The impact of urbanization and the urban heat island effect on day to day temperature variation

• The extent of urbanization may be measured using a temperature variation measure.
• Day to day temperature variation differs between an urban and rural area.
• A greater urban footprint coincides with greater variability in temperature maximum.

Day to day temperature variation of daily temperature minimum (Tmin) and temperature maximum (Tmax) were examined for five urban–rural pairs of climate stations in North America. Day to day temperature variation was measured by averaging the absolute difference between one day and the previous day for a given time period (e.g., month). For rural sites, day to day temperature variation was typically greater for Tmin than Tmax. The opposite was found for urban locations, with statistically significant stronger signals for larger cities. It is proposed that the difference of these measures (day to day Tmax variability less day to day Tmin variability) can be used to distinguish between rural and urban stations and as a measure of increasing urbanization. Also, it is suggested that the magnitude of total change in day to day temperature variability (ΔDTD) can be used to decide a suitable urban/rural pair for any urbanization impact study.