Elevated Source Research Articles

Noise propagation variations over long distances over water

This paper investigates the short temporal variations of noise propagation over a water surface for long distances. Analysis is formed on the results of a measurement campaign for downwind noise propagation over water for elevated sound sources. Noise propagation over water for elevated noise sources is specifically relevant for offshore wind turbines, near shore wind turbines or wind turbines on land close to large water bodies. The measurement setup is a height-adjustable sound source placed at three different heights 81 m, 50 m and 30 m above ground and microphones positioned downwind at shore and ~100 m inland at three different distances over water from the sound source ~3 km, ~5 km and ~7 km. The meteorological conditions wind speed, wind direction, atmospheric stability, temperature, humidity, etc. were monitored continuously at both ends of the setup, utilizing both a tall met mast, a wind profiler and sonic anemometers at multiple heights. The results are used for improving auralisations of noise from offshore wind turbines and offshore wind farms. In addition to this a semi-analytical model for propagation over water is tested.

Elevated noise sources in the European noise prediction model

The prediction model of the Environmental noise directive 2002/49/EC was transposed into Austrian national regulations in 2021 and 2022. In comparison to the Austrian prediction model defined in ONR 305011, which was last updated in 2009, it allows far more acoustic details to be taken into account enabling a more realistic description of noise emissions and propagation than before. For instance, an additional, elevated noise source position is used to model traction noise of aggregates or fans at the upper part of locomotives or motor coaches and aerodynamic noise caused by pantographs at high speeds. For free sound propagation the effect of split source positions is usually negligible, while in case of noise barriers the elevated source position lowers the insertion loss. This article discusses this effect using exemplary calculations with the European prediction model under various conditions (e.g. different barrier heights, and train speeds). The results emphasize the importance of accurate model input parameters describing traction and in case of high speeds aerodynamic noise for predictions, which need high accuracy.

Semi-empirical model for amplitude fluctuations by atmospheric turbulence in aircraft flyover sound

Atmospheric turbulence leads to well-audible fluctuations in the amplitude of sound propagating through the atmospheric boundary layer. However, the best currently available theoretical model is valid only for short propagation distances and low turbulence regimes. A new model for predicting the standard deviation of amplitude fluctuations was developed based on the existing theoretical model of Ostashev and Wilson and the analysis of empirical data. The dataset includes over 5000 aircraft flyover events in different meteorological conditions from March to August. The model considers an effective propagation length based on the boundary layer height, frequency-dependent saturation of amplitude fluctuations, turbulence decay time during periods of decreasing solar radiation, and turbulence production by nocturnal low-level-jets. The model adaptations have significantly reduced the mean squared error from over 10 dB in the pure theoretical model to 0.3 dB in the new model. The findings will help improving the modelling of outdoor sound propagation for elevated sound sources like aircraft and wind turbines. Modelling these fluctuations can considerably improve the realism of the listening experience in aircraft flyover auralisation. Further, it helps estimating the measurement uncertainty in measured aircraft noise, especially for maximum levels.

Controls on the stable Mo isotopic composition of inner-continental precipitation

The molybdenum (Mo) isotope budget of the surface environment has been well characterized in recent decades, facilitating accurate mass balance modeling of the ancient redox-driven Mo cycle. One yet unresolved component is the range of possible processes and sources that result in isotopically heavy river waters relative to continental sources. Following a recent hypothesis that isotopically heavy δ98Mo of precipitation may control the final δ98Mo of river water relative to its continental source bedrock, we investigated the δ98Mo composition of 19 snow samples from three locations in Central Europe: the Swiss Alps (“Alpine” samples) from the Hochalpine Forschungsstation Jungfraujoch (HFSJ) in both summer and winter, the Swiss Jura Mountains in winter and the French Vosges Mountains in winter. Stream waters from two snowmelt-fed streams were additionally collected from the Alpine site. Snow sample δ98Mo compositions were highly variable, ranging from −0.03 to +1.93 ‰, with no clear mixing trends indicating complex sources, source pathways, or post-depositional processing. Only the winter snow samples from the high-altitude HFSJ site had δ98Mo values consistently heavier than typical continental crust. The δ98Mo results were coupled with radiogenic Sr isotopic, major ion, and trace element compositions as tracers for three major sources of airborne ion inputs: sea salt, mineral dust, and anthropogenic aerosols. We found that the most likely source of Mo to precipitation in the lower elevation Vosges and Jura Mountains samples was isotopically light soil mineral dust, which reflected the underlying bedrock sources, with a likely additional anthropogenic component. The isotopically heavy winter snow samples at the elevated HFSJ site were attributed to a higher input of carbonate mineral dust from long-distance transport of carbonate-rich Saharan dust, which was overwritten in the summer by an influx of low elevation sources transported upwards during higher vertical thermal mixing. Finally, we concluded that precipitation has a negligible direct effect on the overall Mo content and isotopic composition of inner continental European streams and rivers relative to other sources, such as bedrock weathering. Future time-series studies may augment these conclusions to show possible heterogeneity of precipitation as well as the addition of sample sites closer to marine sources, where a larger flux of isotopically heavy marine aerosols to streams might be expected.

Modelling and Analysis of Evacuated Tube Solar Collector Working with Hybrid Nanofluid

This research study is concerned with developing a mathematical model for an Evacuated Tube Solar Collector (ETSC) that utilizes a Hybrid Nanofluid flow in a manifold. The model consists of a set of the partial differential equations that, using the dimensional analysis approach, are reduced to a dimensionless system. The exact solution method, assisted by the Mathematica program, is used to solve the system. The study examines the impact of certain factors on flow and heat transmission, including horizontal velocity, temperature variation, heat source, magnetic field, Prandtl Number, and Eckert Number, and provides a detailed analysis of the results. The key findings of the analysis revealed that an increase in hybrid nanoparticle volume effects in a reduce in velocity and heat transfer coefficient. Additionally, elevated heat source and Prandtl number correspond to an increased heat transfer coefficient.

RETRACTED: Assessing nonpoint source pollution risk in watersheds using a water-functioning zone approach

A thorough understanding of the geographical and spatial attributes of nonpoint source pollution risk in watersheds is crucial for conducting nonpoint source pollutant studies and implementing effective scientific administration strategies. The inclusion of a water-related functioning zone was considered during the nonpoint source's pollution risks assessment procedure. Nevertheless, there has not been a thorough investigation into the potential risk of nonpoint sources of pollution to adequately safeguard the quality of water in watersheds having varying capacities to handle contaminants in the water. This research presents an innovative approach for assessing the risk of nonpoint sources contamination. This allows for a quantitative evaluation of the effect of discharges of pollution from a sub-catchment on the quality of water bodies nearby. The nonpoint source losses of nutrients process, as modeled by the Water and Soil Assessment Tool, had been used to assess the hazard of nonpoint source contamination in Le ‘a River Watersheds. This assessment happened on both yearly and monthly scales. The findings indicated that the risk of nonpoint source contamination exhibits both seasonal and regional variations and is significantly impacted by the ability of the fluid ecosystem. Elevated nonpoint sources pollutants do not always equate to elevated pollutant dangers. On the other hand, a small amount of nutrients in the nonpoint sources does not indicate an insignificant degree of susceptibility to region risk. Furthermore, by utilizing a risk assessment method that considers the capacity of the water's environment, it is possible to identify variations in risk levels that may be overlooked when solely considering nonpoint sources contaminant losses, and fluid functioning zone. This approach allows for precise regulation of nonpoint sources of pollution administration.

Interference of the direct and ground-reflected waves in the atmosphere with volumetric scatteringa).

The interference of the direct and ground-reflected sound waves is significantly affected by volumetric scattering in the atmosphere, such as scattering by turbulence and forest. In the present article, the existing theory describing this interference is generalized to three somewhat independent but equally important cases. First, the attenuation of the direct and ground-reflected waves caused by backscattering is addressed. Second, the existing theory is extended for statistically quasi-homogeneous turbulence in which the variances and length scales of the temperature and wind velocity fluctuations depend on the height above the ground. Third, the existing theory, which was previously formulated only for near-horizontal sound propagation, is generalized to slanted sound propagation as pertinent to elevated sound sources. Numerical results for slanted propagation demonstrate that atmospheric turbulence can significantly increase the sound pressure level at the interference minima. The extended theory of the interference of the direct and ground-reflected waves in the atmosphere with volumetric scattering is important for practical applications, such as auralization of flying aircraft and sound propagation in a forest, and can be adapted to radio wave propagation.

Flow regimes in emptying–filling boxes with two buoyancy sources of differing strengths and elevations

Emptying–filling boxes have been studied in a wide range of configurations for decades, but the flow created in the box by two plumes rising from sources of arbitrary strength and elevation was previously unsolved. Guided by experiments and simplified analytical modelling, we reveal a rich array of two- and three-layer stratifications across seven possible flow regimes. The governing equations for these regimes show how the prevailing regime and stratification properties vary with three key parameters: the relative strength of the plumes, the height difference between their sources and a parameter characterising the resistance of the box to emptying. We observe and explain new behaviours not described in previous studies that are crucial to understanding emptying–filling boxes with multiple plumes. In particular, we demonstrate that the oft-assumed premise that $n$ plumes leads to a stratification with $n+1$ layers is not necessarily true, even in the absence of mixing. Two emptying–filling box models are developed: an analytical model addressing all combinations of the governing parameters and an extended model for three-layer stratifications that incorporates two mixing processes observed in the experiments. The predictions of these two models are in generally excellent agreement with measurements from the experimental campaign covering 69 combinations of the governing parameters. This study improves our understanding of emptying–filling boxes and could facilitate improvements to natural ventilation building design, as demonstrated by an example scenario in which occupants feel cooler upon the addition of a second source of heat.

P62/sequestosome-1 as a severity-reflecting plasma biomarker in Charcot–Marie–Tooth disease type 1A

Autophagy is a self-degradation system for recycling to maintain homeostasis. p62/sequestosome-1 (p62) is an autophagy receptor that accumulates in neuroglia in neurodegenerative diseases. The objective of this study was to determine the elevation of plasma p62 protein levels in patients with Charcot–Marie–Tooth disease 1A (CMT1A) for its clinical usefulness to assess disease severity. We collected blood samples from 69 CMT1A patients and 59 healthy controls. Plasma concentrations of p62 were analyzed by ELISA, and we compared them with Charcot-Marie-Tooth neuropathy score version 2 (CMTNSv2). A mouse CMT1A model (C22) was employed to determine the source and mechanism of plasma p62 elevation. Plasma p62 was detected in healthy controls with median value of 1978 pg/ml, and the levels were significantly higher in CMT1A (2465 pg/ml, p < 0.001). The elevated plasma p62 levels were correlated with CMTNSv2 (r = 0.621, p < 0.0001), motor nerve conduction velocity (r = − 0.490, p < 0.0001) and disease duration (r = 0.364, p < 0.01). In C22 model, increased p62 expression was observed not only in pathologic Schwann cells but also in plasma. Our findings indicate that plasma p62 measurement could be a valuable tool for evaluating CMT1A severity and Schwann cell pathology.

Impacts of spatial heterogeneity of anthropogenic aerosol emissions in a regionally refined global aerosol–climate model

Abstract. Emissions of anthropogenic aerosol and their precursors are often prescribed in global aerosol models. Most of these emissions are spatially heterogeneous at model grid scales. When remapped from low-resolution data, the spatial heterogeneity in emissions can be lost, leading to large errors in the simulation. It can also cause the conservation problem if non-conservative remapping is used. The default anthropogenic emission treatment in the Energy Exascale Earth System Model (E3SM) is subject to both problems. In this study, we introduce a revised emission treatment for the E3SM Atmosphere Model (EAM) that ensures conservation of mass fluxes and preserves the original emission heterogeneity at the model-resolved grid scale. We assess the error estimates associated with the default emission treatment and the impact of improved heterogeneity and mass conservation in both globally uniform standard-resolution (∼ 165 km) and regionally refined high-resolution (∼ 42 km) simulations. The default treatment incurs significant errors near the surface, particularly over sharp emission gradient zones. Much larger errors are observed in high-resolution simulations. It substantially underestimates the aerosol burden, surface concentration, and aerosol sources over highly polluted regions, while it overestimates these quantities over less-polluted adjacent areas. Large errors can persist at higher elevation for daily mean estimates, which can affect aerosol extinction profiles and aerosol optical depth (AOD). We find that the revised treatment significantly improves the accuracy of the aerosol emissions from surface and elevated sources near sharp spatial gradient regions, with significant improvement in the spatial heterogeneity and variability of simulated surface concentration in high-resolution simulations. In the next-generation E3SM running at convection-permitting scales where the resolved spatial heterogeneity is significantly increased, the revised emission treatment is expected to better represent the aerosol emissions as well as their lifecycle and impacts on climate.

Notable effects of crustal matters on HONO formation by the redox reaction of NO2 with SO2 in an inland city of China

Nitrous acid (HONO) is a vital precursor of the hydroxyl radicals, which plays a significant role in atmospheric chemistry. HONO can be produced by the redox reaction of NO2 with SO2. However, this reaction has often been neglected in previous studies on the HONO sources. To study this reaction on HONO production, continuous observation was carried out for one year in an inland city of China, and a sandy haze process was selected, divided into clean days (CD) and sand haze days (SHD). The mean HONO concentrations increased from 0.8 ± 0.4 ppb (CD) to 1.4 ± 1.0 ppb (SHD) during the nighttime. Since the rate of HONO sinks higher than that of sources, other elevation sources may contribute to the nighttime HONO concentration. In addition, the daytime HONO concentrations during the SHD periods also increased by 0.2 ppb, primarily due to the elevated photolysis of nitrate (0.20 ppb/h) and unknown sources (0.20 ppb/h) compared to the CD period. The positive correlations between HONO with NO2, SO2, particle pH, and SO42– indicate that HONO might be formed through the NO2 and SO2 redox reaction, and the calculated HONO production rates increased by two orders of magnitude under high pH conditions during the SHD period. In particular, on a heavily polluted SHD, this reaction explained 5% and 22% of HONO formation during the daytime and nighttime, respectively. In short, the NO2 and SO2 redox reaction may be more critical in high pH regions/periods and thus cannot be ignored when analyzing the HONO sources.

Unraveling weak and short South Asian wet season in the Early Eocene warmth

AbstractThe timing and causative factors underlying the Asian summer monsoon initiation remain contentious as recent proxy data and modeling studies suggested the existence of a wet-dry monsoon-like climate from the Cretaceous period. Leveraging an ensemble of deep-time climate simulations focused on the early Eocene (DeepMIP-Eocene), we show that the early Eocene Asian wet season was notably weaker and shorter than present-day in the absence of an elevated heat source like the Tibetan Plateau. The deficient upper-tropospheric meridional temperature gradient was insufficient to propel the seasonal northward migration of the rainband over South Asia. The weaker cross-equatorial moisture flow encountered obstruction of Gangdese mountain along the southern edge of Asia, leading to significant South Asian aridity. The enhanced greenhouse effect was inadequate to augment the seasonal circulation and rainfall variability to current levels. The altered wet and dry seasonality across South Asia during the early Eocene does not meet the criteria to be classified as a monsoon, suggesting that South Asian monsoon initiation is likely contingent upon a specific level of Tibetan Plateau upliftment.

Performance investigation of elevated source EBG TFET based photosensor for near-infrared light sensing applications

In this manuscript, an elevated source TFET with extended back gate (ES-EBG-TFET) based photosensor is designed to offer improvement in optical performance for detecting incident light of narrow-spaced wavelengths (∼100 nm) and low luminous intensity (<0.9 W/cm2) in the near-infrared (IR) range. The proposed photosensor combines the advantages provided by both the elevated top gate and extended back gate in the sense of increasing the line tunneling region at the source-channel (S–C) interface, resulting to improvement in illumination current (ILight), threshold voltage (Vth) and average subthreshold swing (SSavg) under the light state. Furthermore, the inclusion of an L-shaped pocket around the source region helps to reduce the corner effects at S–C interface in the sub-threshold region, thereby improving the signal-to-noise ratio (SNR) of the proposed photosensor for on-chip applications. Due to improved optical generation in the photosensing gate, a high spectral sensitivity (Sn) of ∼54 is achieved for ES-EBG-TFET based photosensor because the variation in wavelength (λ) of incident light from 1050 to 750 nm shows a two order change in ILight (ID at Vgs = 0.2V under light state) from 3.1 × 10−15 A/μm to 1.72 × 10−13 A/μm, respectively. Since the elevated source provides a space to create larger illumination window above the channel region, a high optical generation rate is observed for the proposed photosensor under the incident light with low intensity (<0.9 W/cm2). The maximum value of SNR is observed to be 66.4 dB at a λ of 750 nm, while the quantum efficiency (ƞ) and responsivity (R) are reported to be 74% and 0.59 A/W, respectively, around λ of 1050 nm. Moreover, an optimum length of back-gate underlap with drain (LBGUD) is found to enhance the magnitude of SNR (at λ of 750 nm) and Sn (750–1050 nm) from 25.6 to 63.1 dB and 14 to 52.8, respectively when the photosensor is operated at the ambipolar state (Vgs = −0.6 V and Vds = 0.5 V). Finally, the photosensing parameters such as Sn and SNR are analyzed under the presence of acceptor and donor interface traps and it is found that there is insignificant degradation in the optical performance of the proposed photosensor.

Constructing a database of alien plants in the Himalaya to test patterns structuring diversity.

Differences in the number of alien plant species in different locations may reflect climatic and other controls that similarly affect native species and/or propagule pressure accompanied with delayed spread from the point of introduction. We set out to examine these alternatives for Himalayan plants, in a phylogenetic framework. We build a database of alien plant distributions for the Himalaya. Focusing on the well-documented regions of Jammu & Kashmir (west) and Bhutan (east) we compare alien and native species for (1) richness patterns, (2) degree of phylogenetic clustering, (3) the extent to which species-poor regions are subsets of species-rich regions and (4) continental and climatic affinities/source. We document 1470 alien species (at least 600 naturalised), which comprise ~14% of the vascular plants known from the Himalaya. Alien plant species with tropical affinities decline in richness with elevation and species at high elevations form a subset of those at lower elevations, supporting location of introduction as an important driver of alien plant richness patterns. Separately, elevations which are especially rich in native plant species are also rich in alien plant species, suggesting an important role for climate (high productivity) in determining both native and alien richness. We find no support for the proposition that variance in human disturbance or numbers of native species correlate with alien distributions. Results imply an ongoing expansion of alien species from low elevation sources, some of which are highly invasive.

Physics based analysis of a high-performance dual line tunneling TFET with reduced corner effects

To improve the DC and analog/HF performance, a novel dual line tunneling based TFET (DLT-ES-TFET) with elevated source and L-shaped pocket is proposed in this manuscript. In DLT-ES-TFET, the elevated top (G1) and extended back (G2) gates overlapping the source region enhance the line tunneling of charge carriers in both vertical and horizontal directions across the source-pocket interface. TCAD-based simulation results reveal that DLT-ES-TFET offers an improvement of ∼47% and ∼54% in average subthreshold swing when it is compared with E-VTSFET and L-TFET, respectively. Furthermore, ON-current in DLT-ES-TFET is also found to be improved by an order of ∼1 as compared to other two devices. In fact, the L-shaped pocket reduces the corner effects caused by the electric filed crowding across source-channel (S-C) interface, which eventually suppresses the OFF-state leakage in the proposed DLT-ES-TFET. Moreover, enhancement in the charge carriers tunneling across S-C interface leads to a huge increment in the transconductance (∼157μs/μm) of DLT-ES-TFET, which further helps in achieving a high cut-off frequency of 12.3 GHz. Next, transient response of DLT-ES-TFET-based resistive load inverter suggests a notable improvement in peak over- and under-shoots along with propagation delay as compared to E-VTSFET and L-TFET. Lastly, interface traps and temperature analysis is also found to be in favor of the proposed DLT-ES-TFET.

Study on heat transfer characteristics of pulsating heat pipe heat exchanger with asymmetric structure

The Pulsating Heat Pipe (PHP), lauded for its efficacy in heat transfer, is distinguished by its uncomplicated architecture, economical production, diminutive form, and robust adaptability to environmental conditions. This study delineates the design of an asymmetric PHP heat transfer apparatus, achieved through the alteration of select conduit lengths within the comprehensive circulation system. The thermal transfer efficacy of this apparatus was empirically scrutinized under dual dissipation modalities: natural and forced convection. It was observed that the asymmetric PHP, when devoid of oscillatory activity, maintained a heat source temperature of 25∘C, whereas the temperature escalated to 26∘C upon the initiation of pipe vibration. Under the regime of forced convection, the asymmetric PHP demonstrated expedited activation, reduced initiation temperature, and heightened oscillatory behavior compared to its natural convection counterpart, thereby facilitating the phase change condensation within the condensation segment and ensuring efficient, sustained heat dissipation. Consequently, this bolstered the PHP’s heat transfer capabilities. The thermal resistance exhibited a declining trajectory under both dissipation strategies, with forced convection consistently yielding lower thermal resistance than natural convection. Nonetheless, the decrement in thermal resistance was gradual near the critical startup juncture and throughout the initiation phase. The PHP’s equivalent thermal conductivity displayed an upward trend in tandem with the escalation of the heat source’s temperature under both dissipation methods. Despite the superior heat transfer performance at elevated heat source temperatures, the efficiency of natural convection dissipation remained suboptimal, necessitating the application of forced convection to the condensation segment to further enhance the PHP’s thermal transfer proficiency and the overall device performance.

Enhancing indoor air quality and sustainable living in newly constructed apartments: insights from Dubai

This research paper examines Indoor Air Quality (IAQ) conditions in newly constructed apartments in Dubai to be more sustainable for residents to have healthier lifestyles. Enhanced airtightness and chemical-laden materials contribute to IAQ pollution in these buildings. The study aims to assess pollutant concentrations and variations based on building height. Measurements were conducted in 12 apartment units using the WHO’s IAQ assessment methodology. Most pollutants were within limits, but TVOC exceeded the Dubai Municipality’s standard, measuring at 2634.4 μg/m³, approximately nine times higher than the standard. HCHO (163.4 μg/m³) and toluene (551.4 μg/m³) were identified as significant pollutants with potential health effects. Analysis of pollutant concentrations based on building height revealed higher TVOC levels in upper areas, with 2,828 μg/m³ in the upper area compared to 2,443 μg/m³ in the lower area, indicating more severe indoor air pollution in Ethylbenzene and styrene also highest in upper areas, with ethylbenzene at 122 μg/m³ and styrene at 82 μg/m³ in the upper area, potentially due to elevated sources. Toluene and xylene concentrations were elevated in the middle area, with toluene at 574 μg/m³ and xylene at 321 μg/m³, likely influenced by materials and occupant activities. Benzene concentrations were consistent across all heights at 2.94 μg/m³, suggesting a common source. HCHO concentrations were relatively consistent but slightly higher in the middle and upper areas, with 171 μg/m³ in both, likely influenced by ventilation and emissions. While average pollutant concentrations met WHO standards, many units exceeded recommended limits, requiring targeted interventions. The study highlights the importance of addressing IAQ concerns and implementing strategies to reduce indoor air pollutants and improve ventilation. These findings contribute to IAQ knowledge in Dubai’s residential buildings, guiding policymakers, architects, and developers in effective policies and guidelines. Further research on seasonal variations and other IAQ factors is recommended for better understanding and long-term monitoring. Prioritizing IAQ in newly constructed apartments is crucial for healthier living in Dubai. The residential building sector can protect residents’ health by implementing appropriate measures while delivering upscale living experiences.

A comprehensive attribution analysis of PM2.5 in typical industrial cities during the winter of 2016–2018: Effect of meteorology and emission reduction

The frequent occurrence of air pollution in winter has aroused widespread concern. Identifying the detailed source composition of PM2.5 and assessing the reduction effects of different emission sources are crucial steps in improving pollution levels. In this study, we conducted a comprehensive evaluation of emission source reductions, encompassing ten local and ten regional sources. Furthermore, we analyzed the influence of meteorological changes on the abatement of PM2.5 in Tangshan, Shijiazhuang, Xingtai, and Handan during the winter period from 2016 to 2018. Our findings indicate that, in comparison to the winter of 2016, there were significant decreases in the average concentrations of PM2.5 during the winter of 2017. These decreases were attributed to favorable meteorological conditions and emission reductions. However, during the winter of 2018, there was a rebound in PM2.5 concentrations for all four cities. This rebound was primarily caused by adverse meteorological diffusion conditions. Throughout the entire research period spanning from the winter of 2016 to 2018, emission reduction played a significant role in PM2.5 abatement, contributing to 68% in Tangshan, 87% in Shijiazhuang, 93% in Xingtai, and 96% in Handan, respectively. The source apportionment analysis revealed that industrial and residential sources were the dominant contributors to PM2.5 concentrations in the cities. These findings not only confirm the effectiveness of existing industrial and residential pollution control policies but also highlight the imperative need for implementing non-point source control and joint control measures for regional elevated sources in the future.

Runoff response to the uncertainty from key water-budget variables in a seasonally snow-covered mountain basin

Study regionThe American River Basin, a seasonally snow-covered mountain basin in the northern Sierra Nevada of California, USA. Study focusPrecipitation phase (rain, snow, and mixed rain-snow) partitioning in snowy basins is important for runoff forecasting. This study focuses on how predicted runoff response is affected by uncertainty in rain-snow-transition elevation and other water-budget variables. Using a distributed hydrologic model, we examined predicted runoff differences across 33 extreme-precipitation events and dry seasons during 1982–2020, through a set of modeling experiments with different sources of transition elevation and values of water-budget variables. New hydrological insights for the regionDifferent transition elevations can result in noticeable differences in predictions of peak snow water equivalent (SWE) and dry-season runoff. Transition elevation modulates runoff response in a nonlinear way, with runoff uncertainty increasing during larger precipitation events. In terms of the relative impacts of water-budget variables on runoff response, precipitation has the greatest impact, followed by antecedent soil moisture, transition elevation, and antecedent SWE. A 2 °C warming would push the rain-snow-transition elevation ∼300-m higher, increasing the number and severity of extreme events. Compared to the historical period, the same transition-elevation uncertainty in climate warming conditions nearly triples its impacts on runoff uncertainty, posing additional challenges to flood control. This study provides implications for addressing uncertainty in flood-control and water-supply decisions confronted with hydrologic extremes and climate warming.

Integrative analysis of physiology and genomics provides insights into freeze tolerance adaptations of Acacia koa along an elevational cline.

Natural selection for plant species in heterogeneous environments creates genetic variation for traits such as cold tolerance. While physiological or molecular analyses have been used to evaluate stress tolerance adaptations, combining these approaches may provide deeper insight. Acacia koa (koa) occurs from sea level to 2300 m in Hawai'i, USA. At high elevations, natural koa populations have declined due to deforestation, and freeze tolerance is a limiting factor for tree regeneration. We used physiology and molecular analyses to evaluate cold tolerance of koa populations from low (300-750 m), middle (750-1500 m), and high elevations (1500-2100 m). Half of the seedlings were cold acclimated by exposure to progressively lowered air temperatures for eight weeks (from 25.6/22.2°C to 8/4°C, day/night). Using the whole plant physiology-freezing test and koa C-repeat Binding Factor CBF genes, our results indicated that koa can be cold-acclimated when exposed to low, non-freezing temperatures. Seedlings from high elevations had consistently higher expression of Koa CBF genes associated with cold tolerance, helping to explain variation in cold-hardy phenotypes. Evaluation of the genetic background of 22 koa families across the elevations with low coverage RNA sequencing indicated that high elevation koa had relatively low values of heterozygosity, suggesting that adaptation is more likely to arise in the middle and low elevation sources. This physiology and molecular data for cold tolerance of koa across the elevation gradient of the Hawaiian Islands provides insights into natural selection processes and may help to support guidelines for conservation and seed transfer in forest restoration efforts.