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A mini-lidar system, Vaisala's CL31 ceilometer, was installed within a suburban area of Vancouver, BC, for the purpose of making continuous observations of the boundary layer over a period of 11 months. Initial validation of the ceilometer for use in boundary layer observations was undertaken. This involved the comparison of ceilometer data with eight months of ground-level particulate matter measurements, as well as with 16 vertical profiles of particulate matter and meteorological data. Once a variety of persistent noise structures within the data were accounted for, it was found that the ceilometer data showed good agreement with the particulate matter data, suggesting its usefulness for assessing air-quality throughout the bottom 1km of the atmosphere. Additionally, two algorithms were developed in order to estimate the height of the convective boundary layer, or the mixed-layer height, from the ceilometer data. One involved the fitting of an ideal-profile to the measured data, while the other involved the location of a minimum-gradient in the backscatter profile. The performance of these two techniques were assessed and compared, and it was found that the ideal-profile method was the more robust of the two. Finally, mixed-layer heights were estimated for fair weather, convectively active days. In order to isolate such conditions, an automatic flagging algorithm was developed. However, additional manual assessment was needed to avoided unsuitable conditions. Mixed-layer heights were estimated for 19 days over an 11 month period. the estimates presented here were found to agree with previous observations. Daily maximum mixed-layer heights ranged from 650m in July to 350m in December, indicating that the height of the convective boundary layer within Vancouver is significantly suppressed due to the city's coastal location. / Arts, Faculty of / Geography, Department of / Graduate

The work carried out for this thesis forms part of the air-sea interaction program, which has been under way since 196l at the Institute of Oceanography of the University of British Columbia. Measurements of fluctuations in the vertical and horizontal components of air velocity were made using hot wires in an X-array, in order to study the spectra of the fluctuations, and their co-spectrum over a range of mean wind speeds from 140 – 1000 cm./sec. in the boundary layer over the sea. In order to use the X-wire probe properly in the field, special techniques were developed to mount and calibrate the wires, and to measure directly their responses to the two velocity fluctuations. Analog techniques were developed to analyze the hot wire signals, and final calculations were made by digital computer. Single (U-wire) hot wire probes were used to measure the horizontal velocity fluctuations to check the behaviour of X-wires, and to provide additional checks on the similarity theory of turbulence. Measurements showed that X-wire techniques can be used successfully to measure velocity fluctuations in two directions in the field. Hot wires have responses which give spectral levels which are accurate only within about 35%, but comparison of the horizontal velocity spectrum measured simultaneously with the X- and U-wire probes showed that their spectral shapes were similar, giving confidence in the X-wire measurements. In the high frequency range, the observed spectra of the two velocity fluctuations did not conform to the theoretical predictions. The observed behaviour is believed to be real. The cospectrum gives a direct estimate of contributions to the Reynolds' stress by fluctuations in small ranges of frequency. The stress observed between the frequency limits O.Ol6 to 10 Hz had significant contributions over about one frequency decade, which apparently lies entirely within these extremes. Estimates of the frequencies of dominant waves at the experimental site fell between about 0.2 to 0.5 Hz. Significant stress was present in this interval, but the largest proportion of the observed stress was present at lower frequencies. Ten direct estimates of stress were obtained with the X-wire. Values estimated indirectly from the wind profiles tended to give low estimates and were poorly correlated with the direct estimates. Values determined indirectly using the inertial subrange appeared to be consistently related to the directly estimated stress, but overestimated it by about 40%. Drag coefficients corrected to the 5m height were near 1.5 x 10⁻³ for wind speeds between 1.4 and 10m.sec-¹. Measurements by three U-wires spaced vertically, provided confirmation of the validity of the Monin-Obukhov similarity theory at heights below about 5m. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

One of the basic goals in engineering is to generate models which will provide a means for analytically predicting observed phenomenon. Such a model is often modified several times to obtain better results. The purpose of this study was to generate a model for an equilibrium turbulent boundary layer for steady flow over a flat plate and compare the results obtained by using the model with experimental data. Part of the objective was to also suggest ways in which the model could be modified to obtain better results.

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No description available.

No description available.

No description available.

No description available.