High-temperature Anomaly Research Articles

Significant Northward Jump of the Western Pacific Subtropical High: The Interannual Variability and Mechanisms

AbstractThe intensity and position of the western Pacific subtropical high (WPSH) have crucial effects on climate and disaster events in East Asia during summer. The WPSH significant northward jump (SNJ) events are the main manifestation of the seasonal evolution of WPSH, which are important for the precipitation over East Asia. Using the daily reanalysis data sets from year 1979 to 2020, this study further defines the early and late SNJ events of WPSH on the interannual timescale, which are connected separately with the tropical, midlatitude subseasonal signals and the local air–sea interaction. However, the mechanisms of the WPSH‐SNJ events are different in the anomalous early and late years. In the early SNJ years, the subseasonal signals from the midlevel East Asia–Pacific teleconnection pattern or the low‐level boreal summer intraseasonal oscillation cause the positive 500 hPa geopotential height anomalies, which contributes to the significant WPSH northward jump in the first pentad of July. However, the above factors are unable to cause the WPSH‐SNJ in the late years. Until the second pentad of August, the collaborative effects between midhigh latitudes wave trains over high levels and cold sea surface temperature (SST) anomalies in the core region lead to the barotropic geopotential height anomalies and the lagged northward jump of WPSH. It seems that the meridional position of WPSH has a complex interannual variability, which is modulated by the solar radiation, the atmospheric disturbances at different levels, and the SST anomalies at the same time.

Impact of Pacific Ocean heatwaves on phytoplankton community composition

Since 2013, marine heatwaves have become recurrent throughout the equatorial and northeastern Pacific Ocean and are expected to increase in intensity relative to historic norms. Among the ecological ramifications associated with these high temperature anomalies are increased mortality of higher trophic organisms such as marine mammals and seabirds, which are likely triggered by changes in the composition of phytoplankton, the base of the marine trophic food web. Here, we assimilated satellite ocean color data into an ocean biogeochemical model to describe changes in the abundance of phytoplankton functional types (PFTs) during the last decade’s (2010s) warm anomalies in the equatorial and northeastern Pacific Ocean. We find important changes associated with the “Blob” warm anomaly in the Gulf of Alaska, where reduced silica supply led to a switch in community composition from diatoms to dinoflagellates, resulting in an increase in surface ocean chlorophyll during the Summer–Fall of 2014. A more dramatic change was observed in the equatorial Pacific, where the extreme warm conditions of the 2016 El Niño resulted in a major decline of about 40% in surface chlorophyll, which was associated with a nearly total collapse in diatoms.

High-Temperature Anomaly of the Anionic Conductivity in LaF3 Crystals

High-Temperature Anomaly of the Anionic Conductivity in LaF3 Crystals

Decadal variation of the summer extreme high temperature days in northern Eurasia during 1960–2018

Unprecedented heat waves have been demonstrated sweeping across much of the Northern Hemisphere in recent summers. However, this study reveals that for northern Eurasia (30°–70°N, 10°–130°E), significant increases in summer extreme high temperature days (EHTDs) have already commenced since the mid-1990s, with the peaks centered on the surrounding areas of the Caspian Sea and Lake Baikal. Results indicate that compared with the period of 1960–1994 (P1), during 1995–2018 (P2) high-pressure and anticyclonic anomalies occupy the areas around the Caspian Sea and Lake Baikal, thus suppressing local cloud cover and precipitation, enhancing the solar radiation and high-temperature anomalies. The anticyclonic anomaly over Lake Baikal shows a close relationship with the increasing trend of global temperature, and the anomalous anticyclone over the Caspian Sea is under the influence of the warm North Atlantic and anomalous upper-troposphere jet stream during P2. The warmer than normal North Atlantic leads to the high-pressure anomaly over the Caspian Sea by modulating the Rossby wave activity. In addition, during P2, the temperatures in the middle North Atlantic and Western Europe show greater increments than those over higher latitudes, and thus the temperature gradient enhances the westerly thermal wind, which therefore leads to an anomalous upper-level jet stream to the North of the Caspian Sea. Under this circumstance, the Caspian Sea is located to the right side of the anomalous jet exit, inducing the suppressed upward motion over there and favoring the occurrence of more EHTDs after the mid-1990s.

HIGH-TEMPERATURE ANOMALY OF THE ANIONIC CONDUCTIVITY IN LaF<sub>3</sub> CRYSTALS

The anionic electrical conductivity σdc(T) of the superionic LaF3 conductor single crystal has been studied by impedance spectroscopy in a wide (312–1073 K) temperature range. Electrical measurements in a protective nitrogen atmosphere have been carried out. It is shown that the σdc values change from 1.5 × 10–5 to 7 × 10–2 S/cm (by a factor of ~5 × 103) in the investigated temperature range. A high-temperature anomaly of the σdc(T) dependence has been found at T0 ≈ 970 K, which is apparently indicative of the onset of a diffuse (Faraday) phase transition in the LaF3 tysonite structure.

Sea surface temperature anomalies and cash holdings: Evidence from fisheries companies

This study examines the impact of sea temperature anomalies on the cash holdings of fisheries companies from 27 countries for the period of 2013–2019. The main findings using a dynamic panel regression revealed a positive relationship between temperature anomalies and cash holdings. We find that firms tend to hold more cash to response the high temperature anomalies. This strategy is taken as a precautionary action to tackle climate-related risks, supporting the cash management and nature resource-based view theory. This precautionary cash will lead to underinvestment, hurting the fisheries industry growth. Thus, policymakers and corporate management must prioritize their efforts in the climate change campaign to avoid higher sea temperature anomalies.

Exploring the link between austral stratospheric polar vortex anomalies and surface climate in chemistry-climate models

Abstract. Extreme events in the stratospheric polar vortex can lead to changes in the tropospheric circulation and impact the surface climate on a wide range of timescales. The austral stratospheric vortex shows its largest variability in spring, and a weakened polar vortex is associated with changes in the spring to summer surface climate, including hot and dry extremes in Australia. However, the robustness and extent of the connection between polar vortex strength and surface climate on interannual timescales remain unclear. We assess this relationship by using reanalysis data and time-slice simulations from two chemistry-climate models (CCMs), building on previous work that is mainly based on observations. The CCMs show a similar downward propagation of anomalies in the polar vortex strength to the reanalysis data: a weak polar vortex is on average followed by a negative tropospheric Southern Annular Mode (SAM) in spring to summer, while a strong polar vortex is on average followed by a positive SAM. The signature in the surface climate following polar vortex weakenings is characterized by high surface pressure and warm temperature anomalies over Antarctica, the region where surface signals are most robust across all model and observational datasets. However, the tropospheric SAM response in the two CCMs considered is inconsistent with observations. In one CCM, the SAM is more negative compared to the reanalysis after weak polar vortex events, whereas in the other CCM, it is less negative. In addition, neither model reproduces all the regional changes in midlatitudes, such as the warm and dry anomalies over Australia. We find that these inconsistencies are linked to model biases in the basic state, such as the latitude of the eddy-driven jet and the persistence of the SAM. These results are largely corroborated by models that participated in the Chemistry-Climate Model Initiative (CCMI). Furthermore, bootstrapping of the data reveals sizable uncertainty in the magnitude of the surface signals in both models and observations due to internal variability. Our results demonstrate that anomalies of the austral stratospheric vortex have significant impacts on surface climate, although the ability of models to capture regional effects across the Southern Hemisphere is limited by biases in their representation of the stratospheric and tropospheric circulation.

Dynamical Mechanism of the Summer Circulation Trend Pattern and Surface High Temperature Anomalies over the Russian Far East

Abstract This study investigates the mechanism behind the recent boreal summer circulation trend pattern and associated high surface temperature anomalies over the Russian Far East. This circulation pattern includes a prominent anticyclone over the Kamchatka Peninsula where heat extremes have been trending upward. Observational analysis and numerical model simulations indicate that latent heating anomalies centered over Yakutia, west of Kamchatka Peninsula, can excite this anticyclone and the downstream circulation trend pattern. However, this anticyclone alone is insufficient for generating the anomalously high temperature over the region. Instead, the high temperature emerges when there is an upstream precursor that resembles the Eurasian circulation trend pattern. Warm advection by this upstream circulation initiates a positive temperature anomaly over the Russian Far East, one week prior to the onset of the anticyclone in this region. As this anticyclone develops, the temperature anomalies further intensify by adiabatic warming and shortwave radiative heating. If upstream circulation anomalies are opposite to those of the Eurasian trend pattern, the initial temperature over the Russian Far East is anomalously negative. As a result, the adiabatic warming and shortwave radiative heating within this anticyclonic region are unable to bring the temperature to an extreme condition. These findings indicate that the temperature extremes over the Russian Far East are contributed by a combination of remote and local circulation forcings and provide insights into subseasonal forecasts of heat waves over this region.

The Long and Winding Road of Coral Reef Recovery in the Anthropocene: A Case Study from Puerto Rico

The persistence and resilience of marginal shallow coral reefs at their limits of environmental tolerance have declined due to chronic environmental degradation and climate change. However, the consequences for the natural recovery ability of reefs of disturbance remain poorly understood. This study considered the potential for natural recovery through coral recruitment on fringing reefs across different geographic regions under contrasting environmental conditions in Puerto Rico. Reefs in areas with significant water quality degradation and more severe physical impacts of hurricanes were expected to have lower coral recruit density and diversity, and therefore less potential for recovery. Sixteen reefs were assessed across three geographic regions. Degraded reefs sustained a lower percentage of live coral cover and had higher macroalgae and turf algae abundance. Locations affected by high PO4, NH3+ and optical brightness concentrations, high turbidity, and high sea surface temperature anomalies, chlorophyll-a concentration and light attenuation Kd490 evidenced significantly lower coral recruit density and diversity. Hurricane-decimated reefs also exhibited impoverished coral recruit assemblages. Low coral recruitment could have important long-term implications under projected climate change and sea level rise, particularly in coastal urban habitats. There is a need to implement effective environmental conservation, ecological restoration and community participation strategies that facilitate enhanced coral recruitment success and assisted recovery processes.

Spatial mapping and monitoring thermal anomaly and radiative heat flux using Landsat-8 thermal infrared data – A case study of Lamurde hot spring, upper part of Benue trough, Nigeria

The upper Benue trough, northeastern Nigeria is characterized by prominent geologic and tectonic features of diverse scientific and economic interest. Lamurde hot spring is located within one of several deformational structures of the trough; the Lamurde anticline. In this work, we assessed the geothermal energy potential of the area using the Thermal Infra-Red (TIR) band of Landsat-8 data. We used four datasets representing the four seasons of the year to retrieve the Land Surface Temperature (LST) by converting the pixel digital numbers into LST based on the single-channel algorithm. We also used the retrieved LST to spatially map Radiative Heat Flux (RHF) based on the Stefan-Boltzmann radiation law. We validated the results by comparing the Landsat TIR-retrieved LST with MODIS LST product of the same area using a cross-validation technique. The results indicate a reliable fitting coefficient (R2 = 0.801) and Root Mean Square Error RMSE value of 0.756 K. Although significant seasonal variation of both LST and RHF was observed, the rock outcrops associated with the hot spring high surface temperature and heat loss anomalies for all seasons of the year. Peak LST values of 43.7 °C, 35.6 °C, 29.4 °C, and 27.5 °C were respectively recorded in January, April, July, and October from the active thermal area. The average values of RHF obtained from the active thermal area are 11.78, Wm−2, 10.76 Wm−2, 1.22 Wm−2 and 0.168 Wm−2 for January, April, July and October respectively. These are much higher than the global continental value. Comparison with known active geothermal areas from different parts of the world indicates that the area has significantly high surface geothermal parameter indicators.

The Physics of Heat Waves: What Causes Extremely High Summertime Temperatures?

Abstract We analyze observations and develop a hierarchy of models to understand heat waves—long-lived, high temperature anomalies—and extremely high daily temperatures during summertime in the continental extratropics. Throughout the extratropics, the number of extremely hot days found in the three hottest months is much greater than expected from a random, single-process model. Furthermore, in many locations the temperature skewness switches from negative on daily time scales to positive on monthly time scales (or shifts from positive on daily time scales to higher positive values on monthly time scales) in ways that cannot be explained by averaging alone. These observations motivate a hierarchy of models of the surface energy and moisture budgets that we use to illuminate the physics responsible for daily and monthly averaged temperature variability. Shortwave radiation fluctuations drive much of the variance and the negative skewness found in daily temperature observations. On longer time scales, precipitation-induced soil moisture anomalies are important for temperature variability and account for the shift toward positive skewness in monthly averaged temperature. Our results demonstrate that long-lived heat waves are due to (i) the residence time of soil moisture anomalies and (ii) a nonlinear feedback between temperature and evapotranspiration via the impact of temperature on vapor pressure deficit. For most climates, these two processes give rise to infrequent, long-lived heat waves in response to randomly distributed precipitation forcing. Combined with our results concerning high-frequency variability, extremely hot days are seen to be state-independent filigree driven by shortwave variability acting on top of longer-lived, moisture-driven heat waves.

The Impact of Dynamic Emissivity–Temperature Trends on Spaceborne Data: Applications to the 2001 Mount Etna Eruption

Spaceborne detection and measurements of high-temperature thermal anomalies enable monitoring and forecasts of lava flow propagation. The accuracy of such thermal estimates relies on the knowledge of input parameters, such as emissivity, which notably affects computation of temperature, radiant heat flux, and subsequent analyses (e.g., effusion rate and lava flow distance to run) that rely on the accuracy of observations. To address the deficit of field and laboratory-based emissivity data for inverse and forward modelling, we measured the emissivity of ‘a’a lava samples from the 2001 Mt. Etna eruption, over the wide range of temperatures (773 to 1373 K) and wavelengths (2.17 to 21.0 µm). The results show that emissivity is not only wavelength dependent, but it also increases non-linearly with cooling, revealing considerably lower values than those typically assumed for basalts. This new evidence showed the largest and smallest increase in average emissivity during cooling in the MIR and TIR regions (~30% and ~8% respectively), whereas the shorter wavelengths of the SWIR region showed a moderate increase (~15%). These results applied to spaceborne data confirm that the variable emissivity-derived radiant heat flux is greater than the constant emissivity assumption. For the differences between the radiant heat flux in the case of variable and constant emissivity, we found the median value is 0.06, whereas the 25th and the 75th percentiles are 0.014 and 0.161, respectively. This new evidence has significant impacts on the modelling of lava flow simulations, causing a dissimilarity between the two emissivity approaches of ~16% in the final area and ~7% in the maximum thickness. The multicomponent emissivity input provides means for ‘best practice’ scenario when accurate data required. The novel approach developed here can be used to test an improved version of existing multi-platform, multi-payload volcano monitoring systems.

Dielectric anomalies and structure evolution of annealed (1-x)Pb(Sc1/2Ta1/2)O3-xPb(In1/2Nb1/2)O3 ceramics

The (1-x)Pb(Sc1/2Ta1/2)O3-xPb(In1/2Nb1/2)O3 [(1-x)PST-xPIN] (x = 0.2, 0.4, 0.6, and 0.8) solid-solution ceramics were synthesized by conventional solid-state reaction method. The phase structure, microstructure, and dielectric properties were analysed. In order to obtain various ordering degrees, annealing treatment at 700 °C for 10 h, 20 h, 40 h, and 120 h was conducted on (1-x)PST-xPIN ceramics. The degree of ordering increased significantly with the extension of annealing time in 0.8PST-0.2PIN composition. However, for other compositions, no any superlattice peak was observed at all times of annealing process, which was related to the presence of more pyrochlore phase. In addition to the low-temperature relaxation peaks associated with the disordered arrangement of B-site ions, two new dielectric anomalies were found in the temperature dependence of dielectric constant of annealed (1-x)PST-xPIN solid solution. For annealed 0.8PST-0.2PIN composition, the middle-temperature and high-temperature dielectric anomalies were attributed to the ordered PST region and the incommensurate structure induced by the competition between ordered PST and disordered PST, respectively. The high-temperature dielectric anomalies in 0.6PST-0.4PIN and 0.4PST-0.6PIN compositions originated from the contribution of the ordered PIN region in solid solution. Furthermore, the relatively weak superlattice diffraction spots of (111) were found in selected-area electron diffraction patterns of annealed 0.8PST-0.2PIN ceramic, indicating that the existence of alternately ordering arrangement of B-site ions. Combined with the analysis of element mapping, it was concluded that the annealed (1-x)PST-xPIN solid solution was composed of the ordered PST region, the ordered PIN region, and the disordered region constituted by PST and/or PIN.

Technology Pathways Could Help Drive the U.S. West Coast Grid's Exposure to Hydrometeorological Uncertainty

AbstractPrevious studies investigating deep decarbonization of bulk electric power systems and wholesale electricity markets have not sufficiently explored how future grid pathways could affect the grid's vulnerability to hydrometeorological uncertainty on multiple timescales. Here, we employ a grid operations model and a large synthetic weather ensemble to “stress test” a range of future grid pathways for the U.S. West Coast developed by ReEDS, a well‐known capacity planning model. Our results show that gradual changes in the underlying capacity mix from 2020 to 2050 can cause significant “re‐ranking” of weather years in terms of annual wholesale electricity prices (with “good” years becoming bad, and vice versa). Nonetheless, we find the highest and lowest ranking price years in terms of average electricity price remain mostly tied to extremes in hydropower availability (streamflow) and load (summer temperatures), with the strongest sensitivities related to drought. Seasonal dynamics seen today involving spring snowmelt and hot, dry summers remain well‐defined out to 2050. In California, future supply shortfalls in our model are concentrated in the evening and occur mostly during periods of high temperature anomalies in late summer months and in late winter; in the Pacific Northwest, supply shortfalls are much more strongly tied to negative streamflow anomalies. Under our more robust sampling of stationary hydrometeorological uncertainty, we also find that the ratio of dis‐patchable thermal (i.e., natural gas) capacity to wind and solar required to ensure grid reliability can differ significantly from values reported by ReEDS.

Qualifying Contributions of Teleconnection Patterns to Extremely Hot Summers in Japan

Extremely hot days in Japan are known to persist for a week or more, and they are measured by the temperature anomaly at 850 hPa averaged over Japan derived from the JRA-55 reanalysis data, denoted as T850JP. Severe high-temperature anomalies are often accompanied by multiple teleconnection patterns that affect the weather in Japan, but their relative contribution to individual heat wave events has not yet been quantified. In this study, we examined the effects of three major teleconnection patterns, namely, the Pacific-Japan (PJ), circumglobal teleconnection (CGT), and Siberian patterns, on T850JP in July and August from 1958–2019 using daily low-pass-filtered anomalies with 8 days cutoff timescale derived from the reanalysis.

Geothermal anomalies on the eastern flank of the Cherokee basin, southeastern Kansas, USA

Bottomhole temperature measurements from oil and gas drilling in southeastern Kansas on the eastern flank of the Cherokee basin, in combination with a suite of about 2,200 differential temperature logs recently obtained from wireline logging in coalbed methane wells, define several higher-temperature anomalies at the top of the Mississippian Subsystem strata. Temperatures slightly in excess of 90 oF (35 oC) at depths of about 900 ft (275 m) correspond to geothermal gradients as high as about 60 oC/km.
 Sparse historical measurements of heat flow in the cratonic Cherokee basin indicate that the thermal anomalies are not likely caused by locally high heat flow. Heat flow in the Cherokee basin is probably in line with most other shallow cratonic basins. The higher-temperature thermal anomalies defined by logging temperatures do not correspond to previously mapped faults or other structural features in the Phanerozoic sedimentary section, but some anomalies are underlain by Precambrian basement lineations that are detectable with aeromagnetic and gravity measurements. Well-log determination of shale content in the Pennsylvanian sedimentary strata overlying the Mississippian limestones indicates that low thermal conductivity caused by higher shale content may cause some of the thermal anomalies. 
 Lateral (advective) movement of warmer, highly saline water from the basin axis cannot account for the anomalies because the anomalies are not characterized by exceptionally highly saline water in Mississippian strata. Similarly, recorded static fluid levels of wells disposing of oilfield saltwater into the Mississippian strata and the deeper Cambrian-Ordovician Arbuckle Group indicate that the deeper Arbuckle strata generally do not have sufficient formation pressure to force Arbuckle formation water upward into the Mississippian through either natural fractures or leaky wellbores. Small-scale changes in salinity, in combination with geologic structuring indicating faulting, make a case for vertical (convective) movement of heated, less saline water from the Arbuckle Group into overlying Mississippian limestones in isolated localities. Buoyancy of the Arbuckle formation water (due to temperature and salinity differences with the cooler and more saline Mississippian water) could also be the primary force behind the convection. Convergence of cooler freshwater moving westward off the Ozark dome and more saline basinal water moving eastward also could be a factor in defining the limits of some thermal anomalies.

The 2019 Benguela Niño

High interannual sea surface temperature anomalies of more than 2°C were recorded along the coasts of Angola and Namibia between October 2019 and January 2020. This extreme coastal warm event that has been classified as a Benguela Niño, reached its peak amplitude in November 2019 in the Angola Benguela front region. In contrast to classical Benguela Niños, the 2019 Benguela Niño was generated by a combination of local and remote forcing. In September 2019, a local warming was triggered by positive anomalies of near coastal wind-stress curl leading to downwelling anomalies through Ekman dynamics off Southern Angola and by anomalously weak winds reducing the latent heat loss by the ocean south of 15°S. In addition, downwelling coastal trapped waves were observed along the African coast between mid-October 2019 and early January 2020. Those coastal trapped waves might have partly emanated from the equatorial Atlantic as westerly wind anomalies were observed in the central and eastern equatorial Atlantic between end of September to early December 2019. Additional forcing for the downwelling coastal trapped waves likely resulted from an observed weakening of the prevailing coastal southerly winds along the Angolan coast north of 15°S between October 2019 and mid-February 2020. During the peak of the event, latent heat flux damped the sea surface temperature anomalies mostly in the Angola Benguela front region. In the eastern equatorial Atlantic, relaxation of cross-equatorial southerly winds might have contributed to the equatorial warming in November 2019 during the peak of the 2019 Benguela Niño. Moreover, for the first time, moored velocities off Angola (11°S) revealed a coherent poleward flow in the upper 100 m in October and November 2019 suggesting a contribution of meridional heat advection to the near-surface warming during the early stages of the Benguela Niño. During the Benguela Niño, a reduction of net primary production in the Southern Angola and Angola Benguela front regions was observed.

Investigation of the microstructure damage and mechanical properties evolution of limestone subjected to high-pressure water

The water-weakening effect is one of the most important causes for changes the physical and mechanical characteristics of rock materials, triggering large deformations and failures in rock engineering. To investigate the degradation effect of high-pressure water on a rock material, this study performed laboratory tests on limestone specimens. Scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) were used to examine limestone subjected to different water pressures, and the results showed that with the water pressure increasing, the dissolution degree and porosity of a limestone specimen increased. Meanwhile, an infrared radiation thermal (IRT) imager was used during uniaxial loading to study the temperature evolution laws of the limestone materials under different water pressures. The phase development characteristics of the stress–strain curve were more obvious, and the average infrared radiation temperature (AIRT) rose in a fluctuating manner during different stages. The AIRT reached an extreme value suddenly before the peak stress and gradually returned to the room temperature after a structural failure. The strength and temperature differences for the specimens continuously decreased with water pressure increasing, with temperature decreases of 5.71%, 12.86%, 18.57%, 22.86% and 24.29% respectively under 2–10 MPa water pressure compared to 0 MPa. In addition, the IRT images intuitively reflected the spatial evolution process for the specimen temperature. There were high temperature anomalies on the IRT image before structural failure, which could be used as the omen of the limestone structure failure.

Tree mortality response to drought‐density interactions suggests opportunities to enhance drought resistance

AbstractThe future of dry forests around the world is uncertain given predictions that rising temperatures and enhanced aridity will increase drought‐induced tree mortality. Using forest management and ecological restoration to reduce density and competition for water offers one of the few pathways that forests managers can potentially minimize drought‐induced tree mortality. Competition for water during drought leads to elevated tree mortality in dense stands, although the influence of density on heat‐induced stress and the durations of hot or dry conditions that most impact mortality remain unclear.Understanding how competition interacts with hot‐drought stress is essential to recognize how, where and how much reducing density can help sustain dry forests in a rapidly changing world. Here, we integrated repeat measurements of 28,881 ponderosa pine trees across the western US (2000–2017) with soil moisture estimates from a water balance model to examine how annual mortality responds to competition, temperature and soil moisture conditions.Tree mortality responded most strongly to basal area, and was elevated in places with high mean temperatures, unusually hot 7‐year high temperature anomalies, and unusually dry 8‐year low soil moisture anomalies. Mortality was also lower in places that experienced unusually wet 3‐year soil moisture anomalies between measurements. Importantly, we found that basal area interacts with temperature and soil moisture, exacerbating mortality during times of stress imposed by high temperature or low moisture.Synthesis and applications. Our results imply that a 50% reduction in forest basal area could reduce drought‐driven tree mortality by 20%–80%. The largest impacts of density reduction are seen in areas with high current basal area and places that experience high temperatures and/or severe multiyear droughts. These interactions between competition and drought are critical to understand past and future patterns of tree mortality in the context of climate change, and provide information for resource managers seeking to enhance dry forest drought resistance.

Self-Heating Coal Waste Fire Monitoring and Related Environmental Problems: Case Studies from Poland and Ukraine

Abstract The self-heating of coal waste dumps is considered as a serious environmental issue, wherever active or inactive coal mining has been present. This issue is introduced from two active coal mining regions from Poland (Upper Silesian Coal Basin) and Ukraine (Donetsk Coal Basin) based on mineralogy, organic petrography and geochemistry, and remote sensing techniques. Thermally affected coal wastes reveal changes recorded by organic and mineral matter. Irregular cracks and fissures appear within and at the edges of organic matter particles, which are oxidised, devolatilised and plasticised. Mineral phases underwent oxidation, dehydration, structure rebuilding and recrystallisation. Highest temperatures generated during the fire cause melting and paralava formation. During self-heating, some chalcophile elements like Hg (mostly present as HgS), Pb, Zn can be enriched and released, or different organic pollutants like phenols (originated from vitrinite particles), different PAHs with alkyl substitutes, chlorinated PAHs, or sulphur heterocycles are formed. The introduced remote sensing techniques helped to localise and monitor hot spots with different temperature ranges. Applying SWIR bands of Landsat hot spots from extremely burning dumps in Ukraine were successfully localised, however, only night-time scenes with SWIR can be used. The sun’s disturbing effects should be considered as an influential factor for both thermal imaging camera or satellite images. Thermal cameras can reveal the most detailed signs of low to high temperature anomalies with different cracks and line shapes.