Floods in Bangkok and the Thames delta, salt intrusion in Egypt and Bangladesh: these are just some examples of rising risks to deltas and delta cities driven by climate change. Action is required now. Exchanging scientific knowledge, lessons learnt and best practices is vital. This conference will make that happen.
The impact of urban green spaces on residents’ outdoor thermal comfort – a psychological and physical approach
Green infrastructure has the ability to improve thermal comfort in outdoor urban spaces in moderate climates such as in The Netherlands. Green spaces, like parks, act as ‘cool islands’ within cities and are thermally comfortable places for outdoor activities on warm summer days. Up to now, the impact of greenery on thermal comfort, however, was only studied in physical terms, using meteorological variables and human-biometeorological indices. Little is known about the role of green spaces on people’s behaviour and generally perceived outdoor thermal comfort. Therefore, we studied the impact of green spaces both from a psychological and a physical perspective. We obtained comprehensive insights into the impact of green spaces on outdoor thermal comfort through answering the following research questions (1.) How do people generally perceive green places in urban environments during warm summer days with respect to thermal conditions? (2.) What are the physical thermal comfort conditions in urban green areas (during daytime on warm summer days)?
To identify impacts of green spaces on perceived thermal comfort we investigated inhabitants’ long-term perception of thermal comfort on warm summer days in three Dutch cities in 2011/ 2012. In order to find evidence for people’s perception in the urban environment, we additionally examined the daytime cooling effect of green spaces in Utrecht. To do so, we used bicycles equipped with micrometeorological sensors in summer 2012. We compared thermal conditions of 13 parks with conditions in the city centre and in the open grassland outside the city and analysed dependences with spatial variables of parks (size, tree canopy, upwind vegetation cover).
Our results demonstrate that green spaces generally enhances perceived thermal comfort. People evaluate green urban spaces as the most thermally comfortable spaces. The physical data we obtained show that the physiological equivalent temperatures (PET) in parks are on average 1.9 K lower than in the city center and 5 K lower than in the surrounding grasslands during the hottest period of the day. Thermal variation between the parks is significantly related to tree canopy cover and upwind vegetation cover. In contrast, no significant relationship with park size is found. In general, our study indicates that there is a good fit between people’s perception of urban green and its physical impact on thermal conditions.
The results of our studies emphasize the need to preserve, maintain and develop green infrastructure in cities, to ensure residents’ thermal comfort in present and future urban environments.
Dipl. Ing. Wiebke Klemm, Dr. ir Bert Heusinkveld, Dr. Dipl. Ing Sanda Lenzholzer, Dr. ir Maarten Jacobs, Dr. ir Bert van Hove
Dipl.Ing. Wiebke Klemm, Wageningen University, Landscape Architecture Group
Adres: Droevendaalsesteeg 3, 6708 PB Wageningen, The Netherlands