MODIS-based climatology of the Surface Urban Heat Island at country scale (Romania)

This article provides the first country-scale climatology of the Surface Urban Heat Island (SUHI) investigated across the cities with more than 30,000 inhabitants from Romania using using the MODIS Land Surface Temperature (LST) data set developed within the Land Surface Temperature Climate Change Initiative (CCI) project (LST_cci), funded by European Space Agency. The main findings refer to the relationship between air temperature and LST, temporal variability of the LST over selected urban areas, and the country-scale variations of the SUHI intensity (SUHII), defined as the thermal contrast between the city and its rural proximity. Night-and day-time conditions introduce major differences, the seasonality is an important bias, and the results are presented accordingly. The LST is very well correlated with air temperature (T2m) under clear-sky conditions. At nighttime, the average SUHII is around 0.9 degrees C in all summer months, while at daytime the average SUHII equals 2.5 degrees C, in June, 2.3 degrees C in July, and 1.9 degrees C in August. The results are relevant for clear-sky conditions and show that the city size (mainly the log transformed area size), climate type (i.e., Cfa, and Cfb, by nightime, and Cfb, and Dfb, by daytime), and land use-land cover (LULC) conditions (i.e., Urban fabric) amplify the magnitude of the SUHII across Romania.