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Stratocumulus Topped Boundary Layers Over Coastal Land
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Book Synopsis Stratocumulus-Topped Boundary Layers Over Coastal Land by : Mohamed Sherif Ghonima
Download or read book Stratocumulus-Topped Boundary Layers Over Coastal Land written by Mohamed Sherif Ghonima and published by . This book was released on 2016 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stratocumulus is the most common cloud type and has a strong impact on global climate. Over coastal lands, which are frequently well populated, these clouds have a strong impact on surface temperature and radiation through reflection of incoming solar radiation. The cloud behavior is determined both by small-scale processes such as turbulent mixing between two-phase, two-component, fluids at the cloud top and large-scale circulation such as anticyclones and their climatological occurrence. Due to the large range of spatial scales associated with stratocumulus clouds, global climate models (GCM) and numerical weather prediction models (NWP) parameterize the physical processes occurring in the stratocumulus-topped boundary layer (STBL). However, these models are unable to simulate the clouds accurately. For instance, in the North American Model stratocumulus clouds over the California coast in the summer dissipate earlier than observed via satellite. In this thesis, we first employ high-resolution Large Eddy Simulations (LES) and Mixed Layer Models (MLM) to study mechanisms regulating the timing of the break up. We find that over coastal lands, as the cloud thins during day, turbulence generated by surface fluxes becomes larger than turbulence generated by longwave cooling across the cloud layer. To capture this shift in turbulence generation in the MLM, we extend an existing entrainment parameterization to account for both sources. We find that cloud lifetime depends on a combination of surface moisture content, cloud-top entrainment flux, and large-scale horizontal advection by sea breeze. Next, we evaluate three different planetary boundary layer (PBL) parameterization schemes in the Weather Research and Forecasting (WRF) model in simulating the STBL by benchmarking them against high-resolution LES. We find that the schemes do not take into account the turbulence generated by longwave cooling across the cloud layer and therefore underestimate the mixing of warm-dry tropospheric into the STBL at the cloud top. Thus, we propose a correction to the eddy diffusivity coefficient by adding a term that accounts for turbulence generated throughout the cloud layer as well as at the surface due to buoyancy flux. The modified scheme is then able to simulate the cloud physics similar to that of the LES. The modeling tools developed in this thesis have improved the understanding of and the ability to forecast stratocumulus-topped boundary layers.
Book Synopsis Coastal Stratocumulus-Topped Boundary Layers and the Role of Cloud-Top Entrainment by : Daniel P. Eleuterio
Download or read book Coastal Stratocumulus-Topped Boundary Layers and the Role of Cloud-Top Entrainment written by Daniel P. Eleuterio and published by . This book was released on 2004-06 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ability of the U.S. Navy's Coupled Ocean-Atmosphere Mesoscale Prediction System (COAMPS) (Trademark) to accurately forecast the height and structure of the Marine Boundary Layer (MBL) in the coastal zone is analyzed and compared to surface and aircraft observations from the Dynamics and Evolution of Coastal Stratus (DECS) field study conducted along the central coast of California from June 16 to July 22, 1999. The stratus field was found to have significant mesoscale variability within 100 km of the coast due to interaction between the mean flow and the coastal terrain. This structure is consistent with general hydraulic flow theory and the development of a low-level coastal jet. However, the specific characteristics on any given day were very sensitive to flow direction, inversion height, and synoptic conditions. With some modifications, the model predicted the general evolution of these events with qualitative fidelity, but was slow to dissipate the cloud and frequently produced surface fog versus stratus. A consistent tendency was found in the model's predictions of inversion heights 200-300 meters too low, weak inversion strengths, high integrated liquid water content, and weak buoyancy flux near the cloud top. These observed biases are consistent with underestimating the cloud top entrainment velocity and entrainment fluxes in the modeled boundary layer. An explicit entrainment parameterization was developed to better represent the sub-grid scale processes at cloud top and was tested in the single column and 3D versions of COAMPS. The entrainment parameterization was found to improve the boundary layer height and cloud liquid water content as compared to field observations, but the modeled boundary layer still exhibited a low bias, and the entrainment velocity was higher than is generally expected from field studies for this regime. (2 tables, 53 figures. 80 refs.) ANNOTATION: The Role of Cloud-Top Entrainment in Coastal Stratocumulus-Topped Boundary Layers
Book Synopsis Estimation of Stratocumulus-Topped Boundary Layer Depth Using Sea Surface and Remotely Sensed Cloud-Top Temperatures by : Marvin B. McBride, III
Download or read book Estimation of Stratocumulus-Topped Boundary Layer Depth Using Sea Surface and Remotely Sensed Cloud-Top Temperatures written by Marvin B. McBride, III and published by . This book was released on 2000-06-01 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt: The depth of the marine atmospheric boundary layer (MABL) is an important parameter for both scientific and operational meteorological applications. The depth of the marine boundary layer has a significant influence on the atmospheric dynamics in the coastal zone. Knowledge of the depth of stratocumulus-topped boundary layers (STELs) will enable coastal operations to more accurately anticipate weather, and electromagnetic propagation conditions. This study develops a satellite remote sensing technique for determining the height of MABLs topped with stratocumulus clouds. Validation of the technique using coastal rawinsonde dataset from the Monterey Area Ship Track (MAST) experiment revealed that an assumption of 41% cloud with a moist lapse rate equal to -7.0 deg C/km had the best overall fit to the data. However, for shallow boundary layers with depths below 400m the most accurate assumption was 75% cloud with a moist lapse rate equal to -6.5 deg C/km. The application of this technique to sounding data returned an overall BL depth accuracy of 50m while the satellite application returned an overall accuracy of 65m. A sensitivity analysis of both surface and cloud-top temperature revealed that a 1/2 deg C change in either temperature resulted in an error of 60-70m in boundary layer depth.
Book Synopsis Estimation of Stratocumulus-topped Boundary Layer Depth Using Sea Surface and Remotely Sensed Cloud-top Temperatures by : Marvin B. McBride
Download or read book Estimation of Stratocumulus-topped Boundary Layer Depth Using Sea Surface and Remotely Sensed Cloud-top Temperatures written by Marvin B. McBride and published by . This book was released on 2000 with total page 82 pages. Available in PDF, EPUB and Kindle. Book excerpt: The depth of the marine atmospheric boundary layer (MABL) is an important parameter for both scientific and operational meteorological applications. The depth of the marine boundary layer has a significant influence on the atmospheric dynamics in the coastal zone. Knowledge of the depth of stratocumulus-topped boundary layers (STELs) will enable coastal operations to more accurately anticipate weather, and electromagnetic propagation conditions. This study develops a satellite remote sensing technique for determining the height of MABLs topped with stratocumulus clouds. Validation of the technique using coastal rawinsonde dataset from the Monterey Area Ship Track (MAST) experiment revealed that an assumption of 41% cloud with a moist lapse rate equal to -7.0 deg C/km had the best overall fit to the data. However, for shallow boundary layers with depths below 400m the most accurate assumption was 75% cloud with a moist lapse rate equal to -6.5 deg C/km. The application of this technique to sounding data returned an overall BL depth accuracy of 50m while the satellite application returned an overall accuracy of 65m. A sensitivity analysis of both surface and cloud-top temperature revealed that a 1/2 deg C change in either temperature resulted in an error of 60-70m in boundary layer depth.
Book Synopsis Estimation of Stratocumulus-Topped Boundary Layer Depth Using Sea Surface and Remotely Sensed Cloud-Top Temperatures by :
Download or read book Estimation of Stratocumulus-Topped Boundary Layer Depth Using Sea Surface and Remotely Sensed Cloud-Top Temperatures written by and published by . This book was released on 2000 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt: The depth of the marine atmospheric boundary layer (MABL) is an important parameter for both scientific and operational meteorological applications. The depth of the marine boundary layer has a significant influence on the atmospheric dynamics in the coastal zone. Knowledge of the depth of stratocumulus-topped boundary layers (STELs) will enable coastal operations to more accurately anticipate weather, and electromagnetic propagation conditions. This study develops a satellite remote sensing technique for determining the height of MABLs topped with stratocumulus clouds. Validation of the technique using coastal rawinsonde dataset from the Monterey Area Ship Track (MAST) experiment revealed that an assumption of 41% cloud with a moist lapse rate equal to -7.0 deg C/km had the best overall fit to the data. However, for shallow boundary layers with depths below 400m the most accurate assumption was 75% cloud with a moist lapse rate equal to -6.5 deg C/km. The application of this technique to sounding data returned an overall BL depth accuracy of 50m while the satellite application returned an overall accuracy of 65m. A sensitivity analysis of both surface and cloud-top temperature revealed that a 1/2 deg C change in either temperature resulted in an error of 60-70m in boundary layer depth.
Book Synopsis Understanding Near-Surface and In-Cloud Turbulent Fluxes in the Coastal Stratocumulus-Topped Boundary Layers by :
Download or read book Understanding Near-Surface and In-Cloud Turbulent Fluxes in the Coastal Stratocumulus-Topped Boundary Layers written by and published by . This book was released on 2004 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aircraft data collected in Monterey Bay area from forty flights in the framework of Autonomous Ocean Sampling Network (AOSN-II) project were used to study the spatial variability and bulk parameterization of turbulence surface fluxes in a coastal region. Flight maneuvers were used to calibrate the turbulence wind data obtained from a radome probe. The typical flight pattern consisted of dense near sea surface straight legs. A variety of near surface flow patterns with downcoast and upcoast strong or weak flow as well as offshore flow was observed. The wind field was quite complex due to intense topographical effects like flow channeling and thermal flows. In addition, coastal upwelling and stratocumulus cloud contribute significantly in the complexity of the atmospheric flow in the measurements area. Measured surface turbulent fluxes were found to be systematically lower than bulk estimations. Non-homogeneity of the flow, limited validity of surface similarity functions, low level clouds effects and poor roughness length parameterization especially under stable atmospheric conditions in the coastal area are probable reasons for this deviation.
Book Synopsis Dissipation Time and Spatial Organization of Coastal Stratocumulus Clouds by : Mónica Natalia Zamora Zapata
Download or read book Dissipation Time and Spatial Organization of Coastal Stratocumulus Clouds written by Mónica Natalia Zamora Zapata and published by . This book was released on 2020 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stratocumulus clouds (Sc) cover 23% of the Earth's ocean surface and adjacent coastal areas, greatly affecting the available solar energy resource. Sc clouds are hard to predict in Numerical Weather Prediction (NWP) models due to their complex turbulent structure and challenging parameterizations of physical processes. In the Southern California summer, Sc clouds over coastal land typically dissipate during the morning hours. The cloud layer gradually thins, then breaks, and eventually dissipates completely. This dissertation investigates two aspects of importance for coastal Sc cloud dissipation: how different meteorological variables affect dissipation time, and the effects of wind shear on their spatial organization. In the first part, we analyze the impact of initial states and meteorological forcing parameters on coastal Sc dissipation time using a Mixed-Layer Model. We use a dataset with 15 variables derived from observations and NWP model outputs for 195 days in San Diego, California. Since some variables co-vary in nature, a simple sensitivity analysis can be misleading, hence we follow two approaches. First, we simulate the 195 real cloudy days, allowing for co-variability amongst the initial states and meteorological forcing parameters. Second, we vary a single variable around a reference case. While both analyses agree on initial conditions influencing dissipation time more than forcing parameters, some results with co-variability differ greatly from the traditional sensitivity analysis and previous studies. In the second part, we analyze the effects of wind shear on the organization of Sc clouds. Updraft and downdraft motions are a key component of the Sc topped boundary layer and strong surface shear can yield updraft rolls, while strong top shear can diminish cloud fraction. We investigate the effect of combined variations of surface and top wind shear using Large Eddy Simulations. We focus on the spatial features of updrafts and downdrafts and how their turbulent flux contributions change with varying conditions of shear. Stronger surface shear generates updraft rolls, less well-mixed thermodynamic profiles, and decreases cloud fraction. Stronger top shear also decreases cloud fraction and can shape the top of the cloud field. Larger objects dominate turbulent flux contributions, which are sensitive to wind shear conditions.
Book Synopsis Observational and Numerical Studies of the Boundary Layer, Cloud, and Aerosol Variability in the Southeast Pacific Coastal Marine Stratocumulus by : Xue Zheng
Download or read book Observational and Numerical Studies of the Boundary Layer, Cloud, and Aerosol Variability in the Southeast Pacific Coastal Marine Stratocumulus written by Xue Zheng and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation investigates the impacts of meteorological factors and aerosol indirect effects on the costal marine stratocumulus (Sc) variations in the southeast Pacific, a region that has been largely unexplored and is a major challenge of the modeling community, through both observational and numerical studies. This study provides a unique dataset for documenting the characteristics of the marine Sc-topped BL off the coast of Northern Chile. The observational study shows that the boundary layer (BL) over this region was well mixed and topped by a thin and non-drizzling Sc layer on days synoptically-quiescent with little variability between this region and the coast. The surface wind, the surface fluxes and the BL turbulence appeared to be weaker than those over other ocean regions where stratocumulus clouds exist. The weaker turbulence in the BL may contribute to a relatively low entrainment rate calculated from the near cloud top fluxes. This in-situ data set can help us better understand cloud processes within this coastal regime, and also be valuable for the calibration of the satellite retrievals and the evaluation of numerical models operating at a variety of scales. A strong positive correlation between the liquid water path (LWP) and the cloud condensation nuclei (CCN) was observed under similar boundary layer conditions. This correlation cannot be explained by some of the hypotheses based on previous modeling studies. The satellite retrievals obtained upstream one day prior to the flight observations reveal some sign that the clouds under the high CCN concentrations have minimal LWP loss due to precipitation suppression effects. The results from large eddy simulations with a two-momentum bulk microphysics scheme under different idealized environment scenarios based on aircraft observations indicate that 1) the simulated Sc responds more quickly to changes in large-scale subsidence than to those changes in surface fluxes, free-tropospheric humidity, and the BL-top stability; 2) large-scale vertical wind shear clearly induces cloud-top mixing and enhances entrainment rate; 3) the solar radiation could weaken the BL turbulence, reduce the entrainment rate and decouple the BL; and 4) the impact of the reduced cloud sedimentation due to increasing aerosol on the cloud is small.
Book Synopsis The Atmospheric Boundary Layer by : J. R. Garratt
Download or read book The Atmospheric Boundary Layer written by J. R. Garratt and published by Cambridge University Press. This book was released on 1994-04-21 with total page 340 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book gives a comprehensive and lucid account of the science of the atmospheric boundary layer (ABL). There is an emphasis on the application of the ABL to numerical modelling of the climate. The book comprises nine chapters, several appendices (data tables, information sources, physical constants) and an extensive reference list. Chapter 1 serves as an introduction, with chapters 2 and 3 dealing with the development of mean and turbulence equations, and the many scaling laws and theories that are the cornerstone of any serious ABL treatment. Modelling of the ABL is crucially dependent for its realism on the surface boundary conditions, and chapters 4 and 5 deal with aerodynamic and energy considerations, with attention to both dry and wet land surfaces and sea. The structure of the clear-sky, thermally stratified ABL is treated in chapter 6, including the convective and stable cases over homogeneous land, the marine ABL and the internal boundary layer at the coastline. Chapter 7 then extends the discussion to the cloudy ABL. This is seen as particularly relevant, since the extensive stratocumulus regions over the subtropical oceans and stratus regions over the Arctic are now identified as key players in the climate system. Finally, chapters 8 and 9 bring much of the book's material together in a discussion of appropriate ABL and surface parameterization schemes in general circulation models of the atmosphere that are being used for climate simulation.
Author :Jordi Vilà-Guerau de Arellano Publisher :Cambridge University Press ISBN 13 :1316300277 Total Pages :283 pages Book Rating :4.3/5 (163 download)
Book Synopsis Atmospheric Boundary Layer by : Jordi Vilà-Guerau de Arellano
Download or read book Atmospheric Boundary Layer written by Jordi Vilà-Guerau de Arellano and published by Cambridge University Press. This book was released on 2015-06-04 with total page 283 pages. Available in PDF, EPUB and Kindle. Book excerpt: Based on more than twenty years of research and lecturing, Jordi Vilà-Guerau de Arellano and his team's textbook provides an excellent introduction to the interactions between the atmosphere and the land for advanced undergraduate and graduate students and a reference text for researchers in atmospheric physics and chemistry, hydrology, and plant physiology. The combination of the book, which provides the essential theoretical concepts, and the associated interactive Chemistry Land-surface Atmosphere Soil Slab (CLASS) software, which provides hands-on practical exercises and allows students to design their own numerical experiments, will prove invaluable for learning about many aspects of the soil-vegetation-atmosphere system. This book has a modular and flexible structure, allowing instructors to accommodate it to their own learning-outcome needs.
Book Synopsis The Entrainment Interface Layer of Stratocumulus Topped Boundary Layers During the Physics of Stratocumulus Top Field Campaign by : Samantha Anne Hill
Download or read book The Entrainment Interface Layer of Stratocumulus Topped Boundary Layers During the Physics of Stratocumulus Top Field Campaign written by Samantha Anne Hill and published by . This book was released on 2013 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Current Problems in the Stratocumulus-topped Atmospheric Boundary Layer by : A. G. M. Driedonks
Download or read book Current Problems in the Stratocumulus-topped Atmospheric Boundary Layer written by A. G. M. Driedonks and published by . This book was released on 1988 with total page 35 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Convective Activities Within the Stratocumulus-Topped Boundary Layer by : Michelle K. Whisenhant
Download or read book Convective Activities Within the Stratocumulus-Topped Boundary Layer written by Michelle K. Whisenhant and published by . This book was released on 1999-12-01 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study utilizes aircraft measurements obtained off the California coast to analyze the geometric, thermodynamic, and micro physical characteristics of convective updrafts and down drafts in the stratocumulus- topped boundary layer (BL). The vertical structure of thermodynamic and micro physical properties is consistent. The difference in peak droplet concentration between updrafts, down drafts, and the defined environment increases near the cloud top. We observe larger mean droplet diameters in down drafts near the cloud top, as the number of small droplets in cloud top down drafts appears to decrease. The horizontal variability seen in the cloud droplet spectra and micro physics properties is likely due to aerosol activation and growth in updrafts, cloud top entrainment, and penetrating cumulus. We compute the mass flux, using a mass flux parameterization. Several measured variables produce consistent results and agree with mass flux calculations from other stratocumulus datasets.
Book Synopsis Thermodynamic and Radiative Structure of Stratocumulus-topped Boundary Layers* by :
Download or read book Thermodynamic and Radiative Structure of Stratocumulus-topped Boundary Layers* written by and published by . This book was released on 2015 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stratocumulus Topped Boundary Layers (STBL) observed in three different regions with distinctive environments are described in the context of their thermodynamic and radiative properties. Here, the primary data set consisted of 131 soundings from the South East Pacific (SEP), 90 soundings from the island of Graciosa (GRW) in the North Atlantic and 83 soundings from the US Southern Great Plains (SGP). A new technique that preserves the depths of the sub-layers within a STBL is proposed for averaging the profiles of thermodynamic and radiative variables. The STBL was deepest over SEP and had the strongest radiative cooling rates near cloud top among the three locations. Although the radiative cooling rates were comparable over GRW and SGP, the STBL was deeper over GRW compared to that over SGP. On average the STBL inversion was strongest over SEP (11.7 k and -5.43 g kg-1) and weakest over the SGP (6.89 k and -0.41 g kg-1). Significantly larger liquid water path, integrated water vapor, and variability in these two properties was found over GRW and evidence presented suggests that conditions at cloud top may play a lesser role in determining the resident cloud structure over GRW than over SEP. A modal analysis revealed ~26% of the STBL to be well-mixed, ~20% of STBL to be stable and ~30% STBL having a stable layer in-between a surface mixed layer and the cloud layer. Over all the three locations, the STBL was shallowest in well-mixed mode and deepest in the stable mode.
Book Synopsis The Turbulence Structure of the Marine Stratocumulus-topped Boundary Layer by : Kerry A. Moyer
Download or read book The Turbulence Structure of the Marine Stratocumulus-topped Boundary Layer written by Kerry A. Moyer and published by . This book was released on 1989 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Studies of Stratocumulus-topped Boundary Layers Using a Numerical Weather Prediction Model by : Robert Sigg
Download or read book Studies of Stratocumulus-topped Boundary Layers Using a Numerical Weather Prediction Model written by Robert Sigg and published by . This book was released on 2000 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Two-dimensional Modeling of the Stratocumulus-topped Marine Bounday Layer by : Michael D. Vander Voste
Download or read book Two-dimensional Modeling of the Stratocumulus-topped Marine Bounday Layer written by Michael D. Vander Voste and published by . This book was released on 1995 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt:
