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"Nineteen years of wind data over the North Atlantic are used to calculate a field of wind stress curl. An EOF analysis is performed on this field resulting in variance-qualified spatial patterns of wind stress curl and associated time series. A Monte Carlo technique is used to establish the statistical significance of each spatial pattern. The first four statistically significant EOF modes represent more than 50% of the curl variance. The spatial patterns of curl associated with these modes exhibit many elements of North Atlantic climatology. The associated time series are spectrally analyzed. Most of the variance is contained in annual and semiannual frequencies. Features observed include the individual annual variation of the subtropical high and the subpolar low, the annual oscillation of intensity between the above pressure centers, the influence of localized strong SST gradients and associated cyclogenesis regions, and the constant nature of the trades. The EOF curl patterns are in the form of simple standing waves with wavelength on the order of basin size"--Abstract. / Typescript. / "April, 1986." / "Submitted to the Department of Meteorology in partial fulfillment of the requirements for the degree of Master of Science." / Advisor: James O'Brien, Professor Directing Thesis. / Includes bibliographical references (leaves 35-36).

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A modeling study is undertaken to better understand the physics of katabatic flows. This study is divided into three topics; a comparison between a large eddy simulation (LES) and a mesoscale model of katabatic flows, a sensitivity study of katabatic flows to various physical parameters, and an investigation into the effect of subgrid scale terrain features on katabatic flow models. In the first topic, a comparison between LES, and a mesoscale model, ARPS, of katabatic flows is made to better quantify the accuracy of subgrid parametenzation in ARPS. It is shown that, although the modeled flows agree on a number of parameters, the LES model produces a lower and faster jet than that of ARPS, and also cools more near the surface. The momentum budgets of the two models agree well with each other. The ARPS model has a higher amount of TKE than the LES model, due to an overproduction by shear in the ARPS subgrid parameterizations. The second portion of this thesis represents a sensitivity study of katabatic flows to various physical parameters. The depth and strength of katabatic flows are shown to vary with surface heat fluxes, slope angle, and ambient stratification. Katabatic flows are shown to grow in depth and magnitude as slope angle increases, due to an increase in entrainment of overlying ambient air. The ratio of advection to mixing is shown to collapse to a near universal value regardless of surface heat fluxes. With increasing ambient stratification, entrainment in katabatic flows becomes small and the momentum equation is reduced to a two-way balance between buoyancy and drag. In this case, the heat flux of entrained air into the katabatic flow approaches that of the surface cooling, and the flow ceases to grow in the down-slope direction. Finally, predictions for bulk velocity and buoyancy strength scales are developed as a function of slope angle and surface heat fluxes. The last portion of this study focuses on the effect of subgrid scale terrain features on katabatic flows. It is shown that in areas of inadequate terrain resolution, the effect of the terrain smoothing routine in ARPS is to increase the slope height in areas of concave mountains. The concept of energy conversion in katabatic flows is introduced, and it is shown that the effect of raising terrain is to assign parcels more buoyant potential energy than they would otherwise have, and thus over-predict the magnitude of katabatic flows. Finally, an investigation into the effect of changing upper slope angle on katabatic flows over combined slopes is made. It is concluded that a combined slope cannot be predicted using a linear combination of simple slopes, since the transition portion of the slope results in a turbulent hydraulic jump with enhanced mixing. The magnitude of mixing in the turbulent hydraulic jump in combined slopes is shown to depend on the difference between upper and lower slope angle. / Graduation date: 2004

Thesis (M.S.)--Ohio State University, 1953. / Available online via OhioLINK's ETD Center

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A knowledge of the basic atmospheric parameters and their variability is required both for climatological purposes and theoretical studies. Meteorologists generally use constant pressure maps at a number of levels to study the broad scale structure of the atmosphere. Vertical cross sections are then used to provide a finer structure and also to permit a vertical integration of the various constant pressure levels. Research meteorologists at McGill have analysed hemispheric weather maps and meridional cross sections along 80oW on a daily basis for a three year period to determine major parameters in the general circulation. This study attempts to provide a useful contribution with respect to mean monthly and seasonal cross section parameters. [...]

Atmospheric kinetic energy calculations at 500 mb are carried out for the tropical region 20N to 20S on a daily basis during the month of September 1957. The basic data consist of grid point values of wind direction and speed obtained from streamline and isotach analyses of the tropical charts. [...]

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