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Construction of high-order difference schemes based on Taylor series expansion has long been a hot topic in computational mathematics, while its application in comprehensive weather models is still very rare. Here, the properties of high-order finite difference schemes are studied based on idealized numerical testing, for the purpose of their application in the Global/Regional Assimilation and Prediction System (GRAPES) model. It is found that the pros and cons due to grid staggering choices diminish with higher-order schemes based on linearized analysis of the one-dimensional gravity wave equation. The improvement of higher-order difference schemes is still obvious for the mesh with smooth varied grid distance. The results of discontinuous square wave testing also exhibits the superiority of high-order schemes. For a model grid with severe non-uniformity and non-orthogonality, the advantage of high-order difference schemes is inapparent, as shown by the results of two-dimensional idealized advection tests under a terrain-following coordinate. In addition, the increase in computational expense caused by high-order schemes can be avoided by the precondition technique used in the GRAPES model. In general, a high-order finite difference scheme is a preferable choice for the tropical regional GRAPES model with a quasi-uniform and quasi-orthogonal grid mesh.

Titanium and its alloys are widely used in orthopedic implant surgery due to their good mechanical properties and biocompatibility. Recent studies have shown that the healing process of fractures involve not only the calcification of osteoblasts but also the regulation of the immune system. The functionalization of titanium surface coatings is one of the most important methods for solving implant failures. In this study, monetite (CaHPO4) was coated on the Ti-6Al-4V porous scaffold by hydrothermal method. SEM, XRD and EDS were used to characterize the morphology, phase constitutes, elemental content of the coating, respectively. The results indicated that a well bonded and uniformly distributed monetite coating obtained, and the degradation performance and Ca2+release of the surface coating were also studied. In terms of biology, live/dead staining and CCK8 methods showed the coating had good biocompatibility and BMSCs can adhere and proliferate on the surface. Flow cytometry and ELISA indicated that the surface monetite-coating had good anti-inflammatory properties. Through RNA-seq analysis, it was shown in KEGG that the osteoclast-related pathway was inhibited. In vitro, monetite induced osteogenic gene expression in BMSCs and inhibited the activity of osteoclasts. In vivo experiments showed that the monetite-coating increased bone formation. In summary, monetite-coating can effectively promote the osteogenesis in BMSCs, which may be achieved through bone immune regulation.

Beijing often suffers under heavy smog. During such events which occur mostly in autumn and winter, people are desperate for fresh air. The formation of heavy smog is due to foremost human induced air pollution, but geographic and meteorological conditions, especially below a surface inversion, play an important role. We propose to destroy the inversion by pumping air from above the inversion layer to the surface layer to alleviate the severity of the smog. While long-term air quality improvement depends on the reduction of air pollution emission, air pumping may provide relief in the interim for the Beijing citizens. We estimate that an air pumping at a rate 2×107m3s–1can lead to significantly improved air quality in Beijing, due to (1) direct clean air input; (2) increased instability and vertical mixing and (3) a positive radiation-mixing feedback. The pumping requires an energy input of 10 GW, comparable with the energy consumption in Beijing for air conditioning in summer. We propose to use wind energy from Inner Mongolia for the pumping, which has currently an installed wind energy capacity of 70 GW.

Atmospheric variability is driven not only by internal dynamics, but also by external forcing, such as soil states, SST, snow, sea-ice cover, and so on. To investigate the forecast uncertainties and effects of land surface processes on numerical weather prediction, we added modules to perturb soil moisture and soil temperature into NCEP’s Global Ensemble Forecast System (GEFS), and compared the results of a set of experiments involving different configurations of land surface and atmospheric perturbation. It was found that uncertainties in different soil layers varied due to the multiple timescales of interactions between land surface and atmospheric processes. Perturbations of the soil moisture and soil temperature at the land surface changed sensible and latent heat flux obviously, as compared to the less or indirect land surface perturbation experiment from the day-to-day forecasts. Soil state perturbations led to greater variation in surface heat fluxes that transferred to the upper troposphere, thus reflecting interactions and the response to atmospheric external forcing. Various verification scores were calculated in this study. The results indicated that taking the uncertainties of land surface processes into account in GEFS could contribute a slight improvement in forecast skill in terms of resolution and reliability, a noticeable reduction in forecast error, as well as an increase in ensemble spread in an under-dispersive system. This paper provides a preliminary evaluation of the effects of land surface processes on predictability. Further research using more complex and suitable methods is needed to fully explore our understanding in this area.

Fully digitalized substations using IEC 61850 process bus are being introduced all over the world. Numerous utilities have featured pilot projects, demonstrators or even industrial scale deployment of these Fully Digital Protection, Automation and Control Systems (FD-PACS). Product standards such as profiles for Instrument Transformers have been developed and published (IEC 61869-6 and IEC 61869-9 by TC 38—Instrument Transformers). This raises the question about the standards for digitally interfaced protection functions. In 2016, IEC TC 95 (Measuring relays and protection equipment) charged a working group to investigate this subject and to elaborate recommendations concerning requirements and testing of protection IED with digital inputs and outputs for protection standards (IEC 60255-1xx series). For protection functions, publisher/subscriber based data streams are supposed to comply with IEC 61850 and IEC 61869 standards. This holds in particular for Sampled Values (SV) representing energising inputs of the protection function, and is also applicable to Generic Object Oriented Substation Event (GOOSE) which can be used for input or output of protection functions. Quality attributes of published data depend on the operational and connection status of the function and the hosting IED. In addition, protection functions have to take into account the information regarding the time synchronisation of the received SV and other parameters. This paper gives an overview of these features and the proposed way to take them into account in the IEC 60255 standard series. It describes the progress of WG 2 and relates it to existing standardization documents.

The Ensemble Transform (ET) method has been shown to be useful in providing guidance for adaptive observation deployment. It predicts forecast error variance reduction for each possible deployment using its corresponding transformation matrix in an ensemble subspace. In this paper, a new ET-based sensitivity (ETS) method, which calculates the gradient of forecast error variance reduction in terms of analysis error variance reduction, is proposed to specify regions for possible adaptive observations. ETS is a first order approximation of the ET; it requires just one calculation of a transformation matrix, increasing computational efficiency (60%–80% reduction in computational cost). An explicit mathematical formulation of the ETS gradient is derived and described. Both the ET and ETS methods are applied to the Hurricane Irene (2011) case and a heavy rainfall case for comparison. The numerical results imply that the sensitive areas estimated by the ETS and ET are similar. However, ETS is much more efficient, particularly when the resolution is higher and the number of ensemble members is larger.

The Global/Regional Assimilation and PrEdiction System (GRAPES) is the new-generation numerical weather prediction (NWP) system developed by the China Meteorological Administration. It is a fully compressible non-hydrostatical global/regional unified model that uses a traditional semi-Lagrangian advection scheme with cubic Lagrangian interpolation (referred to as the SL_CL scheme). The SL_CL scheme has been used in many operational NWP models, but there are still some deficiencies, such as the damping effects due to the interpolation and the relatively low accuracy. Based on Reich’s semi-Lagrangian advection scheme (referred to as the R2007 scheme), the Re_R2007 scheme that uses the low- and high-order B-spline function for interpolation at the departure point, is developed in this paper. One- and two-dimensional idealized tests in the rectangular coordinate system with uniform grid cells were conducted to compare the Re_R2007 scheme and the SL_CL scheme. The numerical results showed that: (1) the damping effects were remarkably reduced with the Re_R2007 scheme; and (2) the normalized errors of the Re_R2007 scheme were about 7.5 and 3 times smaller than those of the SL_CL scheme in one- and two-dimensional tests, respectively, indicating the higher accuracy of the Re_R2007 scheme. Furthermore, two solid-body rotation tests were conducted in the latitude-longitude spherical coordinate system with nonuniform grid cells, which also verified the Re_R2007 scheme’s advantages. Finally, in comparison with other global advection schemes, the Re_R2007 scheme was competitive in terms of accuracy and flow independence. An encouraging possibility for the application of the Re_R2007 scheme to the GRAPES model is provided.

A mal-operation case of busbar protection caused by a dead-zone protection abnormality in the Brazilian Midwest Grid on September 19th, 2012, is briefly described. The operation process of pilot distance, automatic re-closure, busbar differential and dead-zone protection, and the emphasis on the logic scheme of dead-zone protection are analyzed. The time delay between the breaker’s main pole and auxiliary contact during re-closure was the main cause in this case, and a defect in the logic allowed it to occur. The differences in dead-zone protection logic between Brazil and China are discussed. A test platform was constructed in the laboratory, and a site simulated experiment was also performed. Possible causes are suggested and test activities are carried out to verify them. Results show the values of practical engineering approaches to the solution. Experience also contributed to avoiding future mal-operations and strengthening the reliability of the protection system, and thus of the power supply in Brazil.

A record‐breaking rainfall event was initiated between the urban heat island (UHI) and a small trumpet‐shaped mountain (Huadu Mountain) to its north in Guangzhou City at midnight of May 6, 2017. Numerically simulating the convection initiation (CI) was challenging due to insufficient model resolution and inaccurate boundary layer parameterization, this study therefore examined the pre‐convective mesoscale processes based on their four‐dimensional analyses obtained through data assimilation of radar and surface observations using the four‐dimensional Variational Doppler Radar Analysis System (VDRAS). Results suggested that the Huadu Mountain to the north of Guangzhou City played a crucial role in the CI through orographic blocking and nighttime cooling. Dynamically, the mountain blocked the upstream airflow causing an accumulation of water vapor in boundary layers; thermally, the large near‐surface temperature gradients between the mountain and its southern foot area induced northerly downslope winds and low‐level convergences and updrafts. The downslope winds enhanced the accumulation of boundary‐layer water vapor, which was then transported to higher altitudes over the CI region by the updrafts, thus resulting in the formation and growth of cloud water above the altitude of 1 km. In addition to the mountain, the UHI also played an important role by increasing the magnitude of the low‐level convergence and influencing its horizontal distribution. These findings urge attentions to the critical roles of small‐scale orography and its interaction with urban underlying surface in initiating local rainstorm events. Orographic blocking and northerly downslope wind resulted in the accumulation of water vapor in the boundary layerThe strong nighttime cooling of the mountain induced low‐level wind convergence and updraft for convection initiationThe urban heat island also played an important role in enhancing the low‐level wind convergence Orographic blocking and northerly downslope wind resulted in the accumulation of water vapor in the boundary layer The strong nighttime cooling of the mountain induced low‐level wind convergence and updraft for convection initiation The urban heat island also played an important role in enhancing the low‐level wind convergence