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High-performance and low-cost ultraviolet (UV) photodetector has always been the desired goals. In this work, Ga-doped ZnO (ZnO:Ga) nanosheets with different Ga doping concentrations from 0 to 6 mol% were synthesized by a hydrothermal method. Furthermore, six ZnO:Ga nanosheets UV photodetectors were fabricated by using the resulting ZnO:Ga nanosheets as the photosensitive layers, their UV detection performances were investigated in detail. The experimental results showed that the 1% Ga-doped ZnO nanosheets UV photodetector had the best performance among these devices, its responsivity was up to 100.2 A/W and response time was only 1.8 s. In addition, first-principles calculation was used to analyze the band structure and density of states from ZnO:Ga nanosheets with different doping concentrations. It was found that the 1% Ga-doped ZnO nanosheets had the narrowest band gap and the most concentrated conduction band density of states. The results indicated that proper Ga doping concentration could effectively improve photoelectric properties of ZnO:Ga nanosheets. [ABSTRACT FROM AUTHOR]

Aims: There are few studies on the interaction between selenium (Se) and various plant hormones in mitigating the harmful effects of cold stress on plants. Here, the effects of Se and various plant hormones on Solanum lycopersicum L. (tomato) under cold stress have been investigated to identify a combination of Se and plant hormones that enhances cold resistance. Methods: The tomato plants were treated with Se and various plant hormones including salicylic acid (SA), melatonin (MT), and abscisic acid (ABA) respectively. The chlorophyll fluorescence was measured by a Chlorophyll fluorescence IMAGING system. The photosynthetic pigments, malondialdehyde, and sugar contents were measured by an ultraviolet spectrophotometer. Results: Among several plant hormones, the co-application of Se and SA was the most effective in mitigating the cold stress of plants. The treatment of Se/SA preserved the plasma membrane integrity and regulated the osmotic substances under cold stress. The interaction between Se and SA modulated some cold-induced genes thereby conferring cold resistance of tomato plants. However, the pretreatment with AIP (SA biosynthesis inhibitor) eliminated the favorable influence of Se on the cold resistance of tomatoes, indicating that regulating the synthesis of SA was one of the mechanisms by which Se enhanced the resistance of tomato plants to cold stress. Conclusions: Our results clarified the roles of Se and its regulation mechanisms in plant cold stress tolerance, as well as the critical involvement of SA in this process, which might provide a theoretical foundation for using Se fertilizer to increase crop production under adversity conditions. Highlights: The combined treatment of Se with SA, MT, and ABA had better effects on enhancing the cold stress resistance of tomato plants than the treatment of Se or hormone alone. Among them, the combined application of Se and SA had the best effect on alleviating the cold stress of tomato plants compared with the ComCat® (a commercial compound plant growth regulator). The co-application of Se and SA also prevented the oxidative damage caused by cold stress on tomato plant chloroplasts and preserved the plasma membrane integrity, as shown by an obvious decrease in MDA, H2O2, and O2−. levels during cold stress. The Se/SA treatment could also reduce the content of reducing sugar, sucrose, total soluble sugar, and starch accumulation caused by cold stress through the regulation of osmotic substances, so as to improve the cold resistance of plants. The interaction between Se and SA modulated the expression of several cold-responsive genes, including PR1, ICE1, CYSb, LEA1, Osmotin, and CBF1, thereby conferring cold tolerance of tomato plants. The pretreatment with a SA inhibitor (AIP) eliminated the favorable influence of Se on the cold resistance of tomato plants indicating that enhancing the cold resistance of plants by regulating the synthesis pathway of SA might be one of the mechanisms by which Se enhanced tomato resistance to cold stress. [ABSTRACT FROM AUTHOR]

In this work, Ag-doped zinc oxide (ZnO:Ag) nanoneedles (NNs) were synthesized by using a low-cost and facile hydrothermal method. The structure, morphology and optical properties of ZnO:Ag NNs were first investigated in detail. We observed a large number of needle-like ZnO:Ag rods with a top diameter in the range of 70–90 nm. The ZnO:Ag NNs were single-crystalline ZnO with hexagonal wurtzite structure. Furthermore, an ultraviolet photodetector (UV PD) was prepared using the ZnO:Ag NNs as a photoactive layer. The device exhibited excellent response to 365 nm light, and its responsivity, photosensitivity and response time were 24.64 A W−1 at 5 V, 58.42 at 0.5 V and 9.58 s, respectively. Also, the performance of ZnO:Ag NN UV PD was much better than that of the undoped ZnO PD, which was attributed to the improved electrical properties of ZnO NNs after Ag doping. [ABSTRACT FROM AUTHOR]

The development of river deltas has considerable economic and ecological benefits; however, owing to sediment interception by dams, river deltas face the risk of shrinking, which is a major environmental challenge of the twenty-first century. The Yellow River contains the highest amount of sediment globally, and accretion and erosion are extremely active in its river delta. The water–sediment regulation scheme (WSRS) of the Yellow River have increased the frequency and unpredictability of the alternation of accretion and erosion areas in the river delta. We studied 25 satellite remote sensing images taken from 1999 to 2019. We used the mean high tide line to calculate the accretion and erosion of the Yellow River delta under different runoff and sediment transport scenarios. WSRS have effectively reversed the erosion of the Yellow River delta that had operated from 2002 to 2019. Runoff and sediment transport during the WSRS period are positively correlated, and both are negatively correlated with erosion area; correlations between variables during the non-WSRS period are not significant. During the WSRS, a sediment and runoff transport ratio greater than 10 kg/m3 results in overall accretion, and a value lower than this results in erosion. In general, during the WSRS period, runoff, sediment transport, and the sediment–runoff ratio jointly control the changes in the accretion area of the river delta. Our research provides a scientific basis for the sustainable development of the Yellow River delta and WSRS scheduling for the Xiaolangdi Reservoir. [ABSTRACT FROM AUTHOR]

The basal ganglia play a key role in integrating a variety of human behaviors through the cortico–basal ganglia–thalamo–cortical loops. Accordingly, basal ganglia disturbances are implicated in a broad range of debilitating neuropsychiatric disorders. Despite accumulating knowledge of the basal ganglia functional organization, the neural substrates and circuitry subserving functions have not been directly mapped in humans. By direct electrical stimulation of distinct basal ganglia regions in 35 refractory epilepsy patients undergoing stereoelectroencephalography recordings, we here offer currently the most complete overview of basal ganglia functional characterization, extending not only to the expected sensorimotor responses, but also to vestibular sensations, autonomic responses, cognitive and multimodal effects. Specifically, some locations identified responses weren't predicted by the model derived from large-scale meta-analyses. Our work may mark an important step toward understanding the functional architecture of the human basal ganglia and provide mechanistic explanations of non-motor symptoms in brain circuit disorders. Direct electrical stimulation of the basal ganglia using implanted SEEG electrodes produced a variety of motor and non-motor effects in human participants, providing insight into the functional architecture of this key brain region. [ABSTRACT FROM AUTHOR]

Understanding the neural correlates of cognitive problems in patients with breast cancer (BC) after systemic treatment have been a topic of increasing investigation. The heterogeneity of the systemic treatment regimens may undermine our ability to identify brain microstructural alterations resulting from any given regimen. We investigated the detrimental effects of the anthracycline-based systemic treatment (AST) regimen (epirubicin and cyclophosphamide + docetaxel + tamoxifen) on brain gray matter (GM) and white matter (WM) microstructural alteration in long-term BC survivors. We performed a battery of neuropsychological tests and structural magnetic resonance imaging (MRI) to 31 long-term BC survivors who had received the AST regimen (AST group) and 43 healthy controls (HC group). Voxel-based morphometry evaluated the whole-brain voxel-wise GM volume, while diffusion tensor imaging technique with tract‐based spatial statistics analysis evaluated whole-brain WM microstructural alteration. Partial least squares regression (PLSR) was used to evaluate the relationship between cognitive impairment and brain microstructural alteration in BC survivors. Compared with the HC group, the AST group exhibited a significantly poorer performance in attention, as well as a marginal significantly poorer performance in verbal working memory and executive function. Significantly lower fractional anisotropy (FA), higher radial diffusivity (RD), and lower axial diffusivity (AD) in multiple brain WM regions were showed in AST group compared with the HC group. Overlap of lower FA and higher RD was found in the body of corpus callosum (CC) and bilateral superior corona radiata (SCR), whereas overlap of lower FA and AD was found in the body of CC and right SCR. The PLSR results showed that the WM regions with overlap of lower FA and AD were significantly associated with executive and verbal working memory decline. No significant difference was observed in the GM volume between groups. Our results suggest that microstructural abnormalities of certain vulnerable WM regions in the AST regimen-exposed brain may provide neuroimaging evidence for the identification of brain injury and cognitive impairment induced by specific chemotherapy regimens. [ABSTRACT FROM AUTHOR]

Many cities in China have invested in the city's rail transit system to reduce urban air pollution and traffic congestion. Earlier studies rarely compare the effects of rail transit on urban air quality in different cities, providing little guidance to urban planners in solving traffic congestion and air quality. Due to the same opening date, we regard Chengdu Metro Line 4 and Nanchang Metro Line 1 as case studies. This paper attempts to examine the effects of the opening of rail transit on local air quality on the same opening date. Data were collected from 17 monitoring stations distributed along the chosen rail transit lines in both cities from 2015 to 2016 and analyzed using the regression discontinuity design to address the potential endogenous location of subway stations. The results show that subway opening in Nanchang has a better reduction from automobile exhaust than that in Chengdu. Specifically, carbon monoxide pollution, one key tailpipe pollutant, experienced a 10.23% greater reduction after Nanchang Metro Line 1 opened. However, the point estimate for carbon monoxide in Chengdu is 22.42% and statistically significant at the 1% level. Nanchang Metro Line 1 does play an important role in road traffic externalities, but the benefit is not huge enough to change the overall air quality. On the contrary, the opening of the Chengdu Metro Line 4 is unlikely to yield improvements in air quality. [ABSTRACT FROM AUTHOR]

The stochastic resonance (SR) phenomenon for an underdamped monostable system with multiplicative and additive noise is investigated. The expression for the stationary probability density is obtained under the condition of the detailed balance and weak noise. The signal-to-noise ratio (SNR) for the monostable system is derived based on two-state theory. The result shows that the SR phenomenon can be observed when the SNR varies with the intensities of the multiplicative and additive white noise, as well as varies with the amplitude of the additive dichotomous noise. One resonance peak can be found when the SNR changes with the damping coefficient and with other system parameters. [ABSTRACT FROM AUTHOR]

Facial expressions are the most direct external manifestation of personal emotions. Different from other pattern recognition problems, the feature difference between facial expressions is smaller. The general methods are difficult to effectively characterize the feature difference, or their parameters are too large to realize real-time processing. This paper proposes a lightweight mobile architecture and a multi-kernel feature facial expression recognition network, which can take into account the speed and accuracy of real-time facial expression recognition. First, a multi-kernel convolution block is designed by using three depthwise separable convolution kernels of different sizes in parallel. The small and the large kernels can extract local details and edge contour information of facial expressions, respectively. Then, the multi-channel information is fused to obtain multi-kernel enhancement features to better describe the differences between facial expressions. Second, a "Channel Split" operation is performed on the input of the multi-kernel convolution block, which can avoid repeated extraction of invalid information and reduce the amount of parameters to one-third of the original. Finally, a lightweight multi-kernel feature expression recognition network is designed by alternately using multi-kernel convolution blocks and depthwise separable convolutions to further improve the feature representation ability. Experimental results show that the proposed network achieves high accuracy of 73.3 and 99.5% on FER-2013 and CK + datasets, respectively. Furthermore, it achieves a speed of 78 frames per second on 640 × 480 video. It is superior to other state-of-the-art methods in terms of speed and accuracy. [ABSTRACT FROM AUTHOR]

Here, using a facile hydrothermal method, the single-crystalline ZnO nanoflowers were firstly synthesized and then annealed at different temperatures from 500 to 900 °C. The results revealed that the as-synthesized samples were flower-like ZnO structures composed of many hollow nanorods; after annealing at 500 °C, hollow nanorods were changed into solid parts. Also, using the as-synthesized and annealed ZnO nanoflowers as photosensitive layers, respectively, a series of ultraviolet photodetectors were built. The results demonstrated that the ultraviolet photodetector based on the ZnO nanoflowers annealed at 800 °C had the best performance when they were exposed to 365 nm light with light intensity of 71 μW/cm2 and its sensitivity, responsivity, gain, response, and decay time were 19,991.3 at − 0.1 V, 9.7 A/W at 5 V, 33.2 at 5 V, 17.1 s, and 49.5 s, respectively. Therefore, a new avenue can be opened to construct low cost and high-sensitivity ultraviolet photodetectors by the annealed ZnO nanoflowers. [ABSTRACT FROM AUTHOR]

Purpose: Seizure originates from different pathological substrate; however, the same pathologies may have distinct mechanisms underlying seizure generation. We aimed to improve the understanding of such mechanisms in patients with temporal lobe epilepsy (TLE) by investigating the stereoelectroencephalography (SEEG) ictal onset patterns (IOPs). Methods: We analyzed data from a cohort of 19 consecutive patients explored by SEEG and had 1–3-year seizure-freedom following temporal lobe resection. Results: Six IOPs were identified. They were low voltage fast activity (LVFA) (36.5%), rhythmic spikes or spike-waves at low frequency and with high amplitude (34.1%), runs of spikes (10.6%), rhythmic sharp waves (8.2%), low frequency high amplitude repetitive spiking (LFRS) (7.1%), and delta activity (3.5%). All six patterns were found in patients with mesial temporal onset and only two patterns were found in patients with temporal neocortical onset. The most prevalent patterns for patients with mesial temporal onset were rhythmic spikes or spike-waves, followed by LVFA with a mean discharge rate 74 Hz. For patients with temporal neocortical onset, the most prevalent IOP pattern was LVFA with a mean discharge rate 35 Hz, followed by runs of spikes. Compared with Lateral TLE (LTLE), the duration between the onset of the IOPs to the onset of the symptom was longer for patients with MTLE (Mesial TLE) (MTLE:55.7 ± 50.6 s vs LTLE:19.5 ± 16.4 s). Conclusion: Multiple IOPs underlie seizure generation in patients with TLE. However, the mesial and lateral temporal lobes share distinct IOPs. [ABSTRACT FROM AUTHOR]

Using panel data from a nationally representative survey in China, this paper simultaneously examines the impact of relative status of reference points from various categories on individual happiness. We find strong evidence supporting asymmetric and adaptation effects in internal comparisons. The marginal effect of current absolute status decreases as achieved relative status rises, and future (positive) status changes matter more than current (negative) status changes, respectively. With respect to external comparisons, the results suggest that relative status of both spatial and predicted reference groups exerts a favorable influence on happiness, whereas those of social reference groups substantially decrease individual happiness. This result remains qualitatively unchanged even correcting for the possible endogeneity of the current absolute status and reference relative status. The two opposite effects are magnified when people are temporarily unemployed or experience high volatility of economic status. A series of further sensitivity tests are consistent with our tunnel and comparison effects conjecture but rule out some alternative explanations, despite suggestive rather than conclusive. Finally, the findings also survive a large set of robustness checks. [ABSTRACT FROM AUTHOR]

Purpose: This research aims to study the ecological risk of metals to Zostera japonica and focuses on two typical sediment environments in the Yellow River estuary, namely, sediment erosion and deposition areas. Materials and methods: Two different sediment habitats of Z. japonica were selected in this research from southern and northern sites in the Yellow River estuary. The plant growth and nutrient and metal concentrations in the sediments and Z. japonica tissue were investigated in the growth period of Z. japonica from April to October 2019. The shoot height of Z. japonica was measured with a centimetre-scale measuring stick, and the dry shoot weight was obtained after drying at 70 °C for 24 h. The total carbon (TC) and total nitrogen (TN) concentrations in the Z. japonica tissue and sediment were determined with an elemental analyser (Vario Macro Cube, Elementar Company, Germany). The total phosphorus (TP), iron (Fe), manganese (Mn), copper (Cu), zinc (Zn), lead (Pb), chromium (Cr) and cadmium (Cd) contents in the digested solutions were measured by high-resolution inductively coupled plasma atomic emission spectrometry (HR-ICP-AES, Spectro Company, Germany). Results and discussion: The growth of Z. japonica was different at the two study sites, with a higher biomass at the southern site than that at the northern site due to higher sediment nutrient concentrations at the southern site. The Cu, Zn, Pb, Cr and Cd concentrations in the sediments at the southern site were 25.1 μg g−1, 74.2 μg g−1, 21.4 μg g−1, 65.4 μg g−1 and 0.32 μg g−1, respectively, which were higher than the levels at the northern site of 13 μg g−1, 47.6 μg g−1, 12.4 μg g−1, 46.4 μg g−1 and 0.17 μg g−1, respectively. However, among the metals, only Cd was bioconcentrated in the Z. japonica tissue, with bioconcentration factor (BCF) values of 5.59 and 10.85 at the southern and northern sites, respectively. Conclusions: The sediments at the southern site in the estuary are composed of clays enriched in nutrients, thus supporting more sustainable growth and higher biomass than the coarse-particle sediments at the northern site in the estuary. Moreover, the sediments at the southern site were also enriched in metals, resulting in high levels of metals in the Z. japonica tissue. Overall, the ecological risk was low except for Cd, which should be considered because of its potential impacts on this seagrass and its related food webs in the estuary ecosystem. [ABSTRACT FROM AUTHOR]

Background: Fear, as one of the basic emotions, is crucial in helping humans to perceive hazards and adapt to social activities. Clinically, fear memory is also involved in a wide spectrum of psychiatric disorders. A better understanding of the neural mechanisms of fear thereby has both neuroscientific and clinical significance. In recent years, data from animal models have demonstrated the key role of the amygdala-hippocampal circuit in the development of fear. However, the neural processing of fear memory remains unclear in humans, which is mainly due to the limitation of indirect measure of neural activity. Methods: Herein, we investigated fear memory by direct intracranial recordings from 8 intractable epilepsy patients with depth electrodes in both the hippocampus and ipsilateral amygdala. All the patients were subjected to a well-established Pavlovian fear memory paradigm consisted of the familiarization task, conditioning task, and retrieval task, respectively. Simultaneous local field potentials from the hippocampus and amygdala were recorded during different stages. The oscillatory activities from the amygdala and hippocampus were analyzed during fear memory retrieval compared with neutral stages. Results: Consistent with previous rodent studies, our results showed that the amygdala was involved in fear memory retrieval rather than neutral memory retrieval, while the hippocampus was involved both in fear memory retrieval and neutral memory retrieval. In particular, we found that there was an enhanced synchronized activity between the amygdala and hippocampus at beta frequencies (14–30 Hz), which suggested that enhanced synchronized activity at beta frequencies between the amygdala and hippocampus play a pivotal role during retrieval of fear memory in human. Conclusions: Thus, our observation that the amygdala-hippocampal system contributing to fear memory retrieval in human with frequency-depended specificity has provided new insights into the mechanism of fear and have potential clinical relevance. [ABSTRACT FROM AUTHOR]

Natural rubber (NR) grafted with 2-ethylhexyl acrylate (2-EHA) and methacrylic acid (MAA, collectively NR-g-PEHA/MAA) was synthesized by emulsion polymerization. Tetraethylenepentamine and cumene hydroperoxide were used as redox initiators. The successful grafting of 2-EHA and MAA onto NR was confirmed by Fourier transform infrared spectroscopy. The morphology of the NR latex particles was observed by transmission electron microscopy. The effects of reaction temperature, initiator dosage, feeding mode, and hard monomer content on the mechanical properties of the modified NR film were investigated. Grafted polymer chains were unevenly wrapped on the outside of NR particles, and smaller particles were more easily grafted. Crosslinking was characterized using a toluene swelling method. Thermal stability and glass transition temperature were examined by differential scanning calorimetry and thermogravimetric analysis. The results showed that the thermal stability of NR-g-PEHA/MAA had been improved, and the glass transition temperature (Tg) was unchanged. [ABSTRACT FROM AUTHOR]

Valosine containing protein (VCP/p97), which involves in several important cellular functions and plays an important role in ubiquitin-mediated misfolding protein degradation, has been found to be a novel target for the treatment of a range of cancers, such as lung cancer and breast cancer. In this study, the atom-based three-dimensional quantitative structure–activity relationship (3D-QSAR) and docking models were developed using PHASE and GLIDE modules of Schrödinger software, respectively. The theoretical models were generated from 38 N-benzylpyrimidin-4-amine inhibitors of p97. An AADRRR model consisting of two hydrogen bond acceptors (A), one hydrogen bond donor (D), and three aromatic rings (R) was obtained. Thirty eight derivatives were divided into a training set with 27 molecules to generate 3D-QSAR models and a test set with 11 molecules to validate 3D-QSAR model. A robust QSAR model with good prediction in internal and external verification was constructed, where R2, Q2, and Pearson-R were 0.924, 0.701, and 0.8783, respectively. QSAR model showed the hydrogen bond donor, electron-withdrawing group, and hydrophobic characteristics affecting the p97 activity. Molecular docking studies indicated that the H-bond and hydrophobic interactions existed between the inhibitors and p97, which was consistent with the results of 3D-QSAR. These results provided some useful information for designing new and effective p97 inhibitors. [ABSTRACT FROM AUTHOR]

Abstract: The views on catalytic activity of zeolite in isomerization of α-pinene have not came to an agreement. Thus, the key active substance in zeolite was further studied through experiments. H-mordenite was treated in three ways: (i) calcination under nitrogen flows, (ii) calcination under oxygen flows, (iii) calcination under nitrogen flows after alkali treatment. The properties of modified zeolites were investigated by methods of SEM, EDS, XRD, nitrogen adsorption, NH3-TPD, Py-IR, and 29Si and 27Al MAS NMR. The results showed that the zeolites produced mesoporous after 0.4M NaOH solution soaking and calcinations above 500 °C, but it had a slight effect on the change of micropore volumes. Comparison of zeolite acid sites amount under different roasting temperature by NH3-TPD showed that the decrease of acid sites amount was mainly related to the roasting temperature. Py-IR and 27Al MAS NMR experiment revealed that Lewis acid was produced by framework aluminum. Finally, Analysis on the influencing factors we studied of H-mordenite catalytic activity in this paper suggested that, in isomerization of α-pinene, the relative concentration of six-coordination aluminum in zeolite is the dominant factor of provided catalytic activity of H-mordenite.Graphical abstract: [ABSTRACT FROM AUTHOR]

This paper investigates a 3-D leader-following formation control problem for a group of missiles with aerodynamic constraints. To cope with the large maneuvering formation flight in bank-to-turn control mode, an integrated backstepping-based distributed control scheme, combining the inner-loop attitude manipulation and outer-loop formation control, is proposed. Command filters are introduced to handle the control surface saturations caused by the physical limitations, and the attitude constraints derived from the coordinated turn requirements. In addition, the B-spline neural networks are adopted to reconstruct the uncertain aerodynamic force and moment coefficients, of which the unknown parameters are then online learned by the adaptive tuning laws. The proposed integrated distributed formation control protocol will guarantee that all states in the closed-loop systems are cooperatively semi-globally uniformly ultimately bounded. The formation tracking errors can converge into a small region around zero by properly adjusting the control parameters. Finally, numerical simulations are conducted to demonstrate the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

Due to increased aerosol emissions and unfavorable weather conditions, severe haze events have occurred frequently in China in the last 10 years. In addition, the interaction between the boundary layer and the aerosol radiative effect may be another important factor in haze formation. To better understand the effect of this interaction, the aerosol radiative effect on a severe haze episode that took place in December 2013 was investigated by using two WRF-Chem model simulations with different aerosol configurations. The results showed that the maximal reduction of regional average surface shortwave radiation, latent heat, and sensible heat during this event were 88, 12, and 37 W m, respectively. The planetary boundary layer height, daytime temperature, and wind speed dropped by 276 m, 1°C, and 0.33 m s, respectively. The ventilation coefficient dropped by 8%-24% for in the central and northwestern Yangtze River Delta (YRD). The upper level of the atmosphere was warmed and the lower level was cooled, which stabilized the stratification. In a word, the dispersion ability of the atmosphere was weakened due to the aerosol radiative feedback. Additional results showed that the PM concentration in the central and northwestern YRD increased by 6-18 μg m, which is less than 15% of the average PM concentration during the severely polluted period in this area. The vertical profile showed that the PM and PM concentrations increased below 950 hPa, with a maximum increase of 7 and 8 μg m, respectively. Concentrations reduced between 950 and 800 hPa, however, with a maximum reduction of 3.5 and 4.5 μg m, respectively. Generally, the aerosol radiative effect aggravated the level of pollution, but the effect was limited, and this haze event was mainly caused by the stagnant meteorological conditions. The interaction between the boundary layer and the aerosol radiative effect may have been less important than the large-scale static weather conditions for the formation of this haze episode. [ABSTRACT FROM AUTHOR]

In this study, the impact of the spectral nudging method on regional climate simulation over the Coordinated Regional Climate Downscaling Experiment East Asia (CORDEX-EA) region is investigated using the Weather Research and Forecasting model (WRF). Driven by the ERA-Interim reanalysis, five continuous simulations covering 1989-2007 are conducted by the WRF model, in which four runs adopt the interior spectral nudging with different wavenumbers, nudging variables and nudging coefficients. Model validation shows that WRF has the ability to simulate spatial distributions and temporal variations of the surface climate (air temperature and precipitation) over CORDEX-EA domain. Comparably the spectral nudging technique is effective in improving the model's skill in the following aspects: (1), the simulated biases and root mean square errors of annual mean temperature and precipitation are obviously reduced. The SN3-UVT (spectral nudging with wavenumber 3 in both zonal and meridional directions applied to U, V and T) and SN6 (spectral nudging with wavenumber 6 in both zonal and meridional directions applied to U and V) experiments give the best simulations for temperature and precipitation respectively. The inter-annual and seasonal variances produced by the SN experiments are also closer to the ERA-Interim observation. (2), the application of spectral nudging in WRF is helpful for simulating the extreme temperature and precipitation, and the SN3-UVT simulation shows a clear advantage over the other simulations in depicting both the spatial distributions and inter-annual variances of temperature and precipitation extremes. With the spectral nudging, WRF is able to preserve the variability in the large scale climate information, and therefore adjust the temperature and precipitation variabilities toward the observation. [ABSTRACT FROM AUTHOR]

An analysis of a 20-year summer time simulation of present-day climate (1989-2008) over China using four regional climate models coupled with different land surface models is carried out. The climatic means, interannual variability, linear trends, and extremes are examined, with focus on precipitation and near surface air temperature. The models are able to reproduce the basic features of the observed summer mean precipitation and temperature over China and the regional detail due to topographic forcing. Overall, the model performance is better for temperature than that of precipitation. The models reasonably grasp the major anomalies and standard deviations over China and the five subregions studied. The models generally reproduce the spatial pattern of high interannual variability over wet regions, and low variability over the dry regions. The models also capture well the variable temperature gradient increase to the north by latitude. Both the observed and simulated linear trend of precipitation shows a drying tendency over the Yangtze River Basin and wetting over South China. The models capture well the relatively small temperature trends in large areas of China. The models reasonably simulate the characteristics of extreme precipitation indices of heavy rain days and heavy precipitation fraction. Most of the models also performed well in capturing both the sign and magnitude of the daily maximum and minimum temperatures over China. [ABSTRACT FROM AUTHOR]

Urbanization is an extreme way in which human being changes the land use/land cover of the earth surface, and anthropogenic heat release occurs at the same time. In this paper, the anthropogenic heat release parameterization scheme in the Weather Research and Forecasting model is modified to consider the spatial heterogeneity of the release; and the impacts of land use change and anthropogenic heat release on urban boundary layer structure in the Pearl River Delta, China, are studied with a series of numerical experiments. The results show that the anthropogenic heat release contributes nearly 75 % to the urban heat island intensity in our studied period. The impact of anthropogenic heat release on near-surface specific humidity is very weak, but that on relative humidity is apparent due to the near-surface air temperature change. The near-surface wind speed decreases after the local land use is changed to urban type due to the increased land surface roughness, but the anthropogenic heat release leads to increases of the low-level wind speed and decreases above in the urban boundary layer because the anthropogenic heat release reduces the boundary layer stability and enhances the vertical mixing. [ABSTRACT FROM AUTHOR]

To evaluate the influence of urban non-uniformity on precipitation, the area of a city was divided into three categories (commercial, high-density residential, and low-density residential) according to the building density data from Landsat satellites. Numerical simulations of three corresponding scenarios (urban non-uniformity, urban uniformity, and non-urban) were performed in Nanjing using the WRF model. The results demonstrate that the existence of the city results in more precipitation, and that urban heterogeneity enhances this phenomenon. For the urban non-uniformity, uniformity, and non-urban experiments, the mean cumulative summer precipitation was 423.09 mm, 407.40 mm, and 389.67 mm, respectively. Urban non-uniformity has a significant effect on the amount of heavy rainfall in summer. The cumulative precipitation from heavy rain in the summer for the three numerical experiments was 278.2 mm, 250.6 mm, and 236.5 mm, respectively. In the nonuniformity experiments, the amount of precipitation between 1500 and 2200 (LST) increased significantly. Furthermore, the adoption of urban non-uniformity into the WRF model could improve the numerical simulation of summer rain and its daily variation. [ABSTRACT FROM AUTHOR]

The COSMO-CLM (CCLM) model is applied to perform regional climate simulation over the second phase of CORDEX-East Asia (CORDEX-EA-II) domain in this study. Driven by the ERAInterim reanalysis data, the model was integrated from 1988 to 2010 with a high resolution of 0.22°. The model's ability to reproduce mean climatology and climatic extremes is evaluated based on various aspects. The CCLM model is capable of capturing the basic features of the East Asia climate, including the seasonal mean patterns, interannual variations, annual cycles and climate extreme indices for both surface air temperature and precipitation. Some biases are evident in certain areas and seasons. Warm and wet biases appear in the arid and semi-arid areas over the northwestern and northern parts of the domain. The simulated climate over the Tibetan Plateau is colder and wetter than the observations, while South China, East China, and India are drier. The model biases may be caused by the simulated anticyclonic and cyclonic biases in low-level circulations, the simulated water vapor content biases, and the inadequate physical parameterizations in the CCLM model. A parallel 0.44° simulation is conducted and the comparison results show some added value introduced by the higher resolution 0.22° simulation. As a result, the CCLM model could be an adequate member for the next stage of the CORDEX-EA project, while further studies should be encouraged. [ABSTRACT FROM AUTHOR]

Urbanization has a substantial effect on urban meteorology. It can alter the atmospheric diffusion capability in urban areas and therefore affect pollutant concentrations. To study the effects of Hangzhou's urban development in most recent decade on its urban meteorological characteristics and pollutant diffusion, 90 weather cases were simulated, covering 9 weather types, with the Nanjing University City Air Quality Prediction System and high-resolution surface-type data and urban construction data for 2000 and 2010. The results show that the most recent decade of urban development in Hangzhou substantially affected its urban meteorology. Specifically, the average urban wind speed decreased by 1.1 m s ; the average intensity of the heat island increased by 0.5°C; and the average urban relative humidity decreased by 9.7%. Based on one case for each of the nine weather types, the impact of urbanization on air pollution diffusion was investigated, revealing that the changes in the meteorological environment decreased the urban atmosphere's diffusion capability, and therefore increased urban pollutant concentrations. For instance, the urban nitrogen oxides concentration increased by 2.1 μg m on average; the fine particulate matter (diameter of 2.5 μm or less; PM) pollution concentration increased by 2.3 μg m on average; in highly urbanized areas, the PM concentration increased by 30 μg m and average visibility decreased by 0.2 km, with a maximum decrease of 1 km; the average number of daily hours of haze increased by 0.46 h; and the haze height lifted by 100-300 m. The 'self-cleaning time' of pollutants increased by an average of 1.5 h. [ABSTRACT FROM AUTHOR]

The large-eddy simulation mode of the Weather Research and Forecasting model is employed to simulate the planetary boundary-layer characteristics and mesoscale circulations forced by an ideal urban heat island (UHI). In our simulations, the horizontal heterogeneity of the UHI intensity distribution in urban areas is considered and idealized as a cosine function. Results indicate that the UHI heating rate and the UHI intensity heterogeneity affect directly the spatial distribution of the wind field; a stronger UHI intensity produces a maximum horizontal wind speed closer to the urban centre. The strong advection of warm air from the urban area to the rural area in the upper part of the planetary boundary-layer causes a more stable atmospheric stratification over both the urban and rural areas. The mesoscale sensible heat flux caused by the UHI circulation increases with UHI intensity but vanishes when the background wind speed is sufficiently high $$(>$$ 3.0 $$\mathrm{{m\,s}}^{-1})$$ . [ABSTRACT FROM AUTHOR]

RegCM3 (REGional Climate Model) simulations of precipitation in China in 1991 and 1998 are very sensitive to the cumulus parameterization. Among the four schemes available, none has superior skills over the whole of China, but each captures certain observed signals in distinct regions. The Grell scheme with the Fritsch-Chappell closure produces the smallest biases over the North; the Grell scheme with the Arakawa-Schubert closure performs the best over the southeast of 100°E; the Anthes-Kuo scheme is superior over the northeast; and the Emanuel scheme is more realistic over the southwest of 100°E and along the Yangtze River Basin. These differences indicate a strong degree of independence and complementarity between the parameterizations. As such, an ensemble is developed from the four schemes, whose relative contributions or weights are optimized locally to yield overall minimum root-mean-square errors from observed daily precipitation. The skill gain is evaluated by applying the identical distribution of the weights in a different period. It is shown that the ensemble always produces gross biases that are smaller than the individual schemes in both 1991 and 1998. The ensemble, however, cannot eliminate the large rainfall deficits over the southwest of 100°E and along the Yangtze River Basin that are systematic across all schemes. Further improve-ments can be made by a super-ensemble based on more cumulus schemes and/or multiple models. [ABSTRACT FROM AUTHOR]