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The propagation and hydrodynamic processes of lock-exchange gravity current through vegetation regions were investigated experimentally. Experimental results show that the presence of vegetation can prominently advance the transition position of the gravity current from the slumping phase to the self-similar phase. The process of two-heads propagation can be divided into three stages: the coordinated advance stage (vegetation height controls), the overtaking stage (entrainment process and vegetation friction dominate), and the merge stage (vegetation density controls). After an adjustment period, the bulk slope angle $$\beta_b$$ of the triangular gravity current converges to a constant terminal value. A modified empirical equation is fitted to better meet the stable convergence of the terminal bulk slope angle $$\beta_b$$ . The mixing layer formed at the transverse boundary between the vegetation and no-vegetation part can promote fluid entrainment. For the submerged vegetation, the gravity current flows over a new “wall boundary”, i.e. the top of the vegetation region, and causes the negative vorticity. The changes in the vorticity field indicate the presence of vegetation can significantly affect the internal flow-field structure of gravity currents.

This study experimentally investigated the impacts of rough and porous (RP) bed and sedimentation processes on the coherent structures, turbulence intermittency, and anisotropy of saline and turbidity currents. The results reveal that the local current concentration responds immediately (saline current) or languidly (turbidity current) to turbulence bursting events. Inside the dense current, the turbulent momentum fluxes in the streamwise ([Formula: see text]) and vertical ([Formula: see text]) directions transfer downstream and downward, which favor the sweep events. Inside the ambient water, [Formula: see text] and [Formula: see text] transfer upstream and upward, contributing to the formation of ejection events. At the current–ambient water interface, [Formula: see text] and [Formula: see text] do not tend to transfer in particular directions resulting in almost equal quantities of sweep and ejection events. The Gram–Charlier series expansion is strictly applicable to probability density functions (PDFs) of the sweep and ejection events but not suitable ideally for PDFs of the outward and inward interaction events. The primary anisotropy invariant map (AIM) of gravity currents starts from the two-component plain strain limit (near the bed). It is followed by the three-dimensional isotropy (inside the dense current and ambient water) and the axisymmetric contraction limit (current–ambient water interface). Finally, it ends in two-dimensional isotropy (near the free surface). This AIM is sensitive to the RP boundary and the sedimentation processes. Along the streamwise direction, the RP boundary causes alternations between the anisotropic and isotropic turbulence, but the arranged pattern of the rough units determines the period of this alternation.

With increasing water resources stress under climate change, it is of great importance to deeply understand the spatio-temporal variation of crop water requirements and their response to climate change for achieving better water resources management and grain production. However, the quantitative evaluation of climate change impacts on crop water requirements and the identification of determining factors should be further explored to reveal the influencing mechanism and actual effects thoroughly. In this study, the water requirements of winter wheat and summer maize from 1981 to 2019 in the lower reaches of the Yellow River Basin were estimated based on the Penman–Monteith model and crop coefficient method using daily meteorological data. Combined with trends test, sensitivity and contribution analysis, the impacts of different meteorological factors on crop water requirement variation were explored, and the dominant factors were then identified. The results indicated that the temperature increased significantly (a significance level of 0.05 was considered), whereas the sunshine duration, relative humidity and wind speed decreased significantly from 1981 to 2019 in the study area. The total water requirements of winter wheat and summer maize presented a significant decreasing trend (−1.36 mm/a) from 1981 to 2019 with a multi-year average value of 936.7 mm. The crop water requirements of winter wheat was higher than that of summer maize, with multi-year average values of 546.6 mm and 390.1 mm, respectively. In terms of spatial distribution patterns, the crop water requirement in the north was generally higher than that in the south. The water requirements of winter wheat and summer maize were most sensitive to wind speed, and were less sensitive to the minimum temperature and relative humidity. Wind speed was the leading factor of crop water requirement variation with the highest contribution rate of 116.26% among the considered meteorological factors. The results of this study will provide important support for strengthening the capacity to cope with climate change and realizing sustainable utilization of agricultural water resources in the lower reaches of the Yellow River Basin.

Fine-scale population gridded datasets are of great significance in emergency response, resource allocation, and traffic planning. Many studies have developed fine-scale population spatialization m...

A series of constant-flux saline and turbidity current experiments were carried out, focusing on the coupling impact of bed roughness and permeability on current propagation, mixing, and turbulence characteristics. The distinct current propagation phases on RI (rough and impermeable) and RP (rough and permeable) beds are identified, respectively. Experimental results revealed that the intermittently undulating bed surface breaks the strict no-slip boundary, thus, increasing local current velocity near the bed, while its roughness reduces the current peak profile velocity. Interbed pores induced vertical fluid exchange, which synchronously decreases the current peak profile velocity and local velocity near the bed, causes the density profile to no longer follow a monotonous variation trend along with water depth. The larger bed surface roughness or the interbed porosity leads to the smaller upper TKE (turbulent kinetic energy) peak. The lower TKE peak is inversely proportional to the bed surface roughness of the RI beds, while it is proportional to the porosity of the RP bed. A rough bed surface intensifies the asymmetry of the mean velocity distribution around peak velocity resulting in a transfer barrier of turbulent momentum triggered by the interbed pores. On the RP bed, the cross-correlation function based on two-point statistics captures the spikes associated with pore-scale eddies locally, but under the RI condition, it only obtains the logical timescale characterizing the largest eddies of the current. The sediment deposition makes the turbidity current easier to separate from the RP and RI bed than the saline type, causing a consequence of growing the current height.

Urban parks have been considered as an effective measure to mitigate the urban heat island (UHI) effects. Many studies have investigated the impacts of shape, size and interior components on the cold island effect (CIE) of parks, while little attention has been given to the impact of neighboring buildings. Thus, taking twenty-two parks in Beijing as samples, this study investigated the impacts of the neighboring building on the CIE of central parks. The results showed that the average land surface temperature (LST) of parks are 30.98 &deg, C in summer and &minus, 1.10 &deg, C in winter. Parks have a strong CIE in summer, and average cold island footprint (CIF) and LST difference are 0.15 km2 and 2.01 &deg, C higher than that in winter. The components of the building in the CIF of parks are dominated by middle-rise building (MRB), followed by low-rise building (LRB), and high-rise building (HRB) is the least dominant. The percentage of landscape (PLAND) and landscape shape index (LSI) of MRB, and perimeter area fractal dimension (PAFRAC) of LRB are significantly related to CIF in summer and winter. This study could extend scientific understanding of the impacts of neighboring buildings on the CIE of central parks, and could guide urban planners in mitigating the UHI effects through the rational allocation of buildings.

Urban parks can effectively mitigate the urban heat island (UHI) effect. Many studies have investigated the relationship between the shape, size, interior components and cooling effect of the park, little attention have been given to explore the relationship between land surface temperature (LST) of central park and buildings in the neighboring areas. This study has explored the effect of the neighboring building on LST of central park, taking Beijing as the study area. The results showed that the cold island footprint of the park in summer was larger than that in winter (with an average area of 0.15 km2 larger). The components of building in cold island footprint of the park were dominated by middle-rese building (MRB). LSI of MRB and AREA_SD of LMB were identified as the key explanatory variables in summer and winter, respectively, which could explained 16.8% and 13.9% of the variance in the park’s LST. This study could extend scientific understanding of the effect of building on park’s LST, and could provide guidance to urban planners on how to mitigate the UHI effects through the rational allocation of buildings.

Urban Heat Island (UHI), a phenomenon characterized by significantly higher air and land surface temperatures (LSTs) in urban areas than in suburban areas, results in land use change from non-urban to urban land and is accompanied by increases in anthropogenic heat release. A variety of land use contribution indexes have been proposed to quantitatively calculate the impact of land use types on UHI. However, these indexes can only show the impact of specific land use types on UHI. In fact, the area and the intensity (which also can be considered as the average temperature) of land use change jointly determine the regional UHI. The purpose of this paper is to develop an algorithm to quantitatively reveal the influence of the area and the intensity of land use change on regional UHI. MODIS LST products and 1:1,000,000 land use data sets were used to quantitatively calculate the seasonal and interannual contributions of land use change on regional UHI between 2005 and 2018 in China. These results have theoretical and practical significance for further understanding the formation mechanism of urban thermal environment and its mitigation measures.

Soil erosion (SE) processes are closely related to natural conditions and human activities, posing a threat to environment and society. Identifying the human impact on regional SE changes is increasingly essential for pertinent SE management. Jiangxi province is studied here as a representative area of hilly-red-soil regions within southern China. The main objectives of this study were to investigate the changing trend of SE within Jiangxi and identify human impacts on regional SE change from the perspective of spatial differences, through a new approach based on a gravity-center model. Our results showed that SE status presented an overall amelioration from 1990 to 2015, while the average soil erosion modulus (SEM) declined from 864 to 281 Mg/(km2&middot, a). Compared to the situation under human and natural impacts, human-induced spatial differences of SE change demonstrated that the western and northwest regions showed stronger negative effects, the southern region shifted towards negative effects, the northeast region presented a much weaker negative effect. Our results indicated that 4 cities with strong negative effects need more attention in further SE management suited to their local conditions and development, and also suggested that the approach based on a gravity-center has potential for identifying the human impact on regional SE change from the perspective of spatial patterns.

Yield gridded datasets are essential for agricultural land management, food security and harmonious human&ndash, land relationships. Many studies have developed yield spatialization models that are based on cropland areas. However, crop planting areas, phenological dates, and net primary production (NPP) have received minimal attention. This study proposes a novel method to simulate winter wheat yields in China from 2000 to 2015 using crop phenological datasets, phenological observations, and NPP. The results showed that the NPP in the growing season and statistical yield showed a significant positive correlation (R2 = 0.93, p &lt, 0.01). The mean prediction error of the gridded yield dataset was 12.01%. The relative errors of the gridded yield dataset for approximately half of the samples were between &minus, 10% and 10%. Furthermore, the yield distribution was high in the east and low in the west. The high yield was primarily concentrated in the North China Plain, while low yield was observed in eastern Gansu, central Shanxi, southern Hebei, and eastern Sichuan. From 2000 to 2015, the yield mainly showed an increasing trend in the study area, with the average rate of 0.17 t ha-1 yr-1, especially in the North China Plain. This study suggests that NPP is a key indicator to evaluate the yield of winter wheat. Furthermore, this method can be used to generate gridded yield maps along with providing credible and fundamental data for climate change and sustainable agricultural development.

Maternally expressed gene 3 (Meg3) encodes a long non-coding RNA that has been shown to play a role in tumorigenesis. Skp2 is a component of the E3 ubiquitin ligase SCF that specifically promotes the ubiquitination-associated degradation of CDK inhibitor p27, and has been shown to promote cancer cell growth in different types of cancers, including non-small cell lung cancer (NSCLC). Nevertheless, a regulatory relationship between Meg3 and Skp2 has not been acknowledged. Here, we showed that NSCLC specimens had significant higher levels of Skp2 and significantly lower levels of Meg3, compared to paired non-tumor lung tissue. The levels of Meg3 and Skp2 were inversely correlated in NSCLC specimens. Patients with low Meg3 levels had a poor survival. Overexpression of Meg3 decreased Skp2 protein and increased p27 protein, while depletion of Meg3 increased Skp2 protein and decreased p27 protein in NSCLC cells, without altering Skp2 mRNA. These data suggest that the Skp2 may be regulated by Meg3 at post-transcriptional level. Bioinformatics analyses showed that miR-3163 bound to 3'-UTR of Skp2 mRNA in NSCLC cells to inhibit its translation, which was supported by luciferase reporter assay. Meg3 augmented the effects of miR-3163 on Skp2 mRNA, possibly through binding-induced function enhancement, which was supported by the double fluorescent in situ hybridization showing co-localized intracellular Meg3 and miR-3163 signals in NSCLC cells. The miR-3163 levels in NSCLC were not different from in NT, suggesting that the regulation of Skp2 in NSCLC by miR-3163 may require coordination of Meg3. Thus, our data suggest that Meg3 and miR-3163 may coordinate suppression of translation of Skp2 mRNA in NSCLC cells to inhibit NSCLC cell growth.