The design, construction and initial operation of the Canterbury University ST radar (2003)
AuthorsCarey-Smith, Trevor K.show all
This thesis describes the design, construction and initial operation of the Canterbury University Stratosphere-Troposphere Atmospheric Radar (CUSTAR), which is capable of continuous measurement of the vertical wind profile from 3 to 15 km in altitude, with a temporal resolution of 2 minutes and a height resolution of 300 metres. A novel, cost-effective antenna array has been designed to maximise the effective aperture, while keeping side-lobes at a minimum. The beam pattern of the array has been investigated in great detail using astronomical radio sources. Vela XYZ and Centaurus A both pass directly over the radar site, and using these strong sources, the best estimate of the pointing angle of the beam, in the east-west plane, was found to be 0.01° ± 0.20° from the zenith. The best estimate of the half-power full-width of the antenna beam was found to be 6.51° ± 0.54°. The Canterbury University ST radar has been operating since September, 2002, during which time the tropopause height has been determined hourly. A seasonal variation in tropopause height of approximately 1 km between September/October and November/December was observed, which agrees with climatalogical radiosonde measurements performed in Christchurch. Comparisons were performed between the radar tropopause height and the tropopause height measured by radiosondes in three locations throughout New Zealand. It was found that the correlation between the radar and radiosonde tropopause heights was similar to the correlation between different radiosonde sites, suggesting that the radar is capable of finding the tropopause height with similar accuracy to radiosonde measurements. The structure of a cold front which passed over Christchurch on September 10, 2002, has been examined in detail using radar signal to noise ratio profiles. Gravity wave oscillations, that were most likely to be caused by orography, were observed underneath the frontal surface, which was found to have a slope of 0.4°. The wave activity was thought to occur due to the strong cross-mountain background wind and also the increase in atmospheric stability associated with the frontal passage.