scholarly journals Sampling Error in Aircraft Flux Measurements Based on a High-Resolution Large Eddy Simulation of the Marine Boundary Layer

2020 ◽  
Author(s):  
Grant W. Petty
Keyword(s):  
Boundary Layer ◽  
High Resolution ◽  
Random Error ◽  
Marine Boundary Layer ◽  
Sampling Error ◽  
Track Length ◽  
Length Scales ◽  
Eddy Simulation ◽  
Flux Measurements ◽  
Aircraft Flux Measurements

Abstract. A high-resolution (1.25 m) LES simulation of the nocturnal cloud-topped marine boundary layer is used to evaluate random error as a function of continuous track length L for virtual aircraft measurements of turbulent fluxes of sensible heat, latent heat, and horizontal momentum. Results are compared with the theoretically derived formula of Lenschow and Stankov (1986). In support of these comparisons, we also evaluate and document the relevant integral length scales and correlations and show that for heights up to approximately 100 m (z / zi = 0.12), the length scales are accurately predicted by empirical expressions of the form If = Azb. The Lenschow and Stankov expression is found to be remarkably accurate at predicting the random error for shorter flight tracks, but our empirically determined errors decay more rapidly with L than the L−1/2 relationship predicted from theory. Consistent with earlier findings, required track lengths to obtain useful precision increase sharply with altitude.

scholarly journals Sampling error in aircraft flux measurements based on a high-resolution large eddy simulation of the marine boundary layer

2021 ◽  
Vol 14 (3) ◽  
pp. 1959-1976
Author(s):  
Grant W. Petty
Keyword(s):  
Boundary Layer ◽  
High Resolution ◽  
Large Eddy Simulation ◽  
Random Error ◽  
Marine Boundary Layer ◽  
Sampling Error ◽  
Track Length ◽  
Length Scales ◽  
Eddy Simulation ◽  
Large Eddy

Abstract. A high-resolution (1.25 m) large eddy simulation (LES) of the nocturnal cloud-topped marine boundary layer is used to evaluate random error as a function of continuous track length L for virtual aircraft measurements of turbulent fluxes of sensible heat, latent heat, and horizontal momentum. Results are compared with the widely used formula of Lenschow and Stankov (1986). In support of these comparisons, the relevant integral length scales and correlations are evaluated and documented. It is shown that for heights up to approximately 100 m (z/zi=0.12), the length scales are accurately predicted by empirical expressions of the form If=Azb. The Lenschow and Stankov expression is found to be remarkably accurate at predicting the random error for shorter (7–10 km) flight tracks, but the empirically determined errors decay more rapidly with L than the L-1/2 relationship predicted from theory. Consistent with earlier findings, required track lengths to obtain useful precision increase sharply with altitude. In addition, an examination is undertaken of the role of uncertainties in empirically determined integral length scales and correlations in flux uncertainties as well as of the flux errors associated with crosswind and along-wind flight tracks. It is found that for 7.2 km flight tracks, flux errors are improved by factor of approximately 1.5 to 2 for most variables by making measurements in the crosswind direction.

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 Vertically nested LES for high-resolution simulation of the surface layer in PALM (version 5.0)

2019 ◽  
Vol 12 (6) ◽  
pp. 2523-2538 ◽  
Author(s):  
Sadiq Huq ◽  
Frederik De Roo ◽  
Siegfried Raasch ◽  
Matthias Mauder
Keyword(s):  
Boundary Layer ◽  
Surface Layer ◽  
High Resolution ◽  
Large Eddy Simulation ◽  
Grid Resolution ◽  
Computational Power ◽  
Fine Grid ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Nesting Algorithm

Abstract. Large-eddy simulation (LES) has become a well-established tool in the atmospheric boundary layer research community to study turbulence. It allows three-dimensional realizations of the turbulent fields, which large-scale models and most experimental studies cannot yield. To resolve the largest eddies in the mixed layer, a moderate grid resolution in the range of 10 to 100 m is often sufficient, and these simulations can be run on a computing cluster with a few hundred processors or even on a workstation for simple configurations. The desired resolution is usually limited by the computational resources. However, to compare with tower measurements of turbulence and exchange fluxes in the surface layer, a much higher resolution is required. In spite of the growth in computational power, a high-resolution LES of the surface layer is often not feasible: to fully resolve the energy-containing eddies near the surface, a grid spacing of O(1 m) is required. One way to tackle this problem is to employ a vertical grid nesting technique, in which the surface is simulated at the necessary fine grid resolution, and it is coupled with a standard, coarse, LES that resolves the turbulence in the whole boundary layer. We modified the LES model PALM (Parallelized Large-eddy simulation Model) and implemented a two-way nesting technique, with coupling in both directions between the coarse and the fine grid. The coupling algorithm has to ensure correct boundary conditions for the fine grid. Our nesting algorithm is realized by modifying the standard third-order Runge–Kutta time stepping to allow communication of data between the two grids. The two grids are concurrently advanced in time while ensuring that the sum of resolved and sub-grid-scale kinetic energy is conserved. We design a validation test and show that the temporally averaged profiles from the fine grid agree well compared to the reference simulation with high resolution in the entire domain. The overall performance and scalability of the nesting algorithm is found to be satisfactory. Our nesting results in more than 80 % savings in computational power for 5 times higher resolution in each direction in the surface layer.

scholarly journals Characterization of the South Atlantic marine boundary layer aerosol using an aerodyne aerosol mass spectrometer

2008 ◽  
Vol 8 (16) ◽  
pp. 4711-4728 ◽  
Author(s):  
S. R. Zorn ◽  
F. Drewnick ◽  
M. Schott ◽  
T. Hoffmann ◽  
S. Borrmann
Keyword(s):  
Boundary Layer ◽  
Sulfuric Acid ◽  
High Resolution ◽  
Marine Boundary Layer ◽  
Methanesulfonic Acid ◽  
Field Measurements ◽  
Size Distributions ◽  
Air Masses ◽  
Unit Mass Resolution ◽  
Mass Concentrations

Abstract. Measurements of the submicron fraction of the atmospheric aerosol in the marine boundary layer were performed from January to March 2007 (Southern Hemisphere summer) onboard the French research vessel Marion Dufresne in the Southern Atlantic and Indian Ocean (20° S–60° S, 70° W–60° E). We used an Aerodyne High-Resolution-Time-of-Flight AMS to characterize the chemical composition and to measure species-resolved size distributions of non-refractory aerosol components in the submicron range. Within the "standard" AMS compounds (ammonium, chloride, nitrate, sulfate, organics) "sulfate" is the dominant species in the marine boundary layer with concentrations ranging between 50 ng m−3 and 3 μg m−3. Furthermore, what is seen as "sulfate" by the AMS is likely comprised mostly of sulfuric acid. Another sulfur containing species that is produced in marine environments is methanesulfonic acid (MSA). There have been previously measurements of MSA using an Aerodyne AMS. However, due to the use of an instrument equipped with a quadrupole detector with unit mass resolution it was not possible to physically separate MSA from other contributions to the same m/z. In order to identify MSA within the HR-ToF-AMS raw data and to extract mass concentrations for MSA from the field measurements the standard high-resolution MSA fragmentation patterns for the measurement conditions during the ship campaign (e.g. vaporizer temperature) needed to be determined. To identify characteristic air masses and their source regions backwards trajectories were used and averaged concentrations for AMS standard compounds were calculated for each air mass type. Sulfate mass size distributions were measured for these periods showing a distinct difference between oceanic air masses and those from African outflow. While the peak in the mass distribution was roughly at 250 nm (vacuum aerodynamic diameter) in marine air masses, it was shifted to 470 nm in African outflow air. Correlations between the mass concentrations of sulfate, organics and MSA show a narrow correlation for MSA with sulfate/sulfuric acid coming from the ocean, but not with continental sulfate.

Application of High-Resolution Large Eddy Simulation to Simplified Turbomachinery Flows

2016 ◽  
Author(s):  
Susumu Teramoto ◽  
Takuya Ouchi ◽  
Hiroki Sanada ◽  
Koji Okamoto
Keyword(s):  
Boundary Layer ◽  
High Resolution ◽  
Turbulent Boundary Layer ◽  
Large Eddy Simulation ◽  
Reynolds Stress ◽  
Sudden Expansion ◽  
Compressor Cascade ◽  
Rans Model ◽  
Eddy Simulation ◽  
Large Eddy

Fully resolved large eddy simulation (LES) is applied to two simple geometry flowfields with well-defined boundary conditions. The LES results are compared with simulations based on a Reynolds-averaged Navier-Stokes (RANS) model with turbulence, and pros and cons of using high-resolution LES for turbomachinery flows are discussed. One flow is a linear compressor cascade flow composed of the tip section of GE rotor B at Rec = 4 × 105 with a clearance, and the other is a Mach 1.76 supersonic turbulent boundary layer at Reδ = 5000 that laminerizes through a 12-degree expansion corner. The grids are prepared fine enough to resolve the turbulent boundary layer through a grid sensitivity study. The liner cascade result shows that all the turbulent shear layers and boundary layers including those in the small tip clearance are well resolved with 800 million grid points. The Reynolds stress derived from the LES results are compared directly with those predicted from the Spalart-Allmaras one-equation RANS turbulence model. The two results agreed qualitatively well except for the shear layer surrounding the tip leakage vortex, demonstrating that the RANS model performs well at least for flowfields near the design condition. From the simulation of the turbulent boundary layer experiencing sudden expansion, noticeable decreases of both Reynolds stress and local friction coefficient were observed, showing that the turbulent boundary layer has relaminarized through the sudden expansion. The boundary layer downstream of the expansion exhibits a nonequilibrium condition and was different from the laminar boundary layer.

Evaluation of the WRF PBL Parameterizations for Marine Boundary Layer Clouds: Cumulus and Stratocumulus

2013 ◽  
Vol 141 (7) ◽  
pp. 2265-2271 ◽  
Author(s):  
Hsin-Yuan Huang ◽  
Alex Hall ◽  
Joao Teixeira
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Marine Boundary Layer ◽  
Layer Structure ◽  
Model Performance ◽  
Simulation Models ◽  
Eddy Diffusivity ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Boundary Layer Cloud

Abstract The performance of five boundary layer parameterizations in the Weather Research and Forecasting Model is examined for marine boundary layer cloud regions running in single-column mode. Most parameterizations show a poor agreement of the vertical boundary layer structure when compared with large-eddy simulation models. These comparisons against large-eddy simulation show that a parameterization based on the eddy-diffusivity/mass-flux approach provides a better performance. The results also illustrate the key role of boundary layer parameterizations in model performance.

scholarly journals Marine boundary layer cloud property retrievals from high-resolution ASTER observations: case studies and comparison with Terra MODIS

2016 ◽  
Vol 9 (12) ◽  
pp. 5869-5894 ◽  
Author(s):  
Frank Werner ◽  
Galina Wind ◽  
Zhibo Zhang ◽  
Steven Platnick ◽  
Larry Di Girolamo ◽  
...  
Keyword(s):  
Boundary Layer ◽  
High Resolution ◽  
Marine Boundary Layer ◽  
Thermal Emission ◽  
Three Dimensional ◽  
Correlation Coefficients ◽  
Retrieval Algorithm ◽  
Research Level ◽  
Boundary Layer Cloud ◽  
Layer Cloud

Abstract. A research-level retrieval algorithm for cloud optical and microphysical properties is developed for the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) aboard the Terra satellite. It is based on the operational MODIS algorithm. This paper documents the technical details of this algorithm and evaluates the retrievals for selected marine boundary layer cloud scenes through comparisons with the operational MODIS Data Collection 6 (C6) cloud product. The newly developed, ASTER-specific cloud masking algorithm is evaluated through comparison with an independent algorithm reported in [Zhao and Di Girolamo(2006)]. To validate and evaluate the cloud optical thickness (τ) and cloud effective radius (reff) from ASTER, the high-spatial-resolution ASTER observations are first aggregated to the same 1000 m resolution as MODIS. Subsequently, τaA and reff, aA retrieved from the aggregated ASTER radiances are compared with the collocated MODIS retrievals. For overcast pixels, the two data sets agree very well with Pearson's product-moment correlation coefficients of R > 0.970. However, for partially cloudy pixels there are significant differences between reff, aA and the MODIS results which can exceed 10 µm. Moreover, it is shown that the numerous delicate cloud structures in the example marine boundary layer scenes, resolved by the high-resolution ASTER retrievals, are smoothed by the MODIS observations. The overall good agreement between the research-level ASTER results and the operational MODIS C6 products proves the feasibility of MODIS-like retrievals from ASTER reflectance measurements and provides the basis for future studies concerning the scale dependency of satellite observations and three-dimensional radiative effects.

scholarly journals Twenty-Four-Hour Observations of the Marine Boundary Layer Using Shipborne NOAA High-Resolution Doppler Lidar

2005 ◽  
Vol 44 (11) ◽  
pp. 1723-1744 ◽  
Author(s):  
Volker Wulfmeyer ◽  
Tijana Janjić
Keyword(s):  
Boundary Layer ◽  
High Resolution ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Wind Shear ◽  
Marine Boundary Layer ◽  
Sea Surface ◽  
Doppler Lidar ◽  
Sensible Heat ◽  
Wind Profiles

Abstract Shipborne observations obtained with the NOAA high-resolution Doppler lidar (HRDL) during the 1999 Nauru (Nauru99) campaign were used to study the structure of the marine boundary layer (MBL) in the tropical Pacific Ocean. During a day with weak mesoscale activity, diurnal variability of the height of the convective MBL was observed using HRDL backscatter data. The observed diurnal variation in the MBL height had an amplitude of about 250 m. Relations between the MBL height and in situ measurements of sea surface temperature as well as latent and sensible heat fluxes were examined. Good correlation was found with the sea surface temperature. The correlation with the latent heat flux was lower, and practically no correlation between the MBL height and the sensible heat and buoyancy fluxes could be detected. Horizontal wind profiles were measured using a velocity–azimuth display scan of HRDL velocity data. Strong wind shear at the top of the MBL was observed in most cases. Comparison of these results with GPS radiosonde data shows discrepancies in the wind intensity and direction, which may be due to different observation times and locations as well as due to multipath effects at the ship’s platform. Vertical wind profiles corrected for ship’s motion were used to derive vertical velocity variance and skewness profiles. Motion compensation had a significant effect on their shape. Normalized by the convective velocity scale and by the top of the mixed layer zi, the variance varied between 0.45 and 0.65 at 0.4z/zi and decreased to 0.2 at 1.0z/zi. The skewness ranged between 0.3 and 0.8 in the MBL and showed in almost all cases a maximum between 1.0z/zi and 1.1z/zi. These profiles revealed the existence of another turbulent layer above the MBL, which was probably driven by wind shear and cloud condensation processes.

Sign in / Sign up

Export Citation Format

Share Document