Urban effects on the diurnal temperature cycle in Phoenix, Arizona

Empirical estimations of urban effects on the diurnal temperature cycle were carried Out for Phoenix, Arizona, through a framework capable of estimating the mean urban effect on air temperature. The analysis of pre-urban and urban differences in hourly temperature data at Sky Harbor International Airport during dry tropical conditions in June and January revealed a significant urban influence. Minimum temperature was most influenced by urbanization with the mean minimum temperature during the urban period exceeding that of the pre-urban period by 4.4 degrees C (2.4 degrees C) in June, (January). A significant. urban heat. sink in January maximum temperatures was evident as the mean maximum temperature during the pre-urban period exceeded that of the urban period by 1.5 degrees C. The greater thermal inertia Clue to urban growth around the airport and the growth of the airport itself has also had an effect on nocturnal cooling rates. Pre-urban January minimum temperatures typically Occurred between 06:00 and 07:00 local standard time (LST) in the pre-urban period and between 07:00 and 08:00 LST in the urban period, Similarly, in June, the minimum temperature Occurred oil average around 05:00 LST during the pre-urban period and between 05:00 and 06:00 LST during the urban period. This apparent decrease in cooling rates was modeled well by the first harmonic fit. to the average hourly temperature data.