Ice thickness,internal layers,and surface and subglacial topography in the vicinity of Chinese Antarctic Taishan station in Princess Elizabeth Land,East Antarctica

We present the results of two ground-based radio-echo-sounding（RES） and GPS surveys performed in the vicinity of new Chinese Taishan station,Princess Elizabeth Land,East Antarctica,obtained in two austral summers during CHINARE 21（2004/2005） and CHINARE 29（2012/2013）.The radar surveys measured ice thickness and internal layers using 60- and 150-MHz radar systems,and GPS measurements showed smooth surface slopes around the station with altitudes of 2607-2636 m above sea level（a.s.l.）.Radar profiles indicate an average ice thickness of 1900 m,with a maximum of 1949 m and a minimum of 1856 m,within a square area measuring approximately 2 km × 2 km in the vicinity of the station.The ice thickness beneath the station site is 1870 m.The subglacial landscape beneath the station is quiet sharp and ranges from 662 to 770 m a.s.l.,revealing part of a mountainous topography.The ice volume in the grid is estimated to be 7.6 km^3.Along a 60-MHz radar profile with a length of 17.6 km at the region covering the station site,some disturbed internal layers are identified and traced;the geometry of internal layers within the englacial stratigraphy may imply a complex depositional process in the area.

Internal layering structure and subglacial conditions along a traverse line from Zhongshan Station to Dome A,East Antarctica,revealed by ground-based radar sounding

During the 21st Chinese National Antarctic Research Expedition(CHINARE 21,2004/05),a radar dataset was collected using a ground-based radar system,along a traverse line from Zhongshan Station to DT401(130 km from the Kunlun station).The internal layering structure and subglacial conditions were revealed along the radar profi le.Continuous internal layers,disturbed layers,and echo-free zones(EFZs)along the profi le were identifi ed and classifi ed,and the spatial distribution was presented.Based on recent surface ice velocity data,we found that the internal layers at a depth of 200-300 m in the upper ice sheet are continuous,smooth,and nearly parallel to the ice surface topography.In addition,the thick band of continuous layers changes little with increasing latitude.At depths below 300 m,the geometric structure of the internal layers and the vertical width of the EFZ band are infl uenced by the surface ice velocity and bed topography.The relatively high disturbance,layer discontinuity,and larger EFZ band width directly correspond to a higher surface ice velocity and a sharper bed topography.In particular,we found that at a depth of 650-950 km,the Lambert Glacier Rift in the Gamburtsev Mountains has a higher ice fl ow;moreover,the revealed internal layers are disturbed or broken,and the maximal vertical width of the EFZ band most likely exceeds 2000 m.

A new image processing method for discriminating internal layers from radio echo sounding data of ice sheets via a combined robust principal component analysis and total variation approach

Discriminating internal layers by radio echo sounding is important in analyzing the thickness and ice deposits in the Antarctic ice sheet.The signal processing method of synthesis aperture radar(SAR)has been widely used for improving the signal to noise ratio(SNR)and discriminating internal layers by radio echo sounding data of ice sheets.This method is not efficient when we use edge detection operators to obtain accurate information of the layers,especially the ice-bed interface.This paper presents a new image processing method via a combined robust principal component analysis-total variation(RPCA-TV)approach for discriminating internal layers of ice sheets by radio echo sounding data.The RPCA-based method is adopted to project the high-dimensional observations to low-dimensional subspace structure to accelerate the operation of the TV-based method,which is used to discriminate the internal layers.The efficiency of the presented method has been tested on simulation data and the dataset of the Institute of Electronics,Chinese Academy of Sciences,collected during CHINARE 28.The results show that the new method is more efficient than the previous method in discriminating internal layers of ice sheets by radio echo sounding data.

Study on the Thermal internal Boundary Layer and Dispersion of Air Pollutant in Coastal Area by Numerical Simulation

In this paper, a scheme on a mesoscale dispersion modeling system was set up. The modeling system was used tostudy the turbulence structure of TIBL and dispersion features under shoreline tlimigation situation. The modelingsystem has successfully solved the problem of meteorological input of stochastic dispersion models and exploited anew approach to comprehensive application of this kind of dispersion models.

Structure of the internal isochronous layers at Dome A,East Antarctica

Dome A (Kunlun Station) is considered a likely place for finding an ice core record reaching back to one million years. The internal isochronous layering of the Antarctic Ice Sheet, revealed by ice radar, is a prerequisite for selecting sites for deep ice core drilling that can be used for studying the paleoclimatic record. In 2004/2005, during the 21st Chinese National Antarctic Research Expedition (CHINARE 21), a 200-km long, continuous radar profile was obtained across Dome A. The internal layers along the profile were derived from the stratigraphy detected by the radar. The morphology of the isochronous layers shows that: (1) The internal layers in the shallow ice sheet (0-500 m) are generally flat, with no more than 50 m of layer intervals, and have typical synclines and anticlines in some localized regions. (2) At 500-2000 m below the surface of the ice sheet, the layers appear as 'bright layers', and the width of the layer intervals expands to 50-100 m. (3) When the basal topographic wavelengths are approximate to the thickness of the ice (3 km), the traced internal layers, with localized bumps or concave folds, are asymptotic parallel to the subglacial topography. For the longer topographic wavelengths (~20 km) wider than the thickness of the ice, the layers do not rise and fall with the basal topography. The internal layers surrounding some mountain peaks representing the most extreme variation in the terrain are sharply disturbed by the subglacial topography. (4) Layer discontinuity and fracture were detected in the basal ice sheet. Finally, by combining this new information with that derived from existing data regarding ice thickness, we were able to select three potential sites for reconstructing the age-depth relationship of the ice core.

Thermal internal boundary layer and its effects on air pollutants during summer in a coastal city in North China

The thermal internal boundary layer（TIBL） is associated with coastal pollution dispersion,which can result in high concentrations of air pollutants near the surface of the Earth. In this study, boundary layer height data which were obtained using a ceilometer were used to assess the effect of the TIBL on atmospheric pollutants in Qinhuangdao, a coastal city in North China.A TIBL formed on 33% of summer days. When a TIBL formed, the sunshine duration was 2.4 hr longer, the wind speed was higher, the wind direction reflected a typical sea breeze, and the boundary layer height was lower from 9：00 LT to 20：00 LT compared to days without a TIBL. If no TIBL formed, the average concentrations of PM2.5 and PM10 decreased with increasing boundary layer height. However, when a TIBL was observed, the average concentrations of PM2.5 and PM10 increased with increasing boundary layer height. Because the air from the sea is clean, PM2.5 and PM10 concentrations reached minimums in the daytime at 16：00 LT. After16：00 LT, the PM2.5 and PM10 concentrations increased rapidly on days when a TIBL formed,which indicated that the TIBL leads to the rapid accumulation of atmospheric pollutants in the evening. Therefore, the maximum concentrations of particulate matters were larger when a TIBL formed compared to when no TIBL was present during the night. These results indicate that it is suitable for outdoor activities in the daytime on days with a TIBL in coastal cities.

Spectra and Cospectra of Turbulence in an Internal Boundary Layer over a Heterogeneously Irrigated Cotton Field

During the Energy Balance Experiment, patch-to-patch irrigation generated gradients in soil moisture in a north-south oriented cotton field. An internal boundary layer （IBL） developed as a result of strong horizontal advection from relatively dry upstream patches to relatively wet downstream patches associated with the prevailing northerly winds. This generated large eddies of multiple sizes, which had significant influences on the structure of turbulence in the IBL. The power spectra and cospectra of wind speed, temperature, humidity, and energy fluxes measured at two heights within the IBL are presented and used to investigate the influence of the IBL on surface layer turbulence. The spectra and cospectra were greatly enhanced by external disturbances at low frequencies. The peak frequencies of these disturbances did not change with height. The spectra and cospectra typically converged and were parallel to the Kansas spectrum at high frequencies （in the inertial subrange）. A clear gap in the spectra of horizontal wind velocity existed at intermediate frequencies when the surface layer was stable. The re^sults indicate that large eddies that originated in the upstream convective boundary layer had considerable impacts on the spectra and cospectra of surface layer turbulence. The influence of these large eddies was greater （1） when the IBL was well-developed in the near surface layer than when the IBL did not exist, （2） at higher levels than at lower levels, and （3） when the atmospheric surface layer （ASL） was unstable than when the ASL was stable. The length scales of these large eddies were consistent with the dominant scales of surface heterogeneity at the experiment site.

Relation between oxidation microstructure and the maximum energy product loss of a Sm_2Co_(17) magnet oxidized at 500℃

The oxidation microstructure and maximum energy product （BH）max loss of a 8m（Co0.76, Fe0.1, Cu0.1, Zr0.04）7 magnet oxidized at 500 ℃ were systematically investigated. Three different oxidation regions were formed in the oxidized magnet： a continuous externM oxide scale, an internal reaction layer, and a diffusion zone. Both room-temperature and high-temperature （BH）max losses exhibited the same parabolic increase with oxidation time. An oxygen diffusion model was proposed to simulate the dependence of （BH）max loss on oxidation time. It is found that the external oxide scale has little effect on the （BH）max loss, and both the internal reaction layer and diffusion zone result in the （BH）max loss. Moreover, the diffusion zone leads to more （BH）max loss than the internal reaction layer. The values of the oxidation rate constant k for internal reaction layer and oxygen diffusion coefficient D for diffusion zone were obtained, which are about 1.91×10^-10 cm^2/s and 6.54×10^-11 cm^2/s, respectively.

A dynamic two-zone model of continuous fluidized bed layering granulation with internal product classification

A dynamic two-zone model is proposed to address the formation of granulation and drying zones in fluidized bed layering granulation processes with internal product classification. The model assumes a constant volume for the granulation zone, but a variable overall volume for the fluidized bed to account for classified product removal. The model is used to study the effect of various process parameters on dynamics and process stability. Stability is shown to depend on the separation diameter of product removal and the flow rate of the injected liquid. A lower and upper range of separation diameters with stable process behavior are found. In an intermediate range instability in the form of self-sustained oscillations is observed. The lower stability boundary is in qualitative agreement with recent experimental observations （Schmidt, Bück, ＆ Tsotsas, 2015）; the upper boundary was reported in a theoretical paper by Vreman, Van Lare, and Hounslow （2009） based on a single zone model.

INFLUENCES OF NONSTATIONARY PROCESS ON INTERNAL PARAMETERS AND WIND PROFILES IN THE PLANETARY BOUNDARY LAYER

In this paper,under the assumption of neutral and barotropic atmosphere,by means of the analytic solution of motion equation of PBL,the influences of nonstationary process on the internal parameters u_*/A(A is the wind speed at the top of PBL)and ■(the angle between winds near the surface and at the top of PBL)of PBL are investigated in which the wind direction at the top of PBL is a periodic function of time but the wind speed at the top of PBL does not change.The u_*/A increases and ■ decreases when the wind direction at the top of PBL rotates anticlockwise and vice versa.Hence the parameterization of PBL in the large-scale models derived under the stationary condition should be corrected by accounting for the nonstationary process.The similar results are obtained in the numerical solution of the motion equation of PBL.The influences of this nonstationary process on the profiles of the wind in PBL are also analyzed.

Asymptotics of the Solution to a Stationary Piecewise-Smooth Reaction-Diffusion-Advection Equation

A singularly perturbed boundary value problem for a piecewise-smooth nonlinear stationary equation of reaction-diffusion-advection type is studied.A new class of problems in the case when the discontinuous curve which separates the domain is monotone with respect to the time variable is considered.The existence of a smooth solution with an internal layer appearing in the neighborhood of some point on the discontinuous curve is studied.An efficient algorithm for constructing the point itself and an asymptotic representation of arbitrary-order accuracy to the solution is proposed.For sufficiently small parameter values,the existence theorem is proved by the technique of matching asymptotic expansions.An example is given to show the effectiveness of their method.

On higher-dimensional contrast structure of singularly perturbed Dirichlet problem

In this paper,we address the existence and asymptotic analysis of higher-dimensional contrast structure of singularly perturbed Dirichlet problem.Based on the existence,an asymptotical analysis of a steplike contrast structure (i.e.,an internal transition layer solution) is studied by the boundary function method via a proposed smooth connection.In the framework of this paper,we propose a first integral condition,under which the existence of a heteroclinic orbit connecting two equilibrium points is ensured in a higher-dimensional fast phase space.Then,the step-like contrast structure is constructed,and the internal transition time is determined.Meanwhile,the uniformly valid asymptotical expansion of such an available step-like contrast structure is obtained.Finally,an example is presented to illustrate the result.

Asymptotics of the solution to a stationary piecewise-smooth reaction-diffusion equation with a multiple root of the degenerate equation

A piecewise-smooth second-order singularly perturbed differential equation whose right-hand side is a nonlinear function with a discontinuity on some curve is investigated. This is a new class of problems in the case where the degenerate equation has a multiple root on the left-hand side of the curve which separates the domain and an isolated root on the right-hand side of that curve. The asymptotics of a solution with an internal layer near a point on the discontinuous curve and the transition point is constructed. The method to construct the internal layer function is proposed. The behavior of the solution in the internal layer consisting of four zones essentially differs from the case of isolated roots. For sufficiently small parameter values, the existence of a smooth solution with an internal layer from the multiple root of the degenerate equation to the isolated root in the neighborhood of a point on the discontinuous curve is proved. The method can be shown to be effective in the given example.

A Sub-Grid Structure Enhanced Discontinuous Galerkin Method for Multiscale Diffusion and Convection-Diffusion Problems

In this paper,we present an efficient computational methodology for diffusion and convection-diffusion problems in highly heterogeneous media as well as convection-dominated diffusion problem.It is well known that the numerical computation for these problems requires a significant amount of computermemory and time.Nevertheless,the solutions to these problems typically contain a coarse component,which is usually the quantity of interest and can be represented with a small number of degrees of freedom.There are many methods that aim at the computation of the coarse component without resolving the full details of the solution.Our proposed method falls into the framework of interior penalty discontinuous Galerkin method,which is proved to be an effective and accurate class of methods for numerical solutions of partial differential equations.A distinctive feature of our method is that the solution space contains two components,namely a coarse space that gives a polynomial approximation to the coarse component in the traditional way and a multiscale space which contains sub-grid structures of the solution and is essential to the computation of the coarse component.In addition,stability of the method is proved.The numerical results indicate that the method can accurately capture the coarse behavior of the solution for problems in highly heterogeneous media as well as boundary and internal layers for convection-dominated problems.