Pub Date : 2024-02-01Epub Date: 2023-08-31DOI: 10.1007/s12070-023-04188-0
Sana Ahuja, Priyanka Singh, Ankita Ratnakar, Sufian Zaheer
Collision tumor comprise of existence of two histologically distinct and separate neoplasms in any organ. Thyroid gland is an uncommon site for these tumors, with frequently involved organs being liver, adrenal and stomach. Even among the synchronous tumors of thyroid, papillary and medullary carcinoma are most commonly reported. The present case reports a rare presentation of a collision tumor comprising of papillary and follicular carcinoma with scalp metastasis from the follicular carcinoma and lymph nodal metastasis from the papillary component. It is essential for the clinician to be aware of such an entity so as to guide further treatment and management.
{"title":"Synchronous Papillary and Follicular Carcinoma with Scalp and Nodal Metastasis: A case report with review of literature.","authors":"Sana Ahuja, Priyanka Singh, Ankita Ratnakar, Sufian Zaheer","doi":"10.1007/s12070-023-04188-0","DOIUrl":"10.1007/s12070-023-04188-0","url":null,"abstract":"<p><p>Collision tumor comprise of existence of two histologically distinct and separate neoplasms in any organ. Thyroid gland is an uncommon site for these tumors, with frequently involved organs being liver, adrenal and stomach. Even among the synchronous tumors of thyroid, papillary and medullary carcinoma are most commonly reported. The present case reports a rare presentation of a collision tumor comprising of papillary and follicular carcinoma with scalp metastasis from the follicular carcinoma and lymph nodal metastasis from the papillary component. It is essential for the clinician to be aware of such an entity so as to guide further treatment and management.</p>","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":"35 1","pages":"1147-1152"},"PeriodicalIF":0.6,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10908663/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86793079","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}
Lu Zhang, Hongsheng Zhang, Xuhui Cai, Yu Song, Xiaoye Zhang
Taklimakan Desert is one of key climate regions in East Asia, both highly influencing and highly sensitive to local/regional climate change. Based on comprehensive observation experiment from 1 to 31 May 2022 in the hinterland of the Taklimakan Desert, the characteristics and mechanisms of turbulence intermittency are investigated in this study, with the purpose to correct turbulent fluxes. Using an improved algorithm to decompose turbulence and submeso motions, two intermittency regimes are recognized in the Taklimakan Desert, namely D&T intermittency and onD intermittency. The former occurs under strongly stable conditions, characterized by the coexistence of dynamic and thermodynamic turbulence intermittency. The latter occurs under strongly unstable conditions and represents only dynamic turbulence intermittency. Physically, the D&T intermittency regime is related to submeso waves, whereas the onD regime is caused by the horizontal convergence/divergence of convective circulations. With the influence of intermittency and submeso motions, the observed turbulent statistics deviate from reality, which would mask the similarity relationships. To overcome the problem, turbulent statistics are corrected by removing submeso components from original fluctuations. The effectiveness of this method is demonstrated based on the flux-gradient relationships. It is also suggested that, for a big dataset, the impact of onD intermittency can be simply corrected by a correction factor while that of D&T intermittency not. The results of this study are helpful to develop the parameterization of turbulent exchange processes in the Taklimakan Desert, which is significant to improve the accuracy of weather forecasting and climate prediction.
{"title":"Characteristics of Turbulence Intermittency, Fine Structures, and Flux Correction in the Taklimakan Desert","authors":"Lu Zhang, Hongsheng Zhang, Xuhui Cai, Yu Song, Xiaoye Zhang","doi":"10.1175/jas-d-23-0107.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0107.1","url":null,"abstract":"\u0000Taklimakan Desert is one of key climate regions in East Asia, both highly influencing and highly sensitive to local/regional climate change. Based on comprehensive observation experiment from 1 to 31 May 2022 in the hinterland of the Taklimakan Desert, the characteristics and mechanisms of turbulence intermittency are investigated in this study, with the purpose to correct turbulent fluxes. Using an improved algorithm to decompose turbulence and submeso motions, two intermittency regimes are recognized in the Taklimakan Desert, namely D&T intermittency and onD intermittency. The former occurs under strongly stable conditions, characterized by the coexistence of dynamic and thermodynamic turbulence intermittency. The latter occurs under strongly unstable conditions and represents only dynamic turbulence intermittency. Physically, the D&T intermittency regime is related to submeso waves, whereas the onD regime is caused by the horizontal convergence/divergence of convective circulations. With the influence of intermittency and submeso motions, the observed turbulent statistics deviate from reality, which would mask the similarity relationships. To overcome the problem, turbulent statistics are corrected by removing submeso components from original fluctuations. The effectiveness of this method is demonstrated based on the flux-gradient relationships. It is also suggested that, for a big dataset, the impact of onD intermittency can be simply corrected by a correction factor while that of D&T intermittency not. The results of this study are helpful to develop the parameterization of turbulent exchange processes in the Taklimakan Desert, which is significant to improve the accuracy of weather forecasting and climate prediction.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":"100 1","pages":""},"PeriodicalIF":3.1,"publicationDate":"2024-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139444433","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}
The vertical velocity distribution in the atmosphere is asymmetric with stronger upward than downward motion. This asymmetry has important implications for the distribution of precipitation and its extremes and for an effective static stability that has been used to represent the effects of latent heating on extratropical eddies. Idealized GCM simulations show that the asymmetry increases as the climate warms, but current moist dynamical theories based around small amplitude modes greatly overestimate the increase in asymmetry with warming found in the simulations. Here, we first analyze the changes in asymmetry with warming using numerical inversions of a moist quasigeostrophic omega equation applied to output from the idealized GCM. The inversions show that increases in the asymmetry with warming in the GCM simulations are primarily related to decreases in moist static stability on the left-hand side of the moist omega equation, whereas the dynamical forcing on the right-hand side of the omega equation is unskewed and contributes little to the asymmetry of the vertical velocity distribution. By contrast, increases in asymmetry with warming for small amplitude modes are related to changes in both moist static stability and dynamical forcing leading to enhanced asymmetry in warm climates. We distill these insights into a toy model of the moist omega equation that is solved for a given moist static stability and wavenumber of the dynamical forcing. In comparison to modal theory, the toy model better reproduces the slow increase of the asymmetry with climate warming in the idealized GCM simulations and over the seasonal cycle from winter to summer in reanalysis.
{"title":"Asymmetry of the Distribution of Vertical Velocities of the Extratropical Atmosphere in Theory, Models and Reanalysis","authors":"M. Kohl, P. O’Gorman","doi":"10.1175/jas-d-23-0128.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0128.1","url":null,"abstract":"\u0000The vertical velocity distribution in the atmosphere is asymmetric with stronger upward than downward motion. This asymmetry has important implications for the distribution of precipitation and its extremes and for an effective static stability that has been used to represent the effects of latent heating on extratropical eddies. Idealized GCM simulations show that the asymmetry increases as the climate warms, but current moist dynamical theories based around small amplitude modes greatly overestimate the increase in asymmetry with warming found in the simulations. Here, we first analyze the changes in asymmetry with warming using numerical inversions of a moist quasigeostrophic omega equation applied to output from the idealized GCM. The inversions show that increases in the asymmetry with warming in the GCM simulations are primarily related to decreases in moist static stability on the left-hand side of the moist omega equation, whereas the dynamical forcing on the right-hand side of the omega equation is unskewed and contributes little to the asymmetry of the vertical velocity distribution. By contrast, increases in asymmetry with warming for small amplitude modes are related to changes in both moist static stability and dynamical forcing leading to enhanced asymmetry in warm climates. We distill these insights into a toy model of the moist omega equation that is solved for a given moist static stability and wavenumber of the dynamical forcing. In comparison to modal theory, the toy model better reproduces the slow increase of the asymmetry with climate warming in the idealized GCM simulations and over the seasonal cycle from winter to summer in reanalysis.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":"52 45","pages":""},"PeriodicalIF":3.1,"publicationDate":"2024-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139447379","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}
The steady response of the stratosphere to tropospheric thermal forcing via an SST perturbation is considered in two separate theoretical models. It is first shown that an SST anomaly imposes a geopotential anomaly at the tropopause. Solutions to the linearized quasi-geostrophic potential vorticity equations are then used to show that the vertical length scale of a tropopause geopotential anomaly is initially shallow, but significantly increased by diabatic heating from radiative relaxation. This process is a quasi-balanced response of the stratosphere to tropospheric forcing. A previously developed, coupled troposphere-stratosphere model is then introduced and modified. Solutions under steady, zonally-symmetric SST forcing in the linear β-plane model show that the upwards stratospheric penetration of the corresponding tropopause geopotential anomaly is controlled by two non-dimensional parameters, (1) a dynamical aspect ratio, and (2) a ratio between tropospheric and stratospheric drag. The meridional scale of the SST anomaly, radiative relaxation rate, and wave-drag all significantly modulate these non-dimensional parameters. Under Earth-like estimates of the non-dimensional parameters, the theoretical model predicts stratospheric temperature anomalies 2-3 larger in magnitude than that in the boundary layer, approximately in line with observational data. Using reanalysis data, the spatial variability of temperature anomalies in the troposphere is shown to have remarkable coherence with that of the lower-stratosphere, which further supports the existence of a quasi-balanced response of the stratosphere to SST forcing. These findings suggest that besides mechanical and radiative forcing, there is a third way the stratosphere can be forced – through the tropopause via tropospheric thermal forcing.
{"title":"Tropospheric thermal forcing of the stratosphere through quasi-balanced dynamics","authors":"Jonathan Lin, Kerry Emanuel","doi":"10.1175/jas-d-23-0081.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0081.1","url":null,"abstract":"\u0000 The steady response of the stratosphere to tropospheric thermal forcing via an SST perturbation is considered in two separate theoretical models. It is first shown that an SST anomaly imposes a geopotential anomaly at the tropopause. Solutions to the linearized quasi-geostrophic potential vorticity equations are then used to show that the vertical length scale of a tropopause geopotential anomaly is initially shallow, but significantly increased by diabatic heating from radiative relaxation. This process is a quasi-balanced response of the stratosphere to tropospheric forcing. A previously developed, coupled troposphere-stratosphere model is then introduced and modified. Solutions under steady, zonally-symmetric SST forcing in the linear β-plane model show that the upwards stratospheric penetration of the corresponding tropopause geopotential anomaly is controlled by two non-dimensional parameters, (1) a dynamical aspect ratio, and (2) a ratio between tropospheric and stratospheric drag. The meridional scale of the SST anomaly, radiative relaxation rate, and wave-drag all significantly modulate these non-dimensional parameters. Under Earth-like estimates of the non-dimensional parameters, the theoretical model predicts stratospheric temperature anomalies 2-3 larger in magnitude than that in the boundary layer, approximately in line with observational data. Using reanalysis data, the spatial variability of temperature anomalies in the troposphere is shown to have remarkable coherence with that of the lower-stratosphere, which further supports the existence of a quasi-balanced response of the stratosphere to SST forcing. These findings suggest that besides mechanical and radiative forcing, there is a third way the stratosphere can be forced – through the tropopause via tropospheric thermal forcing.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":"11 9","pages":""},"PeriodicalIF":3.1,"publicationDate":"2024-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139446941","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}
A simulation of a supercell storm produced for a prior study on tornado predictability is reanalyzed for the purpose of examining the finescale details of tornadogenesis. It is found that the formation of a tornado-like vortex in the simulation differs from how such vortices have been understood to form in previous numerical simulations. The main difference between the present simulation and past ones is the inclusion of a turbulent boundary layer in the storm’s environment in the present case, whereas prior simulations have used a laminar boundary layer. The turbulent environment contains significant near-surface vertical vorticity (ζ > 0.03 s−1 at z = 7.5 m), organized in the form of longitudinal streaks aligned with the southerly ground-relative winds. The ζ streaks are associated with corrugations in the vertical plane in the predominantly horizontal, westward-pointing environmental vortex lines; the vortex-line corrugations are produced by the vertical drafts associated with coherent turbulent structures aligned with the aforementioned southerly ground-relative winds (longitudinal coherent structures in the surface layer such as these are well-known to the boundary layer and turbulence communities). The ζ streaks serve as focal points for tornadogenesis, and may actually facilitate tornadogenesis, given how near-surface ζ in the environment can rapidly amplify when subjected to the strong, persistent convergence beneath a supercell updraft.
{"title":"A new pathway for tornadogenesis exposed by numerical simulations of supercells in turbulent environments","authors":"P. Markowski","doi":"10.1175/jas-d-23-0161.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0161.1","url":null,"abstract":"\u0000A simulation of a supercell storm produced for a prior study on tornado predictability is reanalyzed for the purpose of examining the finescale details of tornadogenesis. It is found that the formation of a tornado-like vortex in the simulation differs from how such vortices have been understood to form in previous numerical simulations. The main difference between the present simulation and past ones is the inclusion of a turbulent boundary layer in the storm’s environment in the present case, whereas prior simulations have used a laminar boundary layer. The turbulent environment contains significant near-surface vertical vorticity (ζ > 0.03 s−1 at z = 7.5 m), organized in the form of longitudinal streaks aligned with the southerly ground-relative winds. The ζ streaks are associated with corrugations in the vertical plane in the predominantly horizontal, westward-pointing environmental vortex lines; the vortex-line corrugations are produced by the vertical drafts associated with coherent turbulent structures aligned with the aforementioned southerly ground-relative winds (longitudinal coherent structures in the surface layer such as these are well-known to the boundary layer and turbulence communities). The ζ streaks serve as focal points for tornadogenesis, and may actually facilitate tornadogenesis, given how near-surface ζ in the environment can rapidly amplify when subjected to the strong, persistent convergence beneath a supercell updraft.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":"55 3","pages":""},"PeriodicalIF":3.1,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139381768","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}
T. J. Zaremba, R. Rauber, Kaylee Heimes, J. Yorks, Joseph A. Finlon, Stephen D. Nicholls, P. Selmer, L. McMurdie, G. McFarquhar
Cloud top phase (CTP) impacts cloud albedo and pathways for ice particle nucleation, growth, and fallout within extratropical cyclones. This study uses airborne lidar, radar, and Rapid Refresh analysis data to characterize CTP within extratropical cyclones as a function of cloud top temperature (CTT). During the 2020, 2022, and 2023 Investigation of Microphysics and Precipitation for Atlantic Coast-Threatening Snowstorms (IMPACTS) field campaign deployments, the Earth-Resources 2 (ER-2) aircraft flew 26 research flights over the Northeast and Midwest U.S. to sample the cloud tops of a variety of extratropical cyclones. A training dataset was developed to create probabilistic phase classifications based on Cloud Physics Lidar measurements of known ice and liquid clouds. These classifications were then used to quantify dominant CTP in the top 150 m of clouds sampled by the Cloud Physics Lidar in storms during IMPACTS. Case studies are presented illustrating examples of supercooled liquid water at cloud top at different CTT ranges(−3°C −20°C. Liquid-bearing cloud tops were found at CTTs as cold as −37°C.
{"title":"Cloud Top Phase Characterization of Extratropical Cyclones over the Northeast and Midwest United States: results from IMPACTS","authors":"T. J. Zaremba, R. Rauber, Kaylee Heimes, J. Yorks, Joseph A. Finlon, Stephen D. Nicholls, P. Selmer, L. McMurdie, G. McFarquhar","doi":"10.1175/jas-d-23-0123.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0123.1","url":null,"abstract":"\u0000Cloud top phase (CTP) impacts cloud albedo and pathways for ice particle nucleation, growth, and fallout within extratropical cyclones. This study uses airborne lidar, radar, and Rapid Refresh analysis data to characterize CTP within extratropical cyclones as a function of cloud top temperature (CTT). During the 2020, 2022, and 2023 Investigation of Microphysics and Precipitation for Atlantic Coast-Threatening Snowstorms (IMPACTS) field campaign deployments, the Earth-Resources 2 (ER-2) aircraft flew 26 research flights over the Northeast and Midwest U.S. to sample the cloud tops of a variety of extratropical cyclones. A training dataset was developed to create probabilistic phase classifications based on Cloud Physics Lidar measurements of known ice and liquid clouds. These classifications were then used to quantify dominant CTP in the top 150 m of clouds sampled by the Cloud Physics Lidar in storms during IMPACTS. Case studies are presented illustrating examples of supercooled liquid water at cloud top at different CTT ranges(−3°C<CTTs<−35°C) within extratropical cyclones. During IMPACTS, 19.2% of clouds had supercooled liquid water present at cloud top. Supercooled liquid was the dominant phase in extratropical cyclone cloud tops when CTTs were > −20°C. Liquid-bearing cloud tops were found at CTTs as cold as −37°C.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":"54 34","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138946347","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}
The traditional approach of using the Monin-Obukhov similarity theory (MOST) to model near-surface processes in large-eddy simulations (LESs) can lead to significant errors in natural convection. In this study, we propose an alternative approach based on feedforward neural networks (FNNs) trained on output from direct numerical simulation (DNS). To evaluate the performance, we conduct both a priori and a posteriori tests. In the a priori (offline) tests, we compare the statistics of the surface shear stress and heat flux, computed from filtered DNS input variables, to the stress and flux obtained from the filtered DNS. Additionally, we investigate the importance of various input features using the Shapley additive explanations value and the conditional average of the filter grid cells. In the a posteriori (online) tests, we implement the trained models in the System for Atmospheric Modeling (SAM) LES and compare the LES-generated surface shear stress and heat flux with those in the DNS. Our findings reveal that vertical velocity, a traditionally overlooked flow quantity, is one of the most important input features for determining the wall fluxes. Increasing the number of input features improves the a priori test results but does not always improve the model performance in the a posteriori tests because of the differences in input variables between the LES and DNS. Lastly, we show that physics-aware FNN models trained with logarithmic and scaled parameters can well extrapolate to more intense convection scenarios than in the training dataset, whereas those trained with primitive flow quantities cannot.
在大涡流模拟（LES）中，使用莫宁-奥布霍夫相似性理论（MOST）来模拟近表面过程的传统方法会导致自然对流出现重大误差。在本研究中，我们提出了一种基于直接数值模拟（DNS）输出训练的前馈神经网络（FNN）的替代方法。为了评估其性能，我们进行了先验和后验测试。在先验（离线）测试中，我们将根据过滤后的 DNS 输入变量计算出的表面剪应力和热通量的统计数据与根据过滤后的 DNS 获得的应力和通量进行了比较。此外，我们还使用沙普利加法解释值和滤波网格单元的条件平均值来研究各种输入特征的重要性。在后验（在线）中，我们在大气建模系统（SAM）LES 中实施了训练有素的模型，并将 LES 生成的地表切应力和热通量与 DNS 中的地表切应力和热通量进行了比较。我们的研究结果表明，垂直速度这个传统上被忽视的流动量是确定壁面通量的最重要输入特征之一。增加输入特征的数量可以改善先验测试结果，但由于 LES 和 DNS 输入变量的差异，并不总能改善模型的后验性能。最后，我们证明了使用对数参数和比例参数训练的物理感知 FNN 模型可以很好地推断出比训练数据集更强烈的对流情景，而使用原始流动量训练的模型则不能。
{"title":"An Investigation of LES Wall Modeling for Rayleigh-Bénard Convection via Interpretable and Physics-Aware Feedforward Neural Networks with DNS","authors":"Aaron Wang, Xiang I. A. Yang, Mikhail Ovchinnikov","doi":"10.1175/jas-d-23-0094.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0094.1","url":null,"abstract":"\u0000The traditional approach of using the Monin-Obukhov similarity theory (MOST) to model near-surface processes in large-eddy simulations (LESs) can lead to significant errors in natural convection. In this study, we propose an alternative approach based on feedforward neural networks (FNNs) trained on output from direct numerical simulation (DNS). To evaluate the performance, we conduct both a priori and a posteriori tests. In the a priori (offline) tests, we compare the statistics of the surface shear stress and heat flux, computed from filtered DNS input variables, to the stress and flux obtained from the filtered DNS. Additionally, we investigate the importance of various input features using the Shapley additive explanations value and the conditional average of the filter grid cells. In the a posteriori (online) tests, we implement the trained models in the System for Atmospheric Modeling (SAM) LES and compare the LES-generated surface shear stress and heat flux with those in the DNS. Our findings reveal that vertical velocity, a traditionally overlooked flow quantity, is one of the most important input features for determining the wall fluxes. Increasing the number of input features improves the a priori test results but does not always improve the model performance in the a posteriori tests because of the differences in input variables between the LES and DNS. Lastly, we show that physics-aware FNN models trained with logarithmic and scaled parameters can well extrapolate to more intense convection scenarios than in the training dataset, whereas those trained with primitive flow quantities cannot.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":"132 25","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138953447","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}
Weak 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.
{"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}
What 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.
{"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}
A. Savazzi, L. Nuijens, Wim C. de Rooy, Martin Janssens, A. P. Siebesma
This 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.
{"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}
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