Positive Surge Research Articles

Defining and Mitigating Flow Instabilities in Open Channels Subjected to Hydropower Operation: Formulations and Experiments

A thorough literature review was conducted on the effects of free surface oscillation in open channels, highlighting the risks of the occurrence of positive and negative surge waves that can lead to overtopping. Experimental analyses were developed to focus on the instability of the flow due to constrictions, gate blockages, and the start-up and shutdown of hydropower plants. A forebay at the downstream end of a tunnel or canal provides the right conditions for the penstock inlet and regulates the temporary demand of the turbines. In tests with a flow of 60 to 100 m3/h, the effects of a gradually and rapidly varying flow in the free surface profile were analyzed. The specific energy and total momentum are used in the mathematical characterization of the boundaries along the free surface water profile. A sudden turbine stoppage or a sudden gate or valve closure can lead to hydraulic drilling and overtopping of the infrastructure wall. At the same time, a PID controller, if programmed appropriately, can reduce flooding by 20–40%. Flooding is limited to 0.8 m from an initial amplitude of 2 m, with a dissipation wave time of between 25 and 5 s, depending on the flow conditions and the parameters of the PID characteristics.

Spatio-temporal features of ionospheric disturbances resulting from March 2023 geomagnetic storm: Comparisons with March 2015 St. Patrick’s Day storm

This study explores the ionospheric disturbances induced by the March 2023 geomagnetic storm, offering insights into the complex interplay between space weather events and the Earth’s upper atmosphere. In this regard, data from ionospheric maps (global and regional electron contents) and topside plasma density (provided by the Swarm satellites) have been used. Furthermore, the findings are compared with those of the March 2015 St. Patrick’s Day storm of solar cycle 24, which exhibited notably similar onset conditions. The Global Electron Content (GEC) displays substantial positive surges in the African, Pacific, and American sectors, with a notable enhancement in the American sector on March 24, 2023. During the recovery phase (March-23 storm), negative storm effects are observed across all longitudinal sectors, with greater intensity at low-latitudes compared to mid-latitudes. Moreover, the study highlights discrepancies in positive storm effects when compared to the St. Patrick’s Day storm. During the March-2023, there was no positive storm effect observed in the pacific mid-latitude regions. This longitudinal difference in occurrence of positive storm may be attributed to potential influences from variations in the z-component of the interplanetary magnetic field and energy inputs into the magnetosphere. A super fountain effect is observed exclusively in the American sectors during both storms, exhibiting a noticeable hemispheric asymmetry. The non-uniform planetary distribution of disturbed thermospheric winds likely played a major role in the ionospheric asymmetry in the American region during the 2023 event.

Mean sea level, tidal components and surges in Guanabara Bay (Rio de Janeiro) from 1990 to 2021

AbstractGuanabara Bay, located in the Metropolitan Region of Rio de Janeiro, one of the largest urban coastal areas in the Southern Hemisphere, is subject to intense maritime traffic due to the presence of several ports. These facilities are affected by sea level fluctuations, influenced by atmospheric and astronomical forces, which motivates synoptic and climatological analysis, including meteorological and astronomical tidal phenomena. This study aimed to assess the evolution of tidal components and the relative mean sea level (MSL) between 1990 and 2021, as well as the atmospheric influence on extreme meteorological tide events, in which the MSL exceeded ±2 and ±3 (±29.98 and ±44.97 cm) standard deviations. The results have shown that, albeit small, the main tidal components (, , , , , , and ) indicated positive trends in the increase of amplitude and phase, despite the small quantities. For the relative MSL, an increase of 0.30 cm·year−1 was observed in agreement with estimates from global series from satellite altimeters and climate model predictions. Pressure and wind field analyses led to the identification of seasonal variability and the pattern of evolution of atmospheric systems associated with extreme events. In the case of positive surges, very intense winds from the SW, extending along the S/SE Brazilian coast, are caused by the presence of a high‐pressure centre over the continent and low‐pressure centres over the ocean, leading to water piling up. In turn, negative surges are caused by the presence of an anticyclone over the ocean, generating NE winds parallel to the coast of Rio de Janeiro, inducing Ekman transport and lowering the sea level. Therefore, the extreme sea level events in the Guanabara Bay are not triggered by local forces, but rather depend on the temporal persistence and direction of winds along the S/SE Brazilian coast.

Effects of tropical cyclone intensity on spatial footprints of storm surges: an idealized numerical experiment

Abstract Storm surges caused by tropical cyclones (TCs) have long ranked first among all types of marine disasters in casualties and economic losses, and can lead to further regional exacerbation of consequences stemming from these losses along different coastlines. Understanding the spatial footprints of storm surges is thus highly important for developing effective risk management and protection plans. To this end, we designed an ideal storm surge model based on FVCOM to explore the relationship between TC intensity and the spatial footprint of storm surges, and its intrinsic mechanism. The spatial footprints of both positive and negative storm surges were positively correlated with TC intensity; however, the latter was more sensitive to the intensity when the TC intensity is weaker than CAT3 TC’s. The average positive storm surge footprint of CAT1 was 574 km, with CAT3 and CAT5 increasing by 6% and 25%, respectively, compared to CAT1. The average spatial footprint of the negative storm surge of CAT1 was 1,407 km, with CAT3 and CAT5 increasing by 18% and 29%, respectively, compared to CAT1. The decomposition and mechanism analysis of the storm surge show that the main contributing component of the total surge at the south end of the storm’s landfall and during the time of the forerunner was the Ekman surge, whereas the contribution of the normal surge component to the north and during the time of the main surge and resurgence was dominant. In addition, not all the spatial footprints of the storm surge components increased with the TC intensity, as the total surge did, similar to the Ekman surge. These quantitative analyses and intrinsic mechanisms provide a theoretical basis for predicting and evaluating storm surge risks.

P-674 Rescue oocyte collection: a strategy to reduce cycle cancellations in natural/natural modified IVF/ ICSI cycles with luteinising hormone (LH) surge among poor responder patients

Abstract Study question Can an early oocyte collection (OC) avoid cycle cancellation due to spontaneous ovulation in poor responders undergoing natural/ natural modified (N/NM) cycle-IVF? Summary answer Rescue OC may prevent premature ovulation following spontaneous LH surge in N/NM-IVF cycles allowing retrieval of mature oocytes, high-grade embryos that may result in livebirths. What is known already Natural IVF cycles carry an inherent higher risk of spontaneous LH surge and ovulation before OC. The introduction of gonadotropin releasing hormone antagonist with low-dose gonadotropin add-back has reduced these risks.Timing of ovulation trigger and trigger to OC interval are important to balance the risks of spontaneous ovulation with the chance of retrieving mature oocyte(s). In the absence of LH surge, the trigger to OC interval is normally 35 hours. However, it is challenging to schedule OC once LH surge has occurred.The effectiveness of rescue OC following LH surge has not been well explored. Study design, size, duration This is a retrospective analysis of all NC/NM-IVF/ICSI cycles in poor responders who had spontaneous urinary LH surge from over a period of 3 years, across five Fertility Centres under one company sharing the same treatment protocol. Participants/materials, setting, methods All women fulfilling the Bologna criteria for poor ovarian response underwent IVF/ICSI cycles with NC/ NM protocol. The study population included those who had a positive urinary LH surge without or despite the use of antagonist. A rescue OC scheduled 18 to 24 hours after a spontaneous urinary LH surge. Choriogonadotropin alfa (Ovitrelle) 250 micg was administered as soon as the surge was detected. Patients were also given indomethacin 8 hourly until OC. Main results and the role of chance Amongst 735 NC/NM-IVF/ ICSI cycles in poor responder women during the study period, 54 cycles (7.3%) had spontaneous urinary LH surge. Twenty-eight cycles were with NC-IVF and 26 NM-IVF protocol. Only 8 (14.8%) cycles did not progress to OC due to spontaneous ovulation. In 46 (85.2%) of cycles, at least one oocyte was successfully retrieved, with a total of59 retrieved oocytes. ICSI cycles identified at least one mature oocyte in 82% of the cycles. Fertilisation rate with IVF and ICSI cycles combined was 49.1% and at least one cleavage-stage embryo was created from 24 (44.4%) of all cycles (52.2% of retrieved cycles). High-grade embryo(s) was obtained in 42.5% of all cycles. Clinical pregnancy rate (CPR) and live birth rate (LBR) per embryo transfer were 18.7% and12.5%, respectively. Limitations, reasons for caution This study was retrospective in nature, without a comparator group. Combination of both NC-IVF and NM-IVF might not have implications in practical terms. Use ofindomethacin also could have delayed ovulation. Although population size was as expected for a rare event, it may not be adequate for a precise LBR. Wider implications of the findings An early scheduling of OC in the event of LH surge is an effective way to reduce cycle cancellation rate which is a risk in NC/NM-IVF cycles. It also can potentially result in livebirths. This approach may encourage clinicians practising NC/NM-IVF to test and validate our findings. Trial registration number not applicable

Cryptocurrency Turmoil: Unraveling the Collapse of a Unified Stablecoin (USTC) through Twitter as a Passive Sensor.

This study sought to explore whether Twitter, as a passive sensor, could have foreseen the collapse of the Unified Stablecoin (USTC). In May 2022, in just a few days, the cryptocurrency went to near-zero valuation. Analyzing 244,312 tweets from 89,449 distinct accounts between April and June 2022, this study delved into the correlation between personal sentiments in tweets and the USTC market value, revealing a moderate correlation with polarity. While sentiment analysis has often been used to predict market prices, the results suggest the challenge of foreseeing sudden catastrophic events like the USTC collapse solely through sentiment analysis. The analysis uncovered unexpected global interest and noted positive sentiments during the collapse. Additionally, it identified events such as the launch of the new Terra blockchain (referred to as "Terra 2.0") that triggered positive surges. Leveraging machine learning clustering techniques, this study also identified distinct user behaviors, providing valuable insights into influential figures in the cryptocurrency space. This comprehensive analysis marks an initial step toward understanding sudden and catastrophic phenomena in the cryptocurrency market.

Emerging Research Interest in Medical and Dental Undergraduates

I am writing this letter to highlight the current encouraging and commendable rise in the involvement of undergraduate medical and dental students in research across Pakistan. A positive surge was detected among the medical and dental institutes reflecting increasing interest and contribution in research activities. A study in Saudi Arabia reported the relationship between rising research trends and its contributing factors, henceforth, stating that admission into residency (56.8%), interest in research (41.8%), and aid in clinical decision-making (31%) were the top three factors for research interest 1.

Dual-directional SCR device with dual-gate controlled mechanism for ESD protection in photoelectric chip

The dual-directional silicon-controlled rectifier (DDSCR) is an electrostatic discharge (ESD) protection device. It can provide positive and negative ESD surge paths and has excellent robustness. However, industry-level sensors operating in strong electromagnetic interference environments impose higher reliability requirements on photoelectric chips. This paper proposed a novel DDSCR with a dual-gate controlled mechanism. By incorporating the gate diode triggering and the gate field modulation mechanism into the traditional DDSCR, and further utilizing additional parasitic bipolar junction transistors (BJTs) for diversion, the proposed device exhibits significantly improved ESD characteristics. Measurement results indicate that, compared to DDSCR, the proposed device exhibits a 27.5% reduction in trigger voltage (Vt1 ), a 96.1% improvement in holding voltage (Vh ), and achieves an equivalent human body model protection level of 11.45 kV, demonstrating exceptional design area efficiency. The experimental findings validate the effectiveness of the proposed device in 5 V photoelectric chip applications.

New Simple Analytical Surge/Swab Pressure Model for Power-Law and Modified Yield-Power-Law Fluid in Concentric/Eccentric Geometry

The axial movement of pipe in and out of the well generates positive (surge) and negative (swab) pressures that will impact the well pressure. When the swab and surge effects cause well pressures outside the allowable operational limits, wellbore instability (well collapse/well fracture), kick, and induced drill string sticking issues will occur. The problems increase the operational and nonproductive time-related costs. Consequently, the drilling budget rises significantly. It is therefore, imperative to predict the differential pressures in order to mitigate the problems. Even though several models have been developed in the past, models work for the considered experimental setup and conditions. In this paper, a simple analytical model was derived for eccentric/concentric annuli. The fluid rheological behaviors were assumed to be described by power law and yielded power-law. The model is derived based on a steady state condition, and the effects of tripping speed, the power-law fluids, the yield-power-law fluids rheological parameters, and well geometries are considered. The model is compared with experimental data from the literature and with the existing model. Parametric sensitivity studies have been conducted. Results show that the model prediction exhibited quite good performance, with an average percentile error deviation of 9.9% and 6.2% for the power-law and yield-power-law fluids, respectively. However, more testing is required to determine the model’s limitations and application.

A Numerical Study on Storm Surge Dynamics Caused by Tropical Depression 29W in the Pahang Region

Amid mounting concerns about climate change’s impact on coastal areas, this study investigates storm surge dynamics induced by Tropical Depression 29W (TD 29W) using the MIKE 21 model. Comprehending the complex mechanisms behind storm surges is crucial considering gaps in understanding their combined influences, including tide–surge interactions, varying typhoon parameters, and changing storm tracks. The impacts of climate change, including accelerating sea level rise and its correlation with storm surge magnitudes, require detailed investigations for effective disaster management in vulnerable coastal communities. Through precise calibration, matching simulations with tidal gauge stations, this research uncovers the intricate interplay between landfall timing, diverse storm tracks, wind intensities, and the amplifying impact of rising sea levels. Findings indicate surge residuals ranging from −0.03m to 0.01m during TD 29W’s landfall, with higher surge residuals during rising tide phases. Moreover, an increase in TD 29W’s maximum wind speed moderately influences positive surges while significantly amplifying negative surge heights by 68% to 92% with wind speed increments. An analysis of typhoon track variations emphasizes the vulnerability of the Pahang coast to changing storm dynamics, underlining the need for tailored resilience strategies. Projections suggest a significant surge height increase by the year 2100, emphasizing the urgency of adaptive measures for the region.

Normal and reverse storm surges along the coast of Florida during the September 2022 Hurricane Ian: Observations, analysis, and modelling

The September 2022 Hurricane Ian was among the most destructive hurricanes to hit the US coasts. Ian was one of the rare events that produced both positive (normal) and negative (reverse) surges. We analyse and model the generation mechanism of these surges through studying sea level, air pressure, and wind observations as well as numerical modelling. Analysis of a rich observation dataset helped us to explain their simultaneous generations for the first time. Among the examined data, maximum wind speed was 50–60 m/s and the minimum air pressure was 961.6 hPa. Although three factors of wind, pressure drop, and geometry contribute to surge generation, we found that wind was the dominant factor. Despite the opposing impacts of pressure drop and wind on reverse surge generation, the amplitudes of reverse surges (2.4 m) were larger than those of normal surges (over 1.8 m). Normal and reverse surges were consistently generated by landward and seaward winds, respectively. Reverse surges occurred at parts of the coast under seaward wind that experienced less intensive pressure drop. We successfully modelled both normal and reverse surges. Our model can be employed for forecasting unique storm surges such as those generated during Hurricane Ian.

Improving the short‐range forecast of storm surges in the southwestern Atlantic continental shelf using 4DEnSRF data assimilation

In this study, the assimilation of tide gauge and altimetry data into a two‐dimensional barotropic numerical model for the southwestern Atlantic continental shelf (SWACS) was developed. To do this, the preoperative 4‐day storm surges ensemble prediction system developed by Dinápoli et al. (2021, Journal of the Royal Meteorological Society 147: 557–572) was implemented for the SWACS. This new configuration, called “Model for Storm Surge Simulations” (M3S), considers a curvilinear grid that covers the SWACS with higher resolution along the shoreline (from 2 to 10 km). M3S was forced with an ensemble of 60 members conformed by the combination of perturbations of the eight principal tidal constituents and of the atmospheric products derived from the Global Ensemble Forecast System. Tidal gauge and altimetry data were assimilated in an asynchronous mode using the four‐dimensional‐ensemble square‐root filter (4DEnSRF). The system was developed and validated forecasting two strong positive storm surges. Results show that 4DEnSRF's innovations produce a positive impact upon the forecast skill up to 2 days. Hence, the 4‐day forecast can be divided into two parts: the first 2 days with a stronger dependence on the initial conditions and the other 2 days purely driven by external forcing. It was found that a symmetric assimilation window of 12 hr length produces the best initial condition. Under this configuration, 4DEnSRF removes biases and improves the timing of the M3S forecasted solutions. The largest improvements were observed at the northern SWACS, where more chaotic processes, such as the atmospheric circulation, explain a large part of the sea‐surface height variability. No significant improvements were found at the southern SWACS, which can be attributed to the strong tidal dynamics that characterise the zone. Our results show that the incorporation of 4DEnSRF into M3S can significantly improve the forecast in the SWACS and also the accuracy of the short‐range detection of storm surges.

Hindcasting and predicting surge heights and waves on the Taiwan coast using a hybrid typhoon wind and tide-surge-wave coupled model

The tide-surge-wave coupled model and hybrid typhoon wind model were developed for the Taiwan coast and employed to predict surge heights and waves under different influential factors during historical typhoon events. The results revealed that the hybrid wind model matched the measured atmospheric pressure and wind speed time series during Typhoon Soudelor (2015) and Typhoon Nesat (2017). Afterward, the measured water level, wave height, and wave period time series at different measuring stations were used to validate the tide-surge-wave coupled model. The coupled model reasonably reproduced the measured data. Subsequently, the validated model was utilized to explore the influence of the radius of maximum wind (RMW), forward speed, atmospheric pressure, wind intensity, and typhoon path on surge height, wave height, and wave setup. The results with model prediction indicate that increasing the RMW causes an increasing negative surge height and wave height and shifts the time of the peak positive surge height and peak wave height. A smaller forward speed results in a larger positive peak surge height and peak wave height at most stations. The maximum ratio changes in negative peak surge height compared with the baseline condition with Typhoon Soudelor (2015) are 105.4% and −116.0% for increasing and decreasing 20 hPa atmospheric pressures at the Linshanbi station, respectively. The differences in maximum peak wave height (ratio change) for an increasing and decreasing 10 m/s wind speed are 6.44 m (47.2%) and −5.80 m (−42.4%), respectively. The predicted results indicate that the difference in the maximum peak positive surge height (maximum ratio change) compared with the baseline condition is 1.1 m (315.2%), thereby shifting the typhoon track to the north by 100 km at the Waipu station.

Modeling the Sea Level Response of the Northern East China Sea to Different Types of Extratropical Cyclones

AbstractSea level response to extratropical cyclones, one of the most disastrous weather systems, varies depending on cyclone types and tracks. This study presents a systematic modeling assessment of storm surge induced by extratropical cyclones in the northern East China Sea using an ocean‐wave coupled model, based on the Coupled Ocean‐Atmosphere‐Wave‐Sediment Transport (COAWST) model system. We identified the type of extratropical cyclone most likely to cause disasters and the areas likely to suffer the worst effects. We conducted sensitivity experiments to analyze the driving mechanisms (such as wind, air pressure, tide, and wave) and influencing mechanisms (such as local and remote meteorological effect and Ekman effect) of storm surge. During strong winds, positive and negative storm surges were consistent with the wind direction, and formed source of coastal trapped waves. When an abnormally high water level occurred in a semi‐enclosed sea area, it propagated mainly along the cyclone direction. The energy of coastal trapped waves was easy to dissipate in case of caps and other locations with large topographic changes. Tide‐surge‐wave interaction and propagation were also greatly affected by coastal trapped waves.

Global and local effects of seismic activity in the ionosphere

We considered ionospheric effects of powerful seismic events using total electron content (TEC) maps of the ionosphere (http:// www.aiub.unibe.ch/download/CODE/) for the northern hemisphere, except the polar region, in the winter seasons of 2012— 2018. It is shown that the seismic-ionospheric effect is global, which is superimposed by local effects over the epicenters of individual earthquakes (EQ). Temporal TEC variations near the time of strong EQs at a great distance from their epicenters (global effect) consist of two maxima: the precursor and the «aftershock» maximum. In TEC variations over the EQ epicenter (local effect), only a precursor is usually registered, the amplitude of which at night (on average, ~ 8 %) is about twice as high as during the day. Always (locally and globally) after a positive surge in TEC, its reduced values are observed for several days. The maximum amplitude zone of the seismic-ionospheric effect belongs to the middle latitudes, especially 35...40° N, and within this zone at longitudes near 30° W (Mid-Atlantic ridge) and 140...150° E (Japanese islands and adjacent waters of the Pacific Ocean). Latitudinal amplitude maxima of the seismic-ionospheric effect are in good agreement with the latitudinal maxima of the EQ number in both geographic and geomagnetic coordinate systems. Changes in the EQ number and, consequently, the effect in the ionosphere on geomagnetic coordinates are more ordered, which indicates a significant impact on the seismicity of the same processes at the boundary of the liquid core and lower mantle, which form the Earth’s magnetic field. In addition to seismic belts and zones of mid-ocean ridges, an increase in TEC has been recorded along the so-called lineaments, marking the weakened zones of the Earth’s crust with increased flows of deep gases. The correspondence between the spatial features of seismicity and the seismic-ionospheric effect testifies in favor of the «radon» mechanism of lithosphere-ionosphere coupling and indirectly confirms the role of deep gases in the formation of seismicity planetary features.

Is green and sustainable technological innovation a potential driver of environmental performance? an empirical investigation across the ASEAN region

Environmental degradation is a significant concern that jeopardizes global sustainable production and consumption. In this instance, ASEAN (Association of South-East Asian Nations) has contributed to a considerable amount of carbon dioxide (CO2) emissions throughout the modernization phase. However, there is a paucity of information within this region on the non-linear impact of transitions in green and sustainable technological innovation on CO2 emissions. In response, the present work endeavors to bridge the existing research gap by examining the asymmetrical and periodic interactions between green and sustainable technological innovation and CO2 emissions by employing cross-sectional time series data of 7-ASEAN economies over the period 1990 to 2017. The co-integrating connections between the specified parameters were established using the Wester-Lund cointegration technique. Further, the Cross-Sectionally Augmented Autoregressive Distributed Lag estimator revealed that negative disruptions in green and sustainable technological innovation lead to CO2 emissions during downturns. Secondarily, the findings confirmed positive surges in green and sustainable technological innovation minimize CO2 emissions during times of economic expansion. Also, as compared to foreign direct investment, current statistics indicate that renewable energy utilization seems to have a substantial impact on reducing carbon emissions. Besides, the robustness analysis corroborated the uniformity and validity of the given outcomes. Consequently, the outcomes divulged a counter-cyclical interaction between green and sustainable technological innovation and CO2 emissions.

Critical analysis of turbulence models for simulating positive surge waves in open channels in a RANS-VOF setup

Critical analysis of turbulence models for simulating positive surge waves in open channels in a RANS-VOF setup

Nonlinear Modeling and Stability of a Doubly-Fed Variable Speed Pumped Storage Power Station with Surge Tank Considering Nonlinear Pump Turbine Characteristics

This paper investigates the nonlinear modeling and stability of a doubly-fed variable speed pumped storage power station (DFVSPSPS). Firstly, the mathematical model of DFVSPSPS with surge tank considering nonlinear pump turbine characteristics was derived and established. Then, Hopf bifurcation analysis of DFVSPSPS was performed. The stable region was identified and verified by example analysis. Moreover, the effect mechanism of nonlinear pump turbine characteristics on the stability of DFVSPSPS was explored. Finally, the influence of factors on the stability and dynamic response of DFVSPSPS was studied. The results indicate that the emerged Hopf bifurcation of DFVSPSPS is supercritical and the region on the low side of the bifurcation line is the stable region. Nonlinear head characteristics have a significant influence on the stability and dynamic response of DFVSPSPS. Nonlinear speed characteristics have an obvious effect on the stability and dynamic response of DFVSPSPS only under positive load disturbance and unstable surge tank. Nonlinear head characteristics are unfavorable for the stability of DFVSPSPS under positive load disturbance and favorable under negative load disturbance. A smaller flow inertia of penstock, a smaller head loss of penstock and a greater unit inertia time constant are favorable for the stability of DFVSPSPS. The stable region under the positive disturbance of active power is larger than that under the negative disturbance of active power. The time constant of the surge tank presents a saturation characteristic on the stability of DFVSPSPS.

An Application of Kolmogorov Complexity and Its Spectrum to Positive Surges

A positive surge is associated with a sudden change in flow that increases the water depth and modifies flow structure in a channel. Positive surges are frequently observed in artificial channels, rivers, and estuaries. This paper presents the application of Kolmogorov complexity and its spectrum to the velocity data collected during the laboratory investigation of a positive surge. Two types of surges were considered: a undular surge and a breaking surge. For both surges, the Kolmogorov complexity (KC) and Kolmogorov complexity spectrum (KCS) were calculated during the unsteady flow (US) associated with the passage of the surge as well as in the preceding steady-state (SS) flow condition. The results show that, while in SS, the vertical distribution of KC for Vx is dominated by the distance from the bed, with KC being the largest at the bed and the lowest at the free surface; in US only the passage of the undular surge was able to drastically modify such vertical distribution of KC resulting in a lower and constant randomness throughout the water depth. The analysis of KCS revealed that Vy values were peaking at about zero, while the distribution of Vx values was related both to the elevation from the bed and to the surge type. A comparative analysis of KC and normal Reynold stresses revealed that these metrics provided different information about the changes observed in the flow as it moves from a steady-state to an unsteady-state due to the surge passage. Ultimately, this preliminary application of Kolmogorov complexity measures to a positive surge provides some novel findings about such intricate hydrodynamics processes.

Water Circulation Driven by Cold Fronts in the Wax Lake Delta (Louisiana, USA)

Atmospheric cold fronts can periodically generate storm surges and affect sediment transport in the Northern Gulf of Mexico (NGOM). In this paper, we evaluate water circulation spatiotemporal patterns induced by six atmospheric cold front events in the Wax Lake Delta (WLD) in coastal Louisiana using the 3-D hydrodynamic model ECOM-si. Model simulations show that channelized and inter-distributary water flow is significantly impacted by cold fronts. Water volume transport throughout the deltaic channel network is not just constrained to the main channels but also occurs laterally across channels accounting for about a quarter of the total flow. Results show that a significant landward flow occurs across the delta prior to the frontal passage, resulting in a positive storm surge on the coast. The along-channel current velocity dominates while cross-channel water transport occurs at the southwest lobe during the post-frontal stage. Depending on local weather conditions, the cold-front-induced flushing event lasts for 1.7 to 7 days and can flush 32–76% of the total water mass out of the system, a greater range of variability than previous reports. The magnitude of water flushed out of the system is not necessarily dependent on the duration of the frontal events. An energy partitioning analysis shows that the relative importance of subtidal energy (10–45% of the total) and tidal energy (20–70%) varies substantially from station to station and is linked to the weather impact. It is important to note that within the WLD region, the weather-induced subtidal energy (46–66% of the total) is much greater than the diurnal tidal energy (13–25% of the total). The wind associated with cold fronts in winter is the main factor controlling water circulation in the WLD and is a major driver in the spatial configuration of the channel network and delta progradation rates.