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Atmospheric rivers (ARs) often cause damaging winds, rainfall, and floods. However, the physical mechanisms governing their evolution remain poorly understood. To close this gap, we perform a global Vapor Kinetic Energy (VKE) budget analysis. Using two formulations of VKE, we show that ARs are governed by similar mechanisms regardless of ocean basins. ARs intensify primarily through the conversion of potential energy to kinetic energy (PE‐to‐KE), with horizontal convergence of vapor kinetic energy providing a secondary contribution in some regions. ARs decay mainly through condensation and turbulent dissipation, while their propagation is governed by the downstream convergence and upstream divergence of vapor kinetic energy. We also find PE‐to‐KE conversion varies spatially and strengthens in regions of greater baroclinic instability or enhanced topographic lifting, for example, along North America's west coast. Collectively, these findings demonstrate that the VKE framework provides a powerful diagnostic for how physical processes shape AR evolution and regional variability.

The goal of a biomaterial is to support the bone tissue regeneration process at the defect site and eventually degrade in situ and get replaced with the newly generated bone tissue. Biomaterials that enhance bone regeneration have a wealth of potential clinical applications from the treatment of non-union fractures to spinal fusion. The use of bone regenerative biomaterials from bioceramics and polymeric components to support bone cell and tissue growth is a longstanding area of interest. Recently, various forms of bone repair materials such as hydrogel, nanofiber scaffolds, and 3D printing composite scaffolds are emerging. Current challenges include the engineering of biomaterials that can match both the mechanical and biological context of bone tissue matrix and support the vascularization of large tissue constructs. Biomaterials with new levels of biofunctionality that attempt to recreate nanoscale topographical, biofactor, and gene delivery cues from the extracellular environment are emerging as interesting candidate bone regenerative biomaterials. This review has been sculptured around a case-by-case basis of current research that is being undertaken in the field of bone regeneration engineering. We will highlight the current progress in the development of physicochemical properties and applications of bone defect repair materials and their perspectives in bone regeneration.

National Centers for Environmental Prediction turbulent kinetic energy (TKE)‐based eddy‐diffusivity mass‐flux (EDMF) scheme is implemented in Geophysical Fluid Dynamics Laboratory atmospheric model (AM4.0) for improving the physical consistency of subgrid‐scale planetary boundary layer (PBL) turbulence parameterization. The mass flux (MF) component represents vertically coherent convective structures responsible for countergradient transport in the upper PBL, which the original AM4.0's ED‐only scheme cannot represent. Consequently, AM4.0 with EDMF produces a deeper and more well‐mixed PBL, leading to better zonal‐mean vertical temperature and humidity profiles and reduced near‐surface wet bias over subtropical and midlatitude oceans. Other model performance changes are generally minor, such as similar biases in global top of atmosphere (TOA) net radiation and shortwave cloud radiative effects, small and compensating changes in low cloud amount and cloud liquid water path, improved low‐level equatorial easterlies but deteriorated extratropical westerlies, slightly increased global‐mean precipitation, and 12%$12\\%$weaker TOA radiative response to uniform sea surface warming. Three adaptations of EDMF are important for its performance at AM4.0's relatively coarse vertical resolution: limiting the overshoot of MF updraft above PBL‐top, reducing the ED‐induced mixing across PBL‐top, and disabling the MF transport of TKE. Low clouds and their radiative effects are also sensitive to four EDMF parameters that control the ED in the lower and upper PBL respectively, the TKE dissipation rate, and the lateral entrainment of MF updraft and downdraft. An automatic linear tuning of these parameters slightly improves the radiative bias, especially for the coastal stratocumulus. More substantial improvements likely require formulation updates of the EDMF scheme and its coupling with other AM4.0 model components. Plain Language Summary Turbulence (small, chaotic air movements) is important for transporting momentum, heat, moisture, and other chemical species across the lowest part of Earth's atmosphere (the boundary layer), but is too small to be seen by the grid of general atmospheric models and must be indirectly represented. We have incorporated a new eddy‐diffusivity mass‐flux method into our atmospheric model AM4.0, whose mass‐flux component captures more faithfully the turbulent transport by the bottom‐up and top‐down thermal plumes, producing a deeper and more evenly mixed boundary layer, leading to better temperature and humidity simulations. Most other aspects of AM4.0's performance, such as how much the clouds reflect sunlight and affect infrared radiation, remain largely unchanged. There are some minor trade‐offs: improvements in low‐level wind near the equator but slight worsening at higher latitudes, a small increase in global precipitation, and a 12%$12\\%$weakening in the model's response of overall radiative budget to 2‐degree Celsius sea surface warming. The model performance is optimized by making careful numerical and parameter choices to adjust the turbulent transport near the surface and at the top of the boundary layer. Further improvement may require renovations on how AM4.0 represents the interaction between turbulence and other atmospheric processes. Key Points National Centers for Environmental Prediction eddy‐diffusivity mass‐flux scheme leads to an almost unchanged radiative budget but improved temperature and humidity profiles in Geophysical Fluid Dynamics Laboratory AM4.0 The vertical transport by mass flux deepens the subcloud layer and helps maintain the subtropical stratocumulus Low clouds are sensitive to the discretization and parameters affecting turbulent mixing across the boundary layer top and in the surface layer

Earth's climate sensitivity is greatly affected by the compensation between temperature feedback and water vapor (WV) feedback. Using abrupt 4xCO2 experiments, we show that the global‐mean WV feedback is nearly a linear function of the temperature feedback, the slope of which is explained by the longwave radiative efficiency of WV (ϵ)$({\\epsilon})$ . Although ϵ${\\epsilon}$remains constant across models in the global mean, it exhibits substantial spatial variations and is particularly weak in Antarctica, where near‐surface inversions decouple the surface from the free troposphere. We introduce a surface–free troposphere temperature difference (SFTD) metric, showing that positive SFTD (e.g., high lifting condensation level) amplifies ϵ${\\epsilon}$ , while negative SFTD (e.g., strong surface inversion) suppresses it. These findings provide a clear explanation of how local climate conditions modulate the radiative compensation between temperature and WV feedbacks.

How tropical low clouds change with climate remains the dominant source of uncertainty in global warming projections. An analysis of an ensemble of CMIP5 climate models reveals that a significant part of the spread in the models’ climate sensitivity can be accounted by differences in the climatological shallowness of tropical low clouds in weak-subsidence regimes: models with shallower low clouds in weak-subsidence regimes tend to have a higher climate sensitivity than models with deeper low clouds. The dynamical mechanisms responsible for the model differences are analyzed. Competing effects of parameterized boundary-layer turbulence and shallow convection are found to be essential. Boundary-layer turbulence and shallow convection are typically represented by distinct parameterization schemes in current models—parameterization schemes that often produce opposing effects on low clouds. Convective drying of the boundary layer tends to deepen low clouds and reduce the cloud fraction at the lowest levels; turbulent moistening tends to make low clouds more shallow but affects the low-cloud fraction less. The relative importance different models assign to these opposing mechanisms contributes to the spread of the climatological shallowness of low clouds and thus to the spread of low-cloud changes under global warming.

Precipitation changes in full response to CO2 increase are widely studied but confidence in future projections remains low. Mechanistic understanding of the direct radiative effect of CO2 on precipitation changes, independent from CO2‐induced SST changes, is therefore necessary. Utilizing global atmospheric models, we identify robust summer precipitation decreases across North America in response to direct CO2 forcing. We find that spatial distribution of CO2 forcing at land surface is likely shaped by climatological distribution of water vapor and clouds. This, coupled with local feedback processes, changes in convection, and moisture supply resulting from CO2‐induced circulation changes, could determine North American hydroclimate changes. In central North America, increasing CO2 may decrease summertime precipitation by warming the surface and inducing dry advection into the region to reduce moisture supply. Meanwhile, for the southwest and the east, CO2‐induced shift of subtropical highs generates wet advection, which might mitigate the drying effect from warming. Plain Language Summary How precipitation changes in full response to increased CO2 remains unclear. Mechanistic understanding of how increasing CO2 alone changes precipitation can help us better predict future precipitation in full response to CO2 increase. We find that the precipitation responses are much stronger during summer than winter in North America. During summer, precipitation significantly decreases in central North America in response to the direct CO2 radiative effect, while in the southwest and the east, precipitation changes are small. There might be stronger longwave radiation forcing near the surface induced by CO2 increase in arid regions due to weaker masking effect of water vapor and clouds. This, along with local feedbacks, significantly warms the central region. Meanwhile, the direct forcing of CO2 induces northward shifts in subtropical highs, consequently generating anticyclonic anomalies. These wind anomalies result in drier air advected into central North America, leading to moisture divergence and hence reducing moisture supply. The reduced water supply, coupled with the warming, may decrease precipitation in the region. For the southwest and the east, the anticyclonic anomalies cause wetter air advected into the regions and generate moisture convergence, which increases moisture supply and might mitigate the drying effect caused by CO2‐induced warming. Key Points Robust precipitation decreases during summer in response to CO2 direct radiative effect are identified in central North America Climatology and changes of hydrological environment may collectively modulate the regional CO2 radiative effect on summer precipitation CO2‐induced circulation changes could alter the moisture supply to reshape the regional hydrological cycle

Global climate models (GCMs) struggle to simulate polar clouds, especially low‐level clouds that contain supercooled liquid and closely interact with both the underlying surface and large‐scale atmosphere. Here we focus on GFDL's latest coupled GCM–CM4–and find that polar low‐level clouds are biased high compared to observations. The CM4 bias is largely due to moisture fluxes that occur within partially ice‐covered grid cells, which enhance low cloud formation in non‐summer seasons. In simulations where these fluxes are suppressed, it is found that open water with an areal fraction less than 5% dominates the formation of low‐level clouds and contributes to more than 50% of the total low‐level cloud response to open water within sea ice. These findings emphasize the importance of accurately modeling open water processes (e.g., sea ice lead‐atmosphere interactions) in the polar regions in GCMs. Plain Language Summary Extensive low‐level clouds have been observed to occur over the Arctic and Antarctic regions throughout the year. These low clouds often contain both liquid droplets and ice crystals and have spatial scales smaller than climate model grid spacing, which causes models to struggle with simulating polar cloudiness. Here we focus on a state‐of‐the‐art climate model, Geophysical Fluid Dynamics Laboratory Climate Model version 4, and investigate the modeled polar low‐level clouds with a focus on the basin‐scale spatial pattern and their seasonal variability. Compared to satellite observations, we find that excessive low‐level clouds are produced over the region covered by sea ice, especially during the winter. This overestimation of low clouds is caused by the open water within sea ice that enhances the turbulent transport of water vapor from open water to the atmosphere during non‐summer seasons, leading to the formation of low clouds. These findings indicate that the treatment of open water within sea ice regions is a highly challenging aspect of polar cloud modeling, which has a great impact on polar climate simulation and prediction. Key Points Polar low‐level clouds are biased high in GFDL's coupled model CM4 Polar low‐level clouds are strongly enhanced due to open water within the ice pack during non‐summer seasons Open water with an areal fraction less than 5% makes the largest contribution to the high bias in low‐level clouds

Traditional strategies of bone repair include autografts, allografts and surgical reconstructions, but they may bring about potential hazard of donor site morbidity, rejection, risk of disease transmission and repetitive surgery. Bone tissue engineering (BTE) is a multidisciplinary field that offers promising substitutes in biopharmaceutical applications, and chitosan (CS)-based bone reconstructions can be a potential candidate in regenerative tissue fields owing to its low immunogenicity, biodegradability, bioresorbable features, low-cost and economic nature. Formulations of CS-based injectable hydrogels with thermo/pH-response are advantageous in terms of their high-water imbibing capability, minimal invasiveness, porous networks, and ability to mold perfectly into an irregular defect. Additionally, CS combined with other naturally-derived or synthetic polymers and bioactive agents has proven to be an effective alternative to autologous bone and dental grafts. In this review, we will highlight the current progress in the development of preparation methods, physicochemical properties and applications of CS-based injectable hydrogels and their perspectives in bone and dental regeneration. We believe this review is intended as starting point and inspiration for future research effort to develop the next generation of tissue-engineering scaffold materials.

This study investigates how climate sensitivity depends upon the spatial pattern of radiative forcing. Sensitivity experiments using a coupled ocean‐atmosphere model were conducted by adding anomalous incoming solar radiation over the entire globe, Northern Hemisphere mid‐latitudes, Southern Ocean, and tropics. The varied forcing patterns led to highly divergent climate sensitivities. Specifically, the climate is nearly twice as sensitive to Southern Ocean forcing as tropical forcing. Strong coupling between the surface and free troposphere in the tropics increases the inversion strength, leading to smaller cloud feedback in the tropical forcing experiments. In contrast, the extratropics exhibit weaker coupling, a decrease or near‐zero change in the inversion strength, and strong positive cloud feedback. These results contrast with the conventional SST‐pattern effect in which tropical surface temperature changes regulate climate sensitivity. They also have important implications for other potentially asymmetric forcings, such as those from geoengineering, volcanic eruptions, and paleoclimatic changes. Plain Language Summary The way surface temperature responds to radiative forcing depends on where such forcing is applied. Numerical model integrations show that the global mean surface temperature change is doubled when the forcing is imposed over the Southern Ocean compared to when the forcing is applied in the tropics. Changes in the vertical temperature profiles and clouds contribute to the dependence of surface temperature change on the forcing geographic locations. Key Points The solar forcing pattern effect is investigated in a coupled ocean‐atmosphere model Climate sensitivity is doubled from tropical forcing to Southern Ocean forcing The radiative forcing pattern effect involves changes in lapse rate feedback, cloud feedback, and tropospheric stability

Using the novel kilometer‐scale global storm‐resolving model Geophysical Fluid Dynamics Laboratory eXperimental System for High‐resolution prediction on Earth‐to‐Local Domains (X‐SHiELD), we investigate the impact of a 4 K increase in sea surface temperatures on Northern Hemisphere midlatitude cyclones, during the January 2020–January 2022 period. X‐SHiELD simulations reveal a poleward shift in cyclone tracks under warming, consistent with CMIP projections. However, X‐SHiELD's high resolution and explicit deep convection allowed for a detailed analysis of the warm and cold sectors, which are instead typically underrepresented in traditional CMIP models. Instead, compositing the 100 most intense midlatitude cyclones in the North Atlantic, we find that the warm sector exhibits statistically significant increases in wind speed and precipitation of up to 15% locally per degree of warming, while changes in the cold sector are less pronounced. This study demonstrates X‐SHiELD's potential to provide a realistic‐looking perspective into the evolving risks posed by midlatitude cyclones in a warming climate. Plain Language Summary In this study, we use a cutting‐edge global storm‐resolving model called Geophysical Fluid Dynamics Laboratory eXperimental System for High‐resolution prediction on Earth‐to‐Local Domains (X‐SHiELD) to understand how intense storms, known as midlatitude cyclones, might change as the climate warms. Specifically, we examine how a 4°$4{}^{\\circ}$ C increase in sea surface temperatures affects these storms in the Northern Hemisphere over a 2‐year period. Our simulations show that the tracks of midlatitude cyclones tend to shift toward the poles as temperatures rise, which is consistent with previous climate model projections. What makes this study unique is the use of X‐SHiELD, a high‐resolution storm‐resolving model that can simulate both the warm and cold parts of these cyclones in far greater detail than traditional models. This allows us to observe changes that other models miss. For example, we find that the warm parts of the cyclones experience much stronger winds and heavier rainfall, with increases by up to 15% locally in wind speeds and in rainfall for every degree of warming. These findings suggest that as the climate warms, midlatitude cyclones will pose greater risks, especially from their warm sectors, and highlighting the importance of storm‐resolving models like X‐SHiELD. Key Points Using kilometer‐scale eXperimental System for High‐resolution prediction on Earth‐to‐Local Domains (X‐SHiELD) we capture fine details of warm and cold sectors of midlatitude cyclones, underrepresented in CMIP models Under +4K warming, X‐SHiELD simulations show a poleward shift in midlatitude cyclone tracks consistent with CMIP projections The warm sector of extreme cyclones intensifies with wind speeds and precipitation increasing by up to 15% per degree of warming