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

A comprehensive analysis of uncertainties in warm rain parameterizations in climate models based on in situ measurements 基于现场测量结果的气候模型暖雨参数化不确定性综合分析

Journal of the Atmospheric Sciences Pub Date : 2024-05-13 DOI: 10.1175/jas-d-23-0198.1

Zhibo Zhang, D. Mechem, J. C. Chiu, J. Covert

{"title":"A comprehensive analysis of uncertainties in warm rain parameterizations in climate models based on in situ measurements","authors":"Zhibo Zhang, D. Mechem, J. C. Chiu, J. Covert","doi":"10.1175/jas-d-23-0198.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0198.1","url":null,"abstract":"\u0000Because of the coarse grid size of Earth system models (ESM), representing warm-rain processes in ESMs is a challenging task involving multiple sources of uncertainty. Previous studies evaluated warm-rain parameterizations mainly according to their performance in emulating collision-coalescence rates for local droplet populations over a short period of a few seconds. The representativeness of these local process rates comes into question when applied in ESMs for grid sizes on the order of 100 kilometers and time steps on the order of 20-30 minutes. We evaluate several widely used warm-rain parameterizations in ESM application scenarios. In the comparison of local and instantaneous autoconversion rates, the two parameterization schemes based on numerical fitting to stochastic collection equation (SCE) results perform best. However, because of Jessen’s inequality, their performance deteriorates when grid-mean, instead of locally-resolved, cloud properties are used in their simulations. In contrast, the effect of Jessen’s inequality partly cancels the overestimation problem of two semi-analytical schemes, leading to an improvement in the ESM-like comparison. In the assessment of uncertainty due to the large time step of ESMs, it is found that the rain-water tendency simulated by the SCE is roughly linear for time steps smaller than 10 minutes, but the nonlinearity effect becomes significant for larger time steps, leading to errors up to a factor of 4 for a time step of 20 minutes. After considering all uncertainties, the grid-mean and time-averaged rain-water tendency based on the parameterization schemes are mostly within a factor of 4 of the local benchmark results simulated by SCE.","PeriodicalId":508177,"journal":{"name":"Journal of the Atmospheric Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140983686","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Kelvin Helmholtz Instability “Tube” and “Knot” Dynamics, Part III: Extension of Elevated Turbulence and Energy Dissipation into Increasingly Viscous Flows 开尔文亥姆霍兹不稳定性 "管 "和 "结 "动力学，第三部分：将升高湍流和能量消耗扩展到粘性增加的流动中

Journal of the Atmospheric Sciences Pub Date : 2024-05-06 DOI: 10.1175/jas-d-23-0085.1

D. Fritts, Ling Wang, Thomas S. Lund, Marvin A. Geller

{"title":"Kelvin Helmholtz Instability “Tube” and “Knot” Dynamics, Part III: Extension of Elevated Turbulence and Energy Dissipation into Increasingly Viscous Flows","authors":"D. Fritts, Ling Wang, Thomas S. Lund, Marvin A. Geller","doi":"10.1175/jas-d-23-0085.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0085.1","url":null,"abstract":"\u0000A companion paper by Fritts et al. (2023) reviews extensive evidence for Kelvin-Helmholtz instability (KHI) “tube” and “knot” (T&K) dynamics at multiple altitudes in the atmosphere and in the oceans that reveal these dynamics to be widespread. A second companion paper by Fritts and Wang (2023) reveals KHI T&K events at larger and smaller scales to arise on multiple highly-stratified sheets in a direct numerical simulation (DNS) of idealized, multi-scale gravity wave – fine structure interactions. These studies reveal the diverse environments in which KHI T&K dynamics arise and suggest their potentially ubiquitous occurrence throughout the atmosphere and oceans. This paper describes DNS of multiple KHI evolutions in wide and narrow domains enabling and excluding T&K dynamics. These DNS employ common initial conditions, but are performed for decreasing Reynolds numbers, Re, to explore whether T&K dynamics enable enhanced KHI-induced turbulence where it would be weaker or not otherwise occur. The major results are that KHI T&K dynamics extend elevated turbulence intensities and energy dissipation rates, ε, to smaller Re. We expect these results to have important implications for improving parameterizations of KHI-induced turbulence in the atmosphere and oceans.","PeriodicalId":508177,"journal":{"name":"Journal of the Atmospheric Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141009568","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Reinterpretation of the Thorpe Length Scale 重新解释索普长度标尺

Journal of the Atmospheric Sciences Pub Date : 2024-05-02 DOI: 10.1175/jas-d-23-0137.1

Lakshmi Kantha

{"title":"Reinterpretation of the Thorpe Length Scale","authors":"Lakshmi Kantha","doi":"10.1175/jas-d-23-0137.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0137.1","url":null,"abstract":"\u0000In 1977, S. A. Thorpe proposed a method to estimate the dissipation rate ε of turbulence kinetic energy (TKE) in an overturning turbulent layer in a lake, by sorting the observed (unstable) density profile to render it stable and thus deriving a length scale LT named after him, from the resulting vertical displacements of water parcels. By further proposing that this purely empirical scale (with no a priori physical basis, unlike many other turbulence length scales) is proportional to the Ozmidov scale LO, definable only for stably (not unstably or neutrally) stratified flows, he was able to extract ε. The simplicity of the approach that requires nothing but CTD (Conductivity, Temperature and Depth) casts in water bodies, including lakes and oceans, made it attractive, until microstructure profilers were developed and perfected in later decades to actually make in-situ measurements of ε. Since equivalent microstructure devices are not available for the atmosphere, Thorpe technique has been resurrected in recent years for application to the atmosphere, using potential temperature profiles obtained from high vertical resolution radiosondes. Its popularity and utility have increased lately, in spite of unresolved issues related to the validity of assuming LT is proportional to LO. In this study, we touch upon these issues and offer an alternative interpretation of the Thorpe length scale as indicative of the turbulence velocity scale σK, which allows Thorpe sorting technique to be applied to all turbulent flows, including those generated by convection.","PeriodicalId":508177,"journal":{"name":"Journal of the Atmospheric Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141020292","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Effect of Turbulence on the Collision Rate between Settling Ice Crystals and Droplets 湍流对沉降冰晶和水滴碰撞率的影响

Journal of the Atmospheric Sciences Pub Date : 2024-05-01 DOI: 10.1175/jas-d-23-0119.1

M. Z. Sheikh, K. Gustavsson, E. Lévêque, B. Mehlig, A. Pumir, A. Naso

{"title":"Effect of Turbulence on the Collision Rate between Settling Ice Crystals and Droplets","authors":"M. Z. Sheikh, K. Gustavsson, E. Lévêque, B. Mehlig, A. Pumir, A. Naso","doi":"10.1175/jas-d-23-0119.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0119.1","url":null,"abstract":"\u0000In mixed-phase clouds, graupel forms by riming, a process whereby ice crystals and supercooled water droplets settling through a turbulent flow collide and aggregate. We consider here the early stage of the collision process of small ice crystals with water droplets and determine numerically the geometric collision kernel in turbulent flows (therefore neglecting all interactions between the particles and assuming a collision efficiency equal to unity), over a range of energy dissipation rate 1–250 cm2 s−3 relevant to cloud microphysics. We take into account the effect of small, but nonzero fluid inertia, which is essential since it favors a biased orientation of the crystals with their broad side down. Since water droplets and ice crystals have different masses and shapes, they generally settle with different velocities. Turbulence does not play any significant role on the collision kernel when the difference between the settling velocities of the two sets of particles is larger than a few millimeters per second. The situation is completely different when the settling speeds of droplets and crystals are comparable, in which case turbulence is the main cause of collisions. Our results are compatible with those of recent experiments according to which turbulence does not clearly increase the growth rate of tethered graupel in a flow transporting water droplets.","PeriodicalId":508177,"journal":{"name":"Journal of the Atmospheric Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141023923","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Toward Building a Virtual Laboratory to Investigate Rainfall Microphysics at Process Scales 建立虚拟实验室，研究过程尺度上的降雨微物理学

Journal of the Atmospheric Sciences Pub Date : 2024-03-28 DOI: 10.1175/jas-d-23-0121.1

Lihui Ji, Ana P. Barros

{"title":"Toward Building a Virtual Laboratory to Investigate Rainfall Microphysics at Process Scales","authors":"Lihui Ji, Ana P. Barros","doi":"10.1175/jas-d-23-0121.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0121.1","url":null,"abstract":"\u0000A 3D numerical model was built to serve as a virtual microphysics laboratory (VML) to investigate rainfall microphysical processes. One key goal for the VML is to elucidate the physical basis of warm precipitation processes toward improving existing parameterizations beyond the constraints of past physical experiments. This manuscript presents results from VML simulations of classical tower experiments of raindrop collisional collection and breakup. The simulations capture large raindrop oscillations in shape and velocity in both horizontal and vertical planes and reveal that drop instability increases with diameter due to the weakening of the surface tension compared to the body force. Detailed evaluation against reference experimental data sets of binary collisions over a wide range of drop sizes shows that the VML reproduces collision outcomes well including coalescence, and disk, sheet, and filament breakups. Furthermore, the VML simulations captured spontaneous breakup, and secondary coalescence and breakup. The breakup type, fragment number, and size distribution are analyzed in the context of collision kinetic energy, diameter ratio, and relative position, with a view to capture the dynamic evolution of the vertical microstructure of rainfall in models and to interpret remote-sensing measurements.","PeriodicalId":508177,"journal":{"name":"Journal of the Atmospheric Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140369740","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Characteristics of Generating Cells in Wintertime Orographic Clouds 冬季睛云中发电单元的特征

Journal of the Atmospheric Sciences Pub Date : 2024-02-28 DOI: 10.1175/jas-d-23-0029.1

S. Tessendorf, Kyoko Ikeda, Roy M. Rasmussen, Jeffrey R. French, R. Rauber, Alexei Korolev, L. Xue, D. Blestrud, Nicholas Dawson, Melinda Meadows, M. Kunkel, S. Parkinson

{"title":"Characteristics of Generating Cells in Wintertime Orographic Clouds","authors":"S. Tessendorf, Kyoko Ikeda, Roy M. Rasmussen, Jeffrey R. French, R. Rauber, Alexei Korolev, L. Xue, D. Blestrud, Nicholas Dawson, Melinda Meadows, M. Kunkel, S. Parkinson","doi":"10.1175/jas-d-23-0029.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0029.1","url":null,"abstract":"\u0000During the Seeded and Natural Orographic Wintertime clouds: the Idaho Experiment (SNOWIE) field campaign, cloud-top generating cells were frequently observed in the very high-resolution W-band airborne cloud radar data. This study examines multiple flight segments from three SNOWIE cases that exhibited cloud-top generating cells structures, focusing on the in-situ measurements inside and outside these cells to characterize the microphysics of these cells. The observed generating cells in these three cases occurred in cloud tops of −15 to −30 °C, with and without overlying cloud layers, but always with shallow layers of atmospheric instability observed at cloud top. The results also indicate that liquid water content, vertical velocity, and drizzle and ice crystal concentrations are greater inside the generating cells compared to the adjacent portions of the cloud. The generating cells were predominantly < 500 m in horizontal width and frequently exhibited drizzle drops coexisting with ice. The particle imagery indicates that ice particle habits included plates, columns, and rimed and irregular crystals, likely formed via primary ice nucleation mechanisms. Understanding the sources of natural ice formation is important to understanding precipitation formation in winter orographic clouds, and is especially relevant for clouds that may be targeted for glaciogenic cloud seeding as well as to improve model representation of these clouds.","PeriodicalId":508177,"journal":{"name":"Journal of the Atmospheric Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140421759","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

The Energetics of the Lagrangian Evolution of Tropical Convective Systems 热带对流系统的拉格朗日演化能量学

Journal of the Atmospheric Sciences Pub Date : 2024-02-28 DOI: 10.1175/jas-d-23-0141.1

H. Masunaga, Hanii Takahashi

{"title":"The Energetics of the Lagrangian Evolution of Tropical Convective Systems","authors":"H. Masunaga, Hanii Takahashi","doi":"10.1175/jas-d-23-0141.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0141.1","url":null,"abstract":"\u0000Convective lifecycle is often conceptualized to progress from congestus to deep convection and develop further to stratiform anvil clouds, accompanied by a systematic change in the vertical structure of vertical motion. This archetype scenario has been developed largely from the Eulerian viewpoint, and has yet to be explored whether or not the same lifecycle emerges itself in a moving system tracked in the Lagrangian manner. To address this question, Lagrangian tracking is applied to tropical convective systems in combination with a thermodynamic budget analysis forced by satellite-retrieved precipitation and radiation. A new method is devised to characterize the vertical motion profiles in terms of the column import or export of moisture and moist static energy (MSE). The Bottom-heavy, Mid-heavy, and Top-heavy regimes are identified for every one-square-degree grid pixel accompanying tracked precipitation systems, making use of the diagnosed column export/import of moisture and MSE. Major findings are as follows. The Lagrangian evolution of convective systems is dominated by a state of dynamic equilibrium among different convective regimes rather than a monotonic progress from one regime to the next. The transition from the Bottom-heavy to Mid-heavy regimes is fed with intensifying precipitation presumably owing to a negative gross moist stability (GMS) of the Bottom-heavy regime, whereas the transition from the Mid-heavy to Top-heavy regimes dissipates the system. The Bottom-heavy to Mid-heavy transition takes a relaxation time of about 5 h in the equilibrating processes, whereas the relaxation time is estimated as roughly 20 h concerning the Mid-heavy to Top-heavy transition.","PeriodicalId":508177,"journal":{"name":"Journal of the Atmospheric Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140418747","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

A parametrization scheme accounting for non-hydrostatic effects on the momentum flux of vertically-propagating orographic gravity waves: Formulae and preliminary tests in the Model for Prediction Across Scales (MPAS) 考虑到垂直传播的地心引力波动量通量的非静水效应的参数化方案：跨尺度预测模型（MPAS）中的公式和初步测试

Journal of the Atmospheric Sciences Pub Date : 2024-02-26 DOI: 10.1175/jas-d-23-0020.1

Xin Xu, Rongrong Zhang, Miguel A. C. Teixeira, Annelize van Niekerk, Ming Xue, Yixiong Lu, Haile Xue, Runqiu Li, Yuan Wang

{"title":"A parametrization scheme accounting for non-hydrostatic effects on the momentum flux of vertically-propagating orographic gravity waves: Formulae and preliminary tests in the Model for Prediction Across Scales (MPAS)","authors":"Xin Xu, Rongrong Zhang, Miguel A. C. Teixeira, Annelize van Niekerk, Ming Xue, Yixiong Lu, Haile Xue, Runqiu Li, Yuan Wang","doi":"10.1175/jas-d-23-0020.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0020.1","url":null,"abstract":"\u0000The momentum transport by orographic gravity waves (OGWs) plays an important role in driving the large-scale circulation throughout the atmosphere and is subject to parameterization in numerical models. Current parameterization schemes, which were originally developed for coarse-resolution models, commonly assume that unresolved OGWs are hydrostatic. With the increase in the horizontal resolution of state-of-the-art numerical models, unresolved OGWs are of smaller horizontal scale and more influenced by nonhydrostatic effects (NHE), thus challenging use of the hydrostatic assumption. Based on the analytical formulae for nonhydrostatic OGWs derived in our recent study, the orographic gravity wave drag (OGWD) parameterization scheme in the Model for Prediction Across Scales is revised by accounting for NHE. Global simulations with 30-km horizontal resolution are conducted to investigate NHE on the momentum transport of OGWs and their impacts on the large-scale circulation in boreal winter. NHE are evident in regions of complex terrain such as the Tibetan Plateau, Rocky Mountains, Southern Andes and Eastern Antarctica. The parameterized surface wave momentum flux can be either reduced or enhanced depending on the relative importance of NHE and model physics-dynamics interactions. The NHE corrections to the OGWD scheme significantly reduce the easterly biases in the polar stratosphere of the Northern Hemisphere, due to both weakened OGWD in the upper troposphere and lower stratosphere and suppressed upward propagation of resolved waves into the stratosphere. However, the revised OGWD scheme only has a weak influence on the large-scale circulation in the Southern Hemisphere during boreal winter.","PeriodicalId":508177,"journal":{"name":"Journal of the Atmospheric Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140428161","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

The stochastic spin-up of vorticity in spontaneous tropical cyclogenesis 自发热带气旋生成过程中涡度的随机旋升

Journal of the Atmospheric Sciences Pub Date : 2024-02-19 DOI: 10.1175/jas-d-23-0186.1

Hao Fu, Morgan O’Neill

{"title":"The stochastic spin-up of vorticity in spontaneous tropical cyclogenesis","authors":"Hao Fu, Morgan O’Neill","doi":"10.1175/jas-d-23-0186.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0186.1","url":null,"abstract":"\u0000Cloud-permitting simulations have shown that tropical cyclones (TCs) can form spontaneously in a quiescent environment with uniform sea surface temperature. While several mesoscale feedbacks are known to amplify an existing midlevel vortex, how the noisy deep convection produces the initial midlevel vortex remains unclear. This paper develops a theoretical framework to understand the evolution of the midlevel mesoscale vorticity’s histogram in the first two days of spontaneous tropical cyclogenesis, which we call the “stochastic spin-up stage”. The mesoscale vorticity is produced by two random processes related to deep convection: the random stretching of planetary vorticity (f) and the tilting of random vertical shear. The mesoscale vorticity is modeled as the sum of three independent normal distributions, which include the cyclones produced by stretching, cyclones produced by tilting, and anticyclones produced by tilting. Their collective effect is calculated with the central limit theorem. The theory predicts that the standard deviation of the midlevel mesoscale vorticity is universally proportional to the square root of the domain-averaged accumulated rainfall, agreeing with simulations. The theory predicts a critical latitude below which tilting is dominant in producing mesoscale vorticity. Treating the magnitude of random vertical shear as a fitting parameter, the critical latitude is shown to be around 12°N. Because the magnitude of vertical shear should be larger in the real atmosphere, this result suggests tilting is an important source of mesoscale vorticity fluctuation in the tropics.","PeriodicalId":508177,"journal":{"name":"Journal of the Atmospheric Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140450962","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

An Approximate Criterion for Morphological Transformations in Small Vapor Grown Ice Crystals 小型蒸汽生长冰晶体形态变化的近似标准

Journal of the Atmospheric Sciences Pub Date : 2024-02-01 DOI: 10.1175/jas-d-23-0131.1

J. Y. Harrington, G. Pokrifka

{"title":"An Approximate Criterion for Morphological Transformations in Small Vapor Grown Ice Crystals","authors":"J. Y. Harrington, G. Pokrifka","doi":"10.1175/jas-d-23-0131.1","DOIUrl":"https://doi.org/10.1175/jas-d-23-0131.1","url":null,"abstract":"\u0000Observations and measurements show that crystals remain relatively compact at low ice supersaturations, but become increasingly hollowed and complex as the ice supersaturation rises. Prior measurements at temperatures >−25°C indicate that the transition from compact, solid ice to morphologically complex crystals occurs when the excess vapor density exceeds a threshold value of about 0.05 g m−3. A comparable threshold is not available at low temperatures. A temperature-dependent criterion for the excess vapor density threshold (Δρthr) that defines morphological transformations to complex ice is derived from laboratory measurements of vapor grown ice at temperatures below −40°C. This criterion depends on the difference between the equilibrium vapor density of liquid () and ice (ρei) multiplied by a measurement-determined constant, . The new criterion is consistent with prior laboratory measurements, theoretical estimates, and it reproduces the classical result of about 0.05 g m−3 above −25°C. Since Δρthr defines the excess vapor density above which crystals transition to a morphologically complex (lower density) growth mode, we can estimate the critical supersaturation (scrit) for step nucleation during vapor growth. The derived values of scrit are consistent with previous measurements at temperatures above −20°C. No direct measurements of scrit are available for temperatures below −40°C; however, our derived values suggest some measurement-based estimates may be too high while estimates from molecular dynamics simulations may be too low.","PeriodicalId":508177,"journal":{"name":"Journal of the Atmospheric Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139686278","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0