Abstract
Abstract. In this letter, the Brussels's urban heat island (UHI) effect on the near-surface air temperature time series of Uccle (the national suburban recording station of the Royal Meteorological Institute of Belgium) was estimated between 1955 and 2006 during the summer months. The UHI of Brussels was estimated using both ground-based weather stations and remote sensing imagery combined with a land surface scheme that includes a state-of-the-art urban parameterization, the Town Energy Balance scheme. Analysis of urban warming based on the remote sensing method reveals that the urban bias on minimum air temperature is rising at a higher rate, 2.5 times (2.85 ground-based observed) more, than on maximum temperature, with a linear trend of 0.15 °C (0.19 °C ground-based observed) and 0.06 °C (0.06 °C ground-based observed) per decade respectively. The summer-mean urban bias on the mean air temperature is 0.8 °C (0.9 °C ground-based observed). The results based on remote sensing imagery are compatible with estimates of urban warming based on weather stations. Therefore, the technique presented in this work is a useful tool in estimating the urban heat island contamination in long time series, countering the drawbacks of an ground-observational approach.
Highlights
It is important to know whether, and to what extent, estimates of global warming trends can be explained by the growth of the urban heat island (UHI) due to increased urbanization
In their study, no observed data were found to compare the results. Their model-based estimate of urban warming was based on calculating the difference between two model integrations: (i) “the rural” scenario representing a hypothetical situation with no urban areas inside the Brussels Capital Region domain and (ii) the “urban” scenario, which represented the climate in the presence of urban areas using the measured historical changes of surface cover fractions
In this work, the UHI effects on the near-surface air temperature time series of Brussels during summer months is estimated using both ground-based weather stations and remote sensing imagery combined with a land surface scheme and the results compared
Summary
It is important to know whether, and to what extent, estimates of global warming trends can be explained by the growth of the urban heat island (UHI) due to increased urbanization. If observations of near-surface air temperatures in growing cities are used in the assessment of global warming trends, these trends may be overestimated. The change in urbanization over time is smaller for a station that originally was established in a densely built-up area than for a station originally installed in a rural or little urbanized environment that has experienced growth. Jones et al (2008) have shown that near-surface air temperatures in central London and Vienna did not rise relative to rural locations nearby in recent decades. Suburban sites continue to warm relative to nearby rural areas until local urbanization is complete, as shown for London’s Heathrow airport by Jones and Lister (2009). The past observational approach compared urban nearsurface air temperature records with records of a rural area. In situ observations usually suffer from inhomogeneities caused by nonclimatic factors such as changes in observation time, instrumentations, location (altitude and latitude), and other local meteorological features
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