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On 18 December 2022, Hawaiian Airlines flight HA35 encountered severe turbulence without warning in a cloud‐free height. We reproduced this incident using the Weather Research and Forecasting Model (WRF) at a convection‐permitting resolution. We found that this case of tropical upper‐level turbulence occurred primarily due to the fast‐growing convective tower in the unstable layer created by gravity wave breaking. At lower altitudes, a mesoscale convective system (MCS) caused a decrease in wind speed in both upstream and downstream regions. At upper levels, a large‐scale jet descended and accelerated after flowing over the top of the MCS, which acted like a barrier and produced a situation similar to a downslope windstorm due to mountain terrain. Upper‐level turbulence is 2–3 km higher than the top of the MCS. The critical level above the jet and the locally self‐induced critical level created the locally enhanced descending jet stream, which destabilized the flow through Kelvin–Helmholtz instabilities. The convective tower existed near the flight route and played an important role in triggering turbulence in the unstable environment through its convective gravity waves. Plain Language Summary: On 18 December 2022, Hawaiian Airlines flight HA35 encountered severe turbulence without warning, resulting in injuries to some passengers and damage to the equipment. This incident requires careful investigation to broaden our understanding of aviation turbulence. A numerical model at kilometer‐scale resolution was used to simulate this case and reveal the dynamics, and we successfully captured the occurrence of turbulence with the simulation. The cause of the turbulence was a previously non‐highlighted mechanism. Severe turbulence was generated by a fast‐growing convective tower at an unstable level. This level was caused by the interaction between the convective system that acted as a barrier and an upper‐level jet. Understanding the causes and spatial distribution of turbulence can help aircraft avoid potential areas with turbulence. Key Points: A regionally convection‐permitting model was used to reproduce a severe turbulence encounterDeep convection acted like terrain and interacted with a jet stream, causing an upper‐level windstorm downstream of the convection topFast‐growing convective tower and downslope windstorm induced turbulence at different locations of the jet stream [ABSTRACT FROM AUTHOR]

Objective: This study aimed to examine the impact of greenness and fine particulate matter <2.5 μm (PM2.5) on overweight/obesity among older adults in China. Methods: A total of 21,355 participants aged ≥65 years were included from the Chinese Longitudinal Healthy Longevity Survey between 2000 and 2018. Normalized difference vegetation index (NDVI) with a radius of 250 m and PM2.5 in a 1 × 1‐km grid resolution were calculated around each participant's residence. Cox proportional hazards models were used to estimate the effects of NDVI and PM2.5 on overweight/obesity. Interaction and mediation analyses were conducted to explore combined effects. Results: The study observed 1895 incident cases of overweight/obesity over 109,566 person‐years. For every 0.1‐unit increase in NDVI the hazard ratio of overweight/obesity was 0.91 (95% CI: 0.88–0.95), and for every 10‐μg/m3 increase in PM2.5 the hazard ratio was 1.11 (95% CI: 1.07–1.14). The effect of NDVI on overweight/obesity was partially mediated by PM2.5, with a relative mediation proportion of 20.10% (95% CI: 1.63%‐38.57%). Conclusions: Greenness exposure appears to lower the risk of overweight/obesity in older adults in China, whereas PM2.5, acting as a mediator, partly mediated this protective effect. [ABSTRACT FROM AUTHOR]

Objective: To compare the outcomes of dichorionic triamniotic (DCTA) triplets who underwent fetal reduction (FR) to singletons or twins with those managed expectantly. Methods: We conducted a retrospective study of DCTA triplets with three living fetuses at 11–14 weeks over a 7‐year period. Pregnancy outcomes were compared following different management strategies. Results: Of 108 included patients, 22 underwent expectant management (EM), 28 were reduced to dichorionic diamniotic twins, and 58 to singletons. The median gestational age at birth for EM, FR to twins, and singletons was 33.1 weeks, 37.0 weeks, and 38.6 weeks, respectively (P < 0.001). Prematurity before 37 and 34 weeks was less common following FR to singletons and twins than in ongoing triplets (18.9%, 46.2% and 90.5%, P < 0.001; 13.2%, 26.9% and 57.1%, P < 0.001). Neonatal birth weight was higher in triplets reduced to singletons and twins compared with EM cases (3140g, 2315g, and 1860g, P < 0.001). However, rates of miscarriage, pregnancies with ≥1 survivor, maternal complications, and adverse neonatal outcomes were comparable among the three groups. Conclusions: In our experience, FR in DCTA triplets could reduce prematurity risk compared to EM, but it confers no survival advantage. Fetal reduction to singletons may result in more favorable outcomes than those reduced to dichorionic twins. Key points: What is already known about this topic? Options for managing dichorionic triamniotic triplets include expectant management, reduction to monochorionic or dichorionic twins, and reduction to singletons. The optimal management strategy is still under debate. What does this study add? Fetal reduction to singletons or dichorionic twins benefits in reducing prematurity risk compared with ongoing dichorionic triamniotic triplets, whereas the risk of pregnancy loss is comparable.Fetal reduction to singletons leads to a decreased risk of prematurity and higher birth weight than those reduced to dichorionic twins. [ABSTRACT FROM AUTHOR]

Previous studies on convective precipitation forecasting in South China have focused on the effects of multiscale dynamics and microphysics parameterizations. However, limited investigation has been conducted on how uncertainty in aerosol data might cause errors in quantitative precipitation forecast for South China's coastal convection. In this case study, we evaluated the impact of aerosol uncertainties on South China's severe coastal convection using convection‐permitting simulations. We estimated the variability range of aerosol concentrations with observations for the pre‐summer months. The simulation results suggest that the rainfall pattern and intensity change notably when aerosol concentrations are varied. Decreasing the concentration of water‐friendly (WF) aerosols intensifies precipitation through reduced cloud water number concentration and increased droplet size. Increasing the concentration of ice‐friendly (IF) aerosols results in up to 40% increase in vertical velocity and latent heat compared to minimal IF aerosol condition, by enhancing the heterogeneous process and dynamically intensifying convection. Consequently, the simulation with minimal WF and maximal IF aerosol concentrations shows prolonged intense precipitation over the entire life cycle of convection. However, when both WF and IF aerosols are set to minimal concentrations, the simulation produces the maximum peak rainfall rate, which is about 50% stronger than the simulation with the climatological mean concentration, due to an enhanced homogeneous process that results in a higher ice concentration and more efficient ice‐phase precipitation growth. Meanwhile, variation in aerosol concentration affects convection initiation (CI), with a lower concentration of WF aerosol inducing earlier CI onset. Decreasing hygroscopicity leads to higher precipitation. Plain Language Summary: Convective weather frequently happens in South China during the pre‐summer season with limited forecast skills. Previous studies have investigated the impact of large‐scale circulation, water vapor conditions, and complex topography in forming convective precipitation systems. However, how chemistry interacts with weather dynamics has limited investigation in the context of convective weather in South China's coastal area. Aerosols can serve as cloud condensation nuclei (CCN) and ice nuclei (IN), and their concentration or property variation can affect various processes in cloud and precipitation formation. To estimate the impact of aerosol uncertainty on South China's pre‐summer rainfall, we conducted simulations of a severe convection case with different aerosol concentrations and properties. We found that the typical aerosol concentration and property variability changed the convective system notably, which further influenced the rainfall pattern and intensity. The aerosols invigorate convection when they cause more latent heating or shift the vertical heating distribution upward, for instance, decreasing the water‐friendly aerosol or increasing the ice‐friendly aerosol can enhance the convection. This work contributes to understanding the aerosol effects of different kinds of aerosols on convection initiation, and precipitation intensity and suggests the potential benefits of increasing aerosol observations in the future to improve the operational numerical forecast. Key Points: Deceasing water‐friendly (WF) aerosol generates more precipitation, and increasing ice‐friendly (IF) aerosol enhances precipitation intensityDeceasing WF aerosol triggers early convection initiation while increasing IF aerosol results in stronger initiationNonlinear relationship exists between the aerosol concentration and convection intensity [ABSTRACT FROM AUTHOR]

The prevalence of peripheral artery disease continues to rise, with major amputations and mortality remaining prominent. Frailty is a significant risk factor for adverse outcomes in the management of the vascular disease. The geriatric nutritional risk index has been used to predict adverse outcomes in lower extremity peripheral artery disease and is a nutrition‐based surrogate for frailty. The authors recruited 126 patients with peripheral artery disease who underwent endovascular stent implantation. As in previous reports, malnutrition was diagnosed by the geriatric nutritional risk index. The authors used Kaplan‐Meier and multivariate Cox proportional hazards regression analyses to analyze the risk of major adverse limb events, which included mortality, major amputation, and target limb revascularization. There were 67 major adverse limb events during a median follow‐up of 480 days. Malnutrition on the basis of the geriatric nutritional risk index was present in 31% of patients. Cox regression analysis showed that malnutrition based on the geriatric nutritional risk index was an independent predictor of major adverse limb events. Kaplan‐Meier analysis showed that major adverse limb events increased with worsening malnutrition. Our single‐center, retrospective evaluation of geriatric nutritional risk index (as a synonym for body health) correlates with an increased risk of major adverse limb events. Future directions should focus not only on identifying these patients but also on modifying risk factors to optimize long‐term outcomes. [ABSTRACT FROM AUTHOR]

The Inner Mongolia Plateau is located in the north of the Late Palaeozoic Hegenshan ophiolitic mélange belt, and its Mesozoic magmatism impacts our understanding of the tectonic evolution affected by the closing of the Mongol‐Okhotsk Ocean and Palaeo‐Pacific Ocean. Here, we present new U–Pb ages, whole‐rock geochemistry and Hf isotopes from the Late Mesozoic magmatic rocks in the Dalai area along the northeastern margin of the Inner Mongolia Plateau. The Late Jurassic rock types include medium‐fine‐grained phenocryst‐bearing and porphyritic monzogranites as well as medium‐fine‐grained monzogranites with the precise age range of 167.7–159.8 Ma. The Early Cretaceous rock types consist of fine‐grained biotite monzogranite and medium‐fine‐grained biotite monzogranite with the precise age range of 140.9–130.7 Ma. The geochemistry data show that the Late Jurassic and Early Cretaceous rocks are peraluminous granites and high‐K calc‐alkaline series and can be classified as A‐type granite. These granites are enriched in large‐ionlithophile elements such as Rb, Th and U, depleted in the high‐field‐strength elements such as Nb, Sr, P, and Ti. Rare earth elements have high total concentrations and present the light rare earth elements enriched with the heavy rare earth elements depleted. Zircon Hf isotopes show that εHf(t) ranges from +8.0 to +15.9 from the Late Jurassic rocks and +6.9 to +13.5 from the Early Cretaceous rocks. Our new results reveal that the Late Jurassic and the Early Cretaceous magmas were derived from partial melting of the younger lower crust, and the Early Cretaceous rocks are more strongly contaminated than the Jurassic intrusions. The Late Jurassic rocks in the Dalai area were formed from a post‐collisional setting related to the closure of the Mongol‐Okhotsk Ocean in the Early‐Middle Jurassic. The Early Cretaceous intrusions were formed from a transition setting from post‐collision to syn‐collision associated with the superposition of the Mongol‐Okhotsk Ocean and the Palaeo‐Pacific Ocean tectonic domain. [ABSTRACT FROM AUTHOR]

Due to miniaturization and environmental friendliness, the electrocaloric effect is expected to be applied to refrigerate electronic chips and microdevices. Unlike the conventional electrocaloric effect that focuses on the temperature change, the ultrafast cooling rate is crucial to heat transport in future device units. In this work, controlling the duration of ultrafast electric field pulse on a nanosecond scale (the frequency ∼ GHz), the instant electrocaloric effect is realized in BaTiO3 and Ba(1−x)SrxTiO3 systems based on the modified phase‐field method. A significant ultrafast cooling rate of 108K s−1 can be achieved due to the application of ultrafast electric field pulse within nanoseconds, which proved to be more efficient than the constant electric field. Furthermore, multiple electric field pulses are designed to realize the cyclic ultrafast cooling. This study provides the fundamental theoretical guidance for ultrafast cooling in solid‐state refrigeration. [ABSTRACT FROM AUTHOR]

Solid‐state refrigeration has received widespread attention recently because of its high refrigeration efficiency and environmental protection. Compared with other solid‐state refrigeration technologies, elastocaloric effects have great application potential. However, the current temperature change of elastocaloric effects is still low. This work explores the change law of phase transition temperature of ferroelectric materials by applying the external stress based on the thermodynamic calculation. It can be found that ferroelectric materials' positive and negative elastocaloric effects can peak at the same temperature, so here a device to combine the positive and negative elastocaloric effects of Ba0.7Sr0.3TiO3 and BaZr0.015Ti0.085O3 is designed. This device can achieve a ΔT of 3.18 K near room temperature under applied stress of 200 MPa, which is twice as large as that of 1.4 K in BCZTO‐Fe under the same stress condition. And it can be raised to 4.1 K after applying an electric field of 10 MV m−1. It is the first time to combine positive and negative elastocaloric effects to achieve high cooling near room temperature, which provides a new solution for efficient cooling near room temperature. [ABSTRACT FROM AUTHOR]

Dielectric energy storage capacitors are receiving a great deal of attention owing to their high energy density and fast charging–discharging speed. The current energy storage density of dielectrics is relatively low and cannot meet the requirements of miniaturization of pulsed power equipment. Therefore, increasing the energy storage density of dielectrics has become a research hotspot. Herein, using phase‐field simulations to design polymorphic nanodomains, the strain engineering of energy storage performance of binary and ternary solid solution relaxor ferroelectric films is investigated. The results show that the energy storage performance of the ternary film is better than that of the binary film due to the polymorphic nanodomains. In addition, as the film in‐plane strain is modified from −2% to 2%, the energy density is improved by 80%, and the efficiency also increases from 52% to 77%. This work proves the remarkable energy storage performance of polymorphic films and provides a theoretical basis to optimize the energy‐storage performance of ferroelectric thin‐film capacitors by adjusting the misfit strain. [ABSTRACT FROM AUTHOR]

With the urgent need to explore low‐cost, high‐efficiency solid‐state refrigeration technology, the electrocaloric effects of ferroelectric materials have attracted much attention in the past decades. With the development of modern computing technology, the phase‐field method is widely used to simulate the evolution of microstructure at mesoscale and predict the properties of different types of ferroelectric materials. In this article, we review the recent progress of electrocaloric effects from phenomenological Landau thermodynamics theory to phase‐field simulation by discussing the microcosmic composition, mesoscopic domain structures, macroscopic size/shape, and external stimulus of strain/stress. More importantly, in searching for new ferroelectric electrocaloric cooling materials, it is possible to find materials whose free energy barrier height changes rapidly with temperature, such materials have a faster change rate with polarization temperature in terms of ferroelectric macroscopic properties, from them could get superior electrocaloric effects. We compile a relatively comprehensive computational design on the high performance of electrocaloric effects in different types of ferroelectrics and offer a perspective on the computational design of electrocaloric refrigeration materials at the mesoscale microstructure level. [ABSTRACT FROM AUTHOR]

Ferroelectric materials subjected to ultrafast external stimuli have been demonstrated to exhibit dynamic phenomena with potential applications in the high‐speed operation of ferroelectric data‐storage devices. A modified phase‐field model is developed to investigate the ferroelectric domain evolution for Pb(Zr,Ti)O3 bulk materials under nano‐second strain‐pulse stimuli. In contrast to the ultrafast electric field pulses, where the ferroelectric domain is switched through domain‐wall motion over the entire duration of the pulses, the nano‐second strain‐pulse induces ultrafast domain switching at the beginning of the pulse, after which the domain structure of the material remains stable. A tensile strain pulse (10 ns) with a critical magnitude of 4.4% is demonstrated to completely switch c domain to a domain. In addition, c domain can also be fully switched to a domain through multiple‐step domain reversals under the periodic small magnitude (2.0%) of strain pulses (5 ns). The theoretical insights obtained in this work are expected to provide useful guidance for exploring and manipulating the ultrafast dynamic functionalities of ferroelectric materials. [ABSTRACT FROM AUTHOR]

Polarization oscillation under GHz electric field stimuli is a key issue for the future development of ultrafast sensor devices. An ultrafast phase‐field model is developed to study the phase diagram of polarization oscillation under sub‐GHz electric field for Pb(Zr,Ti)O3. At the morphotropic phase boundary region, the polarization and strain oscillation show maximum amplitude (electric field stimuli frequency <0.1 GHz). The phase difference of π/2 between the input of electric field and the polarization response, which can be tuned by the frequency of ac electric field stimuli, can lead to a maximum of polarization oscillation amplitude (electric field stimuli frequency >0.1 GHz). Moreover, under this phase difference, the polarization oscillation amplitude can be increased furthermore with the increasing ac electric field strength. With the absence of a phase transition, it is found that the polarization component along the z‐direction has a maximum oscillation amplitude of 0.2, and the strain has a maximum oscillation amplitude of 0.35%. The results provide useful guidance to explore and manipulate dynamic functionalities of ferroelectric sensing materials. [ABSTRACT FROM AUTHOR]

Convective self‐aggregation in radiative‐convective equilibrium (RCE) is a phenomenon of significant interest because of its potential relevance to the organization of tropical storms. However, some previous theories on RCE instability neglected or simplified cloud‐radiative interaction in theoretical models and suggested that water vapor‐radiation feedback is responsible for destabilizing a homogeneous RCE state. Here, through numerical experiments of nonrotating RCE, we first confirm that the predictions from these theories are valid insomuch that dry patches can form in an initially homogeneous domain with uniform sea‐surface temperature when cloud‐radiation interaction is suppressed or eliminated. However, sustained growth of those dry patches is not guaranteed. Developing deep convective circulation can engulf dry patches, and water vapor feedback is not sufficient for overcoming this barrier. Only when the early‐stage cloud radiative forcing is sufficiently strong can self‐aggregation fully develop. Therefore, cloud‐radiative feedback is essential for the eventual realization of self‐aggregation in nonrotating RCE. Plain Language Summary: Radiative‐convective equilibrium (RCE) refers to a balanced atmospheric state with radiative cooling and moist convective heating, a representative idealization of the tropical atmosphere. In RCE simulations, a homogeneous initial state may spontaneously evolve into an inhomogeneous state in which convective clouds cluster in a moist region and are surrounded by dry air. This spontaneous development of organized convection is termed convective self‐aggregation and is thought to be relevant to the organization of tropical weather systems. Convective self‐aggregation starts with the formation of small dry patches in the simulation domain. Previous theories explained their emergence as the result of water vapor‐radiative interaction constrained by atmospheric dynamics. In this study, we find that those theories neglecting cloud‐radiative feedback are only partially correct. After the initial formation of dry patches, the developing deep convection in moist regions may engulf those dry patches due to the downgradient transport of moisture and energy. Only when the cloud‐radiative feedback is sufficiently strong can the barrier due to deep convective circulation be overcome. Thus, cloud‐radiative interaction is essential for the complete development of self‐aggregation and is of great practical importance because clouds are infamous for their uncertainties. Key Points: The initial emergence of dry patches in nonrotating radiative‐convective equilibrium is insensitive to cloud‐radiation interactionStrong cloud forcing is necessary for sustained dry patch growth and the realization of convective self‐aggregationCirculation feedback is initially negative and restrains self‐aggregation but becomes positive as dry patches grow to substantial sizes [ABSTRACT FROM AUTHOR]

This study investigates the mechanisms by which small‐scale turbulence and cloud physics determine the organization of large‐scale convection in radiative‐convective equilibrium (RCE), an idealization of the tropical atmosphere. Under uniform forcings similar to typical tropical conditions, the atmosphere in RCE might spontaneously separate into dry and moist regions on scales of 100–1,000 km, with convective clouds aggregating into a cluster in the latter. This phenomenon is known as convective self‐aggregation. Herein, we demonstrate that subtle changes in assumptions related to cloud physics and turbulence on scales of ≤1 km can dictate the emergence or suppression of convective self‐aggregation, resulting from a bifurcation of the dynamical system. The bifurcation occurs when a small dry patch forms in the domain and is sustained because it contributes to negative effective diffusivity of the circulation. Cloud‐radiation feedbacks and turbulence circulation interactions govern the formation of such dry patches, thereby modulating the bifurcation. This sensitive dependence on subgrid process models might be a fundamental barrier to climate predictability in light of inherent uncertainties in microscale processes. Because without the capability to include exact representations of those processes in climate models, slight differences in the different approximations used by modelers can lead to qualitative changes in climate predictions, at least for some processes. Plain Language Summary: The tropical atmosphere may self‐organize into well‐separated moist and dry regions, with clustered clouds and rain in the former and clear‐sky and dry air in the latter. This phenomenon is called convective self‐aggregation and could dramatically impact tropical weather and climate by changing rainfall patterns and clouds' distribution. However, we found that in an advanced cloud‐resolving model, the atmosphere may either stay in a homogeneous state or exhibit self‐aggregation, depending on how clouds and turbulence are represented. All physical models we chose are state‐of‐the‐art physical models, yet the equilibrium state of the atmosphere is susceptible to subtle details of the cloud and turbulence models. This sensitivity to cloud and turbulence representations may pose another kind of "butterfly effect." Here, instead of facing uncertainties in initial conditions, what can potentially lead to qualitative, dramatic differences in predictions are the relatively small uncertainties in the physical models of cloud and turbulence. To the extent that our cloud and turbulence models can only be imperfect approximations and therefore have inherent uncertainties, the quest to reduce the disagreement between different climate models may eventually meet fundamental barriers. Key Points: Convective self‐aggregation in radiative‐convective equilibrium exhibits nonlinear dependence on cloud and turbulence parameterizationsIts emergence or suppression is governed by a bifurcation of the dynamical system, which is sensitive to subgrid processes in the gray zoneBifurcation mechanisms might be barriers to climate predictability due to inherent uncertainties in cloud and turbulence parameterizations [ABSTRACT FROM AUTHOR]

Achieving a colossal room‐temperature electrocaloric effect is essential for practical solid‐state refrigeration applications with low‐cost and high‐efficiency. Here, through the design of applying external stimuli (hydrostatic pressure and misfit strain), giant room‐temperature electrocaloric effects in the bulk and thin film of metal‐free organic perovskite [MDABCO](NH4)I3 are obtained by using a combination of thermodynamic calculations and phase–field simulations. Under the hydrostatic pressure of 1 GPa, there emerges excellent room‐temperature (300 K) electrocaloric performance with the temperature change (ΔT) of 8.41 K at 30 MV m−1 and electrocaloric strength (ΔT/ΔE) of 0.63 K m MV−1 at 10 MV m−1, respectively. The prominent electrocaloric effects of MDABCO(NH4)I3 may be related to its rapid change rates of free energy barrier height. Additionally, it can be found that some stripe domains and non‐180° domain walls form in the [MDABCO](NH4)I3 bulk, which is consistent with the experimental results. This work not only provides new insights into organic perovskite [MDABCO](NH4)I3, but also guides for further developing to realize remarkable room‐temperature electrocaloric cooling. [ABSTRACT FROM AUTHOR]

The projection of extreme convective precipitation by global climate models (GCM) exhibits significant uncertainty due to coarse resolutions. Direct dynamical downscaling (DDD) of regional climate at kilometer‐scale resolutions provides valuable insight into extreme precipitation changes, but its computational expense is formidable. Here we document the effectiveness of machine learning to enable smart dynamical downscaling (SDD), which selects a small subset of GCM data to conduct downscaling. Trained with data for three subtropical/tropical regions, convolutional neural networks (CNNs) retained 92% to 98% of extreme precipitation events (rain intensity higher than the 99th percentile) while filtering out 88% to 95% of circulation data. When applied to reanalysis data sets differing from training data, the CNNs' skill in retaining extremes decreases modestly in subtropical regions but sharply in the deep tropics. Nonetheless, one of the CNNs can still retain 62% of all extreme events in the deep tropical region in the worst case. Plain Language Summary: Climate scientists use supercomputers to simulate the climate and predict how it may change under global warming. Extreme precipitation, which can disrupt society by causing disasters like floods and landslides, is of great interest in climate studies. However, replicating severe rainstorms on a supercomputer, especially the storms in tropical and subtropical areas, is not easy. This is because those rainstorms often contain fine‐scale details that cannot be represented confidently without extensive computational resources. If we use computationally affordable computer models to simulate those rainstorms, we obtain results with substantial uncertainties. If we use computationally expensive ones, we cannot simulate many scenarios and cannot be confident about the results. The power of machine learning in pattern recognition is here used to help modelers use their computational resources more efficiently. Instead of simulating all kinds of weather events, including unimportant ones, at high resolutions, we use machine learning algorithms to search coarse resolution climate data for those large‐scale weather patterns that are more likely to cause severe rainstorms. Then modelers can make more efficient use of supercomputing resources by simulating severe weather events only and advance our understanding of them. Key Points: Dynamical downscaling at ∼1‐km resolution produces reliable estimations of extreme rainfall but is computationally expensiveMachine learning (ML) makes smart dynamical downscaling (SDD) possible, where ML models filter out irrelevant large‐scale patternsWe demonstrate that SDD can be enabled by deep neural networks, which do not necessarily have to involve sophisticated structures [ABSTRACT FROM AUTHOR]

The variation in presummer precipitation in South China from 1979 to 2015 and its relationship with urbanization were analyzed. The results reveal that the intensity of precipitation and the occurrence of extreme precipitation events during the presummer season in South China have increased significantly, and the upward trend is much more significant in urban areas than in nonurban areas. The mean trends in urban and nonurban areas in South China are, respectively, 1.34 and 0.97 mm/day/year for maximum daily precipitation, 4.41 and 2.79 mm/year for the top 5% of daily precipitation, and 0.26 and 0.16 day/year for extremely heavy precipitation days during the presummer season. In addition to the variability of large‐scale atmospheric circulation, urbanization appears to have a significant effect on the variability of presummer precipitation in South China, especially with regard to the intensity of precipitation and the occurrence of extremely heavy precipitation. From 1979 to 2015, the upward trends of maximum daily precipitation, the top 5% of daily precipitation, and extremely heavy precipitation days during presummer season in urban areas are, respectively, between 38.14% and 39.18%, 55.97% and 59.14%, and 43.75% and 68.75% higher than those in nonurban areas during the investigated period. Urban areas in South China are more exposed to extreme precipitation than nonurban areas during the presummer season. Key Points: The presummer precipitation over South China had undergone a drastic intensification between 1979 and 2015The increasing trend was much more significant in urban areas than in nonurban areasThe effects of urbanization on the intensification of the presummer precipitation over South China were analyzed and discussed [ABSTRACT FROM AUTHOR]

Kilometer‐scale grid spacing is increasingly being used in regional numerical weather prediction and climate simulation. This resolution range is in the terra incognita, where energetic eddies are partially resolved and turbulence parameterization is a challenge. The Smagorinsky and turbulence kinetic energy 1.5‐order models are commonly used at this resolution range, but, as traditional eddy‐diffusivity models, they can only represent forward‐scattering turbulence (downgradient fluxes), whereas the dynamic reconstruction model (DRM), based on explicit filtering, permits countergradient fluxes. Here we perform large‐eddy simulation of deep convection with 100‐m horizontal grid spacing and use these results to evaluate the performance of turbulence schemes at 1‐km horizontal resolution. The Smagorinsky and turbulence kinetic energy 1.5 schemes produce large‐amplitude errors at 1‐km resolution, due to excessively large eddy diffusivities attributable to the formulation of the squared moist Brunt‐Väisälä frequency (Nm2). With this formulation in cloudy regions, eddy diffusivity can be excessively increased in "unstable" regions, which produce downward (downgradient) heat flux in a conditionally unstable environment leading to destabilization and further amplification of eddy diffusivities. A more appropriate criterion based on saturation mixing ratio helps eliminate this problem. However, shallow clouds cannot be simulated well in any case at 1‐km resolution with the traditional models, whereas DRM allows for countergradient heat flux for both shallow and deep convection and predicts the distribution of clouds and fluxes satisfactorily. This is because DRM employs an eddy diffusivity model that is dynamically adjusted and a reconstruction approach that allows countergradient fluxes. Key Points: Traditional LES turbulence models cannot produce countergradient fluxes, which are prominent in deep convectionWhen saturation is defined based on cloud water/ice, traditional models may produce significant errors at kilometer‐scale resolutionDynamic reconstruction model performs well at kilometer‐scale resolution and is insensitive to saturation criteria [ABSTRACT FROM AUTHOR]

This study aims to understand the nature of the tropical intraseasonal oscillations (ISOs) in an aquaplanet simulation performed using Geophysical Fluid Dynamics Laboratory's AM2.1 with a uniform sea surface temperature within the deep tropics. The simulated ISO resembles the observed Madden‐Julian Oscillation in that the spectral peak in precipitation appears at zonal wave number 1 and a period of ~60 days. Vertically integrated moist static energy budget of the simulated ISO shows that enhanced latent heat flux to the east of anomalously active convection causes eastward propagation of the ISO mode, which is weakly opposed by horizontal moisture advection. A series of mechanism denial experiments are conducted either by homogenizing select variables—surface wind stress, longwave radiative heating, and surface evaporation—with their zonal means from the control simulation or by suppressing free‐tropospheric moisture variation. Results of the mechanism denial experiments show that the simulated ISO disappears when the interactive surface evaporation is disabled, suggesting that the wind‐induced surface heat exchange (WISHE) mechanism is essential to the simulated ISO. Longwave cloud‐radiation feedbacks and moisture‐convection feedbacks affect horizontal scale and phase speed of the simulated ISO, respectively. Our results strongly suggest that the simulated ISO is the linear WISHE‐moisture mode of Fuchs and Raymond under horizontally uniform boundary conditions. Key Points: An aquaplanet simulation exhibits a mode of planetary‐scale (wave number 1), eastward propagating intraseasonal variabilityMoist static energy budget and mechanism denial experiments suggest that this mode is the linear WISHE‐moisture mode of Fuchs and RaymondThe WISHE and longwave cloud‐radiation feedbacks serve as scale selection mechanisms for the intraseasonal variability [ABSTRACT FROM AUTHOR]

A rotating radiative-convective equilibrium on a sphere is reached using a global atmospheric model with prescribed globally uniform sea surface temperature and no insolation. In such an equilibrium state, multiple tropical cyclone-like vortices coexist in the extratropics, moving slowly poleward and westward. Many vortices have a lifetime longer than 2 months and travel from the tropics to the polar regions. The typical spacing of simulated tropical cyclone-like vortices is comparable to the deformation radius, while the production of available potential energy is at a scale slightly smaller than those vortices. It is hypothesized that the growth of tropical cyclone-like vortices is driven by the self-aggregation of convection, while baroclinic instability destabilizes any vortices that grow significantly larger than the deformation radius. A weak Hadley circulation dominates in the deep tropics, and an eastward propagating wave number 1 Kelvin-like mode having a period of 30-40 days develops at the equator. The weak Hadley circulation is found to emerge from an initially quiescent atmosphere due to poleward momentum transport by the vortices. [ABSTRACT FROM AUTHOR]

Objectives To explore associations of BMI and waist circumference (WC) with disability among the Chinese oldest old. Methods The 5,495 oldest old in the sixth wave of Chinese Longitudinal Healthy Longevity Study conducted in 2011 were included in this study. Disability was assessed by activities of daily living (ADL); height and weight for BMI and WC were measured; information including socio-demographics, lifestyles, and health status was collected. Results Generalized additive models analysis showed that the association of BMI/WC with ADL disability was nonlinear. Among the males, logistic regression results supported a 'J' shape association between ADL disability with BMI/WC-the highest tertile group in BMI or WC was significantly associated with an increased risk of ADL disability: odds ratio 1.78 (95% confidence interval (CI): 1.26-2.52) for BMI and 2.01 (95% CI: 1.44-2.82) for WC. Among females, an inverse 'J' shape association was found, only the lowest tertile group before the cutoff point had an increased risk of ADL disability: odds ratio 1.42 (95%CI: 1.02-1.97) for BMI and 1.47 (95% CI:1.06-2.04) for WC. Conclusions Associations of BMI and WC with ADL disability are significant even in the oldest old, but differ between the genders. [ABSTRACT FROM AUTHOR]

Summary: Background: Macrosomia is associated with both neonatal complications and adult diseases (obesity, diabetes mellitus, etc.). Previous studies have reported maternal exposure to PM2.5 might influence metabolism and fetal development and cause adverse pregnancy outcomes. Studies conducted in areas with low PM2.5 concentration have found relationship between gestational PM2.5 exposure and birth weight. However, the impact of air pollution on macrosomia has not been studied, especially in highly polluted areas. Objective: To evaluate the association between fine particulate matter (PM2.5) exposure during pregnancy and the risk of macrosomia. Methods: Data from preconception health examination and prenatal and postnatal records were collected from 1 January 2010 to 31 December 2012 in the National Free Preconception Health Examination Project. Monthly mean of PM2.5 concentration during pregnancy was estimated from satellite data using an ensemble machine learning model. A newborn with birth weight above 4000 g was defined as macrosomia. Logistic regression models were used to examine the association between maternal exposure to PM2.5 and the risk of macrosomia, after adjusting for maternal age, pre‐pregnancy body mass index, parity, neonatal sex, duration of gestation, seasonality, educational level, smoking and drinking habits, past history of diabetes mellitus and hypertension, and family history of diabetes mellitus. Restricted cubic spline models were used to evaluate the dose‐response relationship between the risk of macrosomia and PM2.5 concentration. Results: Of 177 841 singleton nonlow birth weight newborns included, 14 598 (8.2%) had macrosomia. The mean PM2.5 concentrations were 70.7, 71.5, and 80.9 μg/m3 in the first, second, and third trimesters. In full‐adjusted logistic regression models, significant associations were found between increased risk of macrosomia and every 10 μg/m3 increase of PM2.5 concentration over the first (odds ratio [OR]: 1.045; 95% CI, 1.037‐1.052), second (OR: 1.035; 95% CI, 1.028‐1.043), and third (OR: 1.033; 95% CI, 1.026‐1.039) trimesters. There was a nonlinear does‐response association between PM2.5 concentration and the risk of macrosomia. Conclusions: Maternal exposure to PM2.5 during pregnancy was associated with an increased risk of macrosomia in China. [ABSTRACT FROM AUTHOR]

There is an increasing demand for permanent magnets with high‐temperature stability. Normally, the magnets are heat treated above the operating temperature range to saturate the irreversible losses, thereby producing magnets that are stable, but with significantly degraded performance. In addition, uncertainty about the losses in differently shaped magnets causes difficulties for efficient magnetic circuit design. The variation of the initial irreversible losses with magnet shape, hysteresis loop, and operating temperature is presented here. Losses are not associated with thermal demagnetization of the whole magnet, but the damage is concentrated in an outer surface "skin" at the pole surfaces, where the demagnetizing field is nonuniform. The initial irreversible remanence loss at room temperature ΔMr′/Mr can be predicted as the product of the slope of the high‐temperature magnetization curve k(T) and the effective demagnetizing factor N. Heat treatment with the vulnerable surfaces in contact with soft iron slabs moves the skin out of the permanent magnet and reduces the irreversible remanence loss by 30% or more, potentially improving the performance of permanent‐magnet motors, generators, bearings, and thrusters. The results deepen the understanding of the magnetism of irreversible losses and will guide the applications of permanent magnets at higher temperatures. [ABSTRACT FROM AUTHOR]

Associations between alcohol use disorders and polymorphisms of genes influencing ethanol metabolism have been widely reported, but gene-gene and gene-sex interaction studies have rarely been examined. Using a set of samples collected during an epidemiological study of alcohol use disorders AUDs in a Tibetan population in China, we performed a case-control study to investigate the relationship between the functional polymorphisms of genes influencing ethanol metabolism and AUDs. The sample included 383 individuals with an AUDIT score >or=10 and 350 control subjects with the AUDIT score