Vertical Structure Research Articles

AirCore Observations at Northern Tibetan Plateau During the Asian Summer Monsoon

AbstractWe present data and analysis of a set of balloon‐borne sounding profiles, which includes co‐located O3, CO, CH4, and particles, over the northern Tibetan Plateau during an Asian summer monsoon (ASM) season. These novel measurements shed light on the ASM transport behavior near the northern edge of the anticyclone. Joint analyses of these species with the temperature and wind profiles and supported by back trajectory modeling identify three distinct transport processes that dominate the vertical chemical structure in the middle troposphere, upper troposphere (UT), and the tropopause region. The correlated changes in profile structures in the middle troposphere highlight the influence of the strong westerly jet. Elevated constituent concentrations in the UT identify the main level of convective transport at the upstream source regions. Observed higher altitude maxima for CH4 characterize the airmasses' continued ascent following convection. These data complement constituent observations from other parts of the ASM anticyclone.

Three-dimensional forest structure features extraction based on TomoSAR

Abstract. Forest structure is an important indicator for evaluating forest ecosystem and an indispensable input parameter for estimating forest carbon sink. Synthetic Aperture Radar (SAR) Tomography (TomoSAR), as a novel microwave remote sensing technique with 3D imaging capability, has been demonstrated to be an valuable tool for accurate inversion of forest structure. At present, the forest vertical structure parameters inversion is almost all concentrated on the forest height estimation. However, the spatial structure of forests is complex, and it is not enough to only use the forest height to express the forest structure. This fails to identify tree canopy, branch layer and underlying vegetation layer, etc., resulting in the partial and inaccurate forest vertical structure information. To solve this problem, this paper constructs 3D structural indices from tomograms, namely Horizontal Structure Index (HS) and Vertical Structure Index (VS). The HS primarily describes canopy density, compensating for the lack of information on the horizontal dimension of forest structure provided by traditional TomoSAR techniques; while VS describes the complexity of canopy distribution in the altitude direction, further enriching information on forest structure vertically. In order to verify their feasibility and validity, HS and VS are extracted using six fully-polarized L-band SAR images covering the Krycklan watershed in Sweden. Moreover, the accuracy is verified by using external high-precision LiDAR data. The results indicate a strong correlation between the structural indices extracted from TomoSAR and those extracted from LiDAR.

Crop Height Estimation Based on a Novel Semi-Empirical Model Considering Double-Bounce Scattering Using RADARSAT-2 PolSAR Data

Abstract. Obtaining precise and rapid crop height is essential to facilitate agricultural production services, field management, disaster monitoring, and yield assessment. With the capability to penetrate vegetation and record vertical structure information, Polarimetric Synthetic Aperture Radar (PolSAR) holds significant potential for application in vegetation height inversion. The Water Cloud Model (WCM) and its enhanced versions are extensively utilized for estimating crop heights from PolSAR data owing to their physical significance and simplicity. However, the method is not practical for stalk crops due to the neglect of double-bounce scattering considerations. Therefore, according to the growth characteristics of stalk crops, a three-component polarimetric coherent backscattering model considering crop target double-bounce scattering is established by simplifying the Random Volume over Ground (RVoG) coherent scattering model. The empirical coefficient is introduced to simplify the model into a semi-empirical for crop height inversion. The suitability of applying the RVoG-B three-component model for crop height inversion at the early stage in corn fields was assessed using Multi-temporal C-band PolSAR RADARSAT-2 data in three polarimetric channels. The results show that the HV channel exhibits superior potential in inverting the height of corn compared with the HH and the VV channels. The results of corn height inversion demonstrate that the RVoG-B three-component semi-empirical model performs effectively in estimating corn height, with its inversion accuracy having an RMSE ranging from 11.66cm to 24.51cm. This study demonstrates the potential application of the RVoG-B three-component semi-empirical model for inverting crop height at the early stage dominated by double-bounce scattering.

Snow Penetration Depth Inversion in Tibetan Plateau Based on Coherence Scattering Model with X-band Data

Abstract. The snow penetration depth is a necessary input parameter to accurately evaluate the thickness and vertical structure of snow layer, which is conducive to understanding the freeze-thaw process of ice and snow and predicting the change of ice and snow mass balance. Interferometric Synthetic Aperture Radar (InSAR) exhibits great potential in estimating snow penetration depth due to the emission of microwave band and the ability of operating under all-day and all-weather conditions. In previous studies, the penetration depth of snow was obtained based on InSAR coherence, but the external factors such as temperature, humidity, topography, dielectric constant and so on also affect the penetration dept. In order to extract the penetration depth in detail, this paper this paper adopts a uniform volume model as the basis, introduces two parameters describing the physical properties of snow: the volume ambiguity height and the volumetric decorrelation. Then, the magnitude of volumetric decorrelation is used to establish the internal relationship between the magnitude and the volume ambiguity height to estimate the snow penetration depth. In order to verify the effectiveness and feasibility of this method, a TSX/TDX InSAR pair covering southeast Tibetan Plateau in 2012 is applied to estimate the snow penetration depth. And results indicate that X-band penetration depths range mainly between −2.753 meters and −4.589 meters with an average value of −3.671 meters m and standard deviation of 0.918 meters in snowy regions on the plateau.

Landcover-based detection of rapid impacts of extreme storm on coastal landscape

On September 24, 2022, Post-Tropical Hurricane Fiona made landfall in Atlantic Canada and caused unprecedented damages to the coastal communities and ecosystems therein. The aftermath triggered local government and communities in Prince Edward Island (PEI), Canada to rethink current policies and practices for coastal protection in the context of climate change. This historic hazard represents the escalating frequency and intensity of extreme weather events that globally threaten coastal regions, accelerating coastal erosion and endangering communities. This study employs landcover-based detection to assess rapid storm impact of Fiona on coastline of PEI using Sentinel-2 satellite images, to gauge the efficacy of landcover-based detection and quantify storm-induced coastal environmental changes. Our results indicate that, following Fiona, over 51 km2 coastal land loss due to the erosion at beach foreshore and inundation at tidal flat, and over 11 km2 sand dune loss mainly on the PEI north shore. This constitutes a 3.5 % loss of coastal land resources within the 1798 km2 PEI coastal zone. Fiona also caused over 194 km2 area in coastal buffer zone showed temporal fluid-mud from the eroded sediments of sand dunes, cliffs, and tidal flats, suggesting the significant sediment loss from vertical structures in addition to the direct retreat. The landcover-based method can be regarded as a valuable tool for the storm impacts on coastal environments. Based on the coastal change pattern, more sustainable coastal protection and adaptation measures should be developed, focusing on reducing hydrodynamic intensity and improving erosion capacity, with consideration of the increasing likelihood of more intense and frequent storm events in a warming climate.

Arctic amplification‐induced intensification of planetary wave modulational instability: A simplified theory of enhanced large‐scale waviness

AbstractIn the mid–high latitude atmosphere, the instability of planetary waves characterizes enhanced planetary wave activity or amplified large‐scale waviness leading to increased regional weather extremes. In this paper, a nonlinear Schrödinger equation is derived to describe the evolution of planetary waves. Then the consequences of Arctic amplification (AA)‐induced meridional background potential vorticity (PVy) changes on the modulational instability of planetary waves are examined. It is found that the modulational instability of uniform planetary wave trains mainly results from the presence of high‐order dispersion and nonlinearity, even though such an instability depends on the amplitude, vertical structure and zonal wavenumber of uniform planetary waves and the atmospheric stratification. Because the nonlinearity and high‐order dispersion depend on the magnitude of PVy, the modulational instability of planetary waves is significantly influenced by the variation of PVy associated with AA. It is also revealed that stronger modulational instability of planetary waves tends to occur in the smaller PVy region or in higher latitudes due to both stronger nonlinearity and weaker high‐order dispersion for fixed background and planetary wave parameters, which is conducive to more intense large‐scale waviness. However, because AA can reduce PVy in the mid–high latitudes mainly in the lower troposphere via reductions of winter zonal winds and meridional temperature gradients, the reduced PVy under AA can significantly enhance the modulational instability. Thus, the role of AA is to amplify planetary wave activity in mid–high latitudes through strengthening the modulational instability of planetary waves due to reduced PVy, which further enhances large‐scale waviness.

Strategic principles for co-existence in a multinodal world

AbstractIn realist international relations theory, world order is assumed to be a vertical structure ordered by relative power, with the hegemon, or the contest of hegemons, at its apex. Power is viewed as the ability to coerce, and security lies in the avoidance of defeat. But the proportional changes in the globalized economy of this century have created a new reality, one in which effective pursuit of one’s own national interest is more complex than compelling or submitting. Differences in relative power and capabilities still matter, and differences in situations create conflicts of interests. But the horizontal dimension of continuing interaction among autonomous actors is more important than the vertical dimension of unilateral imposition. Without hegemony, states have agency, but they face greater uncertainty. The diplomatic calculus of each state is to pursue its national interests, but a major component of this pursuit lies in reducing uncertainty. Strategy for a post-hegemonic multinodal world stresses the complex ecology of action, the importance of relationships, the utility of partnerships, the encouragement of common interests, and the problems of conducting limited conflicts. These are principles of strategic prudence relevant to the global matrix of asymmetric international relationships.

Wave Impacts On Cliffs: From The Field To The Laboratory

Rock coasts occupy over 50% of the global shoreline and many sandy beaches are underlain by coastal platforms and rocky cliffs. The problem of wave-driven cliff erosion is of great societal importance, with many coastal communities located on top of cliffs that are at risk from erosion. Continuing global mean sea level rise and changes in storminess are generally expected to exacerbate the erosion of coastlines (Hurst et al., 2016), as larger waves can reach the cliff toe without breaking offshore. However, the science underpinning wave-induced cliff erosion is still at a relatively early stage. Even the relative contributions of waves to cliff erosion, which include hydraulic forces, impulse pressures and abrasion, are not well resolved. Most insights into wave impacts on cliffs come from field observations of coastal ground motion during storm events (e.g. Young et al., 2011, Huppert et al., 2020). These field investigations demonstrate the dependence of large wave impacts on both water levels and wave conditions, and in some cases the correlation of periods of large ground motion with increased erosion (Earlie et al., 2015). Unsurprisingly, although large impacts generally occur at high tide during storms characterised by large significant wave heights, the largest impacts occur when tidal levels and storm surge combine to provide water levels that are conducive to the incident waves breaking on the cliffs (Thompson et al., 2019; 2022). Larger wave heights or shallower water levels tend to lead to breaking further offshore, with a broken wave interacting with the cliff, while smaller wave heights or deeper water levels may preclude strong wave breaking on the cliffs. There have been relatively few experimental studies into wave-driven cliff erosion; these were generally undertaken under very idealised wave conditions (e.g. Sunamura, 1977) and using materials that were either too soft to approximate natural rocks (e.g. Sunamura, 1977; 1982) or too hard to be eroded (Hansom et al., 2008). Although these experiments have informed the development of rocky coast evolution models, their results have not been replicated or verified, and rigorous scaling laws to link laboratory erosion rates to field time scales are currently lacking. However, considering cliffs as steep or vertical (natural) coastal structures, a large body of experimental work has been undertaken to investigate impact pressures and their implications for the failure of engineered structures (e.g. Peregrine, 2003, Bullock et al., 2007). These investigations are complicated by the inherent variability of the wave impact pressures, even within controlled experiments undertaken with highly repeatable incident wave conditions (Raby et al., 2022). Although field and laboratory data are valuable, it is still very challenging to quantify wave contributions to cliff erosion due to the relatively short durations and variable conditions of most field records. On the other hand, most controlled laboratory investigations have typically focused on loads on non-erodible engineered structures such as seawalls. The current project seeks to advance understanding of the fundamental mechanisms and timescales of wave-driven erosion on rocky cliffs, which will be vital in improving assessments of cliff erosion hazard in high-energy wave environments as sea levels rise.

Predicting the vertical density structure of oceanic gravity current intrusions

Understanding the dynamics and structures in the deep ocean is one of the remaining challenges in oceanography and climate sciences. We present results from large-scale laboratory experiments of rotating down-slope gravity currents intruding into a two-layer stratified ambient, performed in the largest rotating tank in the world, the Coriolis Rotating Platform in Grenoble. By means of velocity and density measurements, we show that no mixing occurs once the current has detached from the boundary. The shape of the vertical density profile in the stratified receiving ambient enables to identify two distinct regimes: the first issued by laminar transport through Ekman dynamics, the second by turbulent transport due to intermittent dense water cascading. Vertical density gradients reveal a piece-wise linear dependence on the density anomaly for the turbulent transport, suggesting an advection-diffusion process. For the turbulent regime, the scale height is deduced and an analytical model based on the critical Froude number is proposed to predict its value. Results show that the total thickness of the intruding current is on average 2.5 times the scale height. For laminar intrusions the scale height diverges whereas the thickness of the intrusion is a few times the Ekman layer thickness. Comparing the intrusion scale height with its measured vertical extension has led to a criteria to distinguish between laminar and turbulent regimes, which is corroborated by two additional independent criteria, one based on the sign of the local vorticity and the other based on the local maxima of the vertical density gradient. The model allows us to connect laboratory experiments to deep sea observations, gravity currents and Meddies and emphasizes the importance of laboratory experiments in understanding climate dynamics.

Carbonyl iron/glass fiber cloth composites: Achieving multi-spectrum stealth in a wide temperature range

Multispectral camouflage in a wide temperature range is still a challenging issue owing to the incompatibility of stealth mechanisms corresponding to different spectra. Herein, we develop a flexible flaky carbonyl iron (FCI)/glass fiber (GF) cloth, using all-in-one design of microwave absorption and infrared (IR) stealth to eliminate the above contradictions. Due to micron-scale gaps and height differences on the surface of GF cloth modified with Fe3O4, FCI gains a special vertical structure, which not only induces multiple eddy centers in FCI to enhance magnetic loss but also reduces the microwave reflection area, achieving a synergistic improvement in attenuation and impedance characteristics. Therefore, FCI/GF cloth with a thickness of 2.0 mm obtains a maximum effective absorbing bandwidth of 5.82 GHz in a range of 25–400 °C. On the other hand, combination of FCI and GF cloth decreases IR emissivity while maintaining wonderful heat insulation performance, allowing objects over 250 °C to obtain promising thermal IR camouflage. The all-in-one design successfully breaks barriers faced by traditional hierarchical radar-IR compatible stealth materials such as strong reflection, great thickness, loss and impedance mismatch.

A numerical study of smoke concentration distribution near low-intensity fires: Sensitivity to vertical canopy structure and fire heat source strength

Abstract Broadly speaking, prediction of the negative impacts of prescribed fire on air quality is limited by gaps in our understanding of the underlying fire, fuels, and atmospheric processes. These knowledge gaps hinder our ability to accurately predict smoke concentration distributions, leading to unintended smoke intrusions into nearby communities and subsequent threats to public health and safety. In this study, numerical simulations are performed using a Lagrangian particle dispersion model (FLEXPART-WRF), with particle motion driven by output from a full-physics atmospheric model with a forest canopy sub-model and 10-m horizontal grid spacing (ARPS-CANOPY), to address two research questions. First, what is the relationship between near-fire (within ~50–150 m of fire) smoke concentration distribution and (i) vertical canopy structure, (ii) fire heat source strength? Second, what roles do mean transport (i.e., transport by the mean wind) and turbulent diffusion play in shaping the near-fire smoke concentration distribution? To address these questions, simulations are run with 25 combinations of plant area density profile and fire sensible heat flux magnitude, and smoke is represented by particles with diameters ≤ 2.5 µm (PM2.5). Results show that near-fire PM2.5 concentration distribution is primarily controlled by vertical canopy structure, with fire heat source strength primarily controlling the PM2.5 concentration magnitude. Analysis of the underlying ARPS-CANOPY variables driving FLEXPART-WRF particle dispersion helps elucidate the roles of mean transport and turbulent diffusion. In total, the study findings suggest that the vertical distribution of canopy vegetation and fire heat source strength are important factors influencing PM2.5 dispersion and concentration distribution near low-intensity fires.

Optimization of thermo-spin voltage in vertical nanostructures by geometrical means

The thermo-spin conversion provides new concepts for further developing the green energy-harvesting technology because spin can be controlled with minimal energy in nanostructures. Through theoretical analysis of thermo-spin generation, transportation and conversion in ferromagnet/non-ferromagnet/heavy metal (FM/NM/HM) vertical structures, we found that the output transverse thermo-spin voltage is independent of the structure’s width, but varies linearly with the structure’s length. To validate our predictions, we fabricated the thermo-spin devices with a CoFeAl/Cu/Pt structure. Our results indicate that FM/NM/HM structures can be utilized to design flexible thermo-spin conversion devices.

Assessing the potential impact of assimilating total surface current velocities in the Met Office’s global ocean forecasting system

Accurate prediction of ocean surface currents is important for marine safety, ship routing, tracking of pollutants and in coupled forecasting. Presently, velocity observations are not routinely assimilated in global ocean forecasting systems, largely due to the sparsity of the observation network. Several satellite missions are now being proposed with the capability to measure Total Surface Current Velocities (TSCV). If successful, these would substantially increase the coverage of ocean current observations and could improve accuracy of ocean current forecasts through data assimilation. In this paper, Observing System Simulation Experiments (OSSEs) are used to assess the impact of assimilating TSCV in the Met Office’s global ocean forecasting system. Synthetic observations are generated from a high-resolution model run for all standard observation types (sea surface temperature, profiles of temperature and salinity, sea level anomaly and sea ice concentration) as well as TSCV observations from a Sea surface KInematics Multiscale monitoring (SKIM) like satellite. The assimilation of SKIM like TSCV observations is tested over an 11 month period. Preliminary experiments assimilating idealised single TSCV observations demonstrate that ageostrophic velocity corrections are not well retained in the model. We propose a method for improving ageostrophic currents through TSCV assimilation by initialising Near Inertial Oscillations with a rotated incremental analysis update (IAU) scheme. The OSSEs show that TSCV assimilation has the potential to significantly improve the prediction of velocities, particularly in the Western Boundary Currents, Antarctic Circumpolar Current and in the near surface equatorial currents. For global surface velocity the analysis root-mean-square-errors (RMSEs) are reduced by 23% and there is a 4-day gain in forecast RMSE. There are some degradations to the subsurface in the tropics, generally in regions with complex vertical salinity structures. However, outside of the tropics, improvements are seen to velocities throughout the water column. Globally there are also improvements to temperature and sea surface height when TSCV are assimilated. The TSCV assimilation largely corrects the geostrophic ocean currents, but results using the rotated IAU method show that the energy at inertial frequencies can be improved with this method. Overall, the experiments demonstrate significant potential benefit of assimilating TSCV observations in a global ocean forecasting system.

On the short-term response of entrained air bubbles in the upper ocean: a case study in the north Adriatic Sea

Abstract. Air bubbles in the upper ocean are generated mainly by waves breaking at the air–sea interface. As such, after the waves break, entrained air bubbles evolve in the form of plumes in the turbulent flow, exchange gas with the surrounding water, and may eventually rise to the surface. To shed light on the short-term response of entrained bubbles in different stormy conditions and to assess the link between bubble plume penetration depth, mechanical and thermal forcings, and the air–sea transfer velocity of CO2, a field experiment was conducted from an oceanographic research tower in the north Adriatic Sea. Air bubble plumes were observed using high-resolution echosounder data from an upward-looking 1000 kHz sonar. The backscatter signal strength was sampled at a high resolution, 0.5 s in time and 2.5 cm along the vertical direction. Time series profiles of the bubble plume depth were established using a variable threshold procedure applied to the backscatter strength. The data show the occurrence of bubbles organized into vertical plume-like structures, drawn downwards by wave-generated turbulence and other near-surface circulations, and reaching the seabed at 17 m depth under strong forcing. We verify that bubble plumes adapt rapidly to wind and wave conditions and have depths that scale approximately linearly with wind speed. Scaling with the wind–wave Reynolds number is also proposed to account for the sea-state severity in the plume depth prediction. Results show a correlation between measured bubble depths and theoretical air–sea CO2 transfer velocity parametrized with wind-only and wind/wave formulations. Further, our measurements corroborate previous results suggesting that the sinking of newly formed cold-water masses helps bring bubbles to greater depths than those reached in stable conditions for the water column. The temperature difference between air and sea seems sufficient for describing this intensification at the leading order of magnitude. The results presented in this study are relevant for air–sea interaction studies and pave the way for progress in CO2 gas exchange formulations.

Transport and retention of sinking microplastics in a well-mixed estuary

Estuaries have been shown to be potential hotspots of microplastic accumulation, but the hydrodynamic conditions and particle properties that control this process need further investigation. We have designed a series of numerical particle-tracking experiments to examine the sensitivity of retention in estuaries to particle size, particle density and varying tides and freshwater flow. At the end of the simulation, over 90 % of sinking particles are retained in the estuary, and the retention rate is further increased by high river runoff. In contrast, increased river discharge increases the number of marginally-buoyant (i.e. density close to estuarine water) particles that escape the estuary. Larger particle size tends to limit the downstream transport of sinking particles but can facilitate the transport of marginally-buoyant particles. Tidal asymmetry, vertical turbulent mixing and the vertical structure of the subtidal circulation are proposed as the underlying mechanisms controlling the fate of particles.

Vertical structures and microphysical characteristics of summer precipitation in North China detected by GPM-DPR

The vertical structure and microphysical characteristics of stratiform precipitation (SP) and convective precipitation (CP) in North China are revealed based on the GPM-DPR product during boreal summer of 2014–2021 in this study. Additionally, the differences in precipitation features between the mountain and the plain are investigated. Under the combined influence of climatic factors and local topography, the precipitation amount is larger in the plain than in the mountain while precipitation frequency exhibits an opposite pattern. The proportions of the two precipitation types are similar in the mountain and the plain, with CP contributing to approximately a quarter of total precipitation frequency. In terms of mean intensity, both SP and CP are roughly 20 % more intense in the plain than in the mountain. The greater number of light SPs is a major contributor to higher precipitation frequency in the mountain, while more intense CPs result in larger precipitation amount in the plain. Compared to the mountain, the precipitation system is deeper in the plain, where higher storm top altitudes (STAs) and larger freezing level heights contribute to more intense CPs. Besides, it is observed that for the STA, more intense CPs occur in the plain compared to the mountain. In both the mountain and the plain, the coalescence process is dominant in the low-level layers for heavy (8–20 mm/h) to storm-level (>20 mm/h) CPs. Compared to the mountain, the low-level growth of hydrometeor size and radar reflectivity is more significant in the plain. These findings are important to quantitative precipitation estimation and precipitation prediction in the mountainous region, and can help understand the influence of local topography on precipitation.

Characterization of heart rate variability in end-stage renal disease patients after kidney transplantation with recurrence quantification analysis.

Heart rate variability (HRV) is a noninvasive approach to studying the autonomic modulation of heart rate in experimental settings, such as active standing sympathetic stimulation. It is known that patients with end-stage renal disease during active standing have few changes in HRV dynamics, which are improved after hemodialysis. However, it is unknown whether the response to active standing is recovered after definitive treatment with kidney transplantation. This work aims to assess the change in HRV dynamics in the supine position and active standing through time and frequency-based metrics, as well as recurrence plot quantitative analysis (RQA). We studied HRV dynamics by obtaining 5-minute electrocardiographic recordings from kidney transplant recipients who underwent an active standing test. The mean duration of heartbeats and their standard deviation diminished in active standing, compared with the supine position. Also, the low-frequency component of HRV and the presence of diagonal and vertical structures in RQA were predominant. A larger estimated glomerular filtration rate was significantly correlated with broader HRV in the supine position and during active standing. The narrower HRV during active standing may indicate a sympathetic response to external stimuli, which is expected in a functional cardiovascular system, and may be influenced by renal function.

Design and High-Frequency Characterization of a Wafer-Scale Vertical Bridge Structure Nanoscale Vacuum Electronic Device

Design and High-Frequency Characterization of a Wafer-Scale Vertical Bridge Structure Nanoscale Vacuum Electronic Device

Study of boundary layer parameterization simulation uncertainties of sand-dust storm windfield using high-resolution three-dimensional Doppler wind lidar data

The processes of dust emission, the development, and dissipation of sand and dust storms all exhibit dynamic and rapidly changing characteristics, posing significant challenges for us to accurately represent their complex behaviors in numerical simulations. In the numerical weather prediction model, the selection and optimization of planetary boundary layer (PBL) parameterization schemes have a direct impact on the simulation results of PBL wind fields, primarily due to the significant uncertainty in the fine-grained simulation of PBL wind field structure. To gain a deeper understanding of the sources of uncertainty in simulating sand-dust storms through vertical wind field structure simulations of the PBL, this study utilizes high-resolution 3D Doppler wind lidar (DWL) data. Focusing on sand-dust storm wind fields with distinctive regional characteristics in Inner Mongolia, China, it examines the turbulent momentum equation and assumptions of the PBL. A comprehensive and systematic evaluation was conducted on the characteristics of horizontal and vertical wind fields, wind shear, as well as the dynamic and thermodynamic differences that arise when simulating typical sand-dust storm wind fields using the Weather Research and Forecasting (WRF) Model with various PBL schemes. This evaluation focused on simulating the typical wind field of sand-dust storms during various stages, including dust generation, occurrence, development, and dissipation. The findings indicate that non-adiabatic heating plays a significant role in the sustainability and evolution of sand-dust storms. The wind shear index holds particular importance as it embodies the dynamic factor in the model. The PBL schemes such as Mellor-Yamada Nakanishi and Niino Level 2.5 (MYNN2), A new version of asymmetric convective model (ACM2), and Grenier-Bretherton-McCaa (GBM), which factor in buoyancy effects, demonstrate more accurate wind shear simulations in sand-dust storms. Furthermore, the ACM2 scheme effectively replicates the fundamental variation characteristics of meteorological elements throughout the sand-dust storm lifecycle.

Impact of surface current and temperature feedback on kinetic energy over the North-East Atlantic from a coupled ocean / atmospheric boundary layer model

A one-dimensional Atmospheric Boundary Layer (ABL1D) model is coupled with the NEMO ocean model and implemented over the Iberian–Biscay–Ireland (IBI) area at 1/36° resolution to investigate the damping effect of the current and the thermal feedback on the kinetic energy (KE) at the mesoscale. This type of coupling between an ocean model and an ABL1D is a newly proposed approach as an alternative of intermediate complexity between bulk forcing and full coupling with an atmosphere model. In ABL1D, the prognostic tracers are nudged toward large-scale variables and the wind is guided by a low-frequency geostrophic wind provided from the ERA-Interim reanalyses.First, the ABL1D is successfully validated against satellite observations regarding the wind, and the dynamic coupling coefficient (linking the near surface wind and wind-stress to the curl of the surface currents) are consistent with the literature, over the period 2016-2017. Our results show that the thermal feedback has a negligible impact on kinetic energy (KE) and does not influence the strength of the current feedback in the region. Given the ABL1D physics, this further indicates that the changes in the vertical wind structure caused by CFB are primarily governed by local mechanical mechanisms associated with surface wind-stress condition, rather than by thermodynamic or non-local processes within the planetary boundary layer.The induced KE reduction by the current feedback amounts to 14% at the surface and propagates down to 2000 m, indicating that it can modify the vertical distribution of KE throughout the water column. KE reductions in the surface boundary layer (0 – 300m) and in the interior (300 – 2000m) are attributed to a reduction of the surface wind work by 4%, and of the pressure work by 7%, respectively. The Ekman pumping anomalies induced by the current feedback tend to attenuate eddy activity and horizontal pressure gradients at depth, illustrating the potential of the current feedback to induce a geostrophic adjustment on the water column. These results illustrate the relevance of the proposed ABL1D coupling approach for reproducing the wind-current coupling (a.k.a. current feedback effect) which cannot be taken into account straightforwardly with simple bulk forcing.