Abstract
Abstract. Urban greenery has various positive micro-climate effects including mitigation of heat islands. The primary root of heat islands in cities is in absorption of solar radiation by the mass of building structures, roads and other solid materials. The absorbed heat is subsequently re-radiated into the surroundings and increases ambient temperatures. The vegetation can stop and absorb most of incoming solar radiation mostly via the photosynthesis and evapotranspiration process. However, vegetation in mild climate of Europe manifests considerable annual seasonality which can also contribute to the seasonal change in the cooling effect of the vegetation on the urban climate. Modern methods of high-resolution mapping and new generations of sensors have brought opportunity to record the dynamics of urban greenery in a high resolution in spatial, spectral, and temporal domains. In this paper, we use the case study of the city of Košice in Eastern Slovakia to demonstrate the methodology of 3D mapping and modelling the urban greenery during one vegetation season in 2016. The purpose of this monitoring is to capture 3D effects of urban greenery on spatial distribution of solar radiation in urban environment. Terrestrial laser scanning was conducted on four selected sites within Košice in ultra-high spatial resolution. The entire study area, which included these four smaller sites, comprised 4 km2 of the central part of the city was flown within a single airborne lidar and photogrammetric mission to capture the upper parts of buildings and vegetation. The acquired airborne data were used to generate a 3D city model and the time series of terrestrial lidar data were integrated with the 3D city model. The results show that the terrestrial and airborne laser scanning techniques can be effectively used to monitor seasonal changes in foliage of trees in order to assess the transmissivity of the canopy for microclimate modelling.
Highlights
The positive micro-climate effects of urban greenery are wellknown
The terrestrial laser scanning (TLS) of urban greenery was done in four study sites during the period April – November 2016 using the Riegl VZ-1000 scanner equipped with the Nikon D700 camera
Its geometrical structure and spectral reflectance influence the effect of greenery in urban space. Contemporary mapping technologies such as terrestrial and airborne laser scanning enable capturing the state of vegetation in high resolution repeatedly
Summary
The positive micro-climate effects of urban greenery are wellknown. During hot summers, they reduce high temperatures caused by urban heat islands and provide numerous other positive environmental effects, such as higher humidity and reduction of dust. The key reason of heat islands in cities is in to the absorption of solar radiation by mass building structures, roads and other hard surfaces. The absorbed heat is subsequently re-radiated into the surroundings and increases ambient temperatures. The vegetation can stop and absorb most of incoming solar radiation mostly by photosynthesis and evapotranspiration process. The cooling effect of urban greenery goes beyond its boundary, in many cases in several hundreds of meters. The phenomenon of urban heat island is elucidated by Oke (1973)
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