Innovative observations and analysis of human thermal comfort in Amsterdam

The Netherlands has a mild mid-latitude climate. Meteorological records for The Netherlands show that the number of hot summer days has increased, and future climate change projections predict the same trend. Heat stress is the major cause of weatherrelated urban human mortality. The urban heat island effect is significant for the Netherlands (summertime nocturnal UHI 95% >7 K) (Steeneveld et al., 2011, Heusinkveld et al., 2014) as more than 80% of the Dutch population live in cities and are thus subject to such added stress. For human thermal comfort during heat waves, shading is more important than wind according to Mayer and Höppe, 1987. However, for the Netherlands wind may also be relevant due to the proximity of the sea and large lake bodies. Here, measurements and analysis results are presented using an innovative mobile measurement system and a dense urban weather station network. The mobile measurements were used to assess the spatial variability of human thermal comfort (Heusinkveld, et al., 2010 & 2014). A key feature of the mobile measurement system is the direct measurement of mean radiant temperature and wind speed. To do so, a special cargo bicycle was equipped with 6 pyranometers, 6 pyrgeometers, 2D wind speed/direction, temperature, humidity, bicycle speed and GPS sensors. Mobile measurements can provide great spatial detail from a large set of sensors. However temporal resolution is limited and therefore a dense urban weather station network of temperature/humidity and wind speed was set up. Within a city the lower average wind speed increases the radiation induced temperature error of a thermometer screen. To minimize such errors, all air temperature/humidity sensors used on the mobile and urban weather stations were equipped with aspirated thermometer screens. References: Heusinkveld BG, LWA van Hove, CMJ Jacobs, GJ Steeneveld, JA Elbers, EJ Moors, AAM Holtslag (2010) Use of a mobile platform for assessing urban heat stress in Rotterdam, Proceedings of the 7th Conference on Biometeorology. Instituts der Albert-Ludwigs- Universität Freiburg 20 (2010). - ISSN 1435-618X - p. 433–438. Freiburg: 2010. Heusinkveld, B.G. , Steeneveld, G.J. , Hove, L.W.A. van , Jacobs, C.M.J. , Holtslag, A.A.M., 2014: Spatial variability of the Rotterdam urban heat island as influenced by urban land use. Journal of Geophysical Research - Atmospheres 119, 677 - 692. Mayer H, Hoppe P (1987) Thermal comfort of man in different urban environments, Theor Appl Clim 38: 43-49. Steeneveld, G.J., S. Koopmans, B.G. Heusinkveld, L.W.A. van Hove, and A.A.M. Holtslag, 2011: Quantifying urban heat island effects and human comfort for cities of variable size and urban morphology in The Netherlands., J. Geophys. Res., 116, D20129, doi:10.1029/2011JD015988.