Spatial and temporal air temperature variability in Berlin, Germany, during the years 2001-2010

Long-term data (2001-2010) were studied to analyse the spatial and temporal variability of air temperatures (T) in Berlin, Germany. Five sites were used to investigate spatial air temperature differences (ΔT). The sites were classified according to the Local Climate Zone concept. Temporal anomalies, being the differences between hourly values and the decadal average at that time, were investigated for air temperatures (T′) and air temperature differences (ΔT′). Decadal ΔT was strongly positive during night-time inside the city compared to the reference site (“scattered trees” - LCZ B) during summer. During winter ΔT was slightly positive throughout the whole day. Comparing two sites with LCZ “dense trees” inside and outside the city revealed a temperature excess of 0.3 K. T′ inside the city compared to T′ outside the built-up structures was damped by at least 10%. The urban canopy responded similar to a forest canopy in damping T′. Hot weather conditions lead to negative ΔT′ during daytime and positive ΔT′ at night. The nocturnal values were related to spatial mean vegetation fractions and sky view factors (SVF) including vegetation. SVF without vegetation did not show this relationship, highlighting the importance of including trees in spatially averaged SVF computation.