for the O_IE15 is much lower than in the numerical model. This is probably due to the spatio temporal interpolation of the AVISO/DUACS altimetry products. More surprisingly, several coastal anticyclones were also formed in the model in the lee of Crete area during summer 2015 when the Etesian winds reach strong values. However, these coastal anticyclones respond differently to the wind forcing since they remain close to the coast, in shallow-waters, unlike the M_IE15 which propagates offshore in deep water. The impact of the bottom friction or the coastal dissipation seems to limit the wind amplification of these coastal anticyclones.

Orthogonal Analysis on Responses Indexes of Asphalt Pavement

2013 ◽  
Vol 361-363 ◽  
pp. 1523-1526
Author(s):  
Ya Li Ye ◽  
Chuan Yi Zhuang ◽  
Jie Yang ◽  
Yan Zhou
Keyword(s):  
Sensitivity Analysis ◽  
Asphalt Pavement ◽  
Compressive Strain ◽  
Maximum Shear Stress ◽  
Three Dimensional ◽  
Material Design ◽  
Structure Design ◽  
Accurate Analysis ◽  
Orthogonal Analysis ◽  
The Impact

The asphalt layer thickness, base thickness, the modulus of the asphalt layer, base modulus and subgrade modulus are selected as the responses indexes of asphalt. The level of each factor corresponding parameters and test results table are established by orthogonal analysis for four-level table of five factors. This paper took the Shell Designing Software BISAR 3.0 as calculation tool to get the three-dimensional response results of the different kinds of asphalt pavement. Based on results, the course bottom tensile strain of the asphalt layer, subgrade compressive strain and maximum shear stress of asphalt pavement are analyzed by intuitive analysis, variance analysis, and sensitivity analysis. It is found that the sensitivity analysis is a more accurate analysis of the factors of the factor in the level of assessment indicators. Response to the degree of influence of various factors on the pavement mechanics, pavement structure design and material design should be selected according to road type of damage specifications. In accordance with the sensitivity analysis of the impact of factors based on balanced other design specifications.

scholarly journals Experimental and Numerical Models of Three-Dimensional Gravity-Driven Flow of Shear-Thinning Polymer Solutions Used in Vaginal Delivery of Microbicides

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
Vitaly O. Kheyfets ◽  
Sarah L. Kieweg
Keyword(s):  
Sensitivity Analysis ◽  
Rheological Properties ◽  
Power Law ◽  
Numerical Models ◽  
Three Dimensional ◽  
Shear Thinning ◽  
Lateral Spreading ◽  
Free Surface Flows ◽  
Experimental Methodology ◽  
The Impact

HIV/AIDS is a growing global pandemic. A microbicide is a formulation of a pharmaceutical agent suspended in a delivery vehicle, and can be used by women to protect themselves against HIV infection during intercourse. We have developed a three-dimensional (3D) computational model of a shear-thinning power-law fluid spreading under the influence of gravity to represent the distribution of a microbicide gel over the vaginal epithelium. This model, accompanied by a new experimental methodology, is a step in developing a tool for optimizing a delivery vehicle's structure/function relationship for clinical application. We compare our model with experiments in order to identify critical considerations for simulating 3D free-surface flows of shear-thinning fluids. Here we found that neglecting lateral spreading, when modeling gravity-induced flow, resulted in up to 47% overestimation of the experimental axial spreading after 90 s. In contrast, the inclusion of lateral spreading in 3D computational models resulted in rms errors in axial spreading under 7%. In addition, the choice of the initial condition for shape in the numerical simulation influences the model's ability to describe early time spreading behavior. Finally, we present a parametric study and sensitivity analysis of the power-law parameters' influence on axial spreading, and to examine the impact of changing rheological properties as a result of dilution or formulation conditions. Both the shear-thinning index (n) and consistency (m) impacted the spreading length and deceleration of the moving front. The sensitivity analysis showed that gels with midrange m and n values (for the ranges in this study) would be most sensitive (over 8% changes in spreading length) to 10% changes (e.g., from dilution) in both rheological properties. This work is applicable to many industrial and geophysical thin-film flow applications of non-Newtonian fluids; in addition to biological applications in microbicide drug delivery.

scholarly journals Vertical Profiles of Radar Reflectivity Factor in Intense Convective Clouds in the Tropics

2016 ◽  
Vol 55 (5) ◽  
pp. 1277-1286 ◽  
Author(s):  
Shailendra Kumar ◽  
G. S. Bhat
Keyword(s):  
South America ◽  
Vertical Structure ◽  
Western Himalaya ◽  
Radar Reflectivity ◽  
Close Similarity ◽  
Vertical Profiles ◽  
Convective Clouds ◽  
Convective Cells ◽  
The Tropics ◽  
Reflectivity Factor

AbstractThis study is based on the analysis of 10 years of data for radar reflectivity factor Ze as derived from the TRMM Precipitation Radar (PR) measurements. The vertical structure of active convective clouds at the PR pixel scale has been extracted by defining two types of convective cells. The first one is cumulonimbus tower (CbT), which contains Ze ≥ 20 dBZ at 12-km altitude and is at least 9 km deep. The other is intense convective cloud (ICC), which belongs to the top 5% of the population of the Ze distribution at a prescribed reference height. Here two reference heights (3 and 8 km) have been chosen. Regional differences in the vertical structure of convective cells have been explored by considering 16 locations distributed across the tropics and two locations in the subtropics. The choice of oceanic locations is based on the sea surface temperature; that of the land locations is based on propensity for intense convection. One of the main findings of the study is the close similarity in the average vertical profiles of CbTs and ICCs in the mid- and lower troposphere across the ocean basins whereas differences over land areas are larger and depend on the selected reference height. The foothills of the western Himalaya, southeastern South America, and the Indo-Gangetic Plain contain the most intense CbTs; equatorial Africa, the foothills of the western Himalaya, and equatorial South America contain the most intense ICCs. Close similarity among the oceanic profiles suggests that the development of vigorous convective cells over warm oceans is similar and that understanding gained in one region is extendable to other areas.

Comparison of Two Methods for Sensitivity Analysis of Compressor Blades

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Robin Schmidt ◽  
Matthias Voigt ◽  
Konrad Vogeler ◽  
Marcus Meyer
Keyword(s):  
Sensitivity Analysis ◽  
Monte Carlo ◽  
Polynomial Regression ◽  
Optical Measurement ◽  
Measurement Techniques ◽  
Three Dimensional ◽  
Sampling Strategy ◽  
Initial Flow ◽  
Efficient Sampling ◽  
The Impact

This paper will compare two approaches of sensitivity analysis, namely (i) the adjoint method which is used to obtain an initial estimate of the geometric sensitivity of the gas-washed surfaces to aerodynamic quantities of interest and (ii) a Monte Carlo type simulation with an efficient sampling strategy. For both approaches, the geometry is parameterized using a modified NACA parameterization. First, the sensitivity of those parameters is calculated using the linear (first-order) adjoint model. Since the effort of the adjoint computational fluid dynamics (CFD) solution is comparable to that of the initial flow CFD solution and the sensitivity calculation is simply a postprocessing step, this approach yields fast results. However, it relies on a linear model which may not be adequate to describe the relationship between relevant aerodynamic quantities and actual geometric shape variations for the derived amplitudes of shape variations. Second, in order to better capture nonlinear and interaction effects, a Monte Carlo type simulation with an efficient sampling strategy is used to carry out the sensitivity analysis. The sensitivities are expressed by means of the coefficient of importance (CoI), which is calculated based on modified polynomial regression and therefore able to describe relationships of higher order. The methods are applied to a typical high-pressure compressor (HPC) stage. The impact of a variable rotor geometry is calculated by three-dimensional (3D) CFD simulations using a steady Reynolds-averaged Navier–Stokes model. The geometric variability of the rotor is based on the analysis of a set of 400 blades which have been measured using high-precision 3D optical measurement techniques.

scholarly journals Sensitivity Analysis of Unsteady Flow Fields and Impact of Measurement Strategy

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Takashi Misaka ◽  
Shigeru Obayashi
Keyword(s):  
Sensitivity Analysis ◽  
Data Assimilation ◽  
Three Dimensional ◽  
Measurement Data ◽  
Flow Fields ◽  
Vortical Flow ◽  
Measurement Strategy ◽  
The Difference ◽  
Flow Variables ◽  
The Impact

Difficulty of data assimilation arises from a large difference between the sizes of a state vector to be determined, that is, the number of spatiotemporal mesh points of a discretized numerical model and a measurement vector, that is, the amount of measurement data. Flow variables on a large number of mesh points are hardly defined by spatiotemporally limited measurements, which poses an underdetermined problem. In this study we conduct the sensitivity analysis of two- and three-dimensional vortical flow fields within a framework of data assimilation. The impact of measurement strategy, which is evaluated by the sensitivity of the 4D-Var cost function with respect to measurements, is investigated to effectively determine a flow field by limited measurements. The assimilation experiment shows that the error defined by the difference between the reference and assimilated flow fields is reduced by using the sensitivity information to locate the limited number of measurement points. To conduct data assimilation for a long time period, the 4D-Var data assimilation and the sensitivity analysis are repeated with a short assimilation window.

Analyzing the Impact of X-Ray Tomography on the Reliability of Integrated Circuits

2015 ◽  
Author(s):  
Halit Dogan ◽  
Md Mahbub Alam ◽  
Navid Asadizanjani ◽  
Sina Shahbazmohamadi ◽  
Domenic Forte ◽  
...  
Keyword(s):  
Integrated Circuits ◽  
Integrated Circuit ◽  
3D Imaging ◽  
Three Dimensional ◽  
Serial Sectioning ◽  
Promising Technique ◽  
Flash Memories ◽  
X Ray ◽  
3D Information ◽  
The Impact

Abstract X-ray tomography is a promising technique that can provide micron level, internal structure, and three dimensional (3D) information of an integrated circuit (IC) component without the need for serial sectioning or decapsulation. This is especially useful for counterfeit IC detection as demonstrated by recent work. Although the components remain physically intact during tomography, the effect of radiation on the electrical functionality is not yet fully investigated. In this paper we analyze the impact of X-ray tomography on the reliability of ICs with different fabrication technologies. We perform a 3D imaging using an advanced X-ray machine on Intel flash memories, Macronix flash memories, Xilinx Spartan 3 and Spartan 6 FPGAs. Electrical functionalities are then tested in a systematic procedure after each round of tomography to estimate the impact of X-ray on Flash erase time, read margin, and program operation, and the frequencies of ring oscillators in the FPGAs. A major finding is that erase times for flash memories of older technology are significantly degraded when exposed to tomography, eventually resulting in failure. However, the flash and Xilinx FPGAs of newer technologies seem less sensitive to tomography, as only minor degradations are observed. Further, we did not identify permanent failures for any chips in the time needed to perform tomography for counterfeit detection (approximately 2 hours).

scholarly journals Robust Inferences from a Before-and-After Study with Multiple Unaffected Control Groups

2013 ◽  
Vol 1 (2) ◽  
pp. 209-234 ◽  
Author(s):  
Pengyuan Wang ◽  
Mikhail Traskin ◽  
Dylan S. Small
Keyword(s):  
Sensitivity Analysis ◽  
Control Groups ◽  
Two Stage ◽  
Time Effects ◽  
Unaffected Control ◽  
Group Time ◽  
Before And After ◽  
Group Variation ◽  
The Impact ◽  
Before And After Study

AbstractThe before-and-after study with multiple unaffected control groups is widely applied to study treatment effects. The current methods usually assume that the control groups’ differences between the before and after periods, i.e. the group time effects, follow a normal distribution. However, there is usually no strong a priori evidence for the normality assumption, and there are not enough control groups to check the assumption. We propose to use a flexible skew-t distribution family to model group time effects, and consider a range of plausible skew-t distributions. Based on the skew-t distribution assumption, we propose a robust-t method to guarantee nominal significance level under a wide range of skew-t distributions, and hence make the inference robust to misspecification of the distribution of group time effects. We also propose a two-stage approach, which has lower power compared to the robust-t method, but provides an opportunity to conduct sensitivity analysis. Hence, the overall method of analysis is to use the robust-t method to test for the overall hypothesized range of shapes of group variation; if the test fails to reject, use the two-stage method to conduct a sensitivity analysis to see if there is a subset of group variation parameters for which we can be confident that there is a treatment effect. We apply the proposed methods to two datasets. One dataset is from the Current Population Survey (CPS) to study the impact of the Mariel Boatlift on Miami unemployment rates between 1979 and 1982.The other dataset contains the student enrollment and grade repeating data in West Germany in the 1960s with which we study the impact of the short school year in 1966–1967 on grade repeating rates.

scholarly journals Numerical simulation of the impact of an integrated renovation project on the Maowei Sea hydrodynamic environment

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Cui Wang ◽  
Ling Cai ◽  
Yaojian Wu ◽  
Yurong Ouyang
Keyword(s):  
Water Exchange ◽  
Land Reclamation ◽  
Three Dimensional ◽  
Exchange Capacity ◽  
Reclamation Project ◽  
Hydrodynamic Environment ◽  
Sea Area ◽  
Water Quality Models ◽  
The Impact ◽  
Main Factor

AbstractIntegrated renovation projects are important for marine ecological environment protection. Three-dimensional hydrodynamics and water quality models are developed for the Maowei Sea to assess the hydrodynamic environment base on the MIKE3 software with high resolution meshes. The results showed that the flow velocity changed minimally after the project, decreasing by approximately 0.12 m/s in the east of the Maowei Sea area and increasing by approximately 0.01 m/s in the northeast of the Shajing Port. The decrease in tidal prism (~ 2.66 × 106 m3) was attributed to land reclamation, and accounted for just 0.86% of the pre-project level. The water exchange half-life increased by approximately 1 day, implying a slightly reduced water exchange capacity. Siltation occurred mainly in the reclamation and dredging areas, amounting to back-silting of approximately 2 cm/year. Reclamation project is the main factor causing the decrease of tidal volume and weakening the hydrodynamics in Maowei Sea. Adaptive management is necessary for such a comprehensive regulation project. According to the result, we suggest that reclamation works should strictly prohibit and dredging schemes should optimize in the subsequent regulation works.

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