Urban Heat Island in Moscow Derived from Satellite Data

The results of surface temperature measurements in the Moscow region by Aqua and Terra satellites are presented for the period of 2008-2015. High correlations between radiometer data and station data on air temperature and surface temperature from the Meteorological Observatory of Mos cow State University are revealed. However, station data on surface temper ature in summer are overestimated by 15 degrees C as compared with satellite data due to the strong heating of the naked site with ground thermometers. The mean intensity of surface urban heat island in Moscow Delta T is 2.6 degrees C; it poorly depends on the selection of boundaries of comparison of the outer area with the city (at distances >60 km differences do not exceed +/- 0.1 degrees C). Numerical experiments demonstrate that if the cloud cover is not higher than 20% of the city area and 50% of the region area, a dis placement in the estimates of DT is small (+/- 0.2 of the value). According to station data at the time of satellite flights, the urban heat island intensity in the air temperature field over Moscow is lower than the corresponding intensity in the surface temperature field obtained from satellite data due to the sparse ground meteorological network and incomplete representativeness of station data (four of five city stations are located in green park zones). According to the ground network data, the intensity of the surface heat island in the daytime hours of satellite flight is by about three times smaller than the mean daily value. On the other hand, Delta T derived from satellite data is overestimated by similar to 40% due to the impact of anticyclones which enhance the heat island and allow the analysis of images. In the annual course, the surface heat island intensity is maximum in June and July (similar to 4.0 degrees C) and minimum in November (0.7 degrees C). The surface temperature field in the Moscow region is also characterized by the geo graphic zonality: a total increase in the values toward southeast.