Global methane and nitrous oxide emissions from non-marine waters

Non-marine waters (i.e., rivers, reservoirs, lakes, ponds, streams and estuaries) are globally significant emitters of methane (CH4) and nitrous oxide (N2O) to the atmosphere, while global estimates of these emissions have been hampered due to the lack of a worldwide comprehensive database with the collection of complete CH4 and N2O flux components. Here we synthesize 2997 in-situ flux or concentration measurements of CH4 and N2O from 277 peer-reviewed publications to examine the role of non-marine waters in shaping climate change. Here we estimate that inland waters including rivers, reservoirs, lakes and streams together release 94.49 Tg CH4 yr− 1 (ebullition plus diffusion) and 1.52 Tg N2O yr− 1 (diffusion) to the atmosphere, yielding an overall CO2-equivalent emission total of 3.05 Pg CO2 yr− 1, representing roughly 59% of CO2 emissions (5.13 Pg CO2 yr− 1) from these four aquatic ecosystems, with lakes acting as the largest emitter for both trace gases. Ebullition is noticed as a dominant flux component, contributing up to 62–84% of total CH4 fluxes across all inland waters. Chamber-derived CH4 flux rates are significantly greater than those determined by diffusion model-based methods for commonly capturing of both diffusive and ebullitive fluxes. The synthesis of global N2O measurements projected that rivers exhibit the highest indirect N2O emission factor (EF5, 0.028%), while streams have the lowest EF5 value (0.015%). Our study reveals a major oversight in regional and global CH4 budgets from inland waters, caused by neglect of the dominant role of ebullition pathways in those emissions. The indirect EF5 values established in this study generally suggest an order of magnitude downward revision is required in current IPCC default EF5 values for inland waters and estuaries. Our findings further indicate that a comprehensive understanding of the magnitude and patterns of CH4 and N2O emissions from non-marine waters is essential in defining the way that these natural ecosystems shape our climate.

Analysis of Large-Scale Dynamics and Gravity Waves under Shedding of Inactive Flow Components

The Ertel’s potential vorticity (EPV) budget equation does not see the contribution of an inactive EPV flux component ∇θ × ∇B because it drops out when taking the divergence. A part of the actual EPV flux can always be interpreted as such an inactive component and is thus likewise shed from the EPV budget equation. The deviation from this inactive EPV flux is called the active EPV flux and the associated wind is called the active wind. The horizontal active wind is comparable to the ageostrophic wind. The vertical active wind component is similar to the isentropic displacement vertical wind. In contrast to the actual wind, the vertical active wind does not vanish at the surface, because the inactive wind blows along isentropes, which may intersect the ground. Transformed governing equations are derived as functions of the active wind components. The terms on the right of the transformed equations can be scrutinized with respect to their effects on the evolution of the atmospheric state. An idealized baroclinic wave in a dry atmosphere is discussed with focus on the fronts and the generation or depletion of kinetic energy. Since the vertical inactive wind does not necessarily vanish at the surface, the arising vertical active wind is responsible for the cooling (raising of isentropes) and the warming (sinking of isentropes) in the different regions of a cyclone. The new method allows for a unique separation of gravity waves and vortical modes. This facilitates the analysis of gravity wave generation and propagation from jets and fronts.

Research on the Method of Predicting Corrosion width of Cables Based on the Spontaneous Magnetic Flux Leakage

The detection of cable corrosion is of great significance to the evaluation of cable safety performance. Based on the principle of spontaneous magnetic flux leakage (SMFL), a new method for predicting the corrosion width of cables is proposed. In this paper, in order to quantify the width of corrosion, the parameter about intersecting point distance between curves of magnetic flux component of x direction at different lift off heights (Dx) is proposed by establishing the theoretical model of the magnetic dipole of the rectangular corrosion defect. The MATLAB software was used to analyze the influencing factors of Dx. The results indicate that there exists an obvious linear relationship between the Dx and the y (lift off height), and the Dx–y curves converge to near the true corrosion width when y = 0. The 1/4 and 3/4 quantiles of the Dx–y image were used for linear fitting, which the intercept of the fitting equation was used to represent the predicted corrosion width. After the experimental study on the corrosion width detection for the parallel steel wire and steel strand, it is found that this method can effectively improve the detection accuracy, which plays an important role in cable safety assessment.

Heat Flux Sources Analysis to the Ross Ice Shelf Polynya Ice Production Time Series and the Impact of Wind Forcing

The variation of Ross Ice Shelf Polynya (RISP) ice production is a synergistic result of several factors. This study aims to analyze the 2003–2017 RISP ice production time series with respect to the impact of wind forcing on heat flux sources. RISP ice production was estimated from passive microwave sea ice concentration images and reanalysis meteorological data using a thermodynamic model. The total ice production was divided into four components according to the amount of ice produced by different heat fluxes: solar radiation component (Vs), longwave radiation component (Vl), sensible heat flux component (Vfs), and latent heat flux component (Vfe). The results show that Vfs made the largest contribution, followed by Vl and Vfe, while Vs had a negative contribution. Our study reveals that total ice production and Vl, Vfs, and Vfe highly correlated with the RISP area size, whereas Vs negatively correlated with the RISP area size in October, and had a weak influence from April to September. Since total ice production strongly correlates with the polynya area and this significantly correlates with the wind speed of the previous day, strong wind events lead to sharply increased ice production most of the time. Strong wind events, however, may only lead to mildly increasing ice production in October, when enlarged Vs reduces the ice production. Wind speed influences ice production by two mechanisms: impact on polynya area, and impact on heat exchange and phase transformation of ice. Vfs and Vfe are influenced by both mechanisms, while Vs and Vl are only influenced by impact on polynya area. These two mechanisms show different degrees of influence on ice production during different periods. Persistent offshore winds were responsible for the large RISP area and high ice production in October 2005 and June 2007.

Effects of waterjet cutting waste addition on properties of building ceramics

The purpose of the paper is to investigate the possibility of using wastes of waterjet metal cutting in the manufacture of building ceramics. A complex study of the composition and properties of the abrasive and hydroabrasive cutting wastes was carried out. The behavior of waste in the composition of the ceramic mass and the ceramic body was investigated. Positive results of the effect of addition of waste on the properties of ceramics were obtained on two types of polymineralic argillaceous raw materials: increase of strength at the optimum content of waste in the mixture, reduction of air and fire shrinkage in all compositions with waste content, possibility of varying the color of products, etc. The similarity of the chemical composition of argillaceous raw materials and wastes was established: oxides of iron, silicon and aluminum are predominant. Electron microscope research has demonstrated that the introduction of waste modifies the structure of the ceramic shard, but does not affect its uniformity. The obtained results allowed to draw conclusions about the possible use of wastes of waterjet metal cutting in the production of ceramics: as a fluxing agent – flux, component for volumetric staining, thinning agent.

The Reasons of Heat Transfer Enhancement in a Laminar Channel Flow With Uniform Heat Flux on the Wall Under a Pair of Longitudinal Vortex Generators Mounted on the Bottom Wall

To find the reasons of heat transfer enhancement of a laminar convective heat transfer process in a channel at a uniform heat flux boundary when a pair of longitudinal vortex generators (VGs) is mounted on the bottom wall, the laminar convective heat transfer process in the channel is investigated numerically in a frame built up by the convective transport equation of the heat flux. The results show that longitudinal vortices greatly increase the local convection contribution terms that determine the local intensity of the convective transport of the heat flux component in the span direction, and that the increased local contribution terms intensify the local convective transport of the heat flux component in the same direction. This process increases the convection contribution terms that determine the convective transports of the heat flux components in the main stream direction and in the normal direction of the channel walls. The increase in these convection contribution terms results in an enhancement of the convective heat transfer ability on the channel walls, and then, the heat transfer is enhanced by longitudinal vortices. When the span-averaged characteristic is numerically counted, longitudinal vortices are found to have no contribution on the span-averaged convective transport of the heat flux in the span direction.