Journal of the Atmospheric Sciences最新文献_第6页

Diurnally Forced Tropical Gravity Waves Under Varying Stability 变化稳定性下的日强迫热带重力波

IF 3.1 3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-08-23 DOI: 10.1175/jas-d-23-0074.1

Ewan Short, T. Lane, C. Bishop, M. Wheeler

{"title":"Diurnally Forced Tropical Gravity Waves Under Varying Stability","authors":"Ewan Short, T. Lane, C. Bishop, M. Wheeler","doi":"10.1175/jas-d-23-0074.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0074.1","url":null,"abstract":"\u0000Diurnal processes play a primary role in tropical weather. A leading hypothesis is that atmospheric gravity waves diurnally forced near coastlines propagate both offshore and inland, encouraging convection as they do so. In this study we extend the linear analytic theory of diurnally forced gravity waves, allowing for discontinuities in stability, and for linear changes in stability over a finite depth “transition-layer”. As an illustrative example, we first consider the response to a commonly studied heating function emulating diurnally oscillating coastal temperature gradients, with a low-level stability change between the boundary layer and troposphere. Gravity wave rays resembling the upper branches of “St. Andrew’s Cross” are forced along the coastline at the surface, with the stability changes inducing reflection, refraction and ducting of the individual waves comprising the rays, with analogous behaviour evident in the rays themselves. Refraction occurs smoothly in the transition-layer solution, with substantially less reflection than in the discontinuous solution. Second, we consider a new heating function which emulates an upper-level convective heating diurnal cycle, and consider stability changes associated with the tropical tropopause. Reflection, refraction and ducting again occur, with the lower branches of St. Andrew’s Cross now evident. We compare these solutions to observations taken during the Years of the Maritime Continent field campaign, noting better qualitative agreement with the transition-layer solution than the discontinuous solution, suggesting the tropopause is an even weaker gravity wave reflector than previously thought.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44601260","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 two- to four-day predictability of midlatitude cyclones: Don’t sweat the small stuff 中纬度气旋的两到四天可预测性：不要为小事而烦恼

IF 3.1 3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-08-22 DOI: 10.1175/jas-d-22-0232.1

D. J. Lloveras, D. Durran, J. Doyle

{"title":"The two- to four-day predictability of midlatitude cyclones: Don’t sweat the small stuff","authors":"D. J. Lloveras, D. Durran, J. Doyle","doi":"10.1175/jas-d-22-0232.1","DOIUrl":"https://doi.org/10.1175/jas-d-22-0232.1","url":null,"abstract":"\u0000We use convection-permitting idealized simulations of moist midlatitude cyclones to compare the growth of synoptic-scale perturbations derived from an adjoint model with the growth of equal-energy-norm, monochromatic-wavelength perturbations at the smallest resolved scale. For initial magnitudes comparable to those of initial-condition uncertainties in present-day data assimilation systems, the adjoint perturbations produce a “forecast bust”, significantly changing the intensity and location of the cyclone and its accompanying precipitation. In contrast, the small-scale-wave perturbations project strongly onto the moist convection, but the upscale growth from the random displacement of individual convective cells does not significantly alter the cyclone’s development nor its accompanying precipitation through 2–4-day lead times. Instead, the differences in convection generated at early times become negligible because the development of subsequent convection is driven by the mostly unchanged synoptic-scale flow. Reducing the perturbation magnitudes by factors of 10 and 100 demonstrates that nonlinear dynamics play an important role in the displacement of the cyclone by the full-magnitude adjoint perturbations, and that the upscale growth of small-magnitude, small-scale perturbations is too slow to significantly change the cyclone. These results suggest that a sensitive dependence on the synoptic-scale initial conditions, analogous to that of the Lorenz (1963) system, may be more relevant to 2–4-day midlatitude-cyclone forecast busts than the upscale error growth in the Lorenz (1969) model.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41954696","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

Assessment of warm and dry bias over ARM SGP site in E3SMv2 and E3SM-MMF E3SMv2和E3SM-MMF中ARM SGP站点的暖偏和干偏评估

IF 3.1 3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-08-16 DOI: 10.1175/jas-d-23-0062.1

Jungmin M. Lee, C. Tao, W. Hannah, S. Xie, D. Bader

{"title":"Assessment of warm and dry bias over ARM SGP site in E3SMv2 and E3SM-MMF","authors":"Jungmin M. Lee, C. Tao, W. Hannah, S. Xie, D. Bader","doi":"10.1175/jas-d-23-0062.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0062.1","url":null,"abstract":"\u0000Many climate models exhibit a dry and warm bias over the central U.S during the summer months, including the Energy Exascale Earth System Model (E3SM) and its multiscale Modelling Framework (MMF) configuration. Understanding the causes of this bias is important to shine a light on this common model error and reduce the uncertainty in future projections. In this study, we use E3SMv2 and E3SM-MMF to assess how parameterized and resolved convection affect temperature and precipitation biases over the Southern Great Plains site of the Atmospheric Radiation Measurement program. Both configurations overestimate near-surface temperature and underestimate precipitation at the ARM SGP site. The bias is associated with a lack of low-level clouds during days without precipitation and too much incoming solar radiation causing the surface to warm. Low-level cloud fraction in E3SM-MMF during the non-precipitating days is lower in comparison to E3SMv2 and observation, consistent with the larger warm bias. We also find that the underestimated precipitation can be characterized as “too frequent, too weak” in E3SMv2 and “too rare, too intense” in E3SM-MMF. These deficiencies conspire to sustain the warm and dry bias over the central US.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45811256","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 Moist Potential Vorticity Model for Mid-Latitude Long-Lived Mesoscale Convective Systems over Land 陆地中纬度长寿命中尺度对流系统的湿润位涡模式

IF 3.1 3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-08-09 DOI: 10.1175/jas-d-22-0244.1

Qiu Yang, L. Leung, Zhe Feng, Xingchao Chen

{"title":"A Moist Potential Vorticity Model for Mid-Latitude Long-Lived Mesoscale Convective Systems over Land","authors":"Qiu Yang, L. Leung, Zhe Feng, Xingchao Chen","doi":"10.1175/jas-d-22-0244.1","DOIUrl":"https://doi.org/10.1175/jas-d-22-0244.1","url":null,"abstract":"\u0000Mesoscale convective systems (MCSs) bring large amounts of rainfall and strong wind gusts to the mid-latitude land regions, with significant impacts on local weather and hydrologic cycle. However, weather and climate models face a huge challenge in accurately modeling the MCS life cycle and the associated precipitation, highlighting an urgent need for a better understanding of the underlying mechanisms of MCS initiation and propagation. From a theoretical perspective, a suitable model to capture the realistic properties of MCSs and isolate the bare-bone mechanisms for their initiation, intensification, and eastward propagation is still lacking. To simulate mid-latitude MCSs over land, we develop a simple moist potential vorticity (PV) model that readily describes the interactions among PV perturbations, air moisture, and soil moisture. Multiple experiments with or without various environmental factors and external forcing are used to investigate their impacts on MCS dynamics and mesoscale circulation vertical structures. The result shows that mechanical forcing can induce lower-level updraft and cooling, providing favorable conditions for MCS initiation. A positive feedback among surface winds, evaporation rate, and air moisture similar to the wind-induced surface heat exchange over tropical ocean is found to support MCS intensification. Both background surface westerlies and vertical westerly wind shear are shown to provide favorable conditions for the eastward propagation of MCSs. Lastly, our result highlights the crucial role of stratiform heating in shaping mesoscale circulation response. The model should serve as a useful tool for understanding the fundamental mechanisms of MCS dynamics.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44311820","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

Bifurcation points for tropical cyclone genesis and intensification in sheared and dry environments 热带气旋在剪切和干燥环境中发生和增强的分岔点

IF 3.1 3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-08-07 DOI: 10.1175/jas-d-22-0100.1

C. Nam, M. Bell, D. Tao

{"title":"Bifurcation points for tropical cyclone genesis and intensification in sheared and dry environments","authors":"C. Nam, M. Bell, D. Tao","doi":"10.1175/jas-d-22-0100.1","DOIUrl":"https://doi.org/10.1175/jas-d-22-0100.1","url":null,"abstract":"\u0000The combination of moderate vertical wind shear (VWS) and dry environments can produce the most uncertain scenarios for tropical cyclone (TC) genesis and intensification. We investigated the sources of increased uncertainty of TC development under moderate VWS and dry environments using a set of Weather Research and Forecasting (WRF) ensemble simulations. Statistical analysis of ensemble members for precursor events and time-lagged correlations indicates that successful TC development is dependent on a specific set of precursor events. A deficiency in any of these precursor events leads to a failure of TC intensification. The uncertainty of TC intensification can be largely attributed to the probabilistic characteristics of precursor events lining up together before TC intensification. The critical bifurcation point between successful and failed trials in these idealized simulations is the sustained vortex alignment process. Even for the failed intensification cases, most simulations showed deep organized convection, which reformed a mid-level vortex. However, for the failed cycles, the new mid-level vortex could not sustain vertical alignment with the low-level center and was carried away by VWS shortly. Under the most uncertain setup (VWS 7.5 m s−1 and 50% moisture), the latest developing ensemble member had seven events of tilt decreasing and increasing again that occurred during the eight days before genesis. Some unsuccessful precursor events looked very close to the successful ones, implying limits on the intrinsic predictability for TC genesis and intensification in moderately sheared and dry environments.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43320920","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: 1

Sub-vortices Within a Numerically Simulated Tornado: The Role of Unstable Vortex Rossby Waves 数值模拟龙卷风中的次涡:不稳定涡罗斯比波的作用

IF 3.1 3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-08-03 DOI: 10.1175/jas-d-22-0237.1

Wei Huang, M. Xue

{"title":"Sub-vortices Within a Numerically Simulated Tornado: The Role of Unstable Vortex Rossby Waves","authors":"Wei Huang, M. Xue","doi":"10.1175/jas-d-22-0237.1","DOIUrl":"https://doi.org/10.1175/jas-d-22-0237.1","url":null,"abstract":"\u0000Multiple sub-vortices corresponding to suction vortices in observations are obtained within a simulated tornado for the EF4 tornado case of Funing, China on June 23, 2016. Within the simulation, the tornado evolves from a one-cell structure with vorticity maximum at its center to a two-cell structure with a ring of vorticity maximum. Five well-defined sub-vortices develop along the ring. The radial profile of tangential wind across the vorticity ring satisfies the necessary condition of barotropic instability associated with phase-locked, counter-propagating vortex Rossby waves (VRWs) along the ring edges. The phased-locked waves revolve around the parent vortex at a speed less than the maximum azimuthal-mean tangential velocity, agreeing with theoretically predicted VRW phase speed. The radii within which the wave activities are confined to are also correctly predicted by the VRW theory where radial group velocity approaches zero. Several other characteristics related to the simulated sub-vortices agree with VRW theories also. The most unstable azimuthal wavenumber depends on the width and the relative magnitude of vorticity of the vortex ring. Their values estimated from the simulation prior to sub-vortex formation correctly predict wavenumber five as the most unstable. The largest contribution to wave kinetic energy is diagnosed to be from the radial shear of azimuthal wind term, consistent with barotropic instability. Vorticity diagnostics show that vertical vorticity stretching is the primary vorticity source for the intensification and maintenance of the simulated sub-vortices.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43066643","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

Simple Analytical Expressions for Steady-State Vapor Growth and Collision-Coalescence Particle Size Distribution Parameter Profiles 稳态蒸气生长和碰撞聚结粒径分布参数剖面的简单解析表达式

IF 3.1 3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-08-01 DOI: 10.1175/jas-d-23-0052.1

E. Dunnavan, A. Ryzhkov

{"title":"Simple Analytical Expressions for Steady-State Vapor Growth and Collision-Coalescence Particle Size Distribution Parameter Profiles","authors":"E. Dunnavan, A. Ryzhkov","doi":"10.1175/jas-d-23-0052.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0052.1","url":null,"abstract":"\u0000This study derives simple analytical expressions for the theoretical height profiles of particle number concentrations (Nt) and mean volume diameters (Dm) during the steady-state balance of vapor growth and collision-coalescence with sedimentation. These equations are general for both rain and snow gamma size distributions with size-dependent power-law functions that dictate particle fall speeds and masses. For collision-coalescence only, Nt (Dm) decreases (increases) as an exponential function of the radar reflectivity difference between two height layers. For vapor deposition only, Dm increases as a generalized power law of this reflectivity difference. Simultaneous vapor deposition and collision-coalescence under steady-state conditions with conservation of number, mass, and reflectivity fluxes lead to a coupled set of first-order, nonlinear ordinary differential equations for Nt and Dm. The solutions to these coupled equations are generalized power-law functions of height z for Dm(z) and Nt(z) whereby each variable is related to one another with an exponent that is independent of collision-coalescence efficiency. Compared to observed profiles derived from descending in-situ aircraft Lagrangian spiral profiles from the CRYSTAL-FACE field campaign, these analytical solutions can on average capture the height profiles of Nt and Dm within 8% and 4% of observations, respectively. Steady-state model projections of radar retrievals aloft are shown to produce the correct rapid enhancement of surface snowfall compared to the lowest-available radar retrievals from 500 m MSL. Future studies can utilize these equations alongside radar measurements to estimate Nt and Dm below radar tilt elevations and to estimate uncertain microphysical parameters such as collision-coalescence efficiencies.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44359631","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

Masthead 桅顶

IF 3.1 3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-08-01 DOI: 10.1175/jas-808masthead

引用次数: 0

Large-Amplitude Quasi-Stationary Rossby Wave Events in ERA5 and the CESM2: Features, Precursors, and Model Biases in Northern Hemisphere Winter ERA5和CESM2的大振幅准平稳Rossby波事件:北半球冬季的特征、前兆和模式偏差

3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-08-01 DOI: 10.1175/jas-d-22-0042.1

Cuiyi Fei, Rachel H. White

{"title":"Large-Amplitude Quasi-Stationary Rossby Wave Events in ERA5 and the CESM2: Features, Precursors, and Model Biases in Northern Hemisphere Winter","authors":"Cuiyi Fei, Rachel H. White","doi":"10.1175/jas-d-22-0042.1","DOIUrl":"https://doi.org/10.1175/jas-d-22-0042.1","url":null,"abstract":"Abstract High-amplitude quasi-stationary Rossby waves (QSWs) have been connected to extreme weather events. By identifying particularly high-amplitude QSW events (QWEs) over Europe and North America, we study their characteristics in ERA5 data and in ensemble simulations from the CESM2 general circulation model. The CESM2 reproduces the overall statistics of QWEs, with ERA5 results within the ensemble spread. The ensemble spread is large, indicating a strong influence of internal variability. Composites of meridional wind anomalies for QWEs show a phase preference in both ERA5 and CESM2, resembling the climatological wave pattern. This is partly due to the definition of QSWs; with the day-of-year climatological meridional wind removed when identifying QSWs, the phase preference remains, albeit with a weaker signal. Significant tropical Pacific precipitation anomalies are seen 5–15 days before observed QWEs; the location of these anomalies is broadly reproduced in CESM2, but the magnitude is substantially underestimated and the time scale is biased. We find a narrowed and strengthened jet stream over the Pacific at the early stage of European QWEs, which may create enhanced waveguidability; this signal is generally reproduced in the models. Overall, the CESM2 can simulate QWEs; differences between the model ensemble mean and the reanalysis could result from model bias or internal variability, although biases are not reduced in CESM2 simulations forced with observed SSTs.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136167466","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 Mean Wind and Potential Temperature Flux Profiles in Convective Boundary Layers 对流边界层的平均风和位温通量廓线

IF 3.1 3区地球科学

Journal of the Atmospheric Sciences Pub Date : 2023-08-01 DOI: 10.1175/JAS-D-22-0159.1

Luoqin Liu, Srinidhi N. Gadde, R. Stevens

{"title":"The Mean Wind and Potential Temperature Flux Profiles in Convective Boundary Layers","authors":"Luoqin Liu, Srinidhi N. Gadde, R. Stevens","doi":"10.1175/JAS-D-22-0159.1","DOIUrl":"https://doi.org/10.1175/JAS-D-22-0159.1","url":null,"abstract":"\u0000We develop innovative analytical expressions for the mean wind and potential temperature flux profiles in convective boundary layers (CBLs). CBLs are frequently observed during daytime as Earth’s surface is warmed by solar radiation. Therefore, their modeling is relevant for weather forecasting, climate modeling, and wind energy applications. For CBLs in the convective-roll-dominated regime, the mean velocity and potential temperature in the bulk region of the mixed layer are approximately uniform. We propose an analytical expression for the normalized potential temperature flux profile as a function of height, using a perturbation method approach in which we employ the horizontally homogeneous and quasi-stationary characteristics of the surface and inversion layers. The velocity profile in the mixed layer and the entrainment zone is constructed based on insights obtained from the proposed potential temperature flux profile and the convective logarithmic friction law. Combining this with the well-known Monin–Obukhov similarity theory allows us to capture the velocity profile over the entire boundary layer height. The proposed profiles agree excellently with large-eddy simulation results over the range of −L/z0 ∈ [3.6 × 102, 0.7 × 105], where L is the Obukhov length and z0 is the roughness length.","PeriodicalId":17231,"journal":{"name":"Journal of the Atmospheric Sciences","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45060359","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: 1