Surface Layer Model Research Articles

Forecasting High Wind Events in the HRRR Model over Wyoming and Colorado. Part II: Sensitivity of Surface Wind Speeds to Model Resolution and Physics

Abstract Strong wind events can cause severe economic loss and societal impacts. Peak winds over Wyoming and Colorado occur during the wintertime months, and in the first part of this two-part series, it was shown that the High-Resolution Rapid Refresh (HRRR) model displays large negative biases with respect to strong wind events. In this part of the study, we address two questions: 1) does increasing the horizontal resolution improve the representation of strong wind events over this region, and 2) are the biases in HRRR-forecasted winds related to the selected planetary boundary layer (PBL), surface layer (SL), and/or land surface model (LSM) parameterizations? We conduct Weather Research and Forecasting (WRF) Model simulations to address these two main questions. Increasing the horizontal resolution leads to a small improvement in the simulation of strong wind speeds over the complex terrain of Wyoming and Colorado. In general, changes in the PBL, SL, and LSM parameterizations show much larger changes in simulated wind speeds compared to increasing the model resolution alone. Specifically, changing from the Mellor–Yamada–Nakanishi–Niino scheme to the Mellor–Yamada–Janjić PBL and SL schemes results in nearly no change in the r2 values, but there is a decrease in the magnitude of the strong wind speed bias (from −12.52 to −10.16 m s−1). We attribute these differences to differences in the diagnosis of surface wind speeds and mixing in the boundary layer. Further analysis is conducted to determine the value of 1-km forecasts of strong winds compared with wind speed diagnostics commonly used by the National Weather Service. Significance Statement Motivated by prior studies showing low skill in the prediction of strong winds using state-of-the-art weather forecast models, in this study, we aim to investigate two questions: 1) does increasing the horizontal resolution improve the prediction of strong wind events over the complex terrain of Wyoming and Colorado, and 2) are the biases in High-Resolution Rapid Refresh (HRRR) forecasted winds related to the selected planetary boundary layer, surface layer, and/or land surface model parameterizations? We find that increasing the horizontal resolution provides a slight improvement in the prediction of strong winds. Further, considerable improvement in the prediction of strong winds is found for varying boundary layer, surface layer, and land surface parameterizations.

Cascade sensitivity tests to model deep convective systems in complex orography with WRF

The goal of the present study is to improve the analysis of the performance of the Weather Research and Forecasting (WRF) model, Version 4.3.3, under different settings, in the prediction of precipitation in case of deep convective events. This is done through a wide cascade sensitivity test involving parameterizations expected to play a major role in the description of precipitation for deep convective events: cloud microphysics (CM), planetary boundary layer (PBL), surface layer (SL) and land-surface (L-S) model. Four significant precipitation events, which were associated to deep convective systems and occurred between 2019 and 2021 in Lombardia and Liguria regions (Northern Italy), have been simulated according to 45 different WRF settings. High resolution simulations are required when dealing with small scale deep convective systems as well as a suitable verification method. So, traditional statistical indexes have been integrated with new-generation verification methods, based on the identification of precipitation patterns in forecast and observed fields and on the evaluation of their similarity through the calculation of a coupling index. This analysis method has been exploited to evaluate the quality of the high-resolution simulations performed, and to individuate the best-performing WRF setting in simulating intense convective events. From the present work emerges how the unique CM parameterization characterized by a triple-moment treatment for cloud ice significantly outperforms all other CM schemes underlying the main role of cloud ice in the description of the precipitation case studies. Furthermore, PBL and L-S schemes show a leading role, at least as much as CM, in the description of the events.

Numerical investigation into hydrodynamic behavior of graded aggregates of high-speed ballastless track considering the degree of saturation

The ballastless track inevitably suffers from some functional defects, such as expansion joint cracking, due to the long term combined effect of dynamic train loads and environmental factors. As a result, water can be somehow retained in the graded aggregates of the roadbed surface layer under ballastless track, which is a key structural component subject to high-speed train loads. Accordingly, it is of significance to study the hydrodynamic behavior of roadbed surface layer that can be prone to depend on variation of the degree of saturation (Sr) in graded aggregates. A coupled hydrodynamic model of roadbed surface layer under ballastless track subject to high speed train loads was established based on homogenization theory and elastic wave theory involving Sr of graded aggregates. The proposed model is validated by degrading to Biot's dynamic model in saturated porous medium and analytical method of unsaturated soil. The effect of different Sr on the pore fluid pressure, spatial seepage velocity of graded aggregates is investigated based on this model with the practical seepage boundaries in ballastless track considered. On this basis, the influence of different spatial locations on the dynamic seepage index is discussed, and the differences in the stress paths in the roadbed surface layer under different Sr at different depths are analysed. The numerical results show that the increase of Sr has a spatial and critical effect on the increase of pore water pressure and seepage velocity in the roadbed surface layer. When the expansion joint of ballastless track cracks, the hydrodynamic erosion in the surface layer of ballastless track roadbed has been accumulating continuously. The erosion is more serious within the depth of 15 cm under the surface of roadbed. For Sr above 0.7, extra attention should be given to prevent internal erosion diseases in the roadbed surface layer during maintenance of ballastless track.

Modification of the surface layer model and establishment of the surface layer thickness model of pure copper

The size effect of flow stress is one of the main factors affecting the deformation behavior of materials in microforming. The traditional surface layer model can well explain the phenomenon that the material flow stress decreases with the declining size of the specimen at sub-millimeter and micron scales, while it also exhibits some deficiencies inconsistent with reality. In order to more accurately describe the deformation behavior of materials at the microscale, the modified surface layer model was proposed based on the experimental results and plastic forming theory, in which the region where the flow stress was lower than that of the internal polycrystalline rather than just a single layer of grains in the surface region was taken as the surface layer. The calculation method of the thickness of the surface layer and the stress in each region was also presented. According to the stress distribution in each region, a surface-layer-thickness model based on grain size was proposed. With the results of micro upsetting experiments, the surface-layer-thickness model of T2 copper was fitted. It was validated that the modified-surface-layer model and surface-layer-thickness model can accurately predict the flow stress of the material at the microscale.

Atomistic and continuum modeling of nanoparticles: Elastic fields, surface constants, and effective stiffness

The elastic fields, surface constants and effective elastic moduli of nanoparticles are studied by means of classical molecular dynamics and continuum mechanics. Two analytical models of isotropic nanoparticles are considered. The first model is a sphere coated with a thin surface layer, which simulates the effect of the free surface energy in the nanoparticle. In the second model, the surface effect is taken into account by applying the boundary conditions in accordance with the Gurtin–Murdoch theory of material surfaces. The effective elastic moduli of nanoparticles are evaluated using the general and consistent from the micromechanical viewpoint surface averaging scheme. The geometric and material parameters of the continuum models are found by fitting the MD data for nanoparticles of three monocrystalline solids with diverse atomic mass, lattice type, and elastic moduli. It is shown that the properly calibrated analytical models correctly predict the size effect of surface free energy on the lattice contraction, residual stress, surface constants, and the elastic stiffness of nanoparticles. Applicability of the developed continuum models to the faceted nanocrystals is discussed. Comparison of the atomistic and continuum models of nanoparticles yields a simple and robust method for evaluating the surface constants. The parametric and asymptotic study of these models is performed. The established analytical relationships between the parameters of the continuum models facilitate using the surface layer model in the numerical simulation of nanostructures.

Influence of nano-sized horizontal inhomogeneities on surface profiling by means of XPS

Quantitative analysis of thin films surface is performed by means of X-ray electron spectroscopy (XPS) according to a calculation model assuming surface layers of the target to be homogeneous and parallel. However, almost every surface of an ultra-thin film is rough. A study of such surface using the plane-parallel layer model will lead to incorrect results. This work proposes to use the model of inhomogeneous stochastic nano-structured surface layer for ultra-thin film profiling. Surface stochastic nano-structured inhomogeneities are described by the normal Gauss distribution function. To determine these inhomogeneities, three parameters are specified: dispersion (spread of thicknesses by the layer), mean and maximal thickness of the surface layer. For the first time, the type of X-ray photoelectron spectrum of an inhomogeneous stochastic nano-structured surface is found that is determined by functions of photoelectron production and transmission through that surface layer. The designed model is based on the following assumptions: photoelectrons are produced in substance and travel straight-forward (Straight Line Approximation) along the surface, photoelectron flux density decreases in the layer according to the Bouguer–Lambert law, photoelectrons of different energies lose energy differently, photoelectron energy losses in bulk and on surface differ. Modeling of X-ray photoelectron spectra of an oxidized metal film is performed using different models: homogeneous plane-parallel layers, an island nano-structured surface layer and an inhomogeneous stochastic nano-structured surface layer. Ranges of applicability of plane-parallel layer models and simple periodical nano-structured island surface layer for inhomogeneous stochastic nano-structured surface profiling are determined. The model of homogeneous plane-parallel layers shows satisfactory profiling results by some values of parameters of an inhomogeneous stochastic surface layer. It is shown that the model of a simple periodically nano-structured island layer leads to inadequate results by profiling of an inhomogeneous stochastic surface. The investigation shows that for more accurate profiling of an inhomogeneous ultra-thin film, it is necessary to consider inhomogeneity of a real surface, otherwise the calculated results would not match the true profile.

Verification of PCSWMM's LID processes and their scalability over time and space

IntroductionThis paper explores the scalability of PCSWMM's Low Impact Development (LID) modeling tools within the urban stormwater computer model.MethodsThe scalability is assessed for a variety of spatial and temporal scales and for event (50-year return storm) and continuous inputs (daily rainfall for an 11 month period), and with a focus on bioretention cells. The model is calibrated for a moderate to large scale, semi-urban watershed on Vancouver Island, British Columbia, Canada. Sensitivity analysis and specialized metrics are used to verify internal model processes at a variety of scales.ResultsWith regard to spatial scaling, changes in flow path length and slope derived from Digital Elevation Models were the most impactful spatial information when modeling flood event and the model's surface layer was the dominant contributor to peak flowrate and volume mitigation by the bioretention cell. However, when modeling the continuous rainfall inputs, storage layer related parameters dominated model outputs. Aside from the soil layer's depth, soil layer parameters such as hydraulic conductivity, showed negligible influence on response to time series rainfall. Parameters that are kept static by the model such as vegetation cover, hydraulic conductivity and storage void ratio (but are naturally dynamic), were tested for their impact on response if allowed to change seasonally or with excessive loading. Runoff coefficients were greatly impacted by storage layer parameter dynamics with very little impact from vegetation. For event simulations, the berm height in the surface layer was the dominant player in reducing peak flow as well as total volume. An analysis to help illustrate sensitivity across spatial scales is proposed.DiscussionThe Spatial Dynamic Sensitivity Analysis shows that parameter sensitivity changes dynamically as LID implementation percentage changes. In particular, the clogging factor, which is a parameter associated with the storage layer, was highly influential for time series rainfall analysis. The LID model concepts in PCSWM seem appropriate for events because the surface layer dominates the response for very large storms. For smaller storms, continuous time series, and larger spatial scales, the model could be revised to better represent soil layer dynamics and vegetation cover, which were both currently inconsequential to the model's output.

Understanding Evaporation Duct Variabilities on Turbulent Eddy Scales

AbstractEvaporative Ducts (ED) are common refractive features that exist due to the persistent/strong vertical moisture gradient inherent to the lowest 10s of meters of the marine atmospheric surface layer (MASL). The ED plays a large role in the propagation of signals from the surface‐ or ship‐based radar/communications systems due to the ducting of electromagnetic (EM) waves. Previous studies have characterized ED structure using mesoscale and surface layer models which are based on the Monin‐Obukhov similarity theory. As a result, only the spatially/temporally averaged mean ED structure has been examined. Conversely, this study focuses on ED variability occurring over turbulent energy‐containing eddy scales by utilizing large‐eddy simulations (LES) of the MASL. This innovative approach reveals that the LES‐resolved refractivity perturbations are directly linked to MASL large eddy dynamic and thermodynamic processes. In the thermally unstable MASL, significant turbulent ED variability is noted, with regions of increased ED heights associated with convective updrafts and positive moisture perturbations. In contrast, the thermally stable MASL is shown to exhibit significantly less ED variability over the LES domain. Since current surface layer models have difficulties in calculating ED properties in the thermally stable MASL, utilization of LES is helpful to gain an understanding of the ED in these conditions. A conceptual model of turbulent ED variation is proposed to describe the relationship between MASL dynamics/thermodynamic processes, state variable perturbations, and refractive variations.

МОДЕЛИРОВАНИЕ ЭЛЕКТРОДИНАМИЧЕСКОЙ СТРУКТУРЫ НЕТУРБУЛЕНТНОГО ПРИЗЕМНОГО СЛОЯ

The article presents an electrodynamic model of the atmospheric surface layer caused bythe action of the electrode effect near the earth's surface, and an analysis of its equations by methodsof similarity theory. Mathematical models of the surface layer electrical state in the approximationsof the classical and turbulent electrode effect are considered separately. In the mathematicalformulation of modeling problems, a number of well-founded physical assumptions were createdthat made it possible to obtain analytical solutions to the equations. Analytical formulas havebeen obtained for calculating the profiles of aeroion concentrations, the density of the space electriccharge and the electric field in the electrode layer. As a result of mathematical modeling, thedependences of the electrical characteristics distribution in the surface layer on the values of theelectric field, the degree of air ionization and aerosol pollution of the atmosphere are investigated.It is shown that the ratio of the electric field values on the earth's surface and at the upper boundaryof the electrode layer is almost constant. The increasing of the electric field, the rate of airionization and the presence of sufficient concentration aerosol particles leads to a decrease in thethickness of the electrode layer and, as a consequence, the scale of distribution of its parameters.An amplification in the degree of ionization increases, and an increase in the concentration ofaerosol particles in the atmosphere decreases the values of the electric charge density in the surfacelayer. Theoretical calculations are in good agreement with experimental data and the resultsof numerical modeling of the surface layer electrical structure. The analytical formulas obtainedin the work for calculating the electrical characteristics of the surface layer and the results ofcalculations can be useful in solving a number of applied problems of geophysics, in particular formonitoring the electrical state of the atmosphere.

A Time-Varying Model for Predicting Formaldehyde Emission Rates in Homes.

Recent studies have succeeded in relating emissions of various volatile organic compounds to material mass diffusion transfer using detailed empirical characteristics of each of the individual emitting materials. While significant, the resulting models are often scenario specific and/or require a host of individual component parameters to estimate emission rates. This study developed an approach to estimate aggregated emissions rates based on a wide number of field measurements. We used a multi-parameter regression model based on previous mass transfer models to predict formaldehyde emission rate for a whole dwelling using field-measured, time-resolved formaldehyde concentrations, air exchange rates, and indoor environmental parameters in 63 California single-family houses built between 2011 and 2017. The resulting model provides time-varying formaldehyde emission rates, normalized by floor area, for each study home, assuming a well-mixed mass balance transport model of the home, and a well-mixed layer transport model of indoor surfaces. The surface layer model asserts an equilibrium concentration within the surface layer of the emitted materials that is a function of temperature and RH; the dwelling ventilation rate serves as a surrogate for indoor concentration. We also developed a more generic emission model that is suitable for broad prediction of emission for a population of buildings. This model is also based on measurements aggregated from 27 homes from the same study. We showed that errors in predicting household formaldehyde concentrations using this approach were substantially less than those using a traditional constant emission rate model, despite requiring less unique building information.

Optical turbulence measurements and modeling over Monterey Bay

Free space optical (FSO) communication in a maritime environment involves unique challenges due to the existing environmental conditions. An important degradation factor is atmospheric turbulence that causes irradiance fluctuations (scintillation) at the detector. A significant amount of theoretical and experimental research has been conducted to quantify those effects. This paper presents the results of an experimental campaign that took place during September and October of 2020 over the Monterey Bay in California. The main goal of this campaign was to measure atmospheric turbulence over the water and compare the results with a theoretical model called the Navy Surface Layer Model (NAVSLaM), developed by the Meteorology Department at the Naval Postgraduate School (NPS), as well as conduct a regression analysis for turbulence predictive modeling based on environmental parameters. The results showed very good agreement between theory and experiment.

Measurements and Modeling of Optical Turbulence in the Coastal Environment

The goal of this study was to characterize optical turbulence in the near-coastal environment. Measurements to obtain the refractive index structure parameter and other meteorological data were taken over the course of a month along the shore of Monterey Bay. The results were compared to a new version of the Navy Vertical Surface Layer Model (NAVSLaM), a model of turbulence originally developed for maritime environments but now extended to terrestrial environments. The new version has not been previously validated by comparisons to experiments, particularly in a complex environment such as near the coastline. Our experimental results showed generally good agreement between measured and modeled levels of turbulence. Specifically, the differences between experimental and modeled values of the refractive index structure parameter were less than an order of magnitude in most conditions and followed the same diurnal trend. There were some greater differences during near-neutral conditions, but this is a known limitation of the model. Overall, this extended model appears to do a good job of predicting turbulence in this environment for the observed time period.

The regionalized modelling and simulation of the micro-tensile process based on 3D Voronoi model

In this work, a regionalized constitutive model based on the surface layer model and intragranular heterogeneities was established. The crystal plasticity simulations of the micro-tensile processes were implemented based on 3D Voronoi model. By applying the proposed constitutive model and the 3D polycrystalline structure, the micro-tensile tests of pure copper were numerically simulated by finite element methods. Through the combination of constitutive model and crystal plasticity finite element simulations, the flow stress-strain curves under different grain sizes and orientations were obtained. Thus, to verify the proposed model, a set of micro-tensile tests of pure copper were carried out to investigate the size effect of deformation behavior. It is found that the simulation results are in good agreement with the experimental results, which confirmed the accuracy of the established regionalized constitutive model and the 3D polycrystalline geometric model. The modeling method proposed in this paper opens new avenues for further insights of the size effect in micro-forming process.

The Influence of Size Effect to Deformation Mechanism of C5131 Bronze Structures of Negative Poisson’s Ratio

3D auxetic structures, which present negative Poisson’s ratio in the uniaxial compression deformation, is an ideal artificial material for meta-implants because of its lightweight, good material property and suitable porosity for bone recovery compared with conventional meta-biomaterials. Selective laser melting (SLM) is commonly used to produce metallic 3D auxetic structures but limited by the melting temperature and reflect rate of the material, and micro assembled (MA) structures is an alternative manufacturing process. However, the influence of size effect in 3D auxetic structures and the difference of the constitutive model of 3D auxetic structure produced by SLM and MA have not been discussed. In tandem of this, the mechanical property comparison of 3D auxetic structures produced by SLM and MA is conducted and a structural surface layer model for 3D auxetic structures is proposed. The result indicated that both SLM and MA structure can achieve auxetic effect. It is found that the Poisson’s ratio of the SLM and MA structures decrease when increasing the size factor of the structure, and the negative Poisson’s ratio effect is more obvious when the Young’s modulus is relatively small. FE simulation result of Poisson’s ratio is closer to experimental result of MA structures due to complexity of 3D auxetic structures. This paper thus provides a relatively helpful constitutive model for the prediction of the mechanical behavior of 3D auxetic structure.

Study of the Surface Layer Model in Microforming and its Modification

Study of the Surface Layer Model in Microforming and its Modification

Mechanism and formability of micro-heading of metal rod by laser dynamic loading

Heading forming can produce special-shaped micro-shafts and serve as the basis of complex parts. This paper proposes a new method of micro-heading of metal rod by laser dynamic loading (MHLDL). The forming process, stress wave propagation and metal flow law of MHLDL, the characteristics of forming section, and the influence of laser energy and grain size on forming size are studied combined with numerical simulation and experiment. Results confirm the feasibility of using MHLDL to prepare micro-heading forming parts. The plastic deformation of the metal inside the workpiece is related to stress wave propagation and its own inertia. The metal on the top of the workpiece can flow freely to the surroundings. When the deformation of the heading is small, the heading shows a mushroom shape with thick top and thin bottom due to the stress wave and inertia effects on high-speed forming. When the heading deformation gradually increases, the friction effect becomes dominant, and the heading assumes a drum shape with equal up and down diameters. These two regular appearances prove that MHLDL can produce a uniform metal flow and improve the forming performance of the material. The forming size of the heading increases with the laser energy, but at a slow rate. The forming size of the heading increases with the increase of the workpiece grain size, which can be explained by the dislocation packing theory and the surface layer model.

Reanalyses and a High-Resolution Model Fail to Capture the “High Tail” of CAPE Distributions

AbstractConvective available potential energy (CAPE) is of strong interest in climate modeling because of its role in both severe weather and in model construction. Extreme levels of CAPE (>2000 J kg−1) are associated with high-impact weather events, and CAPE is widely used in convective parameterizations to help determine the strength and timing of convection. However, to date few studies have systematically evaluated CAPE biases in models in a climatological context, and none have addressed bias in the high tail of CAPE distributions. This work compares CAPE distributions in ~200 000 summertime proximity soundings from four sources: the observational radiosonde network [Integrated Global Radiosonde Archive (IGRA)], 0.125° reanalyses (ERA-Interim and ERA5), and a 4-km convection-permitting regional WRF simulation driven by ERA-Interim. Both reanalyses and the WRF Model consistently show too-narrow distributions of CAPE, with the high tail (>90th percentile) systematically biased low by up to 10% in surface-based CAPE and even more in alternate CAPE definitions. This “missing tail” corresponds to the most impacts-relevant conditions. CAPE bias in all datasets is driven by surface temperature and humidity: reanalyses and the WRF Model underpredict observed cases of extreme heat and moisture. These results suggest that reducing inaccuracies in land surface and boundary layer models is critical for accurately reproducing CAPE.

On the utilization of Sachs model in modeling deformation of surface grains for micro/meso scale deformation processes

Finite element method simulations have become a crucial tool in conventional metal forming process design. Microforming, which is a technology for the production of miniature parts by metal forming, is a potential process for mass production of microcomponents. However, to use finite element analysis in the design of microforming processes, material models that take into account size effects are needed. In this research, the surface layer model and the Hall-Petch relationship are combined to model materials deformation at the meso/micro-scale. Sachs model is used to model the deformation of surface grains. To validate this newly developed materials model, scaled-down compression tests were conducted, and a good agreement between predicted and experimental flow curves was obtained. In addition, the model was used to predict the experimental results of previous research for three other materials, as well. Again, a good agreement between the predicted and experimental results was obtained. Thus, the model showed a satisfactory capability to predict flow curves for different specimen size and grain size combinations for different materials. To further verify the materials model, micro-extrusion experiments were also performed. Simulations of the micro-extrusion experiments were carried out by implementing the newly developed materials model. A reasonable agreement between the experimental and predicted micro-extrusion results was found, which validates the utilization of the newly developed material model in microforming process simulations.

Effects of stacking fault energy and reduction ratio on mechanical properties geometry size effect of cold-rolled pure Cu and CuAl alloy

With the trend of increasing product miniaturisation, it has become necessary to consider the service performances of microparts. If the material exhibits the ‘smaller is stronger’ geometry size effect (GSE), the mechanical properties data of conventional dimension specimens can be used to design the microparts, obtaining improved service safety of the microparts. The surface layer model shows that when the exterior mechanical properties of material are higher than these of the interior, the ‘smaller is stronger’ GSE can be obtained. Stacking fault energy (SFE) and reduction ratio (RR) have been reported to affect the distribution of mechanical properties along the thickness direction of a rolled material, so that they are expected to affect the GSE of rolled sheets. Therefore, the tensile mechanical properties of different SFE Cu-Al alloys cold rolled at different RR were examined in this work. The average grain size of the surface layer of the rolled specimens was smaller than that of the interior, whereas the average strain and microhardness of the surface layer were larger than those of the interior. The difference in the strain between the exterior and interior of the specimen was found to decrease with the specimen thickness t, and increases with RR and SFE. The ‘smaller is stronger’ GSE trend was found in pure Cu and CuAl alloy rolled at 30 –50% RR, while GSE changed to ‘smaller is weaker’ at RR = 70%. The magnitude of the GSE of the rolled specimens increased with increasing RR and SFE, resulting from the effects of RR and SFE on the microstructure, microhardness and strain distribution. New models for the relationship between the strengths and t and SFE were established for three RRs. The results predicted by the models were in good agreement with the experimental values.

A multiscale constitutive model coupled with martensitic transformation kinetics for micro-scaled plastic deformation of metastable metal foils

The mechanical behavior of metastable austenitic foils at the size scale from micron to submillimeter is strongly affected by the coupling between size effect and strain-induced martensitic transformation (SIMT), which remains to be a pressing issue to be explored. In this research, the focus is on developing a multiscale constitutive model to reveal the mechanical behavior of metastable foils and more accurately predict the size effect on SIMT. In tandem with this, the martensitic transformation and hardening behavior of SUS304 foils with different thicknesses and grain sizes were explored. The results figured out that the SIMT is promoted by the increase in grain size and foil thickness. Furthermore, the onset and end of stages II of work-hardening behavior are advanced and the work-hardening rate in stage II increases faster with increasing grain size and foil thickness. The SIMT kinetic model was coupled with the intermediate mixture law and the iso-work hypothesis to identify the stress-strain relationship of individual austenite and martensite at the surface and interior layers, which was used to construct the multiscale constitutive model. The multiscale model was developed based on the framework of the surface layer model and the intermediate mixture law to represent the coupling between the size effect and the SIMT. Through finite element simulation by using the proposed multiscale constitutive model, the dispersion hardening mechanism in micro-scaled deformation of metastable austenitic foils caused by the non-homogeneous plastic deformation at the interface between austenite and martensite was revealed. The multiscale model was validated via the corroboration of finite element simulation with experiments and therefore can provide a robust analysis of the micro-scaled deformation behavior of metastable austenitic foils.