Coastal Circulations Driven by River Outflow

Variable-density, 11/2- and 21/2- layer models are used to examine the behavior of plumes resulting from a fresher outflow of transport Mr and salinity Sr into a pre-existing oceanic layer of initial thickness H1 and salinity S1. It is found that the plumes exhibit a variety of features depending on conditions of the outflow, the situation of the ambient ocean, and external forcing. Perhaps the most interesting feature is that the plume can flow along the upstream (to the left of the river mouth, looking seaward in the northern hemisphere) coast by itself, and the research discussed here is focused on this topic. To illustrate how density variations associated with river plumes drive circulations, several solutions of geostrophic adjustment to an initially-imposed, y-independent density front are investigated. In these solutions, a frontally-trapped alongfront geostrophic current with the fresher water to its right (facing in the current direction) is always generated in response to the initial pressure gradient across the density front. This density-driven geostrophic current is dynamically similar to that resulting from initial disturbances in layer thickness h (equivalently, potential vorticity q = f / h) in constant-density models, with low salinity (density) in the variable-density model being analogous to the low q in the constant-density model. Solutions to the 11/2-layer model driven by river outflow are fundamentally different in low-R0 (Rossby number) and high-R0 regimes. In the low-R0 case, plumes advance along both upstream and downstream coasts. If Mr is less than a critical value Mcr (determined by ΔS = Sj - Sr and H1), plumes are coastally-trapped and all the river water-first flows upstream, with some of it, together with some salty water, reversing direction near the plume nose to flow along the offshore front, this return flow passes the river mouth and continues to flow along the downstream (to the right of the river mouth) coast. When Mr \u3e Mcr, the plumes expand offshore indefinitely, and some river water must flow downstream directly. The evolution of the river plume for the low-R0 solutions can be understood in terms of two distinct flow patterns. One is a downstream coastal current ( coastal mode ) directly forced by the river transport; it is dynamically similar to the response in a linear, constant-density, 11/2-layer model, and is responsible for the downstream motion. The other is an anticyclonic circulation ( gyre mode ) due to geostrophic adjustment of the river plume; the coastal current of this circulation is responsible for the upstream motion. Analytical solutions illustrate that geostrophic adjustment along the offshore density front generates the return flow and that Kelvin waves originating from the plume nose cause the upstream flow. They also allow the plume width L and the upstream nose speed c of the nose to be determined as a function of model parameters. For the high-R0 solutions, river water flows directly offshore in a narrow jet. The angle in which the jet emerges from the river mouth is found to depend on several non-dimensional parameters. Inclusion of entrainment significantly inhibits the upstream plume propagation, and makes it difficult to distinguish low-R0 and high-R0solutions. In solutions to the 21/2-layer model, the upper-layer circulation is not significantly different from that in their 11/2-layer counterparts. A pre-existing downstream coastal current significantly weakens upstream plume propagation; indeed, the upstream advance can be completely stopped if the background current is strong enough. Ekman flow and alongshore currents induced by upwelling-favorable winds push the plume offshore and upstream, whereas downwelling-favorable winds result in a coastally trapped plume that is advected downstream

Social Big Data: Mining, Applications, and Beyond

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Adjustment of wind-drift effect for real-time systematic error correction in radar rainfall data

An effective bias correction procedure using gauge measurement is a significant step for radar data processing to reduce the systematic error in hydrological applications. In these bias correction methods, the spatial matching of precipitation patterns between radar and gauge networks is an important premise. However, the wind-drift effect on radar measurement induces an inconsistent spatial relationship between radar and gauge measurements as the raindrops observed by radar do not fall vertically to the ground. Consequently, a rain gauge does not correspond to the radar pixel based on the projected location of the radar beam. In this study, we introduce an adjustment method to incorporate the wind-drift effect into a bias correlation scheme. We first simulate the trajectory of raindrops in the air using downscaled three-dimensional wind data from the weather research and forecasting model (WRF) and calculate the final location of raindrops on the ground. The displacement of rainfall is then estimated and a radar–gauge spatial relationship is reconstructed. Based on this, the local real-time biases of the bin-average radar data were estimated for 12 selected events. Then, the reference mean local gauge rainfall, mean local bias, and adjusted radar rainfall calculated with and without consideration of the wind-drift effect are compared for different events and locations. There are considerable differences for three estimators, indicating that wind drift has a considerable impact on the real-time radar bias correction. Based on these facts, we suggest bias correction schemes based on the spatial correlation between radar and gauge measurements should consider the adjustment of the wind-drift effect and the proposed adjustment method is a promising solution to achieve this

Indirect damage of urban flooding:Investigation of flood-induced traffic congestion using dynamic modeling

In many countries, industrialization has led to rapid urbanization. Increased frequency of urban flooding is one consequence of the expansion of urban areas which can seriously affect the productivity and livelihoods of urban residents. Therefore, it is of vital importance to study the effects of rainfall and urban flooding on traffic congestion and driver behavior. In this study, a comprehensive method to analyze the influence of urban flooding on traffic congestion was developed. First, a flood simulation was conducted to predict the spatiotemporal distribution of flooding based on Storm Water Management Model (SWMM) and TELAMAC-2D. Second, an agent-based model (ABM) was used to simulate driver behavior during a period of urban flooding, and a car-following model was established. Finally, in order to study the mechanisms behind how urban flooding affects traffic congestion, the impact of flooding on urban traffic was investigated based on a case study of the urban area of Lishui, China, covering an area of 4.4 km2. It was found that for most events, two-hour rainfall has a certain impact on traffic congestion over a five-hour period, with the greatest impact during the hour following the cessation of the rain. Furthermore, the effects of rainfall with 10- and 20-year return periods were found to be similar and small, whereas the effects with a 50-year return period were obvious. Based on a combined analysis of hydrology and transportation, the proposed methods and conclusions could help to reduce traffic congestion during flood seasons, to facilitate early warning and risk management of urban flooding, and to assist users in making informed decisions regarding travel

Roll-to-Roll Manufacturing of Robust Superhydrophobic Coating on Metallic Engineering Materials

Creating a robust superhydrophobic surface on the conventional engineering materials at mass production is of great importance for self–cleaning, anti–icing, non–wetting surface and low flow resistance in industrial applications. Herein, we report a roll–to–roll strategy to create durable and robust superhydrophobic surfaces with designed micro–/nano– scale hierarchical structures on many conventional engineering materials by combining electrical discharge machining, coating of carbon nanoparticles, and followed by oil penetration and drying. The treated surface shows good superhydrophobic properties with static water contact angle of 170±2o and slide angle of 3±1o. The treated surface also exhibits good resilience and maintains the performance after tested in various harsh conditions including water flushing for several days, sand abrasion, scratching with sandpapers and corrosive solution. Significantly, the superhydrophobic surfaces also shows a high efficiency of self–cleaning properties even after oil–contamination during applications

Knockout of the S-acyltransferase Gene, PbPAT14, Confers the Dwarf Yellowing Phenotype in First Generation Pear by ABA Accumulation.

The development of dwarf fruit trees with smaller and compact characteristics leads to significantly increased fruit production, which is a major objective of pear (Pyrus bretschneideri) breeding. We identified the S-acylation activity of PbPAT14, an S-acyltransferase gene related to plant development, using a yeast (Saccharomyces cerevisiae) complementation assay, and also PbPAT14 could rescue the growth defect of the Arabidopsis mutant atpat14. We further studied the function of PbPAT14 by designing three guide RNAs for PbPAT14 to use in the CRISPR/Cas9 system. We obtained 22 positive transgenic pear lines via Agrobacterium-mediated transformation using cotyledons from seeds of Pyrus betulifolia ('Duli'). Six of these lines exhibited the dwarf yellowing phenotype and were homozygous mutations according to sequencing analysis. Ultrastructure analysis suggested that this dwarfism was manifested by shorter, thinner stems due to a reduction in cell number. A higher level of endogenous abscisic acid (ABA) and a higher transcript level of the ABA pathway genes in the mutant lines revealed that the PbPAT14 function was related to the ABA pathway. Overall, our experimental results increase the understanding of how PATs function in plants and help elucidate the mechanism of plant dwarfism