The application of RASS in urban boundary layer meteorology /

This thesis describes the application of a Radio-Acoustic Sounding System (RASS) at an urban site, and proposes a Rank-Order Signal Processing Algorithm (ROSPA) to overcome the problems associated with that type of application. The main problem is clutter of many kinds contaminating the clear-air profiler measurements. ROSPA uses primarily order statistics, and operates in two main stages. The first stage operates on the clear-air Doppler velocity spectra by using a threshold minimum filter on the successive spectral power values at a given Doppler velocity bin for several spectra at a given altitude. The threshold minimum filter is a variant of the minimum filter. The second stage operates on the time-height mean Doppler clear-air velocity data by imposing a median filter. It is shown using theoretical models that the minimum and median filters possess the properties required to eliminate intermittent clutter, namely their insensitivity with respect to outliers. A profiler/RASS at an urban site, another at a rural site, and an airplane flying over mainly rural terrain, are used to study the urban boundary layer on the clear and convective early afternoon of June 28, 1996. The rural profiler/RASS data are free of clutter and show an initially stable rural boundary layer becoming convective in the middle of the observation period, and attaining a depth of about 1 km at the end of the period. The urban profiler/RASS data are treated with ROSPA to eliminate the severe intermittent clutter contamination and show a convective urban boundary layer over the entire observation period, with a depth increasing from 1.5 to 1.8 km. The heat flux profile of the second half of the rural RASS data agrees well with the airplane profile up to about 0.6 km. The surface heat flux estimated by airplane measurements is 146 +/- 0.77 W/m2, while the urban RASS measurements yield 523 +/- 239 W/m2. This result, along with comparisons of the vertical velocity variance profiles, is consis