Surface-AIr Temperature Relationships in the Urban Environment of Phoenix, Arizona

Standard automated weather data were collected over a 70-day period during summer 1989 at three sites in the Phoenix metropolitan area. Mean hourly observations of air temperature at 1.5 m and 3.0 m, infrared surface temperature, vapor pressure, incoming solar radiation, and vector wind velocity are used for a stepwise multiple regression analysis. Hourly regression equations, totalling 144 in number, are derived for each site with air temperature at 1.5 m and 3.0 m as dependent variables. Not surprisingly, surface temperature is the primary independent variable significantly correlated with both levels of air temperature. Atmospheric stability significantly decreases the surface-to-air temperature coupling process at each site. Wind velocity, which displays strong diurnal variability, decouples the surface and air temperature. The surface/air temperature relationships at the two more complex sites studied are significantly influenced by advection from adjacent land uses. Thermal admittance and evapotranspiration are determined to affect strongly the surface-air temperature relationships at a periodically irrigated grass site, and play a less significant role at the more complex sites studied. Helicopter remotely sensed temperatures provide further insights into the representativeness of the ground station data. [Key words: surface-air temperature, urban climate, scale, Phoenix.]