Urbanization Effects on Tmax and Tmin

Urban warming is much larger at night than during the day. Roy Spencer has calculated the cumulative urban heat island effect (UHIE) during the months May, June and July of the recorded and adjusted maximum temperatures (Tmax) and minimum temperatures (Tmin). The results show than the UHIE on Tmin of high population density locations (around 10,000 persons per km2) is 3.5 °C and the UHIE on Tmax is 1.0 °C, both using adjusted GHCN datasets produced by NOAA from land stations from 20°N to 80°N. In other words, the UHIE on Tmin is 3.5 times as large as on Tmax at high population densities. The UHIE on Tmin is 2.8 times as large as on Tmax at medium population densities of about 2000 persons per km2. Calgary’s population density is 1,590 persons per km2.

[drroyspencer.com]