Urban influences on boundary layer temperature and humidity: Results from Christchurch, New Zealand

• Published in: Atmospheric environment. Part B, Urban atmosphere Urban atmosphere, 1990, Vol.24 (1), p.19-27
• Main Author: Tapper, N.J.
• Format: Article
• Language: English
• ISSN: 0957-1272
• DOI: 10.1016/0957-1272(90)90005-F

Boundary layer temperature and humidity data gathered at an urban and rural location using a mobile tethersonde system are presented to show the effects of urban Christchurch on the vertical distribution of these parameters under clear-sky conditions. Nocturnally, an urban temperature excess, amounting to an average 2.5°C in the lowest layers, was consistently observed to approximately 290 m. Above that level there existed a shallow layer of cooler urban temperatures. By day, excess temperatures in the urban boundary layer were less well defined. Consistent with the above observations, nocturnal rural temperature inversions were stronger than for the urban location, while daytime temperature lapse rates were slightly greater at the rural location. Significant urban-rural differences in boundary layer moisture content were also determined, with a nocturnal excess of specific humidity typically observed to about 350 m over the city. Although nocturnal humidity inversions predominated at both locations, they were observed to be lower and more intense at the rural site. Daytime observations indicated that rural humidity lapse profiles were stronger and that an urban moisture deficit existed to approximately 200 m. Possible reasons for the observed urban-rural differences in boundary layer temperature and moisture are discussed.