Cameron R. Homeyer, Matthew J. Bunkers, John T. Allen
et al.
Abstract Supercell storms are recognized to account for a disproportionately large amount of severe weather occurring in the United States and elsewhere. Despite their importance, few studies document their climatological behavior, and those that do focus predominantly or entirely on severe supercells. This study presents an objective and comprehensive radar-based climatology of supercell storms during a 14-yr period over the contiguous United States. Approximately 56 000 supercells are identified, half of which are likely nonsevere. All objectively identified supercells (strongly and persistently rotating storms) are diagnosed as either “right moving” (RM) or “left moving” (LM) based primarily on the deviance of storm motion relative to the 0–6-km environmental wind shear vector. RM supercells outnumber LM supercells at a rate of approximately 3:1 and also live longer. RM supercells are more frequently severe than LM supercells, accounting for ≈99.8% of supercell tornadoes, ≈76.9% of supercell severe hail events, and ≈68.9% of supercell severe wind events. Common to both supercell configurations, numerous sensitivities are identified between storm characteristics and storm severity. Namely, storm severity increases with increasing velocities of storm motion and increasing midlevel rotation. Severity maximizes when storm motion deviates ≈30° left or right of the 0–6-km environmental wind shear vector. Last, severe and nonsevere supercell storm characteristics are compared, and the greatest discriminatory indicators are based on metrics of the depth of high radar reflectivity magnitudes. Significance Statement Rotating thunderstorms (supercells) are responsible for the vast majority of the most significant tornadoes and severe hail events in the United States. Despite their recognized importance, many basic details about them remain unknown, such as their frequency, spatial distribution, and dominant character of motion (right or left moving). In this study, a comprehensive 14-yr statistical analysis of United States supercell storms based on objectively analyzed radar observations is used to address this gap in understanding. Numerous sensitivities between supercell severity and storm characteristics are found and have potential to advance the warning decision-making process.
David Georges, Maurine Montagnat, Pascal Forquin
et al.
Understanding ice flexural behavior is essential for assessing interactions with structures in cold environments. The mechanical response of ice depends on microstructural properties, such as grain size and porosity, which vary widely in natural ice. Existing bending test data often lack detailed microstructural characterization, making it difficult to interpret or generalize the results. In brittle materials such as concrete or rock, pores commonly act as failure-initiating defects. Therefore, porosity (pore size, shape and density) should be considered a key parameter when studying ice fracture. Here, we provide a robust set of bending experiments on well-controlled isotropic polycrystalline ice microstructures and investigate the role of porosity in ice failure. Two porosity levels were studied, characterized at high resolution by micro-computed X-ray tomography. Analyzing the bending failure by means of the Weibull model reveals that the sample failure is initiated by different defect populations, in relation to the porosity. Providing that the Griffith/Irwin failure criterion can be applied, the measured pore distribution allows the prediction of a critical stress for defect activation. Compared with measured failure stress, this prediction enables discriminating the defect population responsible for failure and offers a mechanistic interpretation of the volume effect observed in porous ice flexural strength.
Abstract One of the reasons why people do not act pro-environmentally might be a lack of experience with the consequences of climate change. Studies have shown that higher levels of environmental attitudes and more environmentally friendly behaviours have been observed among people affected by extreme weather events. It is unclear, however, whether the events caused the changes or whether the affected people simply differed in their characteristics from those who were unaffected. We draw on a natural experiment to examine the causal link between flooding experiences, pro-environmental attitudes and pro-environmental behaviour using national survey data collected from 2058 individuals aged 16-29 years across Luxembourg. After people experienced the 2021 European flooding, their pro-environmental attitudes increased significantly. The effect was stronger in regions that were more affected by floods. Higher levels of environmental attitudes partly translated into greater willingness to act in a pro-environmental way. The results have important implications for advancing efforts to address climate change by demonstrating links between extreme weather events attributed to climate change and higher levels of environmental attitudes.
High spatial resolution (HSR) remote sensing imagery presents a rich tapestry of foreground-background intricacies, rendering semantic segmentation in aerial contexts a formidable and vital undertaking. At its core, this challenge revolves around two pivotal questions: 1) Mitigating Background Interference and Enhancing Foreground Clarity. 2) Accurate Segmentation in Dense Small Object Cluster. Conventional semantic segmentation methods primarily cater to the segmentation of large-scale objects in natural scenes, yet they often falter when confronted with aerial imagery’s characteristic traits such as vast background areas, diminutive foreground objects, and densely clustered targets. In response, we propose a novel semantic segmentation framework tailored to overcome these obstacles. To address the first challenge, we leverage PointFlow modules in tandem with the Foreground-Scene (F-S) module. PointFlow modules act as a barrier against extraneous background information, while the F-S module fosters a symbiotic relationship between the scene and foreground, enhancing clarity. For the second challenge, we adopt a dual-branch structure termed disentangled learning, comprising Foreground Precedence Estimation and Small Object Edge Alignment (SOEA). Our foreground saliency guided loss optimally directs the training process by prioritizing foreground examples and challenging background instances. Extensive experimentation on the iSAID and Vaihingen datasets validates the efficacy of our approach. Not only does our method surpass prevailing generic semantic segmentation techniques, but it also outperforms state-of-the-art remote sensing segmentation methods.
Based on the conventional high-altitude and ground observation datasets and the 1-hour rainfall datasets from 93 national auto? matic weather stations in Jiangxi from April to September of 1998 to 2019, a total of 204 selected local hourly heavy rainfall events (hereinaf? ter LHR) in Jiangxi were analyzed and classified. With the analysis of synoptic meteorology, radiosonde, and physical properties, the concep? tual models of each category of these LHR events were established. The results are as follows. LHR in Jiangxi can be classified into 5 catego? ries, including Pre-Trough pattern (PRT), Post-Trough pattern (POT), Tropical System pattern (TS), Edge of Subtropical High pattern (ESH), and Control of Subtropical High (CSH) pattern. PRT is the most common type, which accounts for 48% of the total events. These events usual? ly occur in front of the high-altitude trough, near the mid-low-level shear lines, and are usually associated with cold fronts, stationary fronts, or low-pressure troughs on the surface. The second most frequent one is TS, which accounts for 19.1% of the total events. TS can also be divid? ed into the tropical cyclone type and the east wind wave type. The structure and movement of the tropical systems can significantly affect the area of LHR. ESH is divided into western ESH, southern ESH, and northern ESH. For this type, LHR events usually occur near the edge of the subtropical high 588 dagpm line, the low layer shear line, or the convergence line. CSH accounts for 5.5% of the total events. LHR happens when the subtropical high controls the entire Jiangxi Province. Particularly, when a center temperature at 500 hPa over the northern or eastern Jiangnan regions below -4℃ appears under the background of a cold trough, LHR events frequently occur on the ground convergence line, in the high-temperature area, or windward slope of mountains. POT is the least common type, which accounts for 4.4% of the events. It occurs under the northwesterly flow behind a trough, in the exit zone of the low-level jets, in the convergence zone, or on the surface convergence line.
Abstract Geoelectric fields produced by time‐varying magnetic fields during geomagnetic storms can result in potentially damaging geomagnetically induced currents (GICs) in long conductors at the Earth's surface. GICs can pose a significant risk to the integrity of grounded electrical infrastructure, particularly high‐voltage transformers. In this study, an inferred GIC is calculated using an augmented differential magnetometer measurement (DMM) technique on a 500 kV transmission line in central Alberta and is validated using a proximal transformer neutral‐to‐ground (TNG) current measurement by AltaLink L.P. using a Hall probe at a transformer substation. This research outlines a custom‐built and innovative DMM design by which both DMM sensors deployed around a power line measure the background geomagnetic disturbance (GMD) field and the magnetic field generated locally by the GIC. We show how this modified approach provides two independent estimates for GIC derived using only ΔBy or ΔBz, the magnetic field components perpendicular to the line carrying GIC. Results for a geomagnetic storm on 12 Oct 2021 show contemporaneous peaks in the TNG current and the DMM‐inferred GIC. The two data sets have similar waveforms and are within the same order of magnitude. The background GMD is reconstructed using DMM and shows excellent correlation to the measured GMD at the permanent Canadian Array for Real‐time Investigations of Magnetic Activity magnetic station at Ministik Lake, approximately 48.5 km away. Based on the results presented here, we verify the added utility value of DMM for temporary deployments for assessing GIC risk in electrical power grids.
The inviscid, nonlinear shallow water model developed by Sun was applied to study the inverse of equatorial Rossby solitons, which can be represented by the Korteweg–De Vries equation (KdV equation). The model was integrated forward in time, then the results were used as initial conditions for backward integration by just changing time step from positive to negative. The detailed structure, secondary circulation, and propagating speed of waves from both integrations are in good agreement with analytic solutions. The total mass, energy, and enstrophy are also well conserved. The procedure is much simpler and the results are more accurate than other backward integrations of 2D nonlinear models, which require significant modification of the model and can be contaminated by unwanted diffusion in forward–backward integrations or time-consuming iterative methods. This paper is also different from the numerical method for solving the inverse of the KdV equation.
Atmospheric near-surface stress and boundary layer wind responses to surface currents are examined with high resolution coupled atmosphere–ocean models over the Gulf Stream during winter. Because the ocean and atmosphere are linked through surface stress, the two fluids can cause dramatic changes through feedback processes. When the current feedback is included, we find that the current gradient in the cross-wind direction drives the stress curl pattern and wind curl pattern to have minima and maxima at locations matching those of the ocean surface vorticity pattern. Furthermore, we find the large- (>30 km) and small-scale, or submesoscale (<30 km), stress curl and wind curl responses to ocean surface vorticity are complimentary; however, the large- and small-scale wind divergence responses are counteractive. These responses (commonly called coupling coefficients) are found to depend on the relative position to the Gulf Stream maximum current. Throughout the atmospheric boundary layer, we find including the current feedback also leads to changes in the atmospheric secondary circulation on either side of the Gulf Stream extension. The winter seasonal means suggest the current feedback will impact climate, and investigating individual events, such as an atmospheric front passing over the Gulf Stream, suggests the current feedback will also impact the intensity of weather.
Jacky Fayad, Frédéric Morandini, Gilbert Accary
et al.
This paper reports two experimental fires conducted at field-scale in Corsica, across a particular mountain shrubland. The orientation of the experimental plots was chosen in such a way that the wind was aligned along the main slope direction in order to obtain a high intensity fire. The first objective was to study the high intensity fire behavior by evaluating the propagation conditions related to its speed and intensity, as well as the geometry of the fire front and its impact on different targets. Therefore, an experimental protocol was designed to determine the properties of the fire spread using UAV cameras and its impact using heat flux gauges. Another objective was to study these experiments numerically using a fully physical fire model, namely FireStar3D. Numerical results concerning the fire dynamics, particularly the ROS, were also compared to other predictions of the FireStar2D model. The comparison with experimental measurements showed the robustness of the 3D approach with a maximum difference of 5.2% for the head fire ROS. The fire intensities obtained revealed that these experiments are representative of high intensity fires, which are very difficult to control in the case of real wildfires. Other parameters investigated numerically (flame geometry and heat fluxes) were also in fairly good agreement with the experimental measurements and confirm the capacity of FireStar3D to predict surface fires of high intensity.
The recent rapid economic development in the Yangtze River Delta (YRD) has led to atmospheric destruction; therefore, it is imperative to solve the issue of atmospheric environmental pollution to ensure stable long-term development. Based on the NO<sub>2</sub> column concentration observed by the TROPOMI (a tropospheric monitoring instrument) on the Sentinel-5P, the spatial–temporal distribution characteristics of the NO<sub>2</sub> column concentration in the YRD from 2019 to 2020 were analyzed using the Google Earth Engine (GEE) platform, and the Geographical Detector (Geodetector) model was used to determine the driving factors of the NO<sub>2</sub> column concentration. The results show that the correlation between the NO<sub>2</sub> column concentration and the ground-monitored NO<sub>2</sub> concentrations reached 70%. The annual variation trend of the NO<sub>2</sub> column concentration exhibited a ‘U’-shaped curve, with the characteristics of ‘high in winter and low in summer, with a transition between spring and autumn’. It exhibited obvious agglomeration characteristics in terms of the spatial distribution, with a high-value agglomeration in the central region of the YRD, followed by the northern region, and a low-value agglomeration in the southern region, with higher altitudes. The change in the NO<sub>2</sub> column concentration in the YRD was affected by both physical geographical factors and socio-economic factors; it is clear that the influence of socio-economic factors has increased.
Rafaela Squizzato, Thiago Nogueira, Leila D. Martins
et al.
Abstract Most of the world’s population lives in rural areas or small to medium-sized cities (totalling 68% of the world population), all of which are impacted by distant air pollution sources. In Brazil, primary pollutant emissions have decreased in urban centres because of government actions, while secondary pollutants such as surface ozone (O3) increased. In addition, O3 and its precursors can be worsening air quality in areas already affected by biofuels production, especially ethanol. We provide almost 3 months of hourly data (June 7, 2019 to August 25, 2019) for concentrations of O3, CO2 and other priority pollutants from a mobile station positioned to distinguish among pollutant plumes (biomass burning, metropolitan area of São Paulo (MASP) and other cities). Although the concentrations of O3 and CO2 were highest in the plumes from biomass burning, the MASP accounted for up to 80% of the O3 concentration in communities over 200 km away.
Rural communities in the Koshi River basin, a trans-boundary river basin in the Hindu Kush-Himalayas, have been experiencing unprecedented difficulties for adapting with the livelihood challenges arising from floods, droughts and other climatic, environmental and socio-economic stresses. The single purpose adaptation approach often fails to address the multiple challenges arises from cascading effects of climate change at different scales and stages. To fill this gap, we developed a multi-dimensional flexible adaptation framework looking at the four dimensions of adaptation, structure, issue, time, and space (SITS). The SITS framework provides a comprehensive approach for cascading adaptation at trans-boundary river basin level and it could effectively enhance the adaptive capacity and transform livelihood outcome if properly implemented. Following the SITS framework, we examined four cascading adaptation pathways for: i) reducing disaster stressors on livelihoods, ii) enhancing access to crucial livelihood capitals, iii) improving equal rights to livelihood, and iv) strengthening synergies and exploiting complementarities at trans-boundary river basin level. The findings revealed that in the context of changing climate, it is necessary to employ different livelihood adaptation strategies and multiple responses simultaneously or sequentially to successfully adapt to the cascading effects of changing climate. The cascading adaptation may provide a sound basis on which to cope with the climate uncertainty through realistic scenarios of structure, issue, time and space. Its implementation, however, has several obstacles, for example, differences in national system, investment capacity, complexity of trans-boundary basin, remained particularly in trans-boundary river basin where managing transnational trade-offs and harness spatial synergies are critically important.
Meteorology. Climatology, Social sciences (General)
JESSICA SCHEICK, ELLYN M. ENDERLIN, GORDON HAMILTON
Changes in Greenland's marine-terminating outlet glaciers have led to changes in the flux of icebergs into Greenland's coastal waters, yet icebergs remain a relatively understudied component of the ice-ocean system. We developed a simple iceberg delineation algorithm for Landsat imagery. A machine learning-based cloud mask incorporated into the algorithm enables us to extract iceberg size distributions from open water even in partially cloudy scenes. We applied the algorithm to the Landsat archive covering Disko Bay, West Greenland, to derive a time series of iceberg size distributions from 2000–02 and 2013–15. The time series captures a change in iceberg size distributions, which we interpret as a result of changes in the calving regime of the parent glacier, Sermeq Kujalleq (Jakobshavn Isbræ). The change in calving style associated with the disintegration and disappearance of Sermeq Kujalleq's floating ice tongue resulted in the production of more small icebergs. The increased number of small icebergs resulted in increasingly negative power law slopes fit to iceberg size distributions in Disko Bay, suggesting that iceberg size distribution time series provide useful insights into changes in calving dynamics.
Rose Marie Garay, Ricardo Tapia, Miguel Castillo
et al.
Every housing should fulfill safety, comfort and durability standards, even more when due to climate change disasters occur more often than ever. In Chile, construction standards can be found in the General Urban Planning and Construction Ordinance (OGUC), whose update will include elements for risk management in order to decrease vulnerability. In this study, thermal, mechanic, fire resistant and acoustic isolation standards where evaluated in 5 thermic zones. This information allowed the creation of manufacturing, installation, technical specification manuals, and a bill that regulates emergency housing and transient settlements standards. This experience allowed a critical analysis of the compliance with standards for social housing and wood building, which does not account, for example, for smoke opacity and toxicity, thermal-acoustic insulators and fire resistance: less harmful preservatives or coatings with sustainability in mind. The existence of the ordinance (OGUC) does not imply compliance of energy efficiency, seismic and fire resistance standards simultaneously in practice, as many housing projects do not consider a final reception of work. Multi-criteria discrimination analyzes may help to make design decisions in wood constructions.