Journal of the Atmospheric Sciences最新文献_第7页

Large-Scale Circulations and Dry Tropical Cyclones in Direct Numerical Simulations of Rotating Rayleigh-Bénard Convection 大尺度环流和干燥热带气旋在旋转瑞利-巴萨纳德对流中的直接数值模拟

IF 3.1 3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-07-25 DOI: 10.1175/jas-d-23-0018.1

M. Velez-Pardo, T. Cronin

{"title":"Large-Scale Circulations and Dry Tropical Cyclones in Direct Numerical Simulations of Rotating Rayleigh-Bénard Convection","authors":"M. Velez-Pardo, T. Cronin","doi":"10.1175/jas-d-23-0018.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0018.1","url":null,"abstract":"\u0000The organization of convection into relatively long-lived patterns of large spatial scales, like tropical cyclones, is a common feature of the Earth’s atmosphere. However, many key aspects of convective aggregation and its relationship with tropical cyclone formation remain elusive. In this work, we simulate highly idealized setups of dry convection, inspired by the Rayleigh-Bénard system, to probe the effects of different thermal boundary conditions on the scale of organization of rotating convection, and on the formation of tropical-cyclone-like structures. We find that in domains with sufficiently high aspect ratios, moderately turbulent (Raf ≳ 109), moderately rotating (Roc ≳ 1) convection organizes more persistently and at larger scales when thermal boundary conditions constrain heat fluxes rather than temperatures. Furthermore, for some thermal boundary conditions with asymmetric heat fluxes, convection organizes into persistent vortices with the essential properties of mature tropical cyclones: a warm core, high axisymmetry, a strong azimuthal circulation, and substantially larger size than individual buoyant plumes. We argue that flux asymmetry results in a persistent and localized input of buoyancy which allows spatially aggregated convection to sustain a warm core in a developing large-scale vortex. Crucially, the most intense and axisymmetric cyclone forms for setups where the bottom heat flux is enhanced by the nearby flow and the top boundary is insulating, as long as the convective Rossby number is higher than about 1. Our results demonstrate the great potential for dialogue between classical turbulence research and the study of convective aggregation and tropical cyclones.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43390768","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 role of subtropical Rossby waves in amplifying the divergent circulation of the Madden Julian Oscillation 副热带Rossby波在放大麦登-朱利安振荡发散环流中的作用

IF 3.1 3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-07-24 DOI: 10.1175/jas-d-22-0259.1

P. Barpanda, S. Tulich, J. Dias, G. Kiladis

{"title":"The role of subtropical Rossby waves in amplifying the divergent circulation of the Madden Julian Oscillation","authors":"P. Barpanda, S. Tulich, J. Dias, G. Kiladis","doi":"10.1175/jas-d-22-0259.1","DOIUrl":"https://doi.org/10.1175/jas-d-22-0259.1","url":null,"abstract":"\u0000The composite structure of the Madden-Julian Oscillation (MJO) has long been known to feature pronounced Rossby gyres in the subtropical upper troposphere, whose existence can be interpreted as the forced response to convective heating anomalies in the presence of a subtropical westerly jet. The question of interest here is whether these forced gyre circulations have any subsequent effects on divergence patterns in the tropics and the Kelvin-mode component of the MJO? A nonlinear spherical shallow water model is used to investigate how the introduction of different background jet profiles affects the model’s steady-state response to an imposed MJO-like stationary thermal forcing. Results show that a stronger jet leads to a stronger Kelvin-mode response in the tropics up to a critical jet speed, along with stronger divergence anomalies in the vicinity of the forcing. To understand this behavior, additional calculations are performed in which a localized vorticity forcing is imposed in the extratropics, without any thermal forcing in the tropics. The response is once again seen to include pronounced equatorial Kelvin waves, provided the jet is of sufficient amplitude. A detailed analysis of the vorticity budget reveals that the zonal-mean zonal wind shear plays a key role in amplifying the Kelvin-mode divergent winds near the equator, with the effects of nonlinearities being of negligible importance. These results help to explain why the MJO tends to be strongest during boreal winter when the Indo-Pacific jet is typically at its strongest.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48984027","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

Generation of Multiple Gravity Wave Couplets from Convection 对流产生多重重力波偶

IF 3.1 3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-07-24 DOI: 10.1175/jas-d-22-0212.1

Hongpei Yang, Yu Du, Junhong Wei

{"title":"Generation of Multiple Gravity Wave Couplets from Convection","authors":"Hongpei Yang, Yu Du, Junhong Wei","doi":"10.1175/jas-d-22-0212.1","DOIUrl":"https://doi.org/10.1175/jas-d-22-0212.1","url":null,"abstract":"\u0000The generation of multiple wave couplets with deep tropospheric downdrafts/updrafts by convection is explored through idealized 2D moist numerical simulations as well as dry experiments with prescribed artificial latent heating. These wave couplets are capable of horizontally propagating over a long distance at a fast speed with vertical motions spanning the entire troposphere. The timing of wave generation is determined by the variation in the local heating rate, which arose from the imbalances among latent heating, nonlinear advection and adiabatic heating/cooling. The amplitudes of wave couplets also correspond well with the strength of the local heating rate. The heat budget analysis highlights the crucial roles of both latent heating and nonlinear advection in the generation of the tropospheric wave couplets. Strong latent heating induces the thermodynamic imbalance and thus triggers waves. Meanwhile, latent heating also increases vertical motion in the source region and thus enhances nonlinear advection through transferring heat upward. Nonlinear advection, which has a comparable magnitude to latent heating in the upper troposphere, partially offsets the balancing effect of adiabatic heating/cooling, and results in a more persistent imbalance at high levels, allowing for the emission of consecutive waves even when latent heating becomes weak. In the simulation with weak nonlinear advection, fewer wave couplets are found, as the effect of latent heating is more easily offset by adiabatic cooling before it weakens.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44683285","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

A closer look at the evolution of supercooled cloud droplet temperature and lifetime in different environmental conditions with implications for ice nucleation in the evaporating regions of clouds 仔细观察不同环境条件下过冷云滴温度和寿命的演变，对云蒸发区的冰核产生影响

IF 3.1 3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-07-24 DOI: 10.1175/jas-d-22-0239.1

Puja Roy, R. Rauber, L. Girolamo

{"title":"A closer look at the evolution of supercooled cloud droplet temperature and lifetime in different environmental conditions with implications for ice nucleation in the evaporating regions of clouds","authors":"Puja Roy, R. Rauber, L. Girolamo","doi":"10.1175/jas-d-22-0239.1","DOIUrl":"https://doi.org/10.1175/jas-d-22-0239.1","url":null,"abstract":"\u0000This study investigates the evolution of temperature and lifetime of evaporating, supercooled cloud droplets considering initial droplet radius (r0) and temperature (Tr0), and environmental relative humidity (RH), temperature (T∞) and pressure (P). The time (tss) required by droplets to reach a lower steady-state temperature (Tss) after sudden introduction into a new subsaturated environment, the magnitude of ΔT = T∞ − Tss, and droplet survival time (tst) at Tss are calculated. ΔT is found to increase with T∞, and decrease with RH and P. ΔT was typically 1-5K lower than T∞, with highest values (~10.3K) for very low RH, low P, and T∞ closer to 0°C. Results show that tss is < 0.5s over the range of initial droplet and environmental conditions considered. Larger droplets (r0 = 30 to 50 μm) can survive at Tss for about 15s to over 3 minutes, depending on the subsaturation of the environment. For higher RH and larger droplets, droplet lifetimes can increase by more than 100s compared to those with droplet cooling ignored. Tss of the evaporating droplets can be approximated by the environmental thermodynamic wet-bulb temperature. Radiation was found to play a minor role in influencing droplet temperatures, except for larger droplets in environments close to saturation. The implications for ice nucleation in cloud-top generating cells and near cloud edges are discussed. Using Tss instead of T∞ in widely-used parameterization schemes could lead to enhanced number concentrations of activated ice-nucleating particles (INPs), by a typical factor of 2-30, with the greatest increases (≥100) coincident with low RH, low P, and T∞ closer to 0°C.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47909151","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

Diagnosing tropical cyclone intensity variations from the surface wind field evolution 从地面风场演变诊断热带气旋强度变化

IF 3.1 3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-07-20 DOI: 10.1175/jas-d-22-0208.1

Léo Vinour, Swen Jullien, A. Mouche

{"title":"Diagnosing tropical cyclone intensity variations from the surface wind field evolution","authors":"Léo Vinour, Swen Jullien, A. Mouche","doi":"10.1175/jas-d-22-0208.1","DOIUrl":"https://doi.org/10.1175/jas-d-22-0208.1","url":null,"abstract":"\u0000Tropical cyclone (TC) intensity fluctuations remain a challenge for TC forecasters. Occurring through a wide range of processes, such as vortex contraction, eyewall replacements, or emission of vortex Rossby waves, they are inherently multiscale, transient, and asymmetric. In a recent study, estimates of surface wind field inner-core properties from high-resolution satellite observations were spotted as valuable for the improvement of intensity variations statistical predictability. The present study evaluates how the temporal evolution of the vortex structure, at scales ranging from O(1km) to vortex-wide, further provides insights on the modulation of intensity. The study is based on a set of seven realistic TC simulations with one-kilometer grid spacing. The surface wind field structure is studied through an original set of descriptors which characterize the radial profile, the azimuthal asymmetries, and their spectral distribution. While radial gradients evolve concurrently with intensity, the azimuthal variability of the inner-core shows a stronger connection with shorter-scale intensity modulation. The increase of high wavenumber asymmetries distributed around the ring of maximum winds is shown to precede phases of rapid (re-)intensification by 5-6h, while the concentration of asymmetry in wavenumbers 1 and 2 leads to intensity weakening. A machine learning classification finally highlights that the classification of intensification phases (i.e. intensification or weakening) can be improved by at least 11% (thus reaching ∼75%) when accounting for the evolution of the radial wind gradient and the variance distribution among scales in the ring of maximum wind, relative to the sole use of vortex-averaged parameters.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42481407","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

Regimes of Convective Self-Aggregation in Convection-Permitting Beta-Plane Simulations 允许对流的β平面模拟中对流自聚集的状态

IF 3.1 3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-07-10 DOI: 10.1175/jas-d-22-0222.1

Jacob D. Carstens, A. Wing

{"title":"Regimes of Convective Self-Aggregation in Convection-Permitting Beta-Plane Simulations","authors":"Jacob D. Carstens, A. Wing","doi":"10.1175/jas-d-22-0222.1","DOIUrl":"https://doi.org/10.1175/jas-d-22-0222.1","url":null,"abstract":"\u0000The spontaneous self-aggregation (SA) of convection in idealized model experiments highlights the importance of interactions between tropical convection and the surrounding environment. The authors have shown that SA fundamentally changes with the background rotation in previous f-plane simulations, both in terms of the resulting forms of organized convection, and the relative roles of the physical feedbacks driving them. This study considers the dependence of SA on rotation in one large domain on the β-plane, introducing an additional layer of complexity. Simulations are performed with uniform thermal forcing and explicit convection. Focuses include statistical and structural analysis of the convective modes, process-oriented diagnostics of how they develop, and resulting mean states. Two regimes of SA emerge within the first 15 days, separated by a critical zone where f is analogous to 10-15° latitude. Organized convection at near-equatorial values of f primarily consists of convectively-coupled Kelvin waves. Wind speed-surface enthalpy flux feedbacks are the dominant process driving moisture variability early on, then clear-sky shortwave radiative feedbacks are strongest in wave maintenance. In contrast, at higher f, numerous tropical cyclones develop and co-exist, dominated by surface flux and longwave processes. Tropical cyclogenesis is most pronounced at intermediate f (analogous to 25-40°), but are longer-lived at higher f. The resulting modes of SA at low f differ between these β-plane simulations (convectively-coupled waves) and prior f-plane simulations (weak tropical cyclones or non-rotating clusters). Otherwise, these results provide further evidence for the changing roles of radiative, surface flux, and advective processes in influencing SA as f changes, as found in our previous study.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43579680","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

Diabatic Heat Effects on the Generation of Energy for Evolution of a SACZ Event: A Perspective from the Lorenz Energy Cycle 非绝热效应对SACZ事件演化能量产生的影响:来自洛伦兹能量循环的视角

IF 3.1 3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-07-07 DOI: 10.1175/jas-d-22-0245.1

J. F. António, J. Aravéquia

{"title":"Diabatic Heat Effects on the Generation of Energy for Evolution of a SACZ Event: A Perspective from the Lorenz Energy Cycle","authors":"J. F. António, J. Aravéquia","doi":"10.1175/jas-d-22-0245.1","DOIUrl":"https://doi.org/10.1175/jas-d-22-0245.1","url":null,"abstract":"\u0000Here we used meteorological data sets from ERA-5 reanalysis to study the dynamic and thermodynamic characteristics of a SACZ event that occurred between December 12 and 26, 2013. This is an atypical SACZ episode with considerable variations in cloudiness band positioning and high rainfall amounts, causing enormous problems for society. We study this case through the Lorenz Energy Cycle (LEC), focusing mainly on the role of diabatic heating in energy generation and consequently in circulation aspects, analyzing the event in three stages (formation, development, and dissipation), and discussing it according to the convection localization pattern. The diabatic heat rate has a large impact on the energy generation of SACZ events at midlevels south of 24°S and below 900 hPa in the tropics. In LEC, the generation terms in the SACZ area were larger at the beginning (December 12-15) and smaller at the ending periods (December 23-26), with means of 21.23 and −7.62 W/m2, respectively. The conversion terms follow the LEC directions, except for barotropic instability [C(KE,KM)<0] that dominates throughout the analyzed periods. The convection area expansion to the north between December 16-22, was reflected by the most intense heating in the tropics and weaker barotropic instability. The friction term did not favor the event decay; therefore, we concluded that the cooling through a negative covariance between Q and T contributed to the event decay. We find that these results were largely influenced by a midlatitude wave train configuration that acted to favor the persistence, expansion, and decay of the event.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44267164","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

Use of Smartphone-Based Video Directly Observed Therapy to Increase Tuberculosis Medication Adherence: An Interventional Study. 使用基于智能手机的视频直接观察疗法提高肺结核药物治疗的依从性：一项干预性研究。

IF 0.5 3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-07-03 eCollection Date: 2023-01-01 DOI: 10.31661/gmj.v12i.3067

Manal M Al Daajani, Abdullah J Alsahafi, Abdullah M Algarni, Abdulhamed L Moawwad, Ahmed A Osman, Khalid Y A Algaali, Mohammed Abdalaziz, Muhammad A Halwani, Shrooq M Aldajani, Nazik M H Mohammed, Heassah S Alshamrani, Mohammed N Alshahrani, Ghadah M Albostani, Naif G Alshammari, Rami S Alzahrani, Saadiya O Alsomali, Ibrahim Assiri

{"title":"Use of Smartphone-Based Video Directly Observed Therapy to Increase Tuberculosis Medication Adherence: An Interventional Study.","authors":"Manal M Al Daajani, Abdullah J Alsahafi, Abdullah M Algarni, Abdulhamed L Moawwad, Ahmed A Osman, Khalid Y A Algaali, Mohammed Abdalaziz, Muhammad A Halwani, Shrooq M Aldajani, Nazik M H Mohammed, Heassah S Alshamrani, Mohammed N Alshahrani, Ghadah M Albostani, Naif G Alshammari, Rami S Alzahrani, Saadiya O Alsomali, Ibrahim Assiri","doi":"10.31661/gmj.v12i.3067","DOIUrl":"10.31661/gmj.v12i.3067","url":null,"abstract":"Background: Tuberculosis (TB) treatment through Directly Observed Therapy (DOT) has an alternative form of video surveillance therapy (VOT) that utilizes the technological capabilities of smartphones to provide patients with low-cost access to doctors without impacting their work and personal life. We aimed to assess TB patients' drug compliance, perceptions, and feasibility towards smartphone-based video direct observed therapy (VDOT) in Jeddah, KSA.Materials and methods: We conducted a prospective non-randomized interventional study. We delivered smartphone-based VDOT among previously unstudied patients to monitor adherence to the treatment regimen. The expected total number of VDOT sessions was1200. We conducted post-intervention interviews to assess acceptability and satisfaction.Results: In this study, we included 20 participants, 16 of whom were males, with a mean age of 34.3 (±12.5) years. No side effects to the treatments were identified in all participants. The adherence rate for the total period was 93% and 99.5%, measured by the first and second methods, respectively. Most participants were satisfied with the VDOT experience, the time spent on sessions, and the approach's privacy.Conclusion: This study provides promising results for the feasibility and effectiveness of smartphone-based VDOT for TB treatment to increase adherence which was indicated by a high compliance rate, acceptability, and high satisfaction level.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":"22 1","pages":"1-8"},"PeriodicalIF":0.5,"publicationDate":"2023-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11512422/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86664361","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Intensification Rates of Tropical Cyclone–Like Vortices in a Model with Downtilt Diabatic Forcing and Oceanic Surface Drag 具有向下倾斜非绝热强迫和海洋表面阻力的模式中热带气旋样涡的增强率

IF 3.1 3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-07-01 DOI: 10.1175/jas-d-22-0188.1

D. Schecter

{"title":"Intensification Rates of Tropical Cyclone–Like Vortices in a Model with Downtilt Diabatic Forcing and Oceanic Surface Drag","authors":"D. Schecter","doi":"10.1175/jas-d-22-0188.1","DOIUrl":"https://doi.org/10.1175/jas-d-22-0188.1","url":null,"abstract":"\u0000Tropical cyclones are commonly observed to have appreciable vertical misalignments prior to becoming full-strength hurricanes. The vertical misalignment (tilt) of a tropical cyclone is generally coupled to a pronounced asymmetry of inner-core convection, with the strongest convection tending to concentrate downtilt of the surface vortex center. Neither the mechanisms by which tilted tropical cyclones intensify nor the time scales over which such mechanisms operate are fully understood. The present study offers some insight into the asymmetric intensification process by examining the responses of tilted tropical cyclone–like vortices to downtilt diabatic forcing (heating) in a 3D nonhydrostatic numerical model. The magnitude of the heating is adjusted so as to vary the strength of the downtilt convection that it generates. A fairly consistent picture of intensification is found in various simulation groups that differ in their initial vortex configurations, environmental shear flows, and specific positionings of downtilt heating. The intensification mechanism generally depends on whether the low-level convergence σb produced in the vicinity of the downtilt heat source exceeds a critical value dependent on the local velocity of the low-level nondivergent background flow in a reference frame that drifts with the heat source. Supercritical σb causes fast spinup initiated by downtilt core replacement. Subcritical σb causes a slower intensification process. As measured herein, the supercritical intensification rate is approximately proportional to σb. The subcritical intensification rate has a more subtle scaling, and expectedly becomes negative when σb drops below a threshold for frictional spindown to dominate. The relevance of the foregoing results to real-world tropical cyclones is discussed.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43850330","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

Lagrangian and Eulerian supersaturation statistics in turbulent cloudy Rayleigh–Bénard convection: applications for LES subgrid modeling 湍流多云Rayleigh–Bénard对流中的拉格朗日和欧拉过饱和统计：在LES子网格建模中的应用

IF 3.1 3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-06-27 DOI: 10.1175/jas-d-22-0256.1

K. K. Chandrakar, H. Morrison, R. Shaw

{"title":"Lagrangian and Eulerian supersaturation statistics in turbulent cloudy Rayleigh–Bénard convection: applications for LES subgrid modeling","authors":"K. K. Chandrakar, H. Morrison, R. Shaw","doi":"10.1175/jas-d-22-0256.1","DOIUrl":"https://doi.org/10.1175/jas-d-22-0256.1","url":null,"abstract":"\u0000Turbulent fluctuations of scalar and velocity fields are critical for cloud microphysical processes, e.g., droplet activation and size distribution evolution, and can therefore influence cloud radiative forcing and precipitation formation. Lagrangian and Eulerian water vapor, temperature, and supersaturation statistics are investigated in direct-numerical simulations (DNS) of turbulent Rayleigh–Bénard convection in the Pi Convection Cloud Chamber to provide a foundation for parameterizing subgrid-scale fluctuations in atmospheric models. A subgrid model for water vapor and temperature variances and covariance and supersaturation variance is proposed, valid for both clear and cloudy conditions. Evaluation of phase change contributions through an a priori test using DNS data shows good performance of the model. Supersaturation is a nonlinear function of temperature and water vapor, and relative external fluxes of water vapor and heat (e.g., during entrainment-mixing and phase change) influence turbulent supersaturation fluctuations. Although supersaturation has autocorrelation and structure functions similar to the independent scalars (temperature and water vapor), the autocorrelation timescale of supersaturation differs. Relative scalar fluxes in DNS without cloud make supersaturation PDFs less skewed than the adiabatic case, where they are highly negatively skewed. However, droplet condensation changes the PDF shape response: it becomes positively skewed for the adiabatic case and negatively skewed when the sidewall relative fluxes are large. Condensation also increases correlations between water vapor and temperature in the presence of relative scalar fluxes but decreases correlations for the adiabatic case. These changes in correlation suppress supersaturation variability for the non-adiabatic cases and increase it for the adiabatic case. Implications of this work for subgrid microphysics modeling using a Lagrangian stochastic scheme are also discussed.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43002282","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