scholarly journals The impact of cloud vertical profile on liquid water path retrieval based on the bispectral method: A theoretical study based on large‐eddy simulations of shallow marine boundary layer clouds

2016 ◽  
Vol 121 (8) ◽  
pp. 4122-4141 ◽  
Author(s):  
Daniel J. Miller ◽  
Zhibo Zhang ◽  
Andrew S. Ackerman ◽  
Steven Platnick ◽  
Bryan A. Baum
Keyword(s):  
Boundary Layer ◽  
Vertical Profile ◽  
Marine Boundary Layer ◽  
Theoretical Study ◽  
Large Eddy Simulations ◽  
Liquid Water Path ◽  
Shallow Marine ◽  
Boundary Layer Clouds ◽  
Large Eddy ◽  
The Impact

scholarly journals Large-Eddy Simulations of a Drizzling, Stratocumulus-Topped Marine Boundary Layer

2009 ◽  
Vol 137 (3) ◽  
pp. 1083-1110 ◽  
Author(s):  
Andrew S. Ackerman ◽  
Margreet C. vanZanten ◽  
Bjorn Stevens ◽  
Verica Savic-Jovcic ◽  
Christopher S. Bretherton ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Cloud Water ◽  
Large Eddy Simulations ◽  
Cloud Base ◽  
Entrainment Rate ◽  
Liquid Water Path ◽  
Average Maximum ◽  
Large Eddy ◽  
The Mean

Abstract Cloud water sedimentation and drizzle in a stratocumulus-topped boundary layer are the focus of an intercomparison of large-eddy simulations. The context is an idealized case study of nocturnal stratocumulus under a dry inversion, with embedded pockets of heavily drizzling open cellular convection. Results from 11 groups are used. Two models resolve the size distributions of cloud particles, and the others parameterize cloud water sedimentation and drizzle. For the ensemble of simulations with drizzle and cloud water sedimentation, the mean liquid water path (LWP) is remarkably steady and consistent with the measurements, the mean entrainment rate is at the low end of the measured range, and the ensemble-average maximum vertical wind variance is roughly half that measured. On average, precipitation at the surface and at cloud base is smaller, and the rate of precipitation evaporation greater, than measured. Including drizzle in the simulations reduces convective intensity, increases boundary layer stratification, and decreases LWP for nearly all models. Including cloud water sedimentation substantially decreases entrainment, decreases convective intensity, and increases LWP for most models. In nearly all cases, LWP responds more strongly to cloud water sedimentation than to drizzle. The omission of cloud water sedimentation in simulations is strongly discouraged, regardless of whether or not precipitation is present below cloud base.

Exploring microphysical properties of marine boundary layer clouds through network analysis

2021 ◽  
Author(s):  
Lucile Ricard ◽  
Athanasios Nenes ◽  
Jakob Runge ◽  
Paraskevi Georgakaki
Keyword(s):  
Boundary Layer ◽  
High Resolution ◽  
Network Analysis ◽  
Marine Boundary Layer ◽  
Large Eddy Simulations ◽  
Dynamical Structure ◽  
Boundary Layer Clouds ◽  
Microphysical Properties ◽  
Spatial Coverage ◽  
Large Eddy

<p>Aerosol-cloud interactions remain the largest uncertainty in assessments of anthropogenic climate forcing, while the complexity of these interactions require methods that enable abstractions and simplifications that allow their improved treatment in climate models. Marine boundary layer clouds are an important component of the climate system as their large albedo and spatial coverage strongly affect the planetary radiative balance. High resolution simulations of clouds provide an unprecedented understanding of the structure and behavior of these clouds in the marine atmosphere, but the amount of data is often too large and complex to be useful in climate simulations. Data reduction and inference methods provide a way that to reduce the complexity and dimensionality of datasets generated from high-resolution Large Eddy Simulations.</p><p>In this study we use network analysis, (the δ-Maps method) to study the complex interaction between liquid water, droplet number and vertical velocity in Large Eddy Simulations of Marine Boundary Layer clouds. δ-Maps identifies domains that are spatially contiguous and possibly overlapping and characterizes their connections and temporal interactions. The objective is to better understand microphysical properties of marine boundary layer clouds, and how they are impacted by the variability in aerosols. Here we will capture the dynamical structure of the cloud fields predicted by the MIMICA Large Eddy Simulation (LES) model. The networks inferred from the different simulation fields are compared between them (intra-comparisons) using perturbations in initial conditions and aerosol, using a set of four metrics. The networks are then evaluated for their differences, quantifying how much variability is inherent in the LES simulations versus the robust changes induced by the aerosol fields. </p>

scholarly journals Large-eddy simulations of the Northeastern US coastal marine boundary layer

2020 ◽  
Vol 1618 ◽  
pp. 062038
Author(s):  
Lawrence C. Cheung ◽  
Colleen M. Kaul ◽  
Alan S. Hsieh ◽  
Myra L. Blaylock ◽  
Matthew J. Churchfield
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Large Eddy Simulations ◽  
Coastal Marine ◽  
Large Eddy

scholarly journals Probability Density Functions of Liquid Water Path and Cloud Amount of Marine Boundary Layer Clouds: Geographical and Seasonal Variations and Controlling Meteorological Factors

2010 ◽  
Vol 23 (8) ◽  
pp. 2079-2092 ◽  
Author(s):  
Hideaki Kawai ◽  
João Teixeira
Keyword(s):  
Boundary Layer ◽  
Seasonal Variations ◽  
Marine Boundary Layer ◽  
Meteorological Factors ◽  
Cloud Amount ◽  
Probability Density Functions ◽  
Density Functions ◽  
Subgrid Scale ◽  
Liquid Water Path ◽  
Boundary Layer Clouds

Abstract The subgrid-scale variability of the liquid water path (LWP) of marine boundary layer clouds in areas that correspond to the typical grid size of large-scale (global climate and weather prediction) atmospheric models (200 km × 200 km) is investigated using geostationary satellite visible data. Geographical and seasonal variations of homogeneity, skewness, and kurtosis of probability density functions (PDFs) of LWP are discussed, in addition to cloud amount. It is clear that not only cloud amount but also these subgrid-scale statistics have well-defined geographical patterns and seasonal variations. Furthermore, the meteorological factors that control subgrid-scale statistics of LWP that are related to boundary layer clouds are investigated using reanalysis data and PDFs of LWP data from satellites. Meteorological factors related to stability between 850 and 1000 hPa show high correlations with cloud amount and with the homogeneity, skewness, and kurtosis of PDFs of LWP of marine boundary layer clouds. The corrected gap of low-level moist static energy (CGLMSE) index, which is related to cloud-top entrainment instability, shows the highest correlation with the shape of LWP PDFs.

scholarly journals Probability Density Functions of Liquid Water Path and Total Water Content of Marine Boundary Layer Clouds: Implications for Cloud Parameterization

2012 ◽  
Vol 25 (6) ◽  
pp. 2162-2177 ◽  
Author(s):  
Hideaki Kawai ◽  
João Teixeira
Keyword(s):  
Boundary Layer ◽  
Water Content ◽  
Marine Boundary Layer ◽  
Cloud Amount ◽  
Probability Density Functions ◽  
Total Water Content ◽  
Total Water ◽  
Liquid Water Path ◽  
Boundary Layer Clouds ◽  
The Stability

Abstract Mathematical forms of probability density functions (PDFs) of liquid water path (LWP) and total water content for marine boundary layer clouds are investigated using the homogeneity, skewness, and kurtosis of PDFs of LWP obtained from observations described in a companion paper. First, observed LWP PDF data are divided into four categories depending on the stability between 775 and 1000 hPa in order to investigate the characteristics of the PDFs of LWP depending on stability of the atmospheric boundary layer (ABL). The relationships between cloud amount and higher moments of LWP PDFs for different ABLs show different features. When the stability becomes larger, the LWP PDFs have larger homogeneity, smaller skewness, and smaller kurtosis for similar cloud amounts. To extract useful information about the PDFs of total water content for strongly and moderately stable ABLs, the relationship between LWP PDFs and PDFs of total water content is determined by introducing a set of simple assumptions for the vertical structure of total water content in well-mixed boundary layers. By comparing the observed relationships between cloud amount and higher moments of LWP PDFs, with similar relationships deduced theoretically from various forms of PDFs of total water content, it is found that, in general, the triangular and Gaussian PDFs are a realistic approximation for PDFs of total water content in marine boundary layer clouds for strongly and moderately stable ABLs. Results concerning the correction ratio for the autoconversion rate of cloud water content to precipitation and the reduction factor for shortwave reflectance, as functions of cloud amount, are also discussed.

scholarly journals Comparison of Field Measurements and Large Eddy Simulations of the Scaled Wind Farm Technology (SWiFT) Site

2019 ◽  
Author(s):  
Myra L. Blaylock ◽  
Brent C. Houchens ◽  
David C. Maniaci ◽  
Thomas Herges ◽  
Alan Hsieh ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Wind Farm ◽  
Field Measurements ◽  
Operating Conditions ◽  
Large Eddy Simulations ◽  
Department Of Energy ◽  
Large Eddy ◽  
In Series ◽  
The Impact

Abstract Power production of the turbines at the Department of Energy/Sandia National Laboratories Scaled Wind Farm Technology (SWiFT) facility located at the Texas Tech University’s National Wind Institute Research Center was measured experimentally and simulated for neutral atmospheric boundary layer operating conditions. Two V27 wind turbines were aligned in series with the dominant wind direction, and the upwind turbine was yawed to investigate the impact of wake steering on the downwind turbine. Two conditions were investigated, including that of the leading turbine operating alone and both turbines operating in series. The field measurements include meteorological evaluation tower (MET) data and light detection and ranging (lidar) data. Computations were performed by coupling large eddy simulations (LES) in the three-dimensional, transient code Nalu-Wind with engineering actuator line models of the turbines from OpenFAST. The simulations consist of a coarse precursor without the turbines to set up an atmospheric boundary layer inflow followed by a simulation with refinement near the turbines. Good agreement between simulations and field data are shown. These results demonstrate that Nalu-Wind holds the promise for the prediction of wind plant power and loads for a range of yaw conditions.

Impact of Elevated Kevin-Helmholtz Billows on the Atmospheric Boundary Layer

2021 ◽  
Author(s):  
Qingfang Jiang
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Shear Layer ◽  
Exponential Growth ◽  
Three Dimensional ◽  
Large Eddy Simulations ◽  
Two Dimensional ◽  
Large Eddy ◽  
Saturation Stage ◽  
The Impact

AbstractThe impact of Kelvin-Helmholtz billows (KHBs) in an elevated shear layer (ESL) on the underlying atmospheric boundary layer (BL) is examined utilizing a group of large-eddy simulations. In these simulations, KHBs develop in the ESL and experience exponential growth, saturation, and exponential decay stages. In response, strong wavy motion occurs in the BL, inducing rotor circulations near the surface when the BL is stable. During the saturation stage, secondary instability develops in the ESL and the wavy BL almost simultaneously, followed by the breakdown of the quasi-two-dimensional KH billows and BL waves into three-dimensional turbulence. Consequently, during and after a KH event, the underlying BL becomes more turbulent with its depth increased and stratification weakened substantially, suggestive of significant lasting impact of elevated KH billows on the atmospheric BL. The eventual impact of KHBs on the BL is found to be sensitive to both the ESL and BL characteristics.

scholarly journals Extracting Microphysical Impacts in Large-Eddy Simulations of Shallow Convection

2014 ◽  
Vol 71 (12) ◽  
pp. 4493-4499 ◽  
Author(s):  
Wojciech W. Grabowski
Keyword(s):  
Traditional Approach ◽  
Cloud Droplet ◽  
Cloud Microphysics ◽  
Natural Variability ◽  
Large Eddy Simulations ◽  
Shallow Convection ◽  
Liquid Water Path ◽  
Large Eddy ◽  
The Mean ◽  
The Impact

Abstract A simple methodology is proposed to extract impacts of cloud microphysics on macrophysical cloud-field properties in large-eddy simulations of shallow convection. These impacts are typically difficult to assess because of natural variability of the simulated cloud field. The idea is to use two sets of thermodynamic variables driven by different microphysical schemes or by a single scheme with different parameters as applied here. The first set is coupled to the dynamics as in the standard model, and the second set is applied diagnostically—that is, driven by the flow but without the feedback on the flow dynamics. Having the two schemes operating in the same flow pattern allows for extracting the impact with high confidence. For illustration, the method is applied to simulations of precipitating shallow convection applying a simple bulk representation of warm-rain processes. Because of natural variability, the traditional approach provides an uncertain estimate of the impact of cloud droplet concentration on the mean cloud-field rainfall even with an ensemble of simulations. In contrast, the impact is well constrained while applying the new methodology. The method can even detect minuscule changes of the mean cloud cover and liquid water path despite their large temporal fluctuations and different evolutions within the ensemble.

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