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The statistics of atmospheric stability and non-dimensional wind profiles are studied using the standard surface-layer theory at Egmond aan Zee in the North Sea. Measurements at 21, 70 and 116 m are used to validate the theoretical profiles. Charnock’s relation is used to estimate the sea surface roughness. Bulk Richardson number is used to estimate the Obukhov length. The measured sea water temperature has a positive bias of 0.82?C resulting in the dominance of unstable conditions and a poor agreement of the theoretical wind profiles with the measurements. The conditions at Egmond aan Zee are dominated by unstable and neutral stabilities. The theoretical wind profiles agree very well with the measurements in the unstable and neutral conditions. In stable conditions, the wind profiles are over-predicted significantly as the height increases. The scaling of the wind profile with respect to the boundary layer height is necessary under stable conditions and the addition of another length scale parameter is preferred., Aerodynamics, Wind Energy & Propulsion, Aerospace Engineering

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.), The original document contains color images.

Analytical solutions of a set of equations that couples the Ekman and the Prandtl boundary layer (BL) equations were obtained; closure on the subgrid scale was via the eddy exchange (K) approach, where K was made to depend on both the internal stability (μ) and height raised to an arbitrary power. The boundary layer height (h) wis also made to depend on μs. As byproducts of these solutions, generalized expressions for the universal functions of μ, A, B and C and for the resistance and heat-transfer laws (i. e. a, u*/G ind T*/0, respectively) for a given set of external parameters (X, Ro and S) for the general case of the slope angle 0~~~10 rad were presented. From this, an interesting and novel result is the finding that there are three different regimes of solutions depending on whether S (or ~) is less than, equal to or greater than certain critical value S (or ~ ). The solutions for all three regimes were presented in graphical form, from which the appreciable influence of terrain slope on the cross-isobaric inflow angle, the momentum- and heat-transfer is clearly discernible. Also in a preliminary test of the results of this investigation with observations, it is found that the theoretical values of the cross-isobaric angle are in good agreement with the observed values in Antarctica and therefore encouraging for further research.

The objective of this thesis is to investigate the vertical structure of the atmosphere and to assess the performance of several radiosonde- and lidar-based methods to detect the boundary layer height within the Inn Valley. All of these methods are developed for horizontally homogeneous and flat terrain. Radiosonde methods include different versions of the parcel and Richardson number methods and are, therefore, based on vertical profiles of virtual potential temperature, potential temperature, and horizontal wind speed, while lidar methods are based on vertical profiles of velocity variance, dissipation rate of turbulent kinetic energy, and backscatter intensities. The investigation of the performance of these methods as well as the vertical structure is based on data collected during the CROSSINN field campaign in summer 2019 in the lower Inn Valley near Kolsass and mainly focuses on two case studies. Potential temperature profiles measured by radiosondes during daytime confirm previous studies with regard to the existence of two nearly neutral layers, separated by a region of enhanced stability. The case studies illustrate that the depth of the upper layer is larger than the depth of the lower layer. In both case studies, the elevated near-neutral layer extended above mean crest height. The case studies also indicate that the radiosonde methods and the lidar methods based on turbulence determine mixing heights that can be related to the top of the lower well-mixed layer during convective conditions, while mixing heights derived from backscatter profiles are not determined by unique but rather case-dependent processes. From the radiosondes, it is found that the surface connected mixed layer only extends up to around 300 to 500~m~above ground level on average. Nevertheless, warming occurred above this mixed layer, which is too strong to be explained by large-scale advection alone. This result demonstrates the importance of additional transport and mixing processes, by Paul Josef Ladstätter, Masterarbeit University of Innsbruck 2020

The statistical properties of five boundary layer height definitions were examined in 6,593 NCAR GPS dropsonde observations of the hurricane environment. Based on similar composite analysis studies, these boundary layer height estimates were divided into two categories based on their analytical characteristics. Three dynamical methods of estimating the boundary layer height were combined with two thermodynamical methods of estimating the mixed layer depth to numerically interrogate the physical properties of hurricanes within two primary modes of variability: azimuthal and geographic region. The results confirmed the vertical bifurcation of dynamical and thermodynamical height estimates and indicated a consistent distinction in the radial variability of each class. Moreover, the tangential wind field was well-described by the modified Rankine vortex. A characteristic decrease in boundary layer height with decreasing radius to the storm center was expressed in four of the five definitions. The non-uniform azimuthal distribution of relative radial winds and ill-behaved inflow layer depths precluded meaningful comparisons of boundary layer height in the rear storm-relative semicircle. While boundary layer height estimates failed to exhibit any significant regional variability, the right-front storm-relative quadrant appeared to exhibit non-trivial increases in mean boundary layer height., http://archive.org/details/variabilityinhur1094542751, Lieutenant, United States Navy, Approved for public release; distribution is unlimited.

The objective of this thesis is to investigate the vertical structure of the atmosphere and to assess the performance of several radiosonde- and lidar-based methods to detect the boundary layer height within the Inn Valley. All of these methods are developed for horizontally homogeneous and flat terrain. Radiosonde methods include different versions of the parcel and Richardson number methods and are, therefore, based on vertical profiles of virtual potential temperature, potential temperature, and horizontal wind speed, while lidar methods are based on vertical profiles of velocity variance, dissipation rate of turbulent kinetic energy, and backscatter intensities. The investigation of the performance of these methods as well as the vertical structure is based on data collected during the CROSSINN field campaign in summer 2019 in the lower Inn Valley near Kolsass and mainly focuses on two case studies. Potential temperature profiles measured by radiosondes during daytime confirm previous studies with regard to the existence of two nearly neutral layers, separated by a region of enhanced stability. The case studies illustrate that the depth of the upper layer is larger than the depth of the lower layer. In both case studies, the elevated near-neutral layer extended above mean crest height. The case studies also indicate that the radiosonde methods and the lidar methods based on turbulence determine mixing heights that can be related to the top of the lower well-mixed layer during convective conditions, while mixing heights derived from backscatter profiles are not determined by unique but rather case-dependent processes. From the radiosondes, it is found that the surface connected mixed layer only extends up to around 300 to 500~m~above ground level on average. Nevertheless, warming occurred above this mixed layer, which is too strong to be explained by large-scale advection alone. This result demonstrates the importance of additional transport and mixing processes, by Paul Josef Ladstätter, Masterarbeit University of Innsbruck 2020