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Hailstorms are analyzed across the United States using explicit hailstone size calculations from convection-permitting regional climate simulations for historical, mid-century, and end of twenty-first-century epochs. Near-surface hailstones <4 cm are found to decrease in frequency by an average of 25%, whereas the largest stones are found to increase by 15–75% depending on the greenhouse gas emissions pathway. Decreases in the frequency of near-surface severe hail days are expected across the U.S. High Plains, with 2–4 fewer days projected—primarily in summer. Column-maximum severe hail days are projected to increase robustly in most locations outside of the southern Plains, a distribution that closely mimics projections of thunderstorm days. Primary mechanisms for the changes in hailstone size are linked to future environments supportive of greater instability opposed by thicker melting layers. This results in a future hailstone size dichotomy, whereby stronger updrafts promote more of the largest hailstones, but significant decreases occur for a majority of smaller diameters due to increased melting. [ABSTRACT FROM AUTHOR]

Grasping the physical interactions when two tropical cyclones (TCs) (TC) are in proximity is essential for boosting the accuracy of TC forecasts. This study dissects an uncommon scenario wherein the merging with Tropical Depression 13 W significantly hastened the rapid weakening of Super Typhoon Hinnamnor (2022), utilizing comparative experiments with and without 13 W in simulation's initial field. The findings reveal strong correlations between the merger, amplified environmental vertical wind shear (VWS), and Hinnamnor's consecutive weakening, unfolding in two stages— "top‐down" (Stage 1) and "bottom‐up" weakening (Stage 2) stage. In Stage 1, 13 W led to downdrafts from upper level, hindering the eyewall updrafts and weakening the warm core. In Stage 2, 13 W merged into Hinnamnor's outer rainband, introduced low‐entropy air into the boundary layer and also vied with the eyewall for energy. This research emphasizes that even minor, less‐intense vortices can have profound impacts on the rapid intensity change in TCs. Plain Language Summary: A tropical cyclone (TC)'s intensity and track can be affected by the atmospheric vortices through binary interaction (i.e., Fujiwhara effect). Yet little study has illustrated the merger of TCs with large differences in intensity and size, as well as how it impacts the TC structure and intensity. This study examines the rapid weakening of Super Typhoon Hinnamnor (2022) during its interaction with the tropical depression named 13 W, by two numerical experiments—with and without the existence of 13 W in the initial field. The results find that the merger‐induced increase in environmental vertical wind shear and outer rainband effect caused by 13 W contributed to Hinnamnor's weakening. The process unfolds in two stages. In the first stage, the 13 W in upshear quadrants induced downdrafts from the upper level, disrupting Hinnamnor's eyewall updrafts and diminishing the warm core from top to down. In the second stage, the 13 W in downshear quadrants merged into Hinnamnor's outer rainband, increasing the infusion of low‐entropy air into boundary layer, in turn weakening Hinnamnor from bottom to upper level. This research demonstrates the rainband effect from the other TC during binary interaction, and underlines the attention on impacts from weak and small vortices in TC operational forecasting. Key Points: The merger with Tropical Depression 13 W amplified lower environmental wind and vertical wind shear, leading to Hinnamnor's further weakeningIn early "top‐down" weakening, the 13 W in upshear induced downdrafts, diminishing Hinnamnor's eyewall updrafts and warm coreIn later "bottom‐up" weakening, the 13 W in downshear merged into Hinnamnor's outer rainband, reducing the entropy of boundary layer inflow [ABSTRACT FROM AUTHOR]

In this study we explore aerosol–cloud interactions in liquid-phase clouds over eastern China (EC) and its adjacent ocean (ECO) using the WRF-Chem–SBM model with four-dimensional assimilation. The results show that our simulations and analyses based on each vertical layer provide a more detailed representation of the aerosol–cloud relationship compared to the column-based analyses which have been widely conducted previously. For aerosol activation, cloud droplet number concentration (Nd) generally increases with aerosol number concentration (Naero) at low Naero and decreases with Naero at high Naero. The main difference between EC and ECO is that Nd increases faster in ECO than EC at low Naero due to abundant water vapor, whereas at high Naero , when aerosol activation in ECO is suppressed, Nd in EC shows significant fluctuation due to strong surface effects (longwave radiation cooling and terrain uplift) and intense updrafts. Cloud liquid water content (CLWC) increases with Nd , but the increase rate gradually slows down for precipitating clouds, while CLWC increases and then decreases in non-precipitating clouds. Higher Nd and CLWC can be found in EC than in ECO, and the transition-point Nd value at which CLWC in non-precipitating clouds changes from increasing to decreasing is also higher in EC. Aerosol activation is strongest at moderate Naero , but CLWC increases relatively fast at low Naero. ECO cloud processes are more limited by cooling and humidification, whereas strong and diverse surface and atmospheric processes in EC allow intense cloud processes to occur under significant warming or drying conditions. [ABSTRACT FROM AUTHOR]

Climate models have long‐standing difficulties simulating the South Pacific Convergence Zone (SPCZ) and its variability. For example, the default Zhang‐McFarlane (ZM) convection scheme in the Community Atmosphere Model version 5 (CAM5) produces too much light precipitation and too little heavy precipitation in the SPCZ, with this bias toward light precipitation even more pronounced in the SPCZ than in the tropics as a whole. Here, we show that implementing a recently developed convection scheme in the CAM5 yields significant improvements in the simulated SPCZ during austral summer and discuss the reasons behind these improvements. In addition to intensifying both mean rainfall and its variability in the SPCZ, the new scheme produces a larger heavy rainfall fraction that is more consistent with observations and state‐of‐the‐art reanalyses. This shift toward heavier, more variable rainfall increases both the magnitude and altitude of diabatic heating associated with convective precipitation, intensifying lower tropospheric convergence and increasing the influence of convection on the upper‐level circulation. Increased diabatic production of potential vorticity in the upper troposphere intensifies the distortion effect exerted by convection on transient Rossby waves that pass through the SPCZ. Weaker distortion effects in simulations using the ZM scheme allow waves to propagate continuously through the region rather than dissipating locally, further reducing updrafts and weakening convection in the SPCZ. Our results outline a dynamical framework for evaluating model representations of tropical–extratropical interactions within the SPCZ and clarify why convective parameterizations that produce "top‐heavy" profiles of deep convective heating better represent the SPCZ and its variability. Plain Language Summary: The South Pacific convergence zone (SPCZ), a band of strong rainfall that stretches diagonally across the South Pacific from northwest to southeast, is difficult for climate models to simulate well. Here, we suggest that much of this difficulty stems from underestimating both how much heavy rainfall is produced in the SPCZ and how high above the surface this rainfall forms. The SPCZ has previously been described as a "graveyard" for weather systems. Our hypothesis casts the SPCZ more as a toll collector and suggests that the vertical location of the collection point is key. Simulated weather systems that produce heavier rainfall as they move through the SPCZ region release energy higher in the atmosphere, providing the SPCZ with the means to maintain itself. A model that releases this energy lower in the atmosphere by producing too much light rain allows many weather systems to bypass the toll, weakening the simulated SPCZ and drawing it equatorward in search of the energy it needs. Key Points: Biases in simulated precipitation rate affect diabatic heating and the upper‐level response to transient Rossby wavesAn improved deep convection parameterization reduces biases in the South Pacific Convergence Zone (SPCZ), especially for heavy rainfallMore realistic upper‐level heating strengthens feedbacks between waves and convection, blocking propagation of wave energy locally [ABSTRACT FROM AUTHOR]

Downburst is a hazardous strong wind commonly encountered in thunderstorm weather. Influenced by ambient wind, the downdraft often accompanies horizontal movement while descending. Based on the impinging jet model, this study employs the large eddy simulation method to conduct computational fluid dynamics numerical simulations of stationary and moving downbursts. The evolution process, time-varying wind speed, and wind profile characteristics of the two types of wind fields are compared. This study also discusses the influence of η—which represents the ratio of the storm traveling speed (Vtr) to the jet velocity (Vjet)—on the wind field structure and verifies the applicability of the vector superposition principle in the simulation of the moving downburst. The results show the following: The wind speed and direction time histories obtained from the numerical simulation of moving downbursts have good consistency with the actual wind field records. The movement of the storm causes the near-surface wind field to lose its central symmetry, resulting in a bow-shaped distribution of extreme wind speeds at the storm's leading edge. As η increases, the non-central symmetry of the wind field becomes more pronounced, the maximum horizontal wind speed at the storm's leading edge gradually moves closer to the storm's center, peak wind speeds gradually increase, and the wind speed distribution at the storm's trailing edge shows the opposite trend. The vector superposition principle is not entirely applicable in the simplified analysis of moving downburst, causing significant errors when η is larger than 0.1. [ABSTRACT FROM AUTHOR]

North Atlantic midlatitude cyclones are among the most severe weather systems, causing enormous economic damages and threatening human lives. The cyclone is typically characterized by cyclonic convergent surface winds, strong updrafts, and precipitation. However, extreme surface winds are often observed within the cyclone where downdrafts develop. The present study investigates the dynamical and thermodynamical characteristics of the horizontal winds impinging on the cold frontal surface and the associated downdrafts. It is shown that the cyclonic winds into the cold frontal surface are mainly responsible for the downdrafts that transport the high‐altitude horizontal momentum to the surface and cause intense surface winds. About half of the North Atlantic midlatitude cyclones are accompanied by the downdrafts especially in the southern and western parts of the cyclone center. Plain Language Summary: In the midlatitudes, air temperature decreases toward the poles, and cyclone systems typically travel eastward along regions characterized by strong meridional temperature gradients. Over the cyclone‐influencing area, the cyclonic, counterclockwise rotating, wind induces southward cold advection on the western side of the cyclone center. Therefore, during the early phase of the North Atlantic midlatitude cyclone, the generation of the cold front, which has a steep gradient of temperature to the west of the cyclone center, and that is a common feature. Even after the formation of the cold front, the horizontal winds keep impinging on the frontal surface. Then the horizontal winds blocked by the frontal surface and downdrafts are induced. The downdrafts transport the upper‐level intense wind speed to the lower level strengthening the surface winds. Key Points: Surface winds within North Atlantic midlatitude cyclones are strengthened by strong downdrafts and downward momentum transportsDowndrafts can be generated by the horizontal winds impinging on the cold frontal surfaceCyclones tend to accompany the downdrafts more to the south and west of the cyclone center [ABSTRACT FROM AUTHOR]

This study aims to investigate the effects of different catalysts on biomass gasification. Therefore, red mud (RM) and Aluminum–Nickel alloy were used as catalysts with biomass mixture (BM) for the lab-scale gasification studies by using an updraft and a modifiable-downdraft fixed bed reactor. The maximum volumetric percentage of H 2 , ranging from 51% to 65%, was achieved at 900 °C in both gasifiers. Al–Ni catalyst significantly boosted H 2 content, reaching 65% in the updraft gasifier at 900 °C with 0.05 L/min dry air. H 2 /CO ratio varied from 2 to 4 for BM, while catalyst use expanded the range to 1.6–7 with the Al–Ni catalyst demonstrating the most effective performance. In general, it was seen that RM increased the H 2 component in the syngas between 1 and 7 vol% at 900 °C in updraft gasifier. In the modifiable-downdraft reactor, on the contrary, H 2 concentration in the syngas decreased by 2–6% with the addition of RM. [Display omitted] • Red mud and aluminum - nickel alloy were added to biomass as catalysts. • Two different fixed-bed gasifiers were operated under the same conditions. • The use of the catalyst increased the H 2 vol% in the syngas. • The max. volumetric percentage of H 2 gas was found to be in the range of 51–65%. [ABSTRACT FROM AUTHOR]

An ensemble three‐dimensional ensemble‐variational (3DEnVar) data assimilation (En3DA) approach that directly assimilates radar reflectivity was developed based on the Weather Research and Forecasting model data assimilation system. This system adopts radar reflectivity as the control variable to avoid the need for a tangent linear and adjoint of the observation operator. Flow‐dependent covariance was introduced via ensemble forecasts updated by a group of 3DEnVar. The performance of the En3DA system was examined for two selected cases of high‐impact severe tornadic supercells over China. Results for both cases indicated that the structure of the storms in terms of intensity, coverage, and associated low‐level mesocyclones were analysed more accurately when using the En3DA approach than when adopting the 3DVar method. Hydrometeor analysis showed that En3DA provided a more physically reasonable increment of hydrometeors compared to 3DVar, especially for the graupel mixing ratio. Furthermore, the En3DA forecast was better than the 3DVar forecast throughout the forecast period for both studied cases. En3DA produced smaller errors in terms of intensity and location for supercell forecasts with respect to reflectivity and reflectivity swaths. Furthermore, the quantitative forecast skill of radar reflectivity was improved using En3DA. Errors in the wind, temperature, and water vapor forecast fields produced by En3DA were also reduced compared to those of 3DVar. Diagnostics revealed that En3DA predicted an enhanced low‐level cold pool and stronger outflows in the forward‐flank downdraft and the rear‐flank downdraft regions, which are important for tornadogenesis. [ABSTRACT FROM AUTHOR]

The dual-polarization radar characteristics of severe storms are commonly used as indicators to estimate the size and intensity of deep convective updrafts. In this study, we track rapid fluctuations in updraft intensity and size by objectively identifying polarimetric fingerprints such as ZDR and KDP columns, which serve as proxies for mixed-phase updraft strength. We quantify the volume of ZDR and KDP columns to evaluate their utility in diagnosing temporal variability in lightning flash characteristics. Specifically, we analyze three severe storms that developed in environments with low-to-moderate instability and strong 0–6-km wind shear in northern Alabama during the 2016–17 VORTEX-Southeast field campaign. In these three cases (a tornadic supercell embedded in stratiform precipitation, a nontornadic supercell, and a supercell embedded within a quasi-linear convective system), we find that the volume of the KDP columns exhibits a stronger correlation with the total flash rate. The higher covariability of the KDP column volume with the total flash rate suggests that the overall electrification and precipitation microphysics were dominated by cold cloud processes. The lower covariability with the ZDR column volume indicates the presence of nonsteady updrafts or a less prominent role of warm rain processes in graupel growth and subsequent electrification. Furthermore, we observe that the majority of cloud-to-ground (CG) lightning strikes a carried negative charge to the ground. In contrast to findings from a tornadic supercell over the Great Plains, lightning flash initiations in the Alabama storms primarily occurred outside the footprint of the ZDR and KDP column objects. Significance Statement: This study quantifies the correlation between mixed-phase updraft intensity and total lightning flash rate in three severe storms in northern Alabama. In the absence of direct updraft velocity measurements, we use polarimetric signatures, such as ZDR and KDP columns, as proxies for updraft strength. Our analysis of polarimetric radar and lightning mapping array data reveals that the lightning flash rate is more highly correlated with the KDP column volume than with the ZDR column volume in all three storms examined. This contrasts with previous findings in storms over the central Great Plains, where the ZDR column volume showed higher covariability with flash rate. Interestingly, lightning initiation in the Alabama storms mainly occurred outside the ZDR and KDP column areas, contrary to previous findings. [ABSTRACT FROM AUTHOR]

We examine tropical rainfall from the Geophysical Fluid Dynamics Laboratory's Atmosphere Model version 4 (GFDL AM4) at three horizontal resolutions of 100 km, 50 km, and 25 km. The model produces more intense rainfall at finer resolutions, but a large discrepancy still exists between the simulated and the observed frequency distribution. We use a theoretical precipitation scaling diagnostic to examine the frequency distribution of the simulated rainfall. The scaling accurately produces the frequency distribution at moderate‐to‐high intensity (≥10 mm day−1). Intense tropical rainfall at finer resolutions is produced primarily from the increased contribution of resolved precipitation and enhanced updrafts. The model becomes more sensitive to the grid‐scale updrafts than local thermodynamics at high rain rates as the contribution from the resolved precipitation increases. Plain Language Summary: State of the art global scale climate models have horizontal resolutions of the order of tens of kilometers. However, these resolutions are much lower than the scales required to resolve tropical convection. This study investigates whether a resolution increase from 100 km to 25 km results in notable improvements in simulating tropical rainfall. Higher resolution simulations capture more intense rainfall events that are missed by their coarser counterparts. However, they struggle to capture the accurate frequency distribution of intense rainfall events. Results reported in this study underscore the importance of scrutinizing and carefully interpreting the outcomes of high‐resolution climate model simulations. Key Points: Tropical rainfall distribution is analyzed using simulations from the Geophysical Fluid Dynamics Laboratory's Atmosphere Model version 4 at three horizontal resolutions: 100 km, 50 km, and 25 kmIncreasing horizontal resolution yields more intense tropical rainfall but not the accurate frequency distributionTheoretical precipitation scaling accurately captures the frequency distribution of the simulated precipitation at moderate‐to‐high intensity [ABSTRACT FROM AUTHOR]

The Adrar region (Algeria) has a total of 397,800 date palm trees (Phoenix dactylifera L.). Due to annual palm cleaning, large quantities of lignocellulosic biomass are produced. Depending on the variety, an average of 65 kg of biowaste is obtained per palm tree. Since the value of this biowaste is underrated, most of the palms are burned outdoors, causing air and visual pollution. This work explores the gasification potential of lignocellulosic waste from date palms (Phoenix dactylifera L. Takarbouche variety) into useful energy. The technology investigated is air updraft fixed-bed gasification, thanks to an originally designed and built reactor, with the capability to process 1 kg of feedstock. Four types of palm waste—namely, palms, petioles, bunch, and bunch peduncles—are first characterized (bulk density, proximate analysis, fixed carbon, elemental composition, and calorific value) and then used as feedstock for two gasification tests each. The syngas produced for the four date palm wastes is combustible, with an outlet temperature between 200 and 400 °C. The operating temperature inside the gasifier varies according to the feature of the biomass cuts (from 174 °C for the peduncles to 557 °C for palms). The experimental setup is also equipped with a cyclone, allowing for the recovery of some of the tar produced during the tests. Finally, the results show that the residence time has a positive effect on the conversion rate of date palm waste, which can significantly increase it to values of around 95%. [ABSTRACT FROM AUTHOR]

Overshooting tops (OTs), prominent signatures within deep convective storms, are produced by intense updrafts and are closely linked to heavy rainfall, strong winds, and other severe weather conditions. Using an OT dataset derived from multiyear observations of precipitation radar on board the Global Precipitation Measurement core observatory as a reference, the performances of two commonly used OT detection algorithms are evaluated for the Himawari-8 and Fengyun-4A satellites. The results indicate that the infrared contour-based algorithm based on Himawari-8 is the most effective for objective OT detection in eastern China. It exhibits a probability of detection (POD) of 62.1% and a false-alarm ratio (FAR) of 36.6%, outperforming others by achieving a greater POD and a lower FAR. Furthermore, based on the severe weather records from surface meteorological stations and nearby OT detections, a strong relationship is revealed between GEO-detected OTs and the occurrence of short-term heavy rainfall (e.g., ≥20 mm h−1) and extreme wind speed (e.g., ≥17.2 m s−1) events. The OT matched percentages for these events are 61.8% and 54.0%, respectively. This suggests that GEO satellite-based OT data can serve as an important objective product for forecasters to increase their understanding of severe convective storms. [ABSTRACT FROM AUTHOR]

This study investigates the effect of the initial tropical cyclone (TC) vortex structure on the intensity change during the eyewall replacement cycle (ERC) of TCs based on two idealized simulations using the Weather Research and Forecasting (WRF) model. Results show that an initially smaller TC with weaker outer winds experienced a much more drastic intensity change during the ERC than an initially larger TC with stronger outer winds. It is found that an initially larger TC vortex with stronger outer winds favored the development of more active spiral rainbands outside the outer eyewall, which slowed down the contraction and intensification of the outer eyewall and thus prolonged the duration of the concentric eyewall and slow intensity evolution. In contrast, the initially smaller TC with weaker outer winds corresponded to higher inertial stability in the inner core and weaker inertial stability but stronger filamentation outside the outer eyewall. These led to stronger boundary layer inflow, stronger updraft and convection in the outer eyewall, and suppressed convective activity outside the outer eyewall. These resulted in the rapid weakening during the formation of the outer eyewall, followed by a rapid re-intensification of the TC during the ERC. Our study demonstrates that accurate initialization of the TC structure in numerical models is crucial for predicting changes in TC intensity during the ERC. Additionally, monitoring the activity of spiral rainbands outside the outer eyewall can help to improve short-term intensity forecasts for TCs experiencing ERCs. [ABSTRACT FROM AUTHOR]

Precise estimation of the thermal updraft environment is important for the effective exploration of wind resources in long-endurance drones. Nevertheless, previous regression algorithms exhibit limitations in accurately evaluating updrafts under new operating conditions, and traditional airborne wind measurement methods are constrained by narrow ranges and sparse spatial sampling. This study addresses these challenges by harnessing continuous temperature data acquired via infrared sensors. The proposed methodology employs a data-driven deep operator network (DeepONet) to map the temperature field to the velocity field. Numerical simulations of two-dimensional Rayleigh–Bénard convection are conducted to simulate sensing measurements under various Rayleigh number R a , used as both training and testing datasets. For the DeepONet framework, a convolutional neural network (CNN) structure is employed as the branch network to extract features from the temperature field. Simultaneously, a fully connected neural network (FNN) is adopted as the trunk network, encoding input functions from fixed sensors. In order to assess the estimation performance in new environments, the training data are under operating conditions within the range of R a = 3 × 10 7 – 6 × 10 7 , and the testing data are under other unknown operating conditions. By compared to the conventional FNN network and the standard DeepONet framework, the DeepONet(CNN) in this study manifests a significant enhancement in estimation performance, demonstrating improvements ranging from 20% to 40% under unknown operating conditions. [ABSTRACT FROM AUTHOR]

A big hurdle to using solar chimneys for power generation is their low overall efficiency, which is measured by how effectively energy is converted at different stages of the system. While a taller chimney might help, it is expensive and complex to implement. To address this issue, a new study explored the possibility of using a thermal absorbing assembly at the top of the chimney to increase its efficiency without increasing its height. The study presented both experimental and numerical data on this approach, looking at changes in temperature and heat gains as performance indicators. By adding this low-cost and simple fixture, the study found that the temperature before the chimney outlet increased, and the stack effect was strengthened. The rise of air temperature posed an increase of up to 83.1% by experimental assessment and an increase of 12.75% by numerical assessment with the added fixture of the heat trap. [ABSTRACT FROM AUTHOR]

Air pollution from combustion processes is harming human health and the environment. To mitigate this, one needs to adopt cleaner energy production methods, in particular, to optimize combustion systems in order to minimize pollutants and increase efficiency. Flue gas analysis and particulate matter (PM) monitoring, starting from the prototype phase, is crucial to minimize and regulate pollutant emissions. This article analyses the emissions of pollutants and particulate matter from a combustion test gasifier working on the Top-Lit Updraft (TLUD) principle in order to optimize functionality and reduce exhaust emissions. Three experiments were performed in which the primary (gasification) air flow rate (GA) was kept constant at 25 L/min, and the secondary (combustion) air flow rate (CA) was adjusted to obtain a CA/GA ratio of 2 (50 L/min), 3 (75 L/min), and 4 (100 L/min) respectively. Based on a multi-criterial analysis, the optimal CA/GA ratio for TLUD combustion is 3, offering a well-rounded performance in output temperatures, PM and greenhouse gases (GHG) emissions, and efficiency, while the CA/GA ratio of 4 has good PM and GHG emissions performance but lower efficiency, and the CA/GA ratio of 2 is the least favorable due to its poor performance in output temperatures, PM and GHG emissions. [ABSTRACT FROM AUTHOR]

In this study, we present radar polarimetric characterizations of the storm producing 201.9 mm hourly rainfall on 20 July 2021 in Zhengzhou, China. We employed the separation signatures of enhanced polarimetric observations to investigate hydrometeor size sorting processes, and developed an algorithm to quantify the size sorting directions. Analysis of coupled polarimetric observations unraveled multi‐directional size sorting (MSS) occurred as a low‐level differential reflectivity ZDR backwards arc signature encompassing the rainfall center during the most intensive rainfall period. The rainfall intensification is in step with the increase of size sorting directions. Model simulations with two‐moment microphysics scheme suggest that the presence of arc‐shaped updrafts is conducive to MSS and increased rain rates around the rainfall center. This work sheds novel insights into the kinematics‐driven microphysics in extreme rainfall storms, warranting the potential of using coupled polarimetric signatures for warning catastrophic extreme rainfall events. Plain Language Summary: Raindrops of varying sizes have different fall speeds. In presence of storm‐relative winds, the differential sedimentation between large and small raindrops leads to different sorting distances, redistributing the regional characteristic sizes of raindrops. In radar polarimetric measurements, differential reflectivity ZDR is representative of the characteristic size of raindrops and specific differential phase KDP is proportional to the rain water content. The coupled low‐level polarimetric separation signatures in rainfall storms are indicative of the raindrop size sorting as driven by the storm kinematics. In this study, we identified unusual polarimetric separation signatures characterized by an unprecedented ZDRbackwards arc in the storm producing 201.9 mm hourly rainfall accumulation. Different from previously observed ZDR arc in a single inflow, ZDRbackwards arc is suggestive of multi‐directional size sorting as driven by arc‐shaped updrafts. We found that the intensification of rain rates is associated with increased size sorting directions. Detection of this novel radar polarimetric signature in operational services is recommended for warning such extreme rainfall events in the future. Key Points: Radar polarimetric separation signatures were used to characterize size sorting in the extreme rainfall stormMSS as driven by arc‐shaped updrafts in the storm is evidenced by an unprecedented ZDR backwards arcIncrease of size sorting directions is correlated to rainfall intensification [ABSTRACT FROM AUTHOR]

Results are presented from the Rum Creek fire during the California Fire Dynamics Experiment (CalFiDE). An instrumented payload aboard the NOAA Twin Otter (TO) aircraft, which included a scanning micro‐pulsed Doppler lidar (DL) and in situ chemistry packages, was used to address the evolution of a buoyant plume jet (BPJ) and transport dynamics over the southwest corner of the fire between 09/01/2022 and 09/02/2022. An approach previously developed to isolate updrafts was modified to account for the Gaussian core structure when addressing the evolution of the updraft, plume‐top entrainment, lateral entrainment, and the role of fire‐atmosphere interactions on the characteristics of the BPJ during four overpasses. A persistent cross‐valley flow leading up to the BPJ was observed for all four overpasses, with flow enhancement during the second overpass that coincided with changes in the BPJ structure and turbulence characteristics surrounding the BPJ. Length scales and entrainment rates were estimated at the lateral edges and the top of the plume. In the case of the latter, an analytical form of the BPJ profile above the vertical velocity maximum of the updraft was derived using a simplified form of the vertical momentum equation following a partial budget analysis that accounted for plume‐top entrainment and the boundary layer (BL) inversion. Velocity core strength and characteristics were analyzed away from the updraft with similar relationships between depth‐to‐widths of velocity cores found in a forthcoming study focused on wildfire plumes. Plain Language Summary: The goal of the California Fire Dynamics Experiment (CalFiDE) during the fall of 2022 was to survey wildfire dynamics and impacts on air quality over areas historically affected by wildfires. The Rum Creek fire, which occurred west of Medford, Oregon, was one of several fires observed using data collected aboard the NOAA Twin Otter (TO) aircraft. In this study, we focused on a smoke plume at the southwest corner of the fire that featured strong upward motion. Multiple flyovers of this plume led to an analysis of how the plume changed with time, and how the conditions surrounding the plume supported its development. The work presented details the internal structure of the plume and the influence of background winds on the evolution of the plume, which has implications for understanding the transport of smoke away from the fire. Key Points: Airborne Doppler lidars are capable of resolving small scale dynamics over short distances spanning the width of the firelineComplex interactions between fire‐induced updrafts and the surrounding atmosphere can lead to non‐ideal representation of the updraft profileTerrain and fire‐modified winds are important for updraft evolution and transport dynamics [ABSTRACT FROM AUTHOR]

There are more uncertainties with ice hydrometeor representations and related processes than liquid hydrometeors within microphysics parameterization (MP) schemes because of their complicated geometries and physical properties. Idealized supercell simulations are produced using the WRF model coupled with "full" Hebrew University spectral bin MP (HU-SBM), and NSSL and Thompson bulk MP (BMP) schemes. HU-SBM downdrafts are typically weaker than those of the NSSL and Thompson simulations, accompanied by less rain evaporation. HU-SBM produces more cloud ice (plates), graupel, and hail than the BMPs, yet precipitates less at the surface. The limiting mass bins (and subsequently, particle size) of rimed ice in HU-SBM and slower rimed ice fall speeds lead to smaller melting-level net rimed ice fluxes than those of the BMPs. Aggregation from plates in HU-SBM, together with snow–graupel collisions, leads to a greater snow contribution to rain than those of the BMPs. Replacing HU-SBM's fall speeds using the formulations of the BMPs after aggregating the discrete bin values to mass mixing ratios and total number concentrations increases net rain and rimed ice fluxes. Still, they are smaller in magnitude than bulk rain, NSSL hail, and Thompson graupel net fluxes near the surface. Conversely, the melting-layer net rimed ice fluxes are reduced when the fall speeds for the NSSL and Thompson simulations are calculated using HU-SBM fall speed formulations after discretizing the bulk particle size distributions (PSDs) into spectral bins. The results highlight precipitation sensitivity to storm dynamics, fall speed, hydrometeor evolution governed by process rates, and MP PSD design. [ABSTRACT FROM AUTHOR]

We investigate the representation of individual supercells and intriguing tornado‐like vortices in a simplified, locally refined global atmosphere model. The model, featuring grid stretching, can locally enhance the model resolution and reach cloud‐resolving scales with modest computational resources. Given a conditionally unstable sheared environment, the model can simulate supercells realistically, with a near‐ground vortex and funnel cloud at the center of a rotating updraft reminiscent of a tornado. An analysis of the Eulerian vertical vorticity budget suggests that the updraft core of the supercell tilts horizontal vorticity into the tornado‐like vortex, which is then amplified through vertical stretching by the updraft. Results suggest that the simulated vortex is dynamically similar to observed tornadoes, as well as those simulated in modeling studies at much higher horizontal resolution. Lastly, we discuss the prospects for the study of cross‐scale interactions involving supercells. Plain Language Summary: We use a simplified global model to study individual supercells and intriguing cloudy rotating winds that behave like tornadoes. This model uses grid‐stretching techniques, making it a computationally efficient tool to study supercells on a real‐size Earth. Unlike most numerical models of tornadoes which simulate scales of a few tens of meters, our model can realistically simulate supercells and cloudy tornado‐like rotating winds even at kilometer scales, which appears unprecedented in the literature. We find that the physics behind the rotating winds is consistent with previous studies, including observations of tornado formation and simulations at much higher resolution. The findings of this study open the door to a better understanding of complex interaction between supercells, tornadoes, and their environment. Key Points: The FV3 dynamical core with simple microphysics can simulate individual supercells and cloudy tornado‐like vortices at kilometer scalesA stretched cubed‐sphere grid is used to economically reach cloud‐resolving scales locally on a real‐size EarthThe dynamics of the simulated tornado‐like vortices is consistent with previous studies on tornadogenesis [ABSTRACT FROM AUTHOR]

As an essential moisture transport channel over the Tibetan Plateau (TP), accurate simulation of precipitation over the southeastern TP (SETP) is crucial for downstream moisture transport and water resource assessment. To improve SETP's precipitation simulation accuracy, a Turbulent Orographic Form Drag (TOFD) scheme, which represents the TOFD effect of subgrid orography on model grids, is employed. The impact of TOFD on cloud and precipitation during the summer monsoon over the SETP is investigated from dynamical and cloud microphysical perspectives. Through comparison with ground observations and satellite precipitation data, TOFD reduces the simulated precipitation bias. Despite reducing moisture transport, TOFD enhances low-level convergence and high-level divergence by influencing the low-level wind, thereby strengthening updraft and cloud and precipitation processes before the slope of SETP. TOFD also increases total precipitation before the slope by promoting heavy precipitation and reducing weak precipitation. However, TOFD diminishes the updraft and cloud and precipitation processes over the slope of SETP by influencing low-level wind. The reduced moisture transport by TOFD leads to decreased precipitation over the slope. Additionally, TOFD reduces total precipitation over the slope by promoting weak precipitation and reducing heavy precipitation. Furthermore, the impact mechanism of TOFD on precipitation depends on the wind speed, which is weakened during weak precipitation period with reduced wind speed and enhanced during heavy precipitation period with increased wind speed. These findings enhance the understanding of the complex terrain's influence on cloud and precipitation and provide a basis for improving cloud and precipitation simulation over the SETP. [ABSTRACT FROM AUTHOR]

Tethered balloon systems encounter various complex wind field environments during flight. To investigate the conditions under which the system can operate safely and smoothly, a longitudinal dynamic model for tethered balloon systems is established. The model incorporates a streamlined balloon shape with its aerodynamic center at the body's center. Steady-state aerodynamic force coefficients are calculated through simulations and fitted to a function based on the angle of attack within a specified range. The complex cable model is simplified using the lumped mass method, considering the influence of branch cables on the main node position. Experimental results from windless oscillation tests on scaled tethered balloon systems are compared with numerical solutions obtained using the dynamic model under the same conditions, validating the feasibility of the model for simulating different wind field scenarios. Finally, the motion characteristics of tethered balloon systems in different wind fields are analyzed. The numerical simulation results show that in a horizontal step wind field, the cable tension and cable inclination angle increase with the wind speed, and the slower the wind field changes, the shorter the time required for system stabilization. Updrafts greatly increase the likelihood of balloon escape, while downdrafts greatly increase the likelihood of the system making contact with the ground. The findings of this study can provide a basis for selecting suitable wind field conditions and issuing risk warnings for tethered balloon systems. [ABSTRACT FROM AUTHOR]

Downbursts winds, characterized by strong, localized downdrafts and subsequent horizontal straight-line winds, present a significant risk to civil structures. The transient nature and limited spatial extent present measurement challenges, necessitating analytical models for an accurate understanding and predicting their action on structures. This study analyzes the Sânnicolau Mare downburst event in Romania, on 25 June 2021, using a bi-dimensional analytical model coupled with the teaching–learning-based optimization (TLBO) algorithm. The intent is to understand the distinct solutions generated by the optimization algorithm and assess their physical validity. Supporting this examination are a damage survey and wind speed data recorded during the downburst event. Employed techniques include agglomerative hierarchical K -means clustering (AHK-MC) and principal component analysis (PCA) to categorize and interpret the solutions. Three main clusters emerge, each displaying different storm characteristics. Comparing the simulated maximum velocity with hail damage trajectories indicates that the optimal solution offers the best overlap, affirming its effectiveness in reconstructing downburst wind fields. However, these findings are specific to the Sânnicolau Mare event, underlining the need for a similar examination of multiple downburst events for broader validity. [ABSTRACT FROM AUTHOR]

This research paper presents a comprehensive study on the combustion of wheat straw pellets in a 10 kW fixed-bed reactor through a Computational Fluid Dynamics (CFDs) simulation and experimental validation. The developed 2D CFDs model in ANSYS meshing simulates the combustion process in ANSYS Fluent software 2021 R2. The investigation evaluates key parameters such as equivalence ratio, heating value, and temperature distribution within the reactor to enhance gas production efficiency. The simulated results, including combustion temperature and produced gases (CO2, CO, CH4), demonstrate a significant agreement with experimental combustion data. The impact of the equivalence ratio on the conversion efficiency and lower heating value (LHV) is systematically explored, revealing that an equivalence ratio of 0.35 is optimal for maximum gas production efficiency. The resulting producer gas composition at this optimum condition includes CO (~27.67%), CH4 (~3.29%), CO2 (~11.09%), H2 (~11.09%), and N2 (~51%). The findings contribute valuable insights into improving the efficiency of fixed-bed reactors, offering essential information on performance parameters for sustainable and optimized combustion. [ABSTRACT FROM AUTHOR]

This paper investigates a downdraft multi-injection moving bed reactor (MBR) for the hydrolysis reaction in the copper-chlorine (Cu–Cl) thermochemical cycle for hydrogen production. The numerical modelling is conducted for a variety of system configurations of the MBR, with a focus on reducing the energy requirement of the reactor while achieving high conversion rates. Several design variables are investigated, including reactor volume, injection point location, and quantity of steam injection. The numerical predictions show an approximate 23% increase in CuCl 2 conversion for the multi-injection MBR compared to a single injection design. A maximum conversion of 66.5% is predicted through design parameter variations. Asymptotic behavior for the quantity of injection locations with respect to conversion extent is presented for several different steam to copper ratios. The results and new insights in this paper suggest opportunities for conversion improvement and steam to copper ratio reduction in the hydrolysis reactor through the MBR design. • Multi-injection moving bed hydrolysis reactor simulated with a kinetic model. • Investigates reactor designs/operating conditions for better hydrolysis efficiency. • 23% increase in CuCl 2 hydrolysis conversion through multi-injection MBR model. • Identified maximum hydrolysis conversion asymptote with steam injection quantity. [ABSTRACT FROM AUTHOR]

The diagonal squall line that passed through the Korean Peninsula on the 18 May 2020 was examined using wind data retrieved from multiple Doppler radar synthesis focusing on its kinematic and dynamic aspects. The low-level jet, along with warm and moist air in the lower level, served as the primary source of moisture supply during the initiation and formation process. The presence of a cold pool accompanying the squall line played a role in retaining moisture at the surface. As the squall line approached the Korean Peninsula, the convective bands in the northern segment (NS) and southern segment (SS) of the squall line exhibited distinct evolutionary patterns. The vertical wind shear in the NS area was more pronounced compared to that in the SS. The ascending inflow associated with the tilted updraft in the NS reached an altitude of 7 km, whereas it was only up to 4 km in the SS. The difference was caused by the strong descending rear flow, which obstructed the ascending inflow and let to significant updraft in the SS. [ABSTRACT FROM AUTHOR]

This study investigated the dependence of the early tropical cyclone (TC) weakening rate in response to an imposed moderate environmental vertical wind shear (VWS) on the warm‐core strength and height of the TC vortex using idealized numerical simulations. Results show that the weakening of the warm core by upper‐level ventilation is the primary factor leading to the early TC weakening in response to an imposed environmental VWS. The upper‐level ventilation is dominated by eddy radial advection of the warm‐core air. The TC weakening rate is roughly proportional to the warm‐core strength and height of the initial TC vortex. The boundary‐layer ventilation shows no relationship with the early weakening rate of the TC in response to an imposed moderate VWS. The findings suggest that some previous diverse results regarding the TC weakening in environmental VWS could be partly due to the different warm‐core strengths and heights of the initial TC vortex. Plain Language Summary: The warm core is a basic structural feature of a tropical cyclone (TC), and TC intensity is closely related to the warm‐core strength and height. This study investigated the dependence of the initial TC weakening rate in response to an imposed moderate environmental vertical wind shear (VWS) on the strength and height of the TC vortex during the TC intensifying period using idealized numerical simulations. It is found that the weakening of the warm core is the primary factor leading to the early weakening of the TC, and the TC weakening rate is roughly proportional to the warm‐core strength and height of the TC vortex. It is also found that the boundary‐layer ventilation associated with VWS‐induced convective downdrafts show no relationship with the early weakening rate of the TC in response to an imposed moderate VWS. The findings of this study can help explain why some TCs can continuously develop under the influence of moderate environmental VWS while some others cannot, which are partly due to the different warm‐core strengths and heights of the initial TC vortex. Key Points: The tropical cyclone (TC) weakening rate in response to an imposed moderate environmental vertical wind shear (VWS) is proportional to the strength and height of the TC warm coreThe warm‐core weakening induced by upper‐level ventilation is the primary factor to the early TC weakening induced by the imposed VWSThe boundary‐layer ventilation shows no relationship with the early weakening rate of the TC in response to the imposed moderate VWS [ABSTRACT FROM AUTHOR]

The atmospheric convection is a phenomenon that has a length scale smaller than the resolution at which the state‐of‐the‐art general circulation numerical models are running, and thus the convection needs to be parametrized. In this work, a theoretical formulation for the parametrization of subgrid‐scale convection based on subgrid averaging that represents a generalized eddy‐diffusivity mass‐flux formulation is presented. The subgrid fluxes are derived by considering a decomposition of subgrid variables into convective and turbulent variables, and by assuming that the convection is modeled by round convective plumes with generic radial profiles. The main difference between our formulation and the mass‐flux formulations is that the condition of a very small fractional area occupied by the convection is replaced with the condition that the convective vertical velocity goes to the mean state far from the updraft region of the plume. The plume model can also be generalized by considering that the convective elements are energy‐consistent plumes, governed by the conservation of mass, momentum, kinetic energy, and buoyancy, which provides a physical‐based closure for the entrainment. Therefore, the closing problem of our formulation consists of the specification of the convective radial profiles and the boundary conditions at the initial vertical level. Furthermore, our formulation allows one to consider more realistic profiles for the convective variables, making the formulation suitable for the parametrization of atmospheric convection at the convective gray zone. This aspect is discussed in the last part of this work, where it is showed how the formulation can be implemented at any resolution. Moreover, in the present framework, no distinct assumptions are required for each convective type, thus facilitating the parametrization of convection in a unified way. [ABSTRACT FROM AUTHOR]

Urban breeze is produced by the temperature difference between urban and surrounding rural areas, and its interactions with other atmospheric phenomena are of great interest. In this study, the impacts of background wind on the interactions between urban breeze circulation (UBC) and convective cells are numerically investigated. For this, a large number of idealized ensemble simulations are performed using the Weather Research and Forecasting‐large‐eddy simulation model, where the initial background wind speed varies from 0 to 5 m·s−1 in 0.5 m·s−1 intervals. As the background wind speed increases, the location of the strongest updraft moves from the urban center to the downwind boundary of the urban area. This is associated with different interactions between the UBC and convective cells under different background wind speeds. For no background wind, the UBC is relatively strong and its center is located at the urban center, producing a strong updraft there. Convective cells are advected toward the UBC center and merge with the strong updraft, further intensifying it. For weak background wind, the UBC is relatively weak and its center is located near the downwind urban boundary. Convective cells passing the urban area merge with each other and intensify, and after they pass the downwind urban boundary, the strong vertical wind shear in the right part of the UBC tilts and weakens them. For strong background wind, the UBC is very weak and convective cells are advected mainly by the strong background wind. These changes in the characteristics of convective cells in and around the urban area with background wind speed may lead to the changes in the preferred location of cloud initiation and cloud development. [ABSTRACT FROM AUTHOR]

A heavy orographic precipitation event associated with the postfrontal sector of a midlatitude cyclone over the Australian Snowy Mountains (ASM) was analyzed using field observations and numerical simulations. This event, observed during a 2018 intensive field campaign, was of particular interest as three distinct precipitation episodes were identified within a prolonged postfrontal period. Deep mixed‐phase clouds (MPCs) characterized by cold cloud‐top temperatures (colder than −30°C) and the presence of updrafts extending 3.5–4.5 km above the boundary‐layer height, produced the three enhanced precipitation events over the windward slopes of the ASM. The presence of conditional instabilities and deep updrafts were also found in the sounding and Doppler velocity observations respectively, while the cloud radar observations show the deep MPCs with cloud tops reaching to 6–7 km a.s.l. Orographic convection invigoration was found to be the main mechanism producing the precipitation enhancement over the windward slopes and higher terrain. Using the Weather Research/Forecasting model, we analyzed the rates of microphysical processes to explicitly account for the enhancement of precipitation formation processes in these MPCs. This analysis showed that the precipitation formation processes were further enhanced through depositional and riming growth of ice‐phase hydrometeors during the three precipitation events. Deposition is simulated at higher levels (above the −15°C level) and most likely enabled by deep convective updrafts through the midtroposphere, whereas riming is stronger at lower levels (below −10°C level) due to the persistent production of feeder supercooled liquid water clouds sustained by the orographic lifting. [ABSTRACT FROM AUTHOR]

Considering Malaysia's position as a leading producer of palm oil, it wastes appears to be a promising renewable energy source. Thus, present work compares optimal behavioural performance and power generation potential from the palm oil mill wastes, including empty fruit bunch (EFB) and palm kernel shell (PKS). Aspen Plus software is used to perform a sensitivity study, investigating the influence of temperature and equivalence ratio (ER) on syngas output, syngas composition, and power generation. Temperature increase (600◦C to 1000◦C) leads to increase in H2 and CO and decrease in CO2 and CH4 composition. At optimal operating condition, temperature for EFB and PKS is at 740◦C and 865◦C while ER is at 0.25 for both feedstocks. The low heating value (LHV), cold gas efficiency (CGE) and total syngas output happens to be around 4.84 MJ/Nm3, 48.89% and 259.18 kg/hr for (EFB and 4.01 MJ/Nm3, 51.27 % and 312.97 kg/h for PKS. EFB shows higher capability to produce more quality syngas and generate more power compared to PKS. From economic perspective, EFB brings more revenue (115 million/year) than PKS (111 million/year) for 10 MW plant capacity by considering electricity as the main product. [ABSTRACT FROM AUTHOR]

Long-term observations of deep convective cloud (DCC) vertical velocity and mass flux were collected during the Observations and Modelling of the Green Ocean Amazon (GoAmazon2014/5) experiment. Precipitation echoes from a surveillance weather radar near Manaus, Brazil, are tracked to identify and evaluate the isolated DCC lifecycle evolution during the dry and wet seasons. A radar wind profiler (RWP) provides precipitation and air motion profiles to estimate the vertical velocity, mass flux, and mass transport rates within overpassing DCC cores as a function of the tracked cell lifecycle stage. The average radar reflectivity factor (Z), DCC area (A), and surface rainfall rate (R) increased with DCC lifetime as convective cells were developing, reached a peak as the cells matured, and decreased thereafter as cells dissipated. As the convective cells mature, cumulative DCC properties exhibit stronger updraft behaviors with higher upward mass flux and transport rates above the melting layer (compared with initial and later lifecycle stages). In comparison, developing DCCs have the lowest Z associated with weak updrafts, as well as negative mass flux and transport rates above the melting layer. Over the DCC lifetime, the height of the maximum downward mass flux decreased, whereas the height of the maximum net mass flux increased. During the dry season, the tracked DCCs had higher Z , propagation speed, and DCC area, and were more isolated spatially compared with the wet season. Dry season DCCs exhibit higher Z , mass flux, and mass transport rate while developing, whereas wet season DCCs exhibit higher Z , mass flux, and mass transport rates at later stages. [ABSTRACT FROM AUTHOR]

Disentangling the response of tropical convective updrafts to enhanced aerosol concentrations has been challenging. Leading theories for explaining the influence of aerosol concentrations on tropical convection are based on the dynamical response of convection to changes in cloud microphysics, neglecting possible changes in the environment. In recent years, global convection‐permitting models (GCPM) have been developed to circumvent problems arising from imposing artificial scale separation on physical processes associated with deep convection. Here, we use a global model in the convective gray zone that partially simulates deep convection to investigate how enhanced concentrations of aerosols that act as cloud condensate nuclei (CCN) impact tropical convection features by modulating the convection‐circulation interaction. Results from a pair of idealized non‐rotating radiative‐convective equilibrium simulations show that the enhanced CCN concentration leads to weaker large‐scale circulation, the closeness of deep convective systems to the moist cluster edges, and more mid‐level cloud water at an equilibrium state in which convective self‐aggregation occurred. Correspondingly, the enhanced CCN concentration modulates how the physical processes that support or oppose convective aggregation maintain the aggregated state at equilibrium. Overall, the enhanced CCN concentration facilitates the development of deep convection in a drier environment but reduces mean precipitation. Our results emphasize the importance of allowing atmospheric phenomena to evolve continuously across spatial and temporal scales in simulations when investigating the response of tropical convection to changes in cloud microphysics. Plain Language Summary: How does air pollution affect thunderstorm intensity over the tropical ocean? Past studies have proposed different pieces of evidence but generally neglect the interplay between the development of thunderstorms and the long‐range movement of air that redistributes the Earth's thermal energy and moisture. Here, we address this question by investigating results from idealized numerical experiments in which a global domain is used to simultaneously simulate the response of individual thunderstorms and large‐scale air motion to pollution. We found that pollution makes the thunderstorms keep less moisture in their surroundings, limiting the intensity of thunderstorms and weakening the large‐scale air motion that supplies moisture to thunderstorms. Our results suggest that the interplay between the development of thunderstorms and the long‐range movement of air is crucial in determining the effects of pollution in the tropical atmosphere. Key Points: A global model with horizontal grid length in the convective gray zone is used to investigate aerosol indirect effectsPollution leads to weaker large‐scale circulation, the closeness of convection to the moist cluster edges, and more mid‐level cloud waterPollution facilitates deep convection development in a drier environment but reduces mean precipitation [ABSTRACT FROM AUTHOR]

Background: Spatially explicit simulation models of animal movements through the atmosphere necessarily require a representation of the spatial and temporal variation of atmospheric conditions. In particular, for movements of soaring birds that rely extensively on vertical updrafts to avoid flapping flight, accurate and reliable estimation of the vertical component of wind is critical. The interaction between wind and complex terrain shapes both the horizontal and vertical wind fields, highlighting the need to model the coupling between local terrain features and atmospheric conditions at scales relevant to animal movement. Methods: In this work, we propose a new empirical model for estimating the orographic updraft field. The model is developed using computational fluid dynamics simulations of canonical atmospheric conditions over moderately complex terrain. To isolate buoyancy and thermal effects, and focus on terrain-induced effects, we use only simulations of a neutrally stratified atmosphere to develop the model. The model, which we name Engineering Vertical Velocity Estimator (EVVE), is simple to implement and is a function of the underlying terrain elevation map, the desired height above ground level (AGL), and wind conditions at a reference height (80 m). We validate the model with data from the Alaiz mountain (Spain) field campaign. Results: Compared to observations, the proposed improved model estimates the updrafts at 120 m AGL with a mean error of 0.11 m/s ( σ = 0.28 m/s), compared to 0.85 m/s ( σ = 0.58 m/s) for its baseline. For typical land-based wind turbine hub heights of 80 m AGL, the proposed model has a mean error of 0.04 m/s ( σ = 0.25 m/s), compared to baseline 0.54 m/s ( σ = 0.45 m/s) estimations. We illustrate an application of the model in movement ecology by comparing simulated tracks and presence maps of golden eagles (Aquila chrysaetos) moving across two distinct landscapes. The tracks and presence maps are obtained using a simple heuristic-based movement model, with the updraft field given by the proposed model and a wind vector-based estimation approach that is currently in wide use in movement ecology studies of raptors and other soaring birds. Conclusions: We highlight that movement model results can be sensitive to the underlying orographic updraft model, especially in studies of fine-scale movements in regions of complex topography. We suggest adopting the proposed model rather than the wind vector estimation method for studies of soaring bird movements. [ABSTRACT FROM AUTHOR]

The possibilities of pistachio shell biochar production on laboratory-scale gasification and pyrolysis devices have been described by several previous studies. Nevertheless, the broader results of the pistachio shell co-gasification process on pilot-scale units have not yet been properly investigated or reported, especially regarding the detailed description of the biochar acquired during the routine operation. The biochar was analysed using several analytical techniques, such as ultimate and proximate analysis (62%wt of C), acid–base properties analysis (pH 9.52), Fourier-transform infrared spectroscopy (the presence of –OH bonds and identification of cellulose, hemicellulose and lignin), Raman spectroscopy (no determination of Id/Ig ratio due to high fluorescence), and nitrogen physisorption (specific surface 50.895 m2·g−1). X-ray fluorescence analysis exhibited the composition of the main compounds in the biochar ash (32.5%wt of Cl and 40.02%wt of Na2O). From the energy generation point of view, the lower heating value of the producer gas achieved 6.53 MJ·m−3 during the co-gasification. The relatively high lower heating value of the producer gas was mainly due to the significant volume fractions of CO (6.5%vol.), CH4 (14.2%vol.), and H2 (4.8 %vol.), while hot gas efficiency accomplished 89.6%. [ABSTRACT FROM AUTHOR]

The increased gasification potential of bulk density agricultural residues such as groundnut shell (GS) and rice husk (RH) could aid in the effective implementation of bioenergy for a wider range of applications. Mixing high-carbon biomass with such feedstocks is an appealing option for improving producer gas (PG) quality. Though spent tea waste (STW) has a high-carbon content due to its small particle size and high-moisture levels, it is not directly used in gasifiers for PG generation. However, it could be a promising secondary biomass in the gasification of GS and RH. To establish this strategy, an appropriate mixing method and a study on the gasification potential of the mixture as feedstock for downdraft gasifiers is essential. In this study, STW was mixed with GS and RH at various mixing ratios and tested in a downdraft gasifier. The experimental results showed that, up to a 40% weight ratio of STW with the primary biomasses, the gasifier could operate continuously without any incomplete gasification. The calorific value, cold gas efficiency and hot gas efficiency improvements for GS/STW blends at the best equivalence ratio (ER) were 19.3%, 19.61% and 18.04%, respectively, whereas for the RH/STW blend, the improvements were 16.2%, 14.5% and 13.81%. The best performance of GS/STW and RH/STW blends was found for ERs of 0.3 and 0.25, respectively, which are different from the optimum ERs for the gasification of primary feedstocks alone. [ABSTRACT FROM AUTHOR]

A tornado hit Nobeoka city on the southeast coast of Kyushu Island, Japan on 22 September 2019 when Typhoon Tapah was located about 500 km to the southwest of Kyushu Island and moving northeastward. Triplynested numerical simulations are performed to reproduce the typhoon, a parent storm, and associated tornadoes. The simulation with the coarsest resolution reasonably reproduces Typhoon Tapah and associated outer rainbands at several 500 km east of its center, where the environment around the rainband is found to be favorable for mini-supercells. The simulation with the finest resolution reproduces a train of mini-supercells and associated tornadoes. The mini-supercells have typical structures that cause tornadoes associated with tropical cyclones. The minimum central pressure of the strongest tornado is 945 hPa. The time evolution of the simulated tornadoes is very fast: significant transitions of vortex structure occur within 1 minute before the tornado attains its peak strength. Most of the circulation of the tornado is derived from rear-flank downdrafts. Three tornadoes occur sequentially in association with non-occluding mesocyclogenesis, where a new tornado develops in the northwest of the old one. [ABSTRACT FROM AUTHOR]

An idealized large-eddy simulation of a tropical marine cloud population was performed. At any time, it contained hundreds of clouds, and updraft width in shallow convection emerging from a subcloud layer appeared to be an important indicator of whether specific convective elements deepened. In an environment with 80%–90% relative humidity below the 0°C level, updrafts that penetrated the 0°C level were larger at and above cloud base, which occurred at the lifting condensation level near 600 m. Parcels rising in these updrafts appeared to emerge from boundary layer eddies that averaged ∼200 m wider than those in clouds that only reached 1.5–3 km height. The deeply ascending parcels (growers) possessed statistically similar values of effective buoyancy below the level of free convection (LFC) as parcels that began to ascend in a cloud but stopped before reaching 3000 m (nongrowers). The growers also experienced less dilution above the LFC. Nongrowers were characterized by negative effective buoyancy and rapid deceleration above the LFC, while growers continued to accelerate well above the LFC. Growers occurred in areas with a greater magnitude of background convergence (or weaker divergence) in the subcloud layer, especially between 300 m and cloud base, but whether the convergence actually led to eddy widening is unclear. Significance Statement: Cumulonimbus clouds are responsible for many extreme weather phenomena and are important contributors to Earth's energy balance. However, the processes leading to the growth of individual clouds are not completely understood nor well-represented in weather prediction models. We find that the clouds containing updrafts that start out wider at early stages of their life cycles grow taller, possibly because they are protected more from drier air outside the cloud than narrow clouds. In addition, this work shows how the initial width of clouds might be related to convergence in the lowest part of the atmosphere, at heights where clouds initially develop. However, meteorologists must be careful not to overinterpret these results because numerical simulations inherently include assumptions that may not reflect reality. This reinforces the need to also observe processes occurring at the scales of individual clouds. [ABSTRACT FROM AUTHOR]

Background: There is an ongoing need for improved understanding of wildfire plume dynamics. Aims: To improve process-level understanding of wildfire plume dynamics including strong (>10 m s−1) fire-generated winds and pyrocumulus (pyroCu) development. Methods: Ka-band Doppler radar and two Doppler lidars were used to quantify plume dynamics during a high-intensity prescribed fire and airborne laser scanning (ALS) to quantify the fuel consumption. Key results: We document the development of a strongly rotating (>10 m s−1) pyroCu-topped plume reaching 10 km. Plume rotation develops during merging of discrete plume elements and is characterised by inflow and rotational winds an order of magnitude stronger than the ambient flow. Deep pyroCu is initiated after a sequence of plume-deepening events that push the plume top above its condensation level. The pyroCu exhibits a strong central updraft (~35 m s−1) flanked by mechanically and evaporative forced downdrafts. The downdrafts do not reach the surface and have no impact on fire behaviour. ALS data show plume development is linked to large fuel consumption (~20 kg m−2). Conclusions: Interactions between discrete plume elements contributed to plume rotation and large fuel consumption led to strong updrafts triggering deep pyroCu. Implications: These results identify conditions conducive to strong plume rotation and deep pyroCu initiation. Scanning remote sensing instruments allow us to understand the processes contributing to extreme wildfire fire plume behaviours including the development of strong rotation in the smoke column and fire-generated clouds reaching deep into the atmosphere. These data help us understand which fires are prone to extreme fire behaviour. [ABSTRACT FROM AUTHOR]

The first Meteosat Third Generation (MTG) satellite was launched in December 2022. Its high resolution Flexible Combined Imager (FCI) in combination with the Lightning Imager (LI) herald a new period for geostationary (GEO) weather observations over Europe, Africa, and adjacent regions. Similar instruments are already operational over the U.S., with the Advanced Baseline Imagers (ABIs) and the Geostationary Lightning Mappers (GLMs). The objective of this study is to gain a deeper understanding of GEO data, with a specific emphasis on sudden increases in a storm's lightning activity, referred to as lightning jumps (LJ), and decreases, known as lightning dives (LD), as observed from a geostationary orbit. ABI-based cloud characteristics of thunderstorms are analyzed while storms are categorized by whether they produced LJs, LDs, or severe weather. It is found that the storms with LJs and/or LDs feature overall similar characteristics as the severe thunderstorms. Those storms typically feature elevated, colder cloud tops, more and stronger overshooting tops (OTs), consequently leading to more structured updrafts. As a result, these storms tend to generate higher convective rain rates (CRRs) on average compared to storms lacking LJs, LDs, and those categorized as non-severe. In particular, thunderstorms experiencing multiple LJs throughout their lifecycle exhibit the most and strongest OTs, signifying highly organized updrafts, extremely cold cloud tops, and highest CRRs. Considering the characteristics mentioned above, these storms, especially those featuring multiple LJs and LDs during their lifecycle, are of particular interest for nowcasting potentially dangerous weather phenomena. [ABSTRACT FROM AUTHOR]

A convective cell storm containing two differential reflectivity (ZDR) columns was observed with a dual-polarization phased-array radar (X-PAR) in Xixian County. Since a ZDR column is believed to correspond to a strong updraft and a single convective cell is considered to have a simple dynamic structure with one updraft core, how these two ZDR columns form and coexist is the focus of this study. The dynamic and microphysical structures around the two ZDR columns are studied under the mutual confirmation of the X-PAR observations and a cloud model simulation. The main ZDR column forms and maintains in an updraft whose bottom corresponds to a convergence of low-level and mid-level flow; it lasts from the early stages to the later stages. The secondary ZDR column emerges at the rear of the horizontal reflectivity (ZH) core relative to the moving direction of the cell; it forms in the middle stages and lasts for a shorter period, and its formation is under an air lifting forced by the divergent outflow of precipitation. Therefore, the secondary ZDR column is only a by-product in the middle stages of the convection rather than an indicator of a new or enhanced convection. [ABSTRACT FROM AUTHOR]

The micro-physical characteristics of a typical sea of clouds process in Jiuxian Mountain are investigated by comprehensively analyzing parameters that delineate the micro-physical characteristics of clouds and atmospheric stratification based on data from a cloud radar, wind profiler, meteorological gradient observation in high mountains, and other observations. The results show that water vapor condenses into cloud particles via an entrained and mixing process accompanied by an updraft originating from orographic uplift. During the thickening stage of the sea of clouds, atmospheric motion within the clouds is featured as "downdraft on the top—updraft on the bottom". The zero vertical velocity area is located closely to the maximum of liquid water content. The thermal inversion layer is formed during the maintenance stage; however, the enhancement of inversion on the cloud top could suppress updraft in areas with a high liquid water content. The values mainly concentrate on the cloud top, and repetitively lifting and falling processes caused by the atmospheric upward and downward motion are in favor of the coalescence growth of cloud particles, which result in the persistence of strong radar echo. At the dissipation stage, warming on the cloud top is greater than that on the cloud bottom due to the short-wave absorption of clouds as the solar radiation enhances. As a result, the inversion layer thickens and elevates, evaporation caused by heating outweighs the condensation caused by cooling, a strong radar echo band descends from the top to the middle part of clouds, a sea of clouds dissipates gradually as cloud particles evaporates, and the particle size and concentration number of cloud particles decrease simultaneously. [ABSTRACT FROM AUTHOR]

A custom lightweight, miniaturized, and trackable meteorological probe was launched by a model rocket into the inflow region of an EF4, long-tracked tornado south of Lawrence, Kansas, on 28 May 2019 and sampled tornado core flow. The rocket reached apogee at 439 m a.g.l., releasing the "pseudo-Lagrangian drifter" by parachute directly into the tornado vortex. The probe reached a three-dimensional (3D) speed of 85.1 m s -1 in the first revolution around the tornado, measured an altitude-corrected pressure deficit of - 113.5 hPa at 475 m a.s.l., and sampled a tornadic updraft speed of 65.0 m s -1. The probe then transitioned to an environment exhibiting a more tilted ascent above an altitude of 4300 m a.s.l. at speeds up to 84.0 m s -1 to a maximum altitude of 11 914 m a.s.l. 1 Hz pressure, temperature, relative humidity, GPS, acceleration, gyroscope, and magnetometer data for the flight were transmitted in real time to a ground station until 10 680 m a.s.l. and the probe landed 51 km northeast of the launch position. The probe was recovered without damage, which is attributed to the pseudo-Lagrangian drifter design, and then higher-resolution and complete 10 Hz data were downloaded for the flight. This novel deployment method and design facilitate data collection in real time from within tornadoes, the mesocyclone, and downdraft without requiring the probes to be recovered or for researchers to enter the circulation to deploy equipment. [ABSTRACT FROM AUTHOR]

While recent observational studies of intensifying (IN) versus steady-state (SS) hurricanes have noted several differences in their axisymmetric and asymmetric structures, there remain gaps in the characterization of these differences in a fully three-dimensional framework. To address these limitations, this study investigates differences in the shear-relative asymmetric structure between IN and SS hurricanes using airborne Doppler radar data from a dataset covering an extended period of time. Statistics from individual cases show that IN cases are characterized by peak wavenumber-1 ascent concentrated in the upshear-left (USL) quadrant at ∼12-km height, consistent with previous studies. Moderate updrafts (2–6 m s−1) occur more frequently in the downshear eyewall for IN cases than for SS cases, likely leading to a higher frequency of moderate to strong updrafts USL above 9-km height. Composites of IN cases show that low-level outflow from the eye region associated with maximum wavenumber-1 vorticity inside the radius of maximum wind (RMW) in the downshear-left quadrant converges with low-level inflow outside the RMW, forming a stronger local secondary circulation in the downshear eyewall than SS cases. The vigorous eyewall convection of IN cases produces a net vertical mass flux increasing with height up to ∼5 km and then is almost constant up to 10 km, whereas the net vertical mass flux of SS cases decreases with height above 4 km. Strong USL upper-level ascent provides greater potential for the vertical development of the hurricane vortex, which is argued to be favorable for continued intensification in shear environments. [ABSTRACT FROM AUTHOR]

Understanding the nature of mixing between cloudy air and its surroundings is an important and yet, open question. In this research, we use high‐resolution (10 m) bin‐microphysics Large Eddy Simulation of a cumulus cloud, together with a Lagrangian passive tracer tracking method, to study mixing. We analyze the passive tracers as a function of their trajectories and the thermodynamic conditions they undergo inside and outside the cloud. Three main mixing regimes (core, periphery, and skin) are identified, each determining a subset of tracers with similar trajectories. These mixing regimes can be observed throughout the cloud's lifetime and they provide evidence for the presence of an undiluted core in shallow cumulus clouds. At the dissipation stage, a fourth regime is identified: cloud‐top entrainment followed by downdrafts. Plain Language Summary: The mixing of shallow clouds with their environment is a key open question in climate research and prediction. This topic is challenging due to the complexity of cloud processes and the difficulty of accurately measuring and modeling them. This study uses high‐resolution simulation and Lagrangian tracers to analyze mixing. The study identifies three different mixing regimes in cumulus clouds throughout their lifetime. Each regime is characterized by specific types of tracer trajectories. A fourth regime is identified as part of the clouds' decay. Key Points: Three mixing regimes are identified using subsets of tracers with similar trajectories in the Large Eddy Simulation of a cumulus cloudThese mixing regimes persist throughout the cloud's lifetime, providing insights into cloud mixing dynamicsThe dissipation stage of the cloud reveals cloud‐top entrainment followed by downdrafts [ABSTRACT FROM AUTHOR]

In the present study, the Morrison and Thompson microphysics schemes in the Weather Research and Forecasting model were improved and used to simulate a record‐breaking heavy rainfall event occurred in Henan Province over central China during 19–21 July 2021. In the modified schemes, the terminal velocity of graupel and initial cloud droplet concentration were adjusted based on sensitivity tests. Results showed that the modified Morrison scheme (MORR_MOD) better captured the spatial distribution and temporal evolution of precipitation than the original scheme (MORR). Specifically, it produced a 40‐hr cumulative rainfall amount of 963 mm and an extreme hourly rainfall rate of 157.7 mm, which were closer to observations than MORR. Analysis of the dynamic and microphysical structures of the extreme‐rain‐producing convective clusters revealed that MORR_MOD predicted stronger updrafts, higher rain mass content and larger mean mass diameter of raindrops than MORR. By analyzing the tendencies of rain mass and number concentration, it was found that MORR_MOD predicted stronger accretion rates of cloud droplets by rain and weaker auto‐conversion rates of cloud droplets than MORR, which contributed to the high rain mixing ratio and low number concentration, respectively. In addition, MORR_MOD predicted stronger diabatic heating rates than MORR, which were primarily attributed to stronger condensation of water vapor, and may have been the reason why MORR_MOD simulated stronger updrafts. Plain Language Summary: In this study, the Morrison and Thompson microphysics schemes were improved and used to simulate a heavy rainfall event over Henan Province in central China. The simulation with the modified Morrison scheme (MORR_MOD) better captured the spatial distribution and temporal evolution of precipitation, as well as the extreme‐rain‐producing convective clusters, than the original scheme (MORR). The analysis showed that MORR_MOD predicted stronger accretion rates of cloud droplets by rain and weaker auto‐conversion rates of cloud droplets than MORR, resulting in a high mixing ratio, low number concentration and large mean mass diameter of raindrops. Meanwhile, MORR_MOD produced stronger diabatic heating rates of condensation, which may be the reason why MORR_MOD simulated stronger updrafts. Key Points: An extremely heavy rainfall event in central China is simulated with the modified Morrison (MORR_MOD) and Thompson microphysics schemesMORR_MOD reproduces reasonably well the observed cumulative and hourly rainfall and the rain‐producing quasi‐stationary convective clustersMORR_MOD predicted stronger warm‐rain process and larger raindrops than the original scheme [ABSTRACT FROM AUTHOR]