Wind Episodes Research Articles

Hypoxia Triggered by Expanding River Plume on the East China Sea Inner Shelf During Flood Years

AbstractThe frequency of riverine floods is predicted to increase in East Asia. However, the response of coastal hypoxia (<63 μmol L−1) to floods has not been well understood. In the summer of 2020, characterized by one of the most significant Changjiang water fluxes in three decades, we conducted a cruise during the flood period on the East China Sea inner shelf. Our observations revealed severe bottom hypoxia with a maximum spatial coverage of ∼11,600 km2 and a minimum dissolved oxygen concentration (DO) of 21 μmol L−1. In the surface layer, the relationships between salinity and nitrate, dissolved inorganic carbon (DIC) indicated significant organic matter production, validated by a high‐Chlorophyll‐a (Chl a) patch (>5 μg L−1). Furthermore, the significant relationship between apparent oxygen utilization and DIC of deep waters reveals that the organic matter decomposition primarily drove the hypoxia during the flood period. Episodic wind events also influenced bottom DO and DIC, by transporting surface waters to the deep. Multiple‐years data set shows that the average Changjiang nitrate flux during flood years is about 1.4 times that during non‐flood years. The flood waters mix with estuarine waters, forming the high‐nutrient plume waters, which expanded farther offshore during the flood period. While high turbidity remained confined to the inner estuary. Consequently, the high‐Chl a area significantly expanded, which significantly exacerbated the hypoxia.

Modeling Heat and Water Exchanges between the Atmosphere and an 85-km2 Dimictic Subarctic Reservoir Using the 1D Canadian Small Lake Model

Abstract Accurately modeling the interactions between inland water bodies and the atmosphere in meteorological and climate models is crucial, given the marked differences with surrounding landmasses. Modeling surface heat fluxes remains a challenge because direct observations available for validation are rare, especially at high latitudes. This study presents a detailed evaluation of the Canadian Small Lake Model (CSLM), a one-dimensional mixed-layer dynamic lake model, in reproducing the surface energy budget and the thermal stratification of a subarctic reservoir in eastern Canada. The analysis is supported by multiyear direct observations of turbulent heat fluxes collected on and around the 85-km2 Romaine-2 hydropower reservoir (50.7°N, 63.2°W) by two flux towers: one operating year-round on the shore and one on a raft during ice-free conditions. The CSLM, which simulates the thermal regime of the water body including ice formation and snow physics, is run in offline mode and forced by local weather observations from 25 June 2018 to 8 June 2021. Comparisons between observations and simulations confirm that CSLM can reasonably reproduce the turbulent heat fluxes and the temperature behavior of the reservoir, despite the one-dimensional nature of the model that cannot account for energy inputs and outputs associated with reservoir operations. The best performance is achieved during the first few months after the ice break-up (mean error = −0.3 and −2.7 W m−2 for latent and sensible heat fluxes, respectively). The model overreacts to strong wind events, leading to subsequent poor estimates of water temperature and eventually to an early freeze-up. The model overestimated the measured annual evaporation corrected for the lack of energy balance closure by 5% and 16% in 2019 and 2020. Significance Statement Freshwater bodies impact the regional climate through energy and water exchanges with the atmosphere. It is challenging to model surface energy fluxes over a northern lake due to the succession of stratification and mixing periods over a year. This study focuses on the interactions between the atmosphere of an irregular shaped northern hydropower reservoir. Direct measurements of turbulent fluxes using an eddy covariance system allowed the model assessment. Turbulent fluxes were successfully predicted during the open water period. Comparison between observed and modeled time series showed a good agreement; however, the model overreacted to high wind episodes. Biases mostly occur during freeze-up and breakup, stressing the importance of a good representation of the ice cover processes.

Time-dependent AGN disc winds – I. X-ray irradiation

ABSTRACT We study active galactic nucleus (AGN) line-driven disc winds using time-dependent radiation hydrodynamics. The key criterion for determining wind launching is the coupling strength of the ultraviolet radiation field via the spectral lines of the gas. The strength of these lines in turn relies crucially on the gas ionization state, determined by the local X-ray intensity. We consider a suite of models where the central ionizing radiation is affected by scattering, absorption, and re-emission by the intervening gas. In a pure attenuation model, the disc launches an episodic wind, as previous studies have shown. Including scattering or re-emission tends to weaken the wind, lowering the mass flux and outflow velocity and, if sufficiently dominant, suppressing the outflow entirely. However, the exponential nature of radiative attenuation means that only a modest, factor of a few, increase in the absorption cross-section can overcome the wind suppression due to scattering and re-emission. We find mass outflow rates of ∼20 per cent or more of the assumed inflow rate through the disc, indicating that radiation-driven winds may significantly alter the structure of the accretion flow. The winds also supply a large, time-varying column of material above the nominal constant disc scale height, which will determine the geometry of reprocessed emission from the central source. Our results suggest the need for accurate photoionization modelling, radiation transport, and accretion disc physics, to study their effects on the AGN disc winds.

Recurrent symmetrical bendings cause dwarfing in Hydrangea through spatial molecular regulation of xylem cell walls.

Environmental prejudices progressively lead to the ban of dwarfing molecules in agriculture, and alternatives are urgently required. Mechanical stimulation (MS) is a promising, eco-friendly, and economical technique, but some responses to mechanical stimulation vary from one plant species to another. Additionally, as more frequent and violent wind episodes are forecasted under global climate change, knowledge of plant responses to stimuli mimicking wind sways is decisive for agriculture. However, little is known about plant mechanosensitive responses after long-term, recurrent MS. Here, the effects of 3-week, recurrent, symmetrical bendings (1 or 12 per day) in Hydrangea macrophylla stems are examined. Bendings repressed internode elongation and leaf area development, whereas the diametrical growth of the basal internode is increased. Responses were dose-dependent, and no desensitization was observed during the 3 weeks of treatment. MS was almost as efficient as daminozide for plant dwarfing, and it improved stem robustness. Histological and molecular responses to MS were spatially monitored and were concordant with ongoing primary or secondary growth in the internodes. Our molecular data provide the first knowledge on the molecular paths controlled by mechanical loads in Hydrangea and revealed for the first time the involvement of XYP1 in thigmomorphogenetic responses. MS still had a transcriptional impact 48 h after the last bending session, promoting the expression of XYP1, FLA11, and CAD1 while repressing the expression of EXP3 and XTH33 homologs in accordance with xylogenesis, cell wall thickening, and lignin deposition in the xylem of basal internodes. In upper elongating internodes, repression of XYP1, CAD1, SAMS1, and CDC23 homologs is correlated with ongoing primary, even though stunted, growth. For producers, our findings highlight the potential of MS as a sustainable and economical option for controlling plant compactness in Hydrangea and show valuable reinforcement of stem strength.

Proteomics and transcriptomics explore the effect of mixture of herbal extract on diabetic wound healing process

BackgroundThe annual incidence of diabetic foot ulcers (DFUs) has been reported to vary from 0.2% to 11% in diabetes-specific clinical settings and less than 0.1% to 8% in community- and population-based cohorts. According to the International Diabetes Foundation, approximately 40 million to 60 million people worldwide are affected by DFUs, and a recent meta-analysis indicates a global prevalence of 6.3% among adults with diabetes, or about 33 million individuals. The cost of diabetes care is significant, amounting to $273 billion in direct and $90 billion in indirect expenses annually, in America. Foot complications in diabetes care excess annual expenditures ranging from 50% to 200% above the baseline cost of diabetes-related care. The cost of advanced-stage ulcers can be more than $50,000 per wound episode, and the direct expenses of major amputation are even higher. DFUs can be treated using various methods, including wound dressings, antibiotics, pressure-off loading, skin substitutes, stem cells, debridement, topical oxygen therapy, gene therapy and growth factors. For severe DFUs patients are at risk of amputation if treatment is not timely or appropriate. Amputating limbs not only causes physical pain to patients, but also brings economic burden due to lost productivity, and decreased employment linked to DFUs. Currently, long-term use of local antibiotics in clinical practice is prone to induce drug resistance, while growth factors do not effectively inhibit bacterial growth and control inflammation in wounds. Stem cell and gene therapies are still in the experimental stage. The method of local debridement combined with negative pressure therapy is expensive. Therefore, we urgently need an affordable, non-surgical method to treat diabetic ulcers. Extracts of bark of Bauhinia purpurea, Paeoniae rubrae, Angelica dahurica (Hoffm.) Benth. & Hook.f. ex Franch. & Sav. (Hoffm.) Benth. & Hook.f. ex Franch. & Sav., Acorus calamus L, and Radix Angelicae biseratae have been used as traditional remedies to treat inflammation-related diseases and cutaneous wounds due to their anti-inflammatory properties and their ability to promote vascular renewal. However, there have been few studies on the mixture of these five herbal extracts on diabetic wound healing. PurposeThis study was designed to assess the healing effect of a mixture of five aforementioned herbal extracts on diabetic ulcer wounds in rats, and to reveal the potential mechanisms behind any potential wound healing using transcriptomics and proteomics. Study designWe designed the experiment to explore the effects of five herbal extracts on diabetic wound healing process through in vivo experiments and to investigate the underlying mechanisms through proteomics and transcriptomics. MethodsWe used a mixture of five aforementioned herbal extract to treat rat model of diabetic established by intraperitoneal injection of streptozotocin, and a 2 × 2 cm round full-thickness skin defect was created on the back of the rat. Staphylococcus aureus (1 ml of 1.5 × 109 cfu/ml) was evenly applied to the wound. The wound was then observed for 72 h. The infected ulcer model of diabetic rats was considered to be successfully established if the wound was found to be infected with S. aureus. According to different medications, the rats were divided into three groups, namely mixture of herbal extract (MHE), Kangfuxin solution (KFS) and control (Ctrl). The effects of the medicine on wound healing were observed. HE staining and Masson staining were performed to evaluate the histopathological changes and collagen synthesis. IHC staining was used to assess the neovascularization, and M2 macrophage proliferation was determined by immunofluorescence staining. Proteomic and transcriptomic studies were performed to explore potential mechanism of five herbal extracts to promote wound healing. UHPLC-QE-MS was performed to identify the chemical composition of mixture of herbal extract. ResultsThe study show that the mixed herbal extract promotes angiogenesis, proliferation of M2 macrophages, and collagen synthesis. Transcriptomics showed that rno-miR-1298, rno-miR-144-5p, and rno-miR-92a-1-5p are vital miRNAs which also play a significant role in role in regulating wound healing. Proteomics results showed that the following proteins were important in wounds treated with MHE: Rack1, LOC100362366, Cops2, Cops6, Eif4e, Eif3c, Rpl12, Srp54, Rpl13 and Lsm7. Autophagy, PI3-Akt and mTOR signaling pathways were enriched after treatment with MHE compared to other groups. ConclusionHerein, we have shown that MHE containing extracts of bark of Bauhinia purpurea, P. rubrae, A. dahurica (Hoffm.) Benth. & Hook.f. ex Franch. & Sav., A. calamus L, and R. A. biseratae has significant wound healing effects in the diabetic ulcer wound rat model. These results suggest that local application of MHE in diabetic wounds can accelerate the wound healing process. Moreover, in vivo experiments revealed that the diabetic wound healing process was primarily mediated by angiogenesis and M2 macrophage transition. Therefore, this study may provide a promising and non-surgical therapeutic strategy to accelerate diabetic wound healing, thereby decreasing the number of limb amputations in diabetic patients.

Variability in North Sea wind energy and the potential for prolonged winter wind drought

AbstractThe United Kingdom is committed to substantially increasing offshore wind capacity in its drive to decarbonise electricity production and achieve net zero. If low wind episodes—or ‘wind drought’ events—occur during high energy demand periods, energy security may be threatened without alternative supply. The challenge of managing the variability of wind power will increase into the future as its share in the energy mix increases. This study focuses attention on the North Sea as a centre of current and planned offshore wind resource, and on the winter season, given the occurrence of weather patterns that risk security of supply. We use a large climate model ensemble, providing a dataset an order of magnitude larger than the reanalysis‐based observations, to better sample wind drought events. This leads to a more robust estimate of their frequency and persistence and their dynamical teleconnections compared with the observational record. We define week‐long wind drought events, based on a 20th percentile threshold in 10 m wind speed, during which wind power is estimated to be around half that in a typical week of winter. Wind drought events of up to two consecutive weeks have been observed, but the model indicates a 1‐in‐40 chance of three or more continuous weeks of wind drought each winter, with the single most prolonged simulated event lasting 5 weeks. There is a doubling of the likelihood of these prolonged wind drought events during El Niño, indicating that monitoring and predicting the state of the tropical Pacific may be useful in assessing the risk of wind drought events in an upcoming winter.

Is the Increase in Record of Skin Wounds in Hospitalized Patients in Internal Medicine Units a Side Effect of the COVID-19 Pandemic?

Wound care is an important public health challenge that is present in all areas of the healthcare system, whether in hospitals, long term care institutions or in the community. We aimed to quantify the number of skin wounds reported after and during the COVID-19 pandemic. This descriptive longitudinal retrospective study compared of wound records in patients hospitalized in the internal medicine service during the first year of the COVID-19 pandemic (from 1 March 2020, to 28 February 2021) and previous-year to the outbreak (from 1 January 2019, to 31 December 2019). A sample of 1979 episodes was collected corresponding to 932 inpatients, 434 from the pre-pandemic year and 498 from the first year of COVID-19 pandemic; 147 inpatients were diagnosed with SARS-CoV-2 infection (3.2%). The percentage of wound episodes in the first year of the COVID-19 pandemic was higher than the pre-pandemic year, 17.9% (1092/6090) versus 15% (887/5906), with a significant increase in the months with the highest incidence of COVID cases. This study shows an increase in the burden of wound care during the COVID-19 pandemic, and it could be attributable to the increase in the number of patients hospitalized for SARS-CoV-2 infection in internal medicine units.

Effect of Local Winds on Salinity Intrusion in the Columbia River Estuary

In the highly energetic Columbia River estuary, river discharge and tides are known as dominant factors controlling circulation. In this study, the 3D hydrodynamic unstructured-grid model SELFE is used to investigate the influence of the local wind on salinity intrusion. Numerical simulations are carried out for realistic conditions for the year 2014, with 4 km and 32 km resolution atmospheric forcing. The effect of the wind is further investigated by switching it off in the estuary. Analysis of modeled salinity intrusion length shows that the resolution of atmospheric forcing matters, and strong episodic winds occurring in winter and fall exert some control on this parameter. Energetic easterly winds tend to increase salinity intrusion length, while energetic westerly winds tend to do the reverse. Results also suggest that energetic winds can differentially alter salt intrusion in the two main channels—the north and south channels—of the estuary. These findings offer motivation for future studies to better understand these processes.

Mesoscale Variability of Surface Ducts During Santa Ana Wind Episodes

AbstractMesoscale variability of the marine boundary layer characteristics and the corresponding radio wave ducting conditions over the Southern California Bight (SCB) during three Santa Ana wind events have been examined based on the analysis of field observations and diagnosis of mesoscale model simulations. Under the influence of a dry and the stably stratified airflow from inland, a shallow moist internal boundary layer (MIBL) develops over the coastal waters. The MIBL consists of a thin well‐mixed moist layer capped by an inversion layer where the specific humidity decreases with height sharply. Accordingly, a surface duct (SD) is virtually ubiquitous with its depth compared with the MIBL depth. The wind direction and the SD characteristics exhibit diurnal variations over the SCB area associated with land and sea breezes. In addition, the MIBL interacts with the coastal topography, Channel Islands, and sea surface temperature gradients, resulting in spatial mesoscale variabilities in SD characteristics. Specifically, the SD height and strength grow with the offshore distance owing to the surface latent heat flux over sea, and in the meantime, exhibit substantial along‐shore variations. The shallow MIBL tends to split and flow around the higher elevation of the islands, leading to the formation of wakes with reduced modified refractivity. These island wakes may extend dozens of kilometers downstream with the SD height and strength growing accordingly.

Seismic Signature of Rain and Wind Inferred From Seismic Data

AbstractSeismic stations are increasingly used to monitor river activity and to quantify sediment transport during flood events. In tropical regions, cyclone‐induced floods are often associated with heavy rain and strong wind episodes, generating complex seismic records involving the simultaneous signature of water, sediment, rainfall and wind. Hence, seismic characterization of rain and wind is then required to better decipher each process and improve our understanding of the river seismic signature. In this study, we investigate experimentally the seismic response of rain and wind using data recorded by geophones deployed in various soil types and at different burial depth (BD), co‐located with various meteorological instruments. Our results show that the power spectral density (PSD) of the seismic noise intensifies at a frequency between 60 and 500 Hz for rain and 5 and 500 Hz for wind, in the presence of rain precipitation as low as 0.025 mm/min and/or wind speed ≥3 m/s. PSD analysis indicates that the seismic signal associated with rain decreases with the BD with a value of ∼2–5 dB in a depth difference of 10 cm. We also observe that each soil type has its own seismic signature. The 4‐min root mean square correlation between the seismic signal amplitude and the rain precipitation suggests that they best correlate with Pearson coefficient >0.90 at BD of 30 cm. The transfer function between the precipitation rate (or kinetic energy) and the seismic signal amplitude shows that the signal recorded by the geophone can be used as a robust proxy for these parameters.

Simultaneous Monitoring of Outdoor PAHs and Particles in a French Peri-Urban Site during COVID Restrictions and the Winter Saharan Dust Event

The presence of polycyclic aromatic hydrocarbons (PAHs) and particulate matter (PM) in air is known to provoke deleterious effects on human health. This work focused on the monitoring of PM and PAHs in the air over four weeks in a peri-urban site in Strasbourg (France), using a three-stage cascade impactor and a particle analyser allowing PM1, PM2.5 and PM10 discrimination. Meteorological conditions were monitored to study their influence on the pollutant levels. The average PM10 concentration of the cascade impactor and particle analyser varied from 11.8 to 80.2 µg/m3 and 10.6 to 220.2 µg/m3, respectively. The PAH total concentration ranged in 1.1–7.6 ng/m3 and a predominance of 5- and 6-ring PAHs was observed. PAHs were also more abundant in finer particles (PM1). Specifically, identified PAHs are traffic tracers suggesting that vehicular emission was one of its main sources. Two pollution episodes, associated with either a Saharan dust wind episode or traffic pollution, were observed, and led to PM10 and PM2.5 surpassing the daily limit values established by the European Union despite the traffic limitations according to the COVID restrictions. The total PAH concentrations were the highest during these periods suggesting PAHs might be bound to and transported via dust particles.

Clinical validation of a smartphone application for automated wound measurement in patients with venous leg ulcers.

Chronic wounds are associated with significant clinical, economic and quality-of-life burden. Despite the variety of wound imaging systems available in the market for wound assessment and surveillance, few are clinically validated among patients of Asian ethnicity. We aimed to clinically validate the accuracy of a smartphone wound application (Tissue Analytics [TA], Net Health Systems Inc, Florida, USA), versus conventional wound measurements (visual approximation and paper rulers), in patients of Asian ethnicity with venous leg ulcers (VLU). A prospective cohort study of patients presenting with VLU to a specialist wound nurse clinic over a 5-week duration was conducted. Each patient received seven wound measurements: one by a trained wound nurse clinician, and three separate wound measurements using TA on each of the iOS and Android operating systems. Inter-rater and intra-rater reliability between clinical and TA-based measurements were analysed using intra-class correlation statistics, with values of <0.5, 0.5 to 0.75, 0.75 to 0.9, and >0.9 indicating poor, moderate, good and excellent reliability, respectively. 82 patients (51% males), with a mean age at 65.8 years, completed the 5-week study duration. 25 (30%) had underlying diabetes mellitus. Chinese, Malay and Indian ethnicity comprised 68%, 12% and 11%, respectively. The VLU healed in 26 (32%) of patients within the study period. In total, 358 wound episodes with 2334 wound images were analysed. Inter-rater reliability for length, width and area between wound nurse measurements and TA application measurements was good (range 0.799-0.919, P < 0.001). Separate measurements of intra-rater reliability for length, width and area within the iOS or Android systems were excellent (range 0.967-0.985 and range 0.977-0.984 respectively, P < 0.001). Inter-rater reliability between TA used on the iOS and Android systems was also excellent (0.987-0.989, P < 0.001). Tissue Analytics, a smartphone wound application, is a useful adjunct for wound assessment and surveillance in VLU patients of Asian ethnicity.

Unified Wind-Wave Growth and Spectrum Functions for All Water Depths: Field Observations and Model Results

Abstract Wind-wave development is governed by the fetch- or duration-limited growth principle that is expressed as a pair of similarity functions relating the dimensionless elevation variance (wave energy) and spectral peak frequency to fetch or duration. Combining the pair of similarity functions, the fetch or duration variable can be removed to form a dimensionless function of elevation variance and spectral peak frequency, which is interpreted as the wave energy evolution with wave age. The relationship is initially developed for quasi-neural stability and quasi-steady wind forcing conditions. Further analyses show that the same fetch, duration, and wave-age similarity functions are applicable to unsteady wind forcing conditions, including rapidly accelerating and decelerating mountain gap wind episodes and tropical cyclone (TC) wind fields. Here it is shown that with the dimensionless frequency converted to dimensionless wavenumber using the surface wave dispersion relationship, the same similarity function is applicable in all water depths. Field data collected in shallow to deep waters and mild to TC wind conditions and synthetic data generated by spectrum model computations are assembled to illustrate the applicability. For the simulation work, the finite-depth wind-wave spectrum model and its shoaling function are formulated for variable spectral slopes. Given wind speed, wave age, and water depth, the measured and spectrum-computed significant wave heights and the associated growth parameters are in good agreement in forcing conditions from mild to TC winds and in all depths from deep ocean to shallow lake. Significance Statement This paper presents a growth function and spectrum model to describe wind-wave development in all water depths. Their applicability covers a wide range of wind forcing conditions including steady, accelerating, decelerating, and tropical cyclone events. Support for the unified spectrum model and growth function is presented with field observations and numerical computations.

Wind Exposure Regulates Water Oxygenation in Densely Vegetated Shallow Lakes.

The presence of dense macrophyte canopies in shallow lakes locally generates thermal stratification and the buildup of labile organic matter, which in turn stimulate the biological oxygen demand. The occurrence of hypoxic conditions may, however, be buffered by strong wind episodes, which favor water mixing and reoxygenation. The present study aims at explicitly linking the wind action and water oxygenation within dense hydrophytes stands in shallow lakes. For this purpose, seasonal 24 h-cycle campaigns were carried out for dissolved gases and inorganic compounds measurements in vegetated stands of an oligo-mesotrophic shallow lake. Further, seasonal campaigns were carried out in a eutrophic shallow lake, at wind-sheltered and -exposed sites. Overall results showed that dissolved oxygen (DO) daily and seasonal patterns were greatly affected by the degree of wind exposure. The occurrence of frequent wind episodes favored the near-bottom water mixing, and likely facilitated mechanical oxygen supply from the atmosphere or from the pelagic zone, even during the maximum standing crop of plants (i.e., summer and autumn). A simple model linking wind exposure (Keddy Index) and water oxygenation allowed us to produce an output management map, which geographically identified wind-sheltered sites as the most subjected to critical periods of hypoxia.

Clinical validation of an artificial intelligence-enabled wound imaging mobile application in diabetic foot ulcers.

There is a lifetime risk of 15% to 25% of development of diabetic foot ulcers (DFUs) in patients with diabetes mellitus. DFUs need to be followed up on and assessed for development of complications and/or resolution, which was traditionally performed using manual measurement. Our study aims to compare the intra‐ and inter‐rater reliability of an artificial intelligence‐enabled wound imaging mobile application (CARES4WOUNDS [C4W] system, Tetsuyu, Singapore) with traditional measurement. This is a prospective cross‐sectional study on 28 patients with DFUs from June 2020 to January 2021. The main wound parameters assessed were length and width. For traditional manual measurement, area was calculated by overlaying traced wound on graphical paper. Intra‐ and inter‐rater reliability was analysed using intra‐class correlation statistics. A value of <0.5, 0.5–0.75, 0.75–0.9, and >0.9 indicates poor, moderate, good, and excellent reliability, respectively. Seventy‐five wound episodes from 28 patients were collected and a total of 547 wound images were analysed in this study. The median wound area during the first clinic consultation and all wound episodes was 3.75 cm2 (interquartile range [IQR] 1.40–16.50) and 3.10 cm2 (IQR 0.60–14.84), respectively. There is excellent intra‐rater reliability of C4W on three different image captures of the same wound (intra‐rater reliability ranging 0.933–0.994). There is also excellent inter‐rater reliability between three C4W devices for length (0.947), width (0.923), and area (0.965). Good inter‐rater reliability for length, width, and area (range 0.825–0.934) was obtained between wound nurse measurement and each of the C4W devices. In conclusion, we obtained good inter‐rater and intra‐rater reliability of C4W measurements against traditional wound measurement. The C4W is a useful adjunct in monitoring DFU wound progress.

Observational Signal of the Interaction Between Mountain–Plain Wind and Urban Breeze Under Weak Synoptic Systems

AbstractValley winds and urban breezes induced by thermal circulation have been the subject of numerous studies; however, their interactions deserve further observational study under different geographical conditions globally. We propose quantitative criteria for analysis of observations, including identification of valley and mountain–plain wind episodes, determination of the direction and duration of valley winds, and exclusion of suspect cases induced by strong synoptic systems. We selected a subset of 345 valley wind days that occurred during 2013–2015 in Hangzhou, China. Valley winds in the study area occur mainly in autumn and early winter (annual frequency: 32%). To the west (east) of the urban center of Hangzhou are small mountains (is a plain). At night, the directions of mountain–plain circulation and urban thermal circulation are consistent in the region from the mountains to western parts of the city, resulting in a strengthened mountain wind at the surface. Their interaction also delays the reversal of the mountain wind to the plain wind in the morning, and slightly advances the reversal of the plain wind to the mountain wind in the evening. Conversely, in the plain area to the east of Hangzhou, the interaction delays the time of reversal of the plain wind to the mountain wind in the evening. Our results indicate that interactions between the urban breeze and local thermal circulations could have distinct impact on the environment of the city and surrounding areas, and thus they should be taken into consideration in relation to urban planning and management.

Speciation of VOC emissions related to offshore North Sea oil and gas production

Abstract. The North Sea is Europe's key oil and gas (O&amp;amp;G) basin with the output currently meeting 3 %–4 % of global oil supply. Despite this, there are few observational constraints on the nature of atmospheric emissions from this region, with most information derived from bottom-up inventory estimates. This study reports on airborne measurements of volatile organic compounds (VOCs) emitted from O&amp;amp;G-producing regions in the North Sea. VOC source emission signatures for the primary extraction products from offshore fields (oil, gas, condensate, mixed) were determined in four geographic regions. Measured iso-pentane to n-pentane (iC5 / nC5) ratios were 0.89–1.24 for all regions, used as a confirmatory indicator of O&amp;amp;G activities. Light alkanes (ethane, propane, butane, pentane) were the dominant species emitted in all four regions; however, total OH reactivity was dominated by unsaturated species, such as 1,3-butadiene, despite their relatively low abundance. Benzene to toluene ratios indicated the influence of possible terrestrial combustion sources of emissions in the southern, gas-producing region of the North Sea, seen only during south or south-westerly wind episodes. However, all other regions showed a characteristic signature of O&amp;amp;G operations. Correlations between ethane (C2H6) and methane (CH4) confirmed O&amp;amp;G production to be the primary CH4 source. The enhancement ratio (ΔC2H6/ΔCH4) ranged between 0.03–0.18, indicating a spatial dependence on emissions with both wet and dry CH4 emission sources. The excess mole fraction demonstrated that deepwater oil extraction resulted in a greater proportion of emissions of higher carbon number alkanes relative to CH4, whereas gas extraction, typically from shallow waters, resulted in a less complex mix of emissions dominated by CH4. The VOC source profiles measured were similar to those in the UK National Atmospheric Emissions Inventory (NAEI) for oil production, with consistency between the molar ratios of light alkanes to propane. The largest discrepancies between observations and the inventory were for mono-aromatic compounds, highlighting that these species are not currently fully captured in the inventory. These results demonstrate the applicability of VOC measurements to distinguish unique sources within the O&amp;amp;G sector and give an overview of VOC speciation over the North Sea.

Short-Term Response of Chlorophyll a Concentration Due to Intense Wind and Freshwater Peak Episodes in Estuaries: The Case of Fangar Bay (Ebro Delta)

Estuaries and coastal bays are areas of large spatio-temporal variability in physical and biological variables due to environmental factors such as local wind, light availability, freshwater inputs or tides. This study focuses on the effect of strong wind events and freshwater peaks on short-term chlorophyll a (Chl a) concentration distribution in the small-scale and microtidal, Fangar Bay (Ebro Delta, northwestern Mediterranean). The hydrodynamics of this bay are primarily driven by local wind episodes modulated by stratification in the water column. Results based on field-campaign observations and Sentinel-2 images revealed that intense wind episodes from both NW (offshore) and NE-E (onshore) caused an increase in the concentration of surface Chl a. The mechanisms responsible were horizontal mixing and the bottom resuspension (also linked to the breakage of the stratification) that presumably resuspended Chl a containing biomass (i.e., micropyhtobentos) and/or incorporated nutrients into the water column. On the other hand, sea-breeze was not capable of breaking up the stratification, so the chlorophyll a concentration did not change significantly during these episodes. It was concluded that the mixing produced by the strong winds favoured an accumulation of Chl a concentration, while the stratification that causes a positive estuarine circulation reduced this accumulation. However, the spatial-temporal variability of the Chl a concentration in small-scale estuaries and coastal bays is quite complex due to the many factors involved and deserve further intensive field campaigns and additional numerical modelling efforts.

The Perception of Rural Households on Climate Change Effect on Rural Livelihoods in Lake Victoria Basin

While the science of climate change is well investigated across most disciplines, people’s perception of climate change effects has not been well addressed. This paper sought to address the question of climate change perception and the effect of climate change on rural household livelihoods within the Lake Victoria Basin of Kenya. The study relied on households’ perception on the effect of climate change on the areas of agriculture, and food security, water, and energy supply. Multistage sampling was applied to select 539 households from four eco-ecological zones. The study revealed that most households presented localized explanations of climate change, which included: frequent and prolonged droughts, variations in rainfall onset and cessation, increased temperatures, an increased strong wind episode. Some households perceived climate changes effects resulted into a decrease in crop yield, resulting in increased household food insecurity, while some perceived water stress at household level, but mainly for those who relied on surface water, well water, borehole, and the natural spring. In addition, some of the households perceived shortage in energy sources, particularly hydroelectric power was said to be sensitive to the changes in climate. These perceptions were based on households’ experiences, and partially the results were found to be consistent with physical science of climate change. The paper therefore recommends the need to harmonise household perception with the climate change policy in order to address emerging challenges of climate change at the local level, create more climate change awareness supported through a comprehensive climate change action plan on country’s preparedness of extreme climate events at household level.

Wind-Driven Hydrodynamics in the Shallow, Micro-Tidal Estuary at the Fangar Bay (Ebro Delta, NW Mediterranean Sea)

This article investigates water circulation in small-scale (~10 km2), shallow (less than 4 m) and micro-tidal estuaries. The research characterizes the hydrodynamic wind response in these domains using field data from Fangar Bay (Ebro Delta) jointly with three-dimensional numerical experiments in an idealized domain. During calm periods, field data in Fangar Bay show complex water circulation in the inner part of the estuary owing to its shallow depths and positive estuarine circulation in the mouth. Numerical experiments are conducted to investigate wind-induced water circulation due to laterally varying bathymetry. For intense up-bay wind conditions (wind intensities greater than 9 m·s−1), an axially symmetric transverse structure occurs with outflow in the central channel axis and inflow in the lateral shallow areas. These numerical results explain the water circulation observed in Fangar Bay during strong wind episodes, highlighting the role of the bathymetry in a small-scale environment. During these episodes, the water column tends to homogenize rapidly in Fangar Bay, breaking the stratification and disrupting estuarine circulation, consistent with other observations in similar domains.