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Accurate coupling between the resolved scale dynamics and sub-grid scale physics is essential for accurate modelling of the atmosphere. Previous emphasis has been towards the temporal aspects of this so called physics-dynamics coupling problem, with little attention towards the spatial aspects. When designing a model for numerical weather prediction there is a choice for how to vertically arrange the required variables, namely the Lorenz and Charney-Phillips grids, and there is ongoing debate as to which is the optimal. The Charney-Phillips grid is considered good for capturing the large scale dynamics and wave propagation whereas the Lorenz grid is more suitable for conservation. However the Lorenz grid supports a computational mode. In the first half of this thesis it is argued that the Lorenz grid is preferred for modelling the stably stratified boundary layer. This presents the question: which grid will produce most accurate results when coupling the large scale dynamics to the stably stratified planetary boundary layer? The second half of this thesis addresses this question. The normal mode analysis approach, as used in previous work of a similar nature, is employed. This is an attractive methodology since it allows one to pin down exactly why a particular configuration performs well. In order to apply this method a one dimensional column model is set up, where horizontally wavelike solutions with a given wavenumber are assumed. Applying this method encounters issues when the problem is non normal, as it will be when including boundary layer terms. It is shown that when addressing the coupled problem the lack of orthogonality between eigenvectors can cause mode analysis to break down. Dynamical modes could still be interpreted and compared using the eigenvectors but boundary layer modes could not. It is argued that one can recover some of the usefulness of the methodology by examining singular vectors and singular values; these retain the appropriate physical interpretation and allow for valid comparison due to orthogonality between singular vectors. Despite the problems in using the desirable methodology some interesting results have been gained. It is shown that the Lorenz grid is favoured when the boundary layer is considered on its own; it captures the structures of the steady states and transient singular vectors more accurately than the Charney-Phillips grid. For the coupled boundary layer and dynamics the Charney-Phillips grid is found to be most accurate in terms of capturing the steady state. Dispersion properties of dynamical modes in the coupled problem depend on the choice of horizontal wavenumber. For smaller horizontal wavenumber there is little to distinguish between Lorenz and Charney-Phillips grids, both the frequency and structure of dynamical modes is captured accurately. Dynamical mode structures are found to be harder to interpret when using larger horizontal wavenumbers; for those that are examined the Charney-Phillips grid produces the most sensible and accurate results. It is found that boundary layer modes in the coupled problem cannot be concisely compared between the Lorenz and Charney-Phillips grids due to the issues that arise with the methodology. The Lorenz grid computational mode is found to be suppressed by the boundary layer, but only in the boundary layer region.

Marine stratocumulus clouds often become decoupled from the vertical layer immediately above the ocean surface. This study contrasts cloud chemical composition between coupled and decoupled marine stratocumulus clouds for dissolved nonwater substances. Cloud water and droplet residual particle composition were measured in clouds off the California coast during three airborne experiments in July-August of separate years (Eastern Pacific Emitted Aerosol Cloud Experiment 2011, Nucleation in California Experiment 2013, and Biological and Oceanic Atmospheric Study 2015). Decoupled clouds exhibited significantly lower air-equivalent mass concentrations in both cloud water and droplet residual particles, consistent with reduced cloud droplet number concentration and subcloud aerosol (D-p>100nm) number concentration, owing to detachment from surface sources. Nonrefractory submicrometer aerosol measurements show that coupled clouds exhibit higher sulfate mass fractions in droplet residual particles, owing to more abundant precursor emissions from the ocean and ships. Consequently, decoupled clouds exhibited higher mass fractions of organics, nitrate, and ammonium in droplet residual particles, owing to effects of long-range transport from more distant sources. Sodium and chloride dominated in terms of air-equivalent concentration in cloud water for coupled clouds, and their mass fractions and concentrations exceeded those in decoupled clouds. Conversely, with the exception of sea-salt constituents (e.g., Cl, Na, Mg, and K), cloud water mass fractions of all species examined were higher in decoupled clouds relative to coupled clouds. Satellite and Navy Aerosol Analysis and Prediction System-based reanalysis data are compared with each other, and the airborne data to conclude that limitations in resolving boundary layer processes in a global model prevent it from accurately quantifying observed differences between coupled and decoupled cloud composition.

Atmosphärenmodelle, die mit Hilfe numerischer Methoden nach einer Lösung der thermohydrodynamischen Gleichungen unter bestimmten Randbedingungen über einer vorgegebenen Unterlage (Landschaft) suchen, prognostizieren Volumenmittel entsprechender Größen. Zur Validierung der Modelle benötigte experimentell erfaßte meteorologische Größen repräsentieren meist Punktwerte. Im folgenden werden theoretische Ansätze und eine experimentelle Meßmethode vorgestellt, die es ermöglichen, volumengemittelte Werte meteorologischer Größen bereitzustellen und somit zu numerischen Atmosphärenmodellen weitgehend konsistente Daten zu liefern. Die Verfahren verwenden die horizontale Ausbreitung von Schallwellen in der Atmosphärischen Grenzschicht. Die Ableitung volumenbezogener Größen erfolgt über die Invertierung von Schallparameterwerten (akustische Tomographie). / Atmospheric models, which searching by means of numerical methods after a solution of the thermodynamic equations under determined border conditions over a given underground (landscape), forecast volume averaged values of corresponding parameters. The experimental registrated values for meteorolgical parameters used for the validation of models represent usually point values. In following chapters theoretical estimations and an experimental measuring method are presented which volume averaged values of meteorolgical parameters provide and so rather firm data for numerical atmospheric models deliver. The proceedings use horizontal spreading of acoustic waves in the Atmospheric Boundary Layer. Derivation of volume averaged parameters results from the invertation of acoustic parameter values (acoustic tomography).

Die Surface Renewal Analysis wurde zur Bestimmung sensibler Wärmeflußdichten im bodennahen Bereich der atmosphärischen Grenzschicht genutzt und mit der Eddy - Korrelations - Methode verglichen. Dazu wurden beide Berechnungsmethoden auf Temperatur - und Vertikalwinddaten angewandt, die unter Verwendung von Strukturfunktionen simuliert wurden. Zur Überprüfung der Resultate wurden über zwei verschiedenen Unterlagen (Wiese und Düne) hochfrequente Zeitreihen von Temperatur und Vertikalwind gemessen und mit der Surface Renewal Analysis und der Eddy - Korrelations - Methode analysiert. / The Surface Renewal Analysis was used to estimate the sensible heat flux density in the ground near area of the boundary layer. The results were compared with eddy correlation method. For it both methods were used to analyse temperature- and vertical velocity-data, which were simulated by the application of structure functions. Time series of high frequency temperature- and vertical velocity-data over two different canopies (meadow and dune) were measured to examine the results. The data were analysed with surface renewal analysis and eddy correlation.

Determining the factors affecting drizzle formation in marine boundary layer (MBL) clouds remains a challenge for both observation and modeling communities. To investigate the roles of vertical wind shear and buoyancy (static instability) in drizzle formation, ground-based observations from the Atmospheric Radiation Measurement Program at the Azores are analyzed for two types of conditions. The type I clouds should last for at least 5h and more than 90% time must be nondrizzling and then followed by at least 2h of drizzling periods, while the type II clouds are characterized by mesoscale convection cellular structures with drizzle occur every 2 to 4h. By analyzing the boundary layer wind profiles (direction and speed), it was found that either directional or speed shear is required to promote drizzle production in the type I clouds. Observations and a recent model study both suggest that vertical wind shear helps the production of turbulent kinetic energy (TKE), stimulates turbulence within cloud layer, and enhances drizzle formation near the cloud top. The type II clouds do not require strong wind shear to produce drizzle. The small values of lower tropospheric stability (LTS) and negative Richardson number (R-i) in the type II cases suggest that boundary layer instability plays an important role in TKE production and cloud-drizzle processes. By analyzing the relationships between LTS and wind shear for all cases and all time periods, a stronger connection was found between LTS and wind directional shear than that between LTS and wind speed shear.

Approved for public release; distribution is unlimited / The Navy's CASS/GRAB sonar model is used to accurately simulate a side-scan sonar image with a mine-like object present through its reverberation characteristics. The acoustic impact of a suspended sediment layer is investigated numerically using CASS/GRAB through changing the volume scattering characteristics of the lower water column. A range of critical values of volume scattering strength were discovered through repeated model simulations. An understanding of the acoustic characteristics of suspended sediment layers can aid the Navy in the detection of mines that might exist within these layers. / Lieutenant, United States Navy

During an upwelling event the cold bottom-water is brought to the sea surface. This cools the atmosphere from below and the stratification becomes more stable. When the atmosphere is more stable the turbulence is reduced and, as a consequence, so are the turbulent fluxes. This study is investigating four periods of upwelling from the Östergarnsholm-site, in the Baltic Sea east of Gotland, during the summer of 2005. The air measurements are taken at a tower at the southernmost tip of Östergarnsholm while the measurements in the water are from a buoy moored 1 km south-southeast of the tower. During all the upwelling events the wind is south-westerly, along the coast of Gotland. This means that the buoy is not within the flux footprint area and is perhaps not always representative of what happens there. All the periods show a stabilization of the atmosphere as the SST (Sea Surface Temperature) decreases. The heat fluxes, especially the latent heat flux, decreases as the SST decreases. The amount of CO2 in the atmosphere, in the summer, is usually higher than the amount in the surface water of the seas because the oceans are a net sink of CO2. The air-sea flux of CO2 is to a large extent controlled by this difference. Therefore the flux of CO2 is usually directed to the sea. The deep-water contains more CO2 than the surface water because the phytoplankton near the surface removes CO2 through photosynthesis. The deep-water is also colder and can solve more CO2. During an upwelling event this CO2-rich water is brought to the surface. As an upwelling event progresses the difference in CO2-concentration between the air and the sea is reduced, sometimes reversed, and the flux decreases. This is what happens in three of the investigated periods in this study. During the fourth period a counter gradient flux is observed. / När en uppvällning inträffar förs kallt djupvatten upp till havsytan. Det kalla vattnet kyler atmosfären nedifrån, något som leder till mer stabil skiktning. När atmosfären blir mer stabilt skiktad dämpas turbulensen och det medför att de turbulenta flödena också avtar. I den här studien analyseras fyra perioder med uppvällning. Mätningarna kommer från Östergarnsholm, öster om Gotland, under sommaren 2005. Mätningarna i luften är tagna från en mast vid Östergarnsholms södra udde. Mätningarna i vattnet kommer från en boj som är förankrad 1 km sydsydöst om masten. Vid samtliga uppvällnings-perioder i den här studien är vinden sydvästlig (längs Gotlandskusten). Det betyder att bojen inte befinner sig inom flödenas footprint-area och dess mätningar är kanske inte hela tiden representativa för vad som händer i footprint-arean. Samtliga undersökta perioder visar på en stabilisering av atmosfären då havsytans temperatur avtar. Värmeflödena, i synnerhet det latenta värmeflödet, avtar i samband med att temperaturen i havsytan sjunker. Halten av CO2 i atmosfären är vanligtvis högre än halten i havens ytvatten (under sommaren) eftersom de är en nettosänka för CO2 globalt sett. CO2-flödet mellan havsytan och atmosfären styr till en stor del av denna skillnaden i CO2-halt. Det innebär att CO2-flödet är riktat neråt, mot havet. Havens djupvatten innehåller mer CO2 därför att växtplankton nära ytan reducerar CO2-halten genom fotosyntesen. Djupvattnet är också kallare och kan därför lösa mer CO2. Under en uppvällning förs detta CO2-rika vatten upp till ytan. När en uppvällning fortskrider minskar skillnaden i CO2-halt mellan hav och atmosfär (ibland kan CO2-halten i ytvattnet även komma att överstiga atmosfärens halt) och flödet avtar. Tre av perioderna i den här studien visar på ett avtagande flöde. Den fjärde perioden uppvisar ett flöde motriktat CO2-gradienten.

<div>A sharp, circular 7° half-angle cone was tested in the Boeing/AFOSR Mach-6 Quiet Tunnel</div><div>at 6° angle of attack, extending several previous experiments on the growth and breakdown of</div><div>stationary crossflow instabilities in the boundary layer. </div><div><br></div><div>Measurements were made using infrared</div><div>imaging and surface pressure sensors. Detailed measurements of the stationary and traveling</div><div>crossflow vortices, as well as various secondary instability modes, were collected over a large</div><div>region of the cone.</div><div><br></div><div>The Rod Insertion Method (RIM) roughness, first developed for use on a flared cone, was</div><div>adapted for application to crossflow work. It was demonstrated that the roughness elements were</div><div>the primary factor responsible for the appearance of the specific pattern of stationary streaks</div><div>downstream, which are the footprints of the stationary crossflow vortices. In addition, a roughness</div><div>insert was created with a high RMS level of normally-distributed roughness to excite the naturally</div><div>most-amplified stationary mode.</div><div><br></div><div>The nonlinear breakdown mechanism induced by each type of roughness appears to be</div><div>different. When using the discrete RIM roughness, the dominant mechanism seems to be the</div><div>modulated second mode, which is significantly destabilized by the large stationary vortices. This</div><div>is consistent with recent computations. There is no evidence of the presence of traveling crossflow</div><div>when using the RIM roughness, though surface measurements cannot provide a complete picture.</div><div>The modulated second mode shows strong nonlinearity and harmonic development just prior</div><div>to breakdown. In addition, pairs of hot streaks merge together within a constant azimuthal</div><div>band, leading to a peak in the heating simultaneously with the peak amplitude of the measured</div><div>secondary instability. The heating then decays before rising again to turbulent levels. This nonmonotonic</div><div>heating pattern is reminiscent of experiments on a flared cone and earlier computations</div><div>of crossflow on an elliptic cone.</div><div><br></div><div>When using the distributed roughness there are several differences in the nonlinear breakdown</div><div>behavior. The hot streaks appear to be much more uniform and form at a higher wavenumber,</div><div>which is expected given computational results. Furthermore, the traveling crossflow waves become</div><div>very prominent in the surface pressure fluctuations and weakly nonlinear. In addition there</div><div>appears in the spectra a higher-frequency peak which is hypothesized to be a type-I secondary instability</div><div>under the upwelling of the stationary vortices. The traveling crossflow and the secondary</div><div>instability interact nonlinearly prior to breakdown.</div>

The velocity and temperature fields of several air cavities have been surveyed. The cavities operated in the transitional boundary layer regime with vertical, opposing, isothermal heated and cooled walls. The cavity height, width, temperature difference and wall insulation were all changed during the study, with the aspect ratio varying from 4 to 10, and RaH varying from 2,263x10 to 4.486x101e. The local velocity and temperature were measured simultaneously using a laser Doppler anemometer and a 25jim chromel-alumel thermocouple. This allowed the turbulence quantity tT to be measured directly, as well as the mean and root mean square of the fluctuations of velocity and temperature. Several other quantities, which have not previously been available, were derived from the measured data, these were the wall shear stress, the mean lateral velocity, u'v', and v'T'. The effect of a decrease of the level of insulation on the vertical walls was to decrease the non-dimensional temperature of the fluid at the vertical centre-line. Different thermal boundary conditions on the horizontal walls resulted in significant differences between the heated and cooled wall, thermal and velocity, boundary layers. A decrease in the cavity width was seen to alter the characteristics of the mean velocity and temperature profiles when the width was less than twice the lateral extent of either boundary layer in a cavity with a larger width. Near wall distributions of u'v' have shown that the viscous sub-layer was approximately 4mm thick. Calculations of power spectral density, together with inspection of time histories, have confirmed that a laminar flow was present at the bottom of the heated wall. P.S.D. calculations showed that the dominant frequencies of transition were multiples of a base frequency and dependent on the local temperature drop between the wall and the "environment". The power relationship between frequency and power spectral density has been shown to depend on the local vertical temperature gradient. Three sub-ranges were identified in the velocity spectra, whereas four were identified in the temperature spectra. The equivalent ranges in the velocity and temperature spectra exhibited different powers on the frequency, with those of the temperature field being larger.