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Wind and storms
Introduces wind, including why it occurs, how it is useful, and how excessive amounts of wind can cause such dangerous conditions as tornadoes, hurricanes, and thunderstorms.
Book
Multiple Large‐Scale Dynamical Pathways for Pan–Atlantic Compound Cold and Windy Extremes
Winter cold spells over North America have been correlated with European wind extremes, but the physical mechanisms behind such “pan‐Atlantic” compound extremes have not been clarified yet. In this study, we propose that pan–Atlantic cold and windy extremes occur following two possible dynamical pathways. The first one involves the propagation of a Rossby wave train from the Pacific Ocean, associated with windstorms over north‐western Europe in the 5–10 days after the cold spell peak. The second is associated with a high‐latitude anticyclone over the North Atlantic and an equatorward‐shifted jet, leading to windstorms over south‐western Europe already in the days preceding the cold spell peak. European windstorms are thus systematically tied to North American cold spells according to the different flow configuration. The analysis underscores that apparently similar surface extremes might be driven by different processes, and conflating them together could lead to misleading conclusions. Plain Language Summary Previous research noticed that cold spells over North America and windstorms over Europe tend to occur within a few days of each other. This connection is supported by the fact that winds usually blow from west to east over the North Atlantic, so that cyclones forming off the coast of North America move toward western Europe. However, the chain of processes behind this connection remained not fully clarified. Here we explain the complex relationship between the occurrence of North American cold spells and European windstorms. While previous work tried to identify a single physical mechanism, we suggest that two separate pathways can connect the two types of extremes. The first pathway involves the propagation of a train of cyclones and anticyclones from the North Pacific to the North Atlantic, leading to a cold spell over central North America and, a few days later, to windstorms over north‐western Europe. The second pathway, on the other hand, involves an anomalous anticyclone over the North Atlantic, which acts to induce cold spells over North America and windstorms over south‐western Europe roughly at the same time: this still leads to a correlation between the two extremes, but without a clear causality direction. Key Points North American cold extremes and European windy extremes can be connected physically by two distinct dynamical pathways The first pathway involves Rossby wave propagation from the North Pacific and the cold spell preceding the European windstorm The second pathway features both extremes occurring roughly at the same time thanks to an upper‐level anticyclone west of Greenland
Journal Article
Fire, fragmentation, and windstorms: A recipe for tropical forest degradation
1. Widespread degradation of tropical forests is caused by a variety of disturbances that interact in ways that are not well understood. 2. To explore potential synergies between edge effects, fire and windstorm damage as causes of Amazonian forest degradation, we quantified vegetation responses to a 30-min, high-intensity windstorm that in 2012, swept through a large-scale fire experiment that borders an agricultural field. Our pre- and postwindstorm measurements include tree mortality rates and modes of death, above-ground biomass, and airborne LiDAR-based estimates of tree heights and canopy disturbance (i.e., number and size of gaps). The experimental area in the southeastern Amazonia includes three 50-ha plots established in 2004 that were unbumed (Control), burned annually (Blyr), or burned at 3-year intervals (B3yr). 3. The windstorm caused greater damage to trees (>10 cm DBH) in the burned plots (B1yr: 13 ± 9% of 785 trees; B3yr 17 ± 13% of 433) than in the Control plot (8 ± 4% of 2,300; ± CI). It substantially reduced vegetation height by 14% in B1yr, 20% in B3yr and 12% in the Control plots, while it reduced above-ground biomass by 18% of 77.7 Mg/ha (B1yr), 31% of 56.6 (B3yr), and 15% of 120 (Control). Tree damage was greatest near the agricultural field edge in all three plots, especially among large trees and in B3yr. Trunk snapping (70%) and uprooting (20%) were the most common modes of tree damage and mortality, with the height of trunk failure on the burned plots often corresponding with the height of historical fire scars. Of the windstorm-damaged trees, 80% (B1yr), 90% and s57% (Control) were dead 4 years later. Trees that had crown damage experienced the least mortality (22%-60%), followed by those that were snapped (55%-94%) and uprooted (88%-94%). 4. Synthesis. We demonstrate the synergistic effects of three kinds of disturbances on a tropical forest. Our results show that the effects of windstorms are exacerbated by prior degradation by fire and fragmentation. We highlight that understorey fires can produce long-lasting effects on tropical forests not only by directly killing trees but also by increasing tree vulnerability to wind damage due to fire scars and a more open canopy.
Journal Article
Quantification of extremal dependence in spatial natural hazard footprints: independence of windstorm gust speeds and its impact on aggregate losses
Natural hazards, such as European windstorms, have widespread effects that result in insured losses at multiple locations throughout a continent. Multivariate extreme-value statistical models for such environmental phenomena must therefore accommodate very high dimensional spatial data, as well as correctly representing dependence in the extremes to ensure accurate estimation of these losses. Ideally one would employ a flexible model, able to characterise all forms of extremal dependence. However, such models are restricted to a few dozen dimensions, hence an a priori diagnostic approach must be used to identify the dominant form of extremal dependence.
Journal Article
Spatial structure of local winds “Rokko‐oroshi”: A case study using Doppler lidar observation and WRF simulation
Rokko‐oroshi is a northerly local wind blowing in the mega‐city Kobe, Japan. This wind blows from the Rokko Mountains. This study analyzed the three‐dimensional structure of Rokko‐oroshi observed with a near‐surface anemometer and Doppler lidar on January 16, 2023. Furthermore, numerical simulations using the Weather Research and Forecasting (WRF) model revealed the factors responsible for the strong winds. The results showed that Rokko‐oroshi on January 16, 2023 was a bora‐type downslope windstorm. The Doppler lidar observed the strong winds of Rokko‐oroshi and a stagnant layer immediately above them. Numerical simulation results indicated the stagnant layer was formed by mountain‐wave breaking. Under this stagnant layer, the airflow transitioned from subcritical to supercritical, resulting in the strong winds of Rokko‐oroshi. This Rokko‐oroshi was accompanied by a hydraulic jump. The occurrence of the Rokko‐oroshi was supported by an upper‐level critical layer and a lower‐level strong stable layer on the windward side of the Rokko Mountains. This study revealed that the local winds known as “Rokko‐oroshi” in the megacity of Kobe, Japan, is a bora‐type downslope windstorm. Numerical simulation results showed the presence of a strong stable layer and a critical layer at slightly higher altitudes than the mountaintop on the windward side during the downslope windstorm event. Additionally, the results of numerical simulation and a Doppler lidar observation indicated the weak wind region above the downslope windstorm.
Journal Article
On the Systematic Occurrence of Compound Cold Spells in North America and Wet or Windy Extremes in Europe
The repeated co‐occurrence of cold spells over Eastern North America and wet or windy extremes over Western Continental Europe during recent winters, has led to hypothesize a link between the two. Here, we analyze the interplay between the large‐scale atmospheric circulation and co‐occurring cold spells in North America and wet or windy extremes in Europe. We collectively term these occurrences compound cold–wet–windy extremes. We leverage a recent approach grounded in dynamical systems theory, which provides an analytically and computationally efficient analysis of spatially resolved, multivariate climate extremes. We find that there are specific, recurrent large‐scale atmospheric circulation patterns systematically associated with both the individual extremes and co‐occurring cold–wet–windy anomalies. Evidence for this is also found when focusing on compound cold–wet–windy extremes, although with a weaker signal. This motivates further analyses focusing specifically on the statistics and drivers of these compound extreme occurrences. Plain Language Summary In recent winters, very cold weather over the eastern part of North America and stormy weather or heavy rainfall in Europe have often made the news. One may think that these events are independent, since they occur several thousands of kilometres apart. However, researchers have hypothesized that there may be weather patterns that connect these different episodes. Here we test this idea. We find that there is indeed a connection between unusually cold weather in Eastern North America and unusually stormy weather and heavy rainfall in Western Continental Europe. We also find a link, albeit weaker, when focusing specifically on extreme events—namely only the coldest of the cold spells, the windiest of the stormy days and the wettest of the heavy rainfall days. The strongest connection, however, emerges when looking at unusual but not extreme weather episodes. Key Points North American cold spells and European wet or windy extremes are very strongly coupled to recurrent large‐scale atmospheric patterns The compound occurrence of North American cold spells and European wet or windy extremes is associated with common atmospheric patterns Extremes show weaker evidence of common atmospheric patterns than all temperature, precipitation and wind anomalies
Journal Article
Impacts of salvage logging on biodiversity: A meta-analysis
1. Logging to \"salvage\" economic returns from forests affected by natural disturbances has become increasingly prevalent globally. Despite potential negative effects on biodiversity, salvage logging is often conducted, even in areas otherwise excluded from logging and reserved for nature conservation, inter alia because strategic priorities for post-disturbance management are widely lacking. 2. A review of the existing literature revealed that most studies investigating the effects of salvage logging on biodiversity have been conducted less than 5 years following natural disturbances, and focused on non-saproxylic organisms. 3. A meta-analysis across 24 species groups revealed that salvage logging significantly decreases numbers of species of eight taxonomic groups. Richness of dead wood dependent taxa (i.e. saproxylic organisms) decreased more strongly than richness of non-saproxylic taxa. In contrast, taxonomic groups typically associated with open habitats increased in the number of species after salvage logging. 4. By analysing 134 original species abundance matrices, we demonstrate that salvage logging significantly alters community composition in 7 of 17 species groups, particularly affecting saproxylic assemblages. 5. Synthesis and applications. Our results suggest that salvage logging is not consistent with the management objectives of protected areas. Substantial changes, such as the retention of dead wood in naturally disturbed forests, are needed to support biodiversity. Future research should investigate the amount and spatio-temporal distribution of retained dead wood needed to maintain all components of biodiversity.
Journal Article
A Sentinel-2 Based Multi-Temporal Monitoring Framework for Wind and Bark Beetle Detection and Damage Mapping
The occurrence of extreme windstorms and increasing heat and drought events induced by climate change leads to severe damage and stress in coniferous forests, making trees more vulnerable to spruce bark beetle infestations. The combination of abiotic and biotic disturbances in forests can cause drastic environmental and economic losses. The first step to containing such damage is establishing a monitoring framework for the early detection of vulnerable plots and distinguishing the cause of forest damage at scales from the management unit to the region. To develop and evaluate the functionality of such a monitoring framework, we first selected an area of interest affected by windthrow damage and bark beetles at the border between Italy and Austria in the Friulian Dolomites, Carnic and Julian Alps and the Carinthian Gailtal. Secondly, we implemented a framework for time-series analysis with open-access Sentinel-2 data over four years (2017–2020) by quantifying single-band sensitivity to disturbances. Additionally, we enhanced the framework by deploying vegetation indices to monitor spectral changes and perform supervised image classification for change detection. A mean overall accuracy of 89% was achieved; thus, Sentinel-2 imagery proved to be suitable for distinguishing stressed stands, bark-beetle-attacked canopies and wind-felled patches. The advantages of our methodology are its large-scale applicability to monitoring forest health and forest-cover changes and its usability to support the development of forest management strategies for dealing with massive bark beetle outbreaks.
Journal Article
The Future of Midlatitude Cyclones
Purpose of Review
This review brings together recent research on the structure, characteristics, dynamics, and impacts of extratropical cyclones in the future. It draws on research using idealized models and complex climate simulations, to evaluate what is known and unknown about these future changes.
Recent Findings
There are interacting processes that contribute to the uncertainties in future extratropical cyclone changes, e.g., changes in the horizontal and vertical structure of the atmosphere and increasing moisture content due to rising temperatures.
Summary
While precipitation intensity will most likely increase, along with associated increased latent heating, it is unclear to what extent and for which particular climate conditions this will feedback to increase the intensity of the cyclones. Future research could focus on bridging the gap between idealized models and complex climate models, as well as better understanding of the regional impacts of future changes in extratropical cyclones.
Journal Article
The 30 December 2021 Colorado Front Range Windstorm and Marshall Fire: Evolution of Surface and 3D Structure, NWP Guidance, NWS Forecasts, and Decision Support
The Marshall Fire on 30 December 2021 became the most destructive wildfire costwise in Colorado history as it evolved into a suburban firestorm in southeastern Boulder County, driven by strong winds and a snow-free and drought-influenced fuel state. The fire was driven by a strong downslope windstorm that maintained its intensity for nearly 11 hours. The southward movement of a large-scale jet axis across Boulder County brought a quick transition that day into a zone of upper-level descent, enhancing the midlevel inversion providing a favorable environment for an amplifying downstream mountain wave. In several aspects, this windstorm did not follow typical downslope windstorm behavior. NOAA rapidly updating numerical weather prediction guidance (including the High-Resolution Rapid Refresh) provided operationally useful forecasts of the windstorm, leading to the issuance of a High-Wind Warning (HWW) for eastern Boulder County. No Red Flag Warning was issued due to a too restrictive relative humidity criterion (already published alternatives are recommended); however, owing to the HWW, a countywide burn ban was issued for that day. Consideration of spatial (vertical and horizontal) and temporal (both valid time and initialization time) neighborhoods allows some quantification of forecast uncertainty from deterministic forecasts—important in real-time use for forecasting and public warnings of extreme events. Essentially, dimensions of the deterministic model were used to roughly estimate an ensemble forecast. These dimensions including run-to-run consistency are also important for subsequent evaluation of forecasts for small-scale features such as downslope windstorms and the tropospheric features responsible for them, similar to forecasts of deep, moist convection and related severe weather.
Journal Article