Journal of the Atmospheric Sciences最新文献_第2页

Diurnally-varying Ekman layer in a Rossby wave 罗斯比波中昼夜变化的埃克曼层

IF 3.1 3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-12-21 DOI: 10.1175/jas-d-23-0070.1

Alan Shapiro, Jason Chiappa, David B. Parsons

{"title":"Diurnally-varying Ekman layer in a Rossby wave","authors":"Alan Shapiro, Jason Chiappa, David B. Parsons","doi":"10.1175/jas-d-23-0070.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0070.1","url":null,"abstract":"\u0000Weak but persistent synoptic-scale ascent may play a role in the initiation or maintenance of nocturnal convection over the central United States. An analytical model is used to explore the nocturnal low-level jets (NLLJ) and ascent that develop in an idealized diurnally-varying frictional (Ekman) boundary layer in a neutrally stratified barotropic environment when the flow aloft is a zonally-propagating Rossby wave. Steady-periodic solutions are obtained of the linearized Reynolds-averaged Boussinesq-approximated equations of motion on a beta plane with an eddy viscosity that is specified to increase abruptly at sunrise and decrease abruptly at sunset. Rayleigh damping terms are used to parameterize momentum loss due to radiation of inertia-gravity waves. The model-predicted vertical velocity is (approximately) proportional to the wavenumber and wave amplitude. There are two main modes of ascent in mid-latitudes, an afternoon mode and a nocturnal mode. The latter arises as a gentle but persistent surge induced by the decrease of turbulence at sunset, the same mechanism that triggers inertial oscillations in the Blackadar theory of NLLJs. If the Rayleigh damping terms are omitted, the boundary layer depth becomes infinite at three critical latitudes, and the vertical velocity becomes infinite far above the ground at two of those latitudes. With the damping terms retained, the solution is well-behaved. Peak daytime ascent in the model occurs progressively later in the afternoon at more southern locations (in the northern hemisphere) until the first (most northern) critical latitude is reached; south of that latitude the nocturnal mode is dominant.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":"56 7","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138951892","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

The small-amplitude dynamics of spontaneous tropical cyclogenesis. Part 1: experiments with amplified longwave radiative feedback 自发热带气旋生成的小振幅动力学。第 1 部分：放大长波辐射反馈实验

IF 3.1 3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-12-20 DOI: 10.1175/jas-d-23-0170.1

Hao Fu, Morgan O’Neill

{"title":"The small-amplitude dynamics of spontaneous tropical cyclogenesis. Part 1: experiments with amplified longwave radiative feedback","authors":"Hao Fu, Morgan O’Neill","doi":"10.1175/jas-d-23-0170.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0170.1","url":null,"abstract":"\u0000What determines the vortex size at the small-amplitude stage of spontaneous tropical cyclogenesis remains unclear. A doubly periodic domain is a standard setup for numerically studying this problem, but the convectively coupled standing waves inherent to the setup could directly trigger vortices, rendering an unrealistic path for tropical cyclogenesis. We increase the Coriolis parameter to suppress the wave and double the longwave radiative feedback to make the more realistic moisture-radiation instability dominant. Experiments show that the moisture-radiation instability has a short-wavelength cutoff due to the smoothing effect of convective dynamics, which includes the nonlocal convective triggering by cold pools and the nonlocal longwave radiative effect of anvil clouds. By approximating the spread of convective activity as a Gaussian filter on the column humidity, we derive a bulk convective spreading length lcp+av to parameterize the combined effect of cold pools and anvils. Using a novel diagnostic method, the lcp+av is shown to be around 10 km. The contribution of cold pools and anvil clouds to convective spreading is comparable in the doubled radiative feedback experiments. An extrapolation to the normal radiative feedback state shows the anvil clouds play a smaller yet non-negligible role.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":"65 4","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138956963","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Cloud-Resolving ICON Simulations of Secondary Ice Production in Arctic Mixed-Phase Stratocumuli Observed during M-PACE M-PACE 期间观测到的北极混合相层积物中二次生冰的云解析 ICON 模拟

IF 3.1 3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-12-14 DOI: 10.1175/jas-d-23-0069.1

A. Possner, K. Pfannkuch, V. Ramadoss

{"title":"Cloud-Resolving ICON Simulations of Secondary Ice Production in Arctic Mixed-Phase Stratocumuli Observed during M-PACE","authors":"A. Possner, K. Pfannkuch, V. Ramadoss","doi":"10.1175/jas-d-23-0069.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0069.1","url":null,"abstract":"\u0000Field measurements and modeling studies suggest that secondary ice production (SIP) may close the gap between observed Arctic ice nucleating particle (INP) concentrations and ice crystal number concentrations (ni). Here, we explore sensitivities with respect to the complexity of different INP parameterizations under the premise that ni is governed by SIP. Idealized, cloud-resolving simulations are performed for the marine cold air outbreak cloud deck sampled during M-PACE with the ICOsahedralNonhydrostatic (ICON) model. The impact of the droplet shattering (DS) of raindrops and collisional breakup (BR) in addition to the existing Hallet-Mossop rime splintering mechanism were investigated. Overall, 12 different model experiments (12 h runs) were performed and analyzed. Despite the considerable amount of uncertainty remaining with regard to SIP mechanisms and their process representation in numerical models, we conclude from these experiments that: (i) only simulations where DS dominates the SIP signal (potentially amplified by BR) capture observed ice-phase and liquid-phase cloud properties, and (ii) SIP events cluster around the convective outflow region and are structurally linked to mesoscale cloud organization. In addition, interactions with primary nucleation parameterizations of varied complexity were investigated. Here, our simulations show that: (i) a stable long-lived mixed-phase cloud (MPC) can be maintained in the absence of primary nucleation once SIP is established, (ii) experiments using a computationally more efficient relaxation-based parameterization of primary nucleation are statistically invariant from simulations considering prognostic INP, and (iii) primary nucleation at cloud-top controls the areal extent of the mixed-phase cloud region, and reduces SIP efficacy via DS due increased depletion of cloud liquid throughout the entire cloud column.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":"26 2","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139002915","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Momentum transport in organised shallow cumulus convection 有组织浅积云对流中的动量传输

IF 3.1 3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-12-14 DOI: 10.1175/jas-d-23-0098.1

A. Savazzi, L. Nuijens, Wim C. de Rooy, Martin Janssens, A. P. Siebesma

{"title":"Momentum transport in organised shallow cumulus convection","authors":"A. Savazzi, L. Nuijens, Wim C. de Rooy, Martin Janssens, A. P. Siebesma","doi":"10.1175/jas-d-23-0098.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0098.1","url":null,"abstract":"\u0000This study investigates momentum transport in shallow cumulus clouds as simulated with the Dutch Atmospheric Large Eddy Simulation (DALES) for a 150 x 150-km2 domain east of Barbados during nine days of EUREC4A. DALES is initialized and forced with the mesoscale weather model HARMONIE-AROME and subjectively reproduces observed cloud patterns. This study examines the evolution of momentum transport, which scales contribute to it, and how they modulate the trade-winds. Daily-mean momentum flux profiles show down-gradient zonal momentum transport in the sub-cloud layer, which turns counter-gradient in the cloud layer. The meridional momentum transport is non-trivial, with mostly down-gradient transport throughout the trade-wind layer except near the top of the surface layer and near cloud tops. Substantial spatial and temporal heterogeneity in momentum flux is observed with much stronger tendencies imposed in areas of organised convection. The study finds that while scales <2 km dominate momentum flux at 200 m in unorganized fields, sub-mesoscales O(2-20 km) carry up to 50% of the zonal momentum flux in the cloud layer in organised fields. For the meridional momentum flux, this fraction is even larger near the surface and in the sub-cloud layer. The scale-dependence of the momentum flux is not explained by changes in convective or boundary layer depth. Instead, the results suggest the importance of spatial heterogeneity, increasing horizontal length scales, and counter-gradient transport in the presence of organised convection.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":"46 1","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138975573","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Droplet growth or evaporation does not buffer the variability in supersaturation in clean clouds 液滴增长或蒸发并不能缓冲洁净云中过饱和度的变化

IF 3.1 3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-12-06 DOI: 10.1175/jas-d-23-0104.1

Jesse C. Anderson, Ian Helman, R. A. Shaw, W. Cantrell

{"title":"Droplet growth or evaporation does not buffer the variability in supersaturation in clean clouds","authors":"Jesse C. Anderson, Ian Helman, R. A. Shaw, W. Cantrell","doi":"10.1175/jas-d-23-0104.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0104.1","url":null,"abstract":"\u0000Water vapor supersaturation in clouds is a random variable that drives activation and growth of cloud droplets. The Pi Convection-Cloud Chamber generates a turbulent cloud with a microphysical steady-state that can be varied from clean to polluted by adjusting the aerosol injection rate. The supersaturation distribution and its moments, e.g., mean and variance, are investigated for varying cloud microphysical conditions. High-speed and co-located Eulerian measurements of temperature and water vapor concentration are combined to obtain the temporally resolved supersaturation distribution. This allows quantification of the contributions of variances and covariances between water vapor and temperature. Results are consistent with expectations for a convection chamber, with strong correlation between water vapor and temperature; departures from ideal behavior can be explained as resulting from dry regions on the warm boundary, analogous to entrainment. The saturation ratio distribution is measured under conditions that show monotonic increase of liquid water content and decrease of mean droplet diameter with increasing aerosol injection rate. The change in liquid water content is proportional to the change in water vapor concentration between no-cloud and cloudy conditions. Variability in the supersaturation remains even after cloud droplets are formed, and no significant buffering is observed. Results are interpreted in terms of a cloud microphysical Damköhler number (Da), under conditions corresponding to Da ≲ 1, i.e., the slow-microphysics regime. This implies that clouds with very clean regions, such that Da ≲ 1 is satisfied, will experience supersaturation fluctuations without them being buffered by cloud droplet growth.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":"68 24","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138594838","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Updraft Width Implications for Cumulonimbus Growth in a Moist Marine Environment 上升气流宽度对潮湿海洋环境中积雨云生长的影响

IF 3.1 3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-12-06 DOI: 10.1175/jas-d-23-0065.1

Scott W. Powell

{"title":"Updraft Width Implications for Cumulonimbus Growth in a Moist Marine Environment","authors":"Scott W. Powell","doi":"10.1175/jas-d-23-0065.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0065.1","url":null,"abstract":"\u0000An 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 sub-cloud 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 (non-growers). The growers also experienced less dilution above the LFC. Non-growers 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 greater magnitude of background convergence (or weaker divergence) in the sub-cloud layer, especially between 300 m and cloud base, but whether the convergence actually led to eddy widening is unclear.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":"60 47","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138594781","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Exploring the Differences in Kinetic Energy Spectra between the NCEP-FNL and ERA5 Datasets 探索 NCEP-FNL 和 ERA5 数据集之间动能谱的差异

IF 3.1 3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-12-04 DOI: 10.1175/jas-d-23-0043.1

Zongheng Li, Jun Peng, Lifeng Zhang, Jiping Guan

{"title":"Exploring the Differences in Kinetic Energy Spectra between the NCEP-FNL and ERA5 Datasets","authors":"Zongheng Li, Jun Peng, Lifeng Zhang, Jiping Guan","doi":"10.1175/jas-d-23-0043.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0043.1","url":null,"abstract":"\u0000Two global atmospheric circulation datasets (ERA5 and NCEP-FNL) with horizontal resolutions of 0.25°×0.25° are investigated in terms of kinetic energy (KE) spectra at 200 hPa (roughly between 11 and 12 km). The horizontal KE (HKE) in NCEP-FNL is larger and flatter than that in ERA5 at subsynoptic scales and mesoscales. Restoring the energy of this wavenumber range to the physical space shows that the HKE in NCEP-FNL is larger than that in ERA5 over most areas but smaller mainly in the Indo-Pacific warm pool. The spectral budgets show that at these scales, the positive contribution from net vertical flux in ERA5 is stronger than that in NCEP-FNL, while the negative contribution from available potential energy (APE) conversion is smaller; assuming that the atmosphere is in a quasi-stationary state, more dissipation is found in ERA5 than in NCEP-FNL, which should be responsible for the HKE spectrum in ERA5 to be steeper and weaker than that in NCEP-FNL. Our formulation shows that the APE conversion and net vertical flux are related to the pressure vertical velocity (PVV). The APE conversion and net vertical flux differences between the two datasets, like the PVV difference, are mainly from the tropical region. At large scales, the vertical motion in ERA5 is larger than that in NCEP-FNL. The amplitude differences of the PVV spectra between two datasets are consistent with those of the large-scale precipitation spectra associated with microphysics parameterizations. These results support that vertical motion is a key dynamical factor explaining energy discrepancies at mesoscales.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":"67 11","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138604789","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Diverging Behaviors of Simulated Tropical Cyclones in Moderate Vertical Wind Shear 模拟热带气旋在中度垂直风切变中的分歧行为

IF 3.1 3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-12-01 DOI: 10.1175/jas-d-23-0048.1

Chau-Lam Yu, Brian Tang, R. Fovell

{"title":"Diverging Behaviors of Simulated Tropical Cyclones in Moderate Vertical Wind Shear","authors":"Chau-Lam Yu, Brian Tang, R. Fovell","doi":"10.1175/jas-d-23-0048.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0048.1","url":null,"abstract":"\u0000As a follow-on to a previous study that examined the tilt and precession evolution of tropical cyclones (TCs) in a critical shear regime, this study examines the processes leading to the subsequent divergent evolutions in tilt and intensity. The control experiment fails to resume its precession and reintensify, while the perturbed experiments with enhanced upper-level inner-core vorticity resume the precession after a precession hiatus period. In the control experiment, a mesoscale negative absolute vorticity region forms at the upper levels due to tilting in strong downtilt convection. This upper-level, negative-vorticity region is inertially unstable, causing the inward acceleration of upper-level radial inflow. This upper-level inflow subsequently becomes negatively buoyant due to diabatic cooling and descends, bringing midlevel, low equivalent potential temperature (θE) air into the inner-core TC boundary layer, significantly disrupting the low-level TC circulation. Consequently, the disrupted TC vortex in the control is unable to recover. The upper-level negative vorticity region is absent in the perturbed experiments due to weaker downtilt convection, preventing the emergence of the disruptive inner-core downdraft. The weaker downtilt convection is caused by several factors. First, a stronger circulation aloft advects hydrometeors farther downwind, resulting in greater separation of the cooling-driven downdraft from the convective updraft region, and thus weaker dynamically forced lifting at low levels. Second, the mean θE of the low-level air feeding downtilt convection is smaller. Third, there is stronger and deeper adiabatic descent uptilt, causing more low-θE air diluting the downtilt updraft region. These results show how the full vortex structure is important to diverging TC evolutions in moderately sheared environments.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":" 7","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138618228","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Symmetry Invariant Solutions in Atmospheric Boundary Layers 大气边界层中的对称不变解

IF 3.1 3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-12-01 DOI: 10.1175/jas-d-23-0168.1

Jun-Ichi Yano, Marta Wac lawczyk

{"title":"Symmetry Invariant Solutions in Atmospheric Boundary Layers","authors":"Jun-Ichi Yano, Marta Wac lawczyk","doi":"10.1175/jas-d-23-0168.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0168.1","url":null,"abstract":"\u0000The symmetries of the governing equations of atmospheric flows constrain the solutions. The present study applies those symmetries identified from the governing equations to the atmospheric boundary layers under relatively weak stratifications (stable and unstable). More specifically, the invariant solutions are analyzed, which conserve their forms under possible symmetry transformations of a governing–equation system. The key question is whether those invariant solutions can re–derive the known vertical profiles of both vertical fluxes and the means for the horizontal wind and the potential temperature. The mean profiles for the wind and the potential temperature in the surface layer predicted from the Monin–Obukhov theory can be recovered as invariant solutions. However, the consistent vertical fluxes both for the momentum and heat no longer remain constant with height, as assumed in the Monin–Obukhov theory, but linearly and parabolically change with height over the dynamic sublayer and the above, respectively, in stable conditions. The present study suggests that a deviation from the constancy, though observationally known to be weak, is a crucial part of the surface–layer dynamics to maintain its symmetry consistency.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":"43 S206","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138622729","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

The Influence of Midlevel Shear and Horizontal Rotors on Supercell Updraft Dynamics 中层切变和水平旋涡对超级单体上升气流动力学的影响

3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-11-14 DOI: 10.1175/jas-d-23-0082.1

Andrew J. Muehr, James H. Ruppert, Matthew D. Flournoy, John M. Peters

{"title":"The Influence of Midlevel Shear and Horizontal Rotors on Supercell Updraft Dynamics","authors":"Andrew J. Muehr, James H. Ruppert, Matthew D. Flournoy, John M. Peters","doi":"10.1175/jas-d-23-0082.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0082.1","url":null,"abstract":"Abstract Large midlevel (3–6 km AGL) shear is commonly observed in supercell environments. However, any possible influence of midlevel shear on an updraft has been relatively unexplored until now. To investigate, we ran ten simulations of supercells in a range of environments with varying midlevel shear magnitudes. In most cases, larger midlevel shear results in a storm motion that is faster relative to the low-level hodograph, meaning that larger midlevel shear leads to stronger low-level storm-relative flow. Because they are physically connected, we present an analysis of the effects of both midlevel shear and low-level storm-relative flow on supercell updraft dynamics. Larger midlevel shear does not lead to an increase in cohesive updraft rotation. The tilting of midlevel environmental vorticity does lead to localized areas of larger vertical vorticity on the southern edge of the updraft, but any dynamical influence of this is overshadowed by that of much larger horizontal vorticity in the same area associated with rotor-like circulations. This storm-generated horizontal vorticity is the primary driver behind lower nonlinear dynamic pressure on the southern flank of the midlevel updraft when midlevel shear and low-level storm-relative flow are larger, which leads to a larger nonlinear dynamic pressure acceleration in those cases. Storm-generated horizontal vorticity is responsible for the lowest nonlinear dynamic pressure anywhere in the midlevel updraft, unless the mesocyclone becomes particularly intense. These results clarify the influence of midlevel shear on a supercell thunderstorm, and provide additional insight on the role of low-level storm-relative flow on updraft dynamics.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":"55 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134902959","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0