Numerical characterization of spatial and temporal evolution of summer urban heat island intensity in São Paulo, Brazil

Abstract The WRF model was used to simulate the air temperature field in January in Sao Paulo, Brazil, for 10 consecutive years (2004–2013), and to estimate the intensity of the urban heat island (UHI). The analysis considered: days with sea breeze passages, days with cold fronts, days with no sea breeze or cold front passages, and all days. The UHI intensity varied from 1.5 to 2.5 K between 0000 local time (LT) and 1100 LT, and from 2.5 to 3.5 K between 1200 LT and 2300 LT. The UHI core was aligned in the SW-NE direction during daytime. At night, the UHI core was larger, expanding over the urban area. The synoptic conditions substantially impacted the UHI intensity, spatial variability, and diurnal pattern: sea breeze days presented the highest UHI intensity and amplitude during the day; cold front days presented the smallest amplitude of UHI diurnal variability; and days with no fronts presented a larger area of higher temperatures, particularly at night. The UHI intensity for January 2014 was compared to the 10-year average for January. It presented a higher UHI intensity at night than the average for January and showed a UHI diurnal pattern similar to the sea breeze pattern.