Download or read book An Observational Study of the Processes of Entrainment and Detrainment of Cumulus Clouds Using in Situ and Airborne Cloud Radar Data written by Yonggang Wang and published by . This book was released on 2012 with total page 213 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation combines aircraft in situ and airborne mm-wave cloud radar measurements to make contributions to one fundamental aspect of the study of cumulus clouds: the effect of turbulent mixing. The objective is to improve the understanding of processes of entrainment and detrainment of cumulus clouds and their impacts on ambient air. The method used is compositing, i.e. the characterization of typical patterns, and their variations, by combining numerous samples, in this case samples of shallow to mediocre cumulus clouds. Clear evidence is produced to prove the existence of horizontal vortex-ring structures commonly observed within the top of cumulus clouds. Significant lateral and vertical entrainment of ambient air into clouds is described. The lateral entrainment occurs through relatively small eddies and the typical lateral mixing length is 10-15% of the cloud diameter, whereas vertical entrainment mainly occurs through a vortex-ring concentration within the upper half of cloud. In the developing stage of cumulus clouds, the cloud-scale vortex-ring circulation at cloud top has a more erosive effect on clouds than laterally-mixing eddies because the former penetrates deeper and thus reduces the buoyancy more effectively than the latter. The detrainment signature of a life cycle of non-precipitating moist convection is described as well. The layer containing orographic cumuli clearly becomes enriched with moist static energy immediately downwind of the cumuli. This enrichment reduces potential instability but increases ambient humidity, which may facilitate successive cumulus growth.
Download or read book An Observational Study of the Role of Cloud Top Entrainment in Cumulus Clouds written by Joey F. Boatman and published by . This book was released on 1981 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scale Dependence of Entrainment mixing Mechanisms in Cumulus Clouds written by and published by . This book was released on 2014 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work empirically examines the dependence of entrainment-mixing mechanisms on the averaging scale in cumulus clouds using in situ aircraft observations during the Routine Atmospheric Radiation Measurement Aerial Facility Clouds with Low Optical Water Depths Optical Radiative Observations (RACORO) field campaign. A new measure of homogeneous mixing degree is defined that can encompass all types of mixing mechanisms. Analysis of the dependence of the homogenous mixing degree on the averaging scale shows that, on average, the homogenous mixing degree decreases with increasing averaging scales, suggesting that apparent mixing mechanisms gradually approach from homogeneous mixing to extreme inhomogeneous mixing with increasing scales. The scale dependence can be well quantified by an exponential function, providing first attempt at developing a scale-dependent parameterization for the entrainment-mixing mechanism. The influences of three factors on the scale dependence are further examined: droplet-free filament properties (size and fraction), microphysical properties (mean volume radius and liquid water content of cloud droplet size distributions adjacent to droplet-free filaments), and relative humidity of entrained dry air. It is found that the decreasing rate of homogeneous mixing degree with increasing averaging scales becomes larger with larger droplet-free filament size and fraction, larger mean volume radius and liquid water content, or higher relative humidity. The results underscore the necessity and possibility of considering averaging scale in representation of entrainment-mixing processes in atmospheric models.
Download or read book A Quantitative Investigation of Entrainment and Detrainment in Numerically Simulated Convective Clouds Pt 1 written by Charles Cohen and published by BiblioGov. This book was released on 2013-08 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: A method is developed which uses numerical tracers to make accurate diagnoses of entraimnent and detrainment rates and of the properties of the entrained and detrained air in numerically simulated clouds. The numerical advection scheme is modified to make it nondispersive, as required by the use of the tracers. Tests of the new method are made, and an appropriate definition of clouds is selected. Distributions of mixing fractions in the model consistently show maximums at the end points, for nearly undilute environmental air or nearly undilute cloud air, with a uniform distribution between. The cumulonimbus clouds simulated here entrain air that had been substantially changed by the clouds, and detrained air that is not necessarily representative of the cloud air at the same level.
Download or read book Studies Of Cloud Convection And Precipitation Processes Using Satellite Observations written by William B Rossow and published by World Scientific. This book was released on 2022-10-26 with total page 333 pages. Available in PDF, EPUB and Kindle. Book excerpt: Clouds, convection and precipitation processes are central components of Earth's weather and climate. They are produced by atmospheric motions across a very wide range of space-time scales from local weather to long-term global climate variation. They feedback on these motions by perturbing the heating/cooling that drive the atmospheric circulation. These processes also perturb the oceanic circulation and land surface properties that affect the atmospheric circulation.Because of the coupling of the atmosphere-ocean-land system across all scales by cloud, convection and precipitation processes, studying their behaviors requires measurements in space-time variations across all these scales simultaneously. Satellite constellations with global coverage and high time resolution offer the ideal platforms for such observations. This book summarizes some of the latest research using combinations of various satellite observations to study these processes and to evaluate their representations in global weather and climate models.Included with this publication are downloadable electronic slides and accompanying notes of each lecture for students, teachers, and public speakers around the world to be better able to understand cloud, convection and precipitation processes.
Download or read book An Observational Study of Entrainment Rate in Deep Convection written by and published by . This book was released on 2015 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study estimates entrainment rate and investigates its relationships with cloud properties in 156 deep convective clouds based on in-situ aircraft observations during the TOGA-COARE (Tropical Ocean Global Atmosphere Coupled Ocean Atmosphere Response Experiment) field campaign over the western Pacific. To the authors' knowledge, this is the first study on the probability density function of entrainment rate, the relationships between entrainment rate and cloud microphysics, and the effects of dry air sources on the calculated entrainment rate in deep convection from an observational perspective. Results show that the probability density function of entrainment rate can be well fitted by lognormal, gamma or Weibull distribution, with coefficients of determination being 0.82, 0.85 and 0.80, respectively. Entrainment tends to reduce temperature, water vapor content and moist static energy in cloud due to evaporative cooling and dilution. Inspection of the relationships between entrainment rate and microphysical properties reveals a negative correlation between volume-mean radius and entrainment rate, suggesting the potential dominance of homogeneous mechanism in the clouds examined. The entrainment rate and environmental water vapor content show similar tendencies of variation with the distance of the assumed environmental air to the cloud edges. Their variation tendencies are non-monotonic due to the relatively short distance between adjacent clouds.
Download or read book Cumulus Dynamics written by Chao Jih-Ping and published by . This book was released on 1969 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Summary of Studies of Cumulus Clouds written by University of Chicago. Cloud Physics Laboratory and published by . This book was released on 1957 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Observational Studies of the Microphysics and Dynamics of Warm Cumulus Clouds written by Jennifer D. Small and published by . This book was released on 2009 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aerosol cloud precipitation Interaction in Ultraclean Layers and Optically Thin Veil Cloud System in the Stratocumulus to Cumulus Transition written by Kuan-Ting O and published by . This book was released on 2019 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent observational studies have shown that ultraclean layers (UCLs) and optically thin veil clouds associated with precipitating deep cumulus are common features of the marine boundary layer in the stratocumulus to cumulus transition. The very low number concentration of cloud droplet and cloud condensation nuclei in UCLs, strong precipitation in the associated cumulus, together with the low optical thickness of optically thin veil clouds, make such a system particularly appealing for the study of aerosol-cloud-precipitation interactions. More importantly, low cloud radiative properties biases (i.e., too few, too bright low cloud bias) in the current generation of global climate models (GCMs) seems strongly associated with the uncertainty in representing optically thin veil clouds, and these clouds may serve as an important constraint on the too few, too bright problem. However, systematic investigation of (1) global contribution and seasonal variability of optically thin veil clouds and (2) aerosol-cloud-precipitation interactions in UCLs and optically thin veil clouds is still lacking. We aim to investigate these problems with aircraft remote sensing, satellite measurements and a cloud resolving model. The dissertation is organized into the following three sections: • Using high resolution aircraft remote sensing measurement to characterize optically thin veil clouds in the stratocumulus to cumulus transition (SCT): Aircraft remote sensing measurements (i.e., lidar and radar) taken abroad NSF/NCAR GV-HIAPER research flights flown during the Cloud System Evolution in the Trades field campaign (CSET) sampled marine air masses between Sacramento, California (38.68N, 121.58W), and Kona (19.68N, 156.08W) are used in our study. Optically thin veil clouds, defined as the subset of low clouds with cloud bases > 1 km that do not fully attenuate high-spectral-resolution lidar signal (HSRL) (i.e., indicating optical depths 3), comprise considerable cover of low clouds (~ 40 %) over the SCT. It is found that optically thin veil clouds are also geometrically thin with cloud thickness ~ 200 m, and commonly reside in the upper boundary layer with average cloud base 1.5 km. • Investigating deeper, precipitating PBLs associated with optically thin veil clouds in the Sc-Cu Transition using spaceborne satellite measurements: Variability and vertical structure of optically thin veil clouds over SCT regions around the globe are investigated using both passive and active satellite observations. These observations reveal pronounced relationships between optically thin veil clouds, strong precipitation, deep planetary boundary layer (PBL) height and low cloud droplet number concentration (CDNC). The results are in agreement with the hypothesis that the low optical thickness of veil clouds over the SCT is contingent on the low CDNC caused by strong precipitation scavenging occurring in active cumuli, a process whose efficiency is strongly dependent on maximum condensate amount in updrafts and thus is highly constrained by PBL height. • Exploring aerosol-cloud-precipitation processes in UCLs and optically thin veil clouds system using a cloud resolving model: Characteristics of UCLs and optically thin veil clouds are investigated in the cloud resolving model (CRM). The domain mean cloud and aerosol properties in UCLs and optically thin veil clouds from CRM simulations agree with recent observational studies in general. The simulation results show that the detrainment from active precipitating cumulus produces the stratiform veil clouds, which are strongly depleted in particle concentration due to very efficient coalescence-scavenging process in ascending parcels passing through cumulus towers. The simulation shows a median CDNC in thin veil clouds of 5.8 cm−3, implying that majority of thin veil clouds are UCLs as well and confirming the strong connection between veil clouds and UCLs. In addition, there is a strong correlation between surface precipitation and the fraction of low clouds that are UCLs, and such correlation implies the importance of precipitation scavenging for the formation of UCLs. A cloud resolving model coupled with a prognostic aerosol scheme is used in our study, enabling characterization of the spatiotemporal variability of aerosol in the boundary layer. The results show that depletion of aerosol concentration starts first in the upper boundary layer that is associated with in-cloud coalescence scavenging process. The evaporation of veil clouds leaves very low CCN number concentration (Na
Download or read book METEOROLOGY OF CLOUDS written by L.L. Downing and published by Author House. This book was released on 2013 with total page 159 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This publication is a presentation of cloud meteorology as experienced by a seasoned Aviation Meteorologist. It contains a comprehensive discussion of Cloud Meteorology, presenting explanations of cloud formation, cloud types and cloud dynamics, the atmospheric forces internal and external to cloud existence. It discusses the earths' atmospheric-chaotic-nature and it's impact on clouds and cloud systems. Clouds are visual indicators of the atmospheres' dynamics and related weather phenomena, and, to some extent, predictors of coming weather conditions. Clouds are beautiful icons of nature and at the same time, complicated creatures studied by meteorology. It is the authors' purpose to present the subject in a fashion comprehensible to both practicing meteorologist's, and also the weather-neophyte. This material requires no more than an avid interest in CLOUDS, and a grasp of the American language, to acquire much insight into the wonders of our cloud-form nuturing atmosphere."
Download or read book On the Maximum Vertical Extent of Convective Clouds written by Charles L. Jordan and published by . This book was released on 1962 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: An attempt is made to examine the credibility and explore the implications of the reports of convective clouds to extreme heights which have been indicated by radar in recent years. The extreme cases have not been verified by independent observations and it is shown that inherent limitations in radar observations of convective cloud heights are such as to raise serious doubts in regard to the accuracy of many of the extreme echo heights which have been reported. (Author).
Download or read book Atmospheric Turbulence in and Near Cumulonimbus Clouds written by V. S. Aleksandrov and published by . This book was released on 1969 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: A summary is made of the modern theories concerning eddies in a Cb zone. Data concerning the structure of the turbulent zones inside and in the vicinity of Cb clouds are given according to the materials of special flight studies, as are the energy spectra of the vertical turbulent gusts of wind inside, below, and above the Cb clouds. The statistical characteristics of the disturbed motion of an aircraft in turbulent zones linked with Cb clouds are investigated.
Download or read book Mixed Phase Clouds written by Constantin Andronache and published by Elsevier. This book was released on 2017-09-28 with total page 302 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mixed-Phase Clouds: Observations and Modeling presents advanced research topics on mixed-phase clouds. As the societal impacts of extreme weather and its forecasting grow, there is a continuous need to refine atmospheric observations, techniques and numerical models. Understanding the role of clouds in the atmosphere is increasingly vital for current applications, such as prediction and prevention of aircraft icing, weather modification, and the assessment of the effects of cloud phase partition in climate models. This book provides the essential information needed to address these problems with a focus on current observations, simulations and applications. Provides in-depth knowledge and simulation of mixed-phase clouds over many regions of Earth, explaining their role in weather and climate Features current research examples and case studies, including those on advanced research methods from authors with experience in both academia and the industry Discusses the latest advances in this subject area, providing the reader with access to best practices for remote sensing and numerical modeling
Download or read book Mixed phase Cloud Microphysics Over Mountainous Terrain Emphasizing Airborne Dual wavelength Retrieval Approach written by Coltin Dale Grasmick and published by . This book was released on 2021 with total page 151 pages. Available in PDF, EPUB and Kindle. Book excerpt: Kelvin-Helmholtz (KH) waves are common in deep stratiform precipitation systems associated with frontal disturbances, especially in the vicinity of complex terrain, as is evident from transects of vertical velocity and 2D circulation, obtained from a 3-mm airborne Doppler radar, the Wyoming Cloud Radar. These waves are observed in a variety of wavelengths, depths, amplitudes, and turbulence intensities. Complex terrain may locally enhance wind shear which reduces the Richardson number and leads to KH instability. KH waves are frequently locked to the terrain, and occur at various heights, including within the free troposphere, at the boundary layer top, and close to the surface. They are observed not only upwind of terrain barriers, as has been documented before, but also in the wake of steep terrain, where the waves can be highly turbulent. KH waves are a source of turbulence in stratiform precipitation systems over mountainous terrain. They introduce large eddies into otherwise laminar flow, with updrafts and downdrafts breaking down into small-scale turbulence. When they occur in-cloud, such dynamics influence microphysical processes that impact precipitation growth and fallout. Measurements within KH wave updrafts reveal the production of liquid water in otherwise ice-dominated clouds, which can contribute to snow generation or enhancement via depositional and accretional growth. Fallstreaks beneath KH waves contain higher ice water content, composed of larger and more numerous ice particles, suggesting that KH waves and associated turbulence may also increase ice nucleation. A Large-Eddy Simulation (LES), designed to model the microphysical response to the KH wave eddies in mixed phase cloud, shows that depositional and accretional growth can be enhanced in KH waves, resulting in more precipitation when compared to a baseline simulation.Properties of frozen hydrometeors in clouds remain difficult to remotely sense. Estimates of number concentration, distribution shape, ice particle density, and ice water content are essential for connecting cloud processes to surface precipitation. Researching the microphysical effects of dynamic features like KH waves heavily relies on in situ measurements on an aircraft or at the surface but these observations substantially under-sample the cloud and miss the effects of the KH waves. Progress has been made with dual-frequency radars, but validation has been difficult because of a lack of cloud microphysical observations collocated with the radar measurements Here, data are used from two airborne profiling (up & down) radars, the W-band Wyoming Cloud Radar and the Ka-band Profiling Radar, allowing for Ka-W-band Dual-Wavelength Ratio (DWR) profiles. The aircraft (the University of Wyoming King Air) also carried a suite of in situ cloud and precipitation probes. This arrangement is optimal for relating the “flight-level” DWR (an average from radar gates below and above flight level) to ice particle size distributions measured by in situ optical array probes, as well as bulk properties such as minimum snow particle density and ice water content. This comparison reveals a strong relationship between DWR and the ice particle median volume diameter. The DWR-defined size distribution shape is used with a Mie scattering model and an experimental mass-diameter relationship to estimate ice particle concentration and ice water content. Comparison with flight-level cloud-probe data indicate good performance, allowing microphysical interpretations for vertical radar transects.
Download or read book A First Course in Turbulence written by Henk Tennekes and published by MIT Press. This book was released on 2018-04-27 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the first book specifically designed to offer the student a smooth transitionary course between elementary fluid dynamics (which gives only last-minute attention to turbulence) and the professional literature on turbulent flow, where an advanced viewpoint is assumed. The subject of turbulence, the most forbidding in fluid dynamics, has usually proved treacherous to the beginner, caught in the whirls and eddies of its nonlinearities and statistical imponderables. This is the first book specifically designed to offer the student a smooth transitionary course between elementary fluid dynamics (which gives only last-minute attention to turbulence) and the professional literature on turbulent flow, where an advanced viewpoint is assumed. Moreover, the text has been developed for students, engineers, and scientists with different technical backgrounds and interests. Almost all flows, natural and man-made, are turbulent. Thus the subject is the concern of geophysical and environmental scientists (in dealing with atmospheric jet streams, ocean currents, and the flow of rivers, for example), of astrophysicists (in studying the photospheres of the sun and stars or mapping gaseous nebulae), and of engineers (in calculating pipe flows, jets, or wakes). Many such examples are discussed in the book. The approach taken avoids the difficulties of advanced mathematical development on the one side and the morass of experimental detail and empirical data on the other. As a result of following its midstream course, the text gives the student a physical understanding of the subject and deepens his intuitive insight into those problems that cannot now be rigorously solved. In particular, dimensional analysis is used extensively in dealing with those problems whose exact solution is mathematically elusive. Dimensional reasoning, scale arguments, and similarity rules are introduced at the beginning and are applied throughout. A discussion of Reynolds stress and the kinetic theory of gases provides the contrast needed to put mixing-length theory into proper perspective: the authors present a thorough comparison between the mixing-length models and dimensional analysis of shear flows. This is followed by an extensive treatment of vorticity dynamics, including vortex stretching and vorticity budgets. Two chapters are devoted to boundary-free shear flows and well-bounded turbulent shear flows. The examples presented include wakes, jets, shear layers, thermal plumes, atmospheric boundary layers, pipe and channel flow, and boundary layers in pressure gradients. The spatial structure of turbulent flow has been the subject of analysis in the book up to this point, at which a compact but thorough introduction to statistical methods is given. This prepares the reader to understand the stochastic and spectral structure of turbulence. The remainder of the book consists of applications of the statistical approach to the study of turbulent transport (including diffusion and mixing) and turbulent spectra.
Download or read book Physical Processes in Clouds and Cloud Modeling written by Alexander P. Khain and published by Cambridge University Press. This book was released on 2018-07-05 with total page 643 pages. Available in PDF, EPUB and Kindle. Book excerpt: Provides a comprehensive analysis of modern theories of cloud microphysical processes and their representation in numerical cloud models.
