Landscape and Urban Planning 122 (2014) 78–88 Contents lists available at ScienceDirect Landscape and Urban Planning jou rn al hom epage : www.elsevier.com/locate/landurbplan Research Paper Human-biometeorological assessment of heat stress reduction by replanning measures in Stuttgart, Germany Christine Ketterer ∗ , Andreas Matzarakis 1 Chair of Meteorology and Climatology, Albert-Ludwigs-University Freiburg, Werthmannstrasse 10, 79085 Freiburg, Germany h i g h l i g h t s Reconstruction changes have been assessed using PET. Small green areas have only local effects on thermal comfortable conditions. Single mitigation and adaptation measures can reduce PET by two assessment classes. A NW–SE oriented street canyon (H/W ratio > 1.5) provides best thermal conditions. a r t i c l e i n f o Article history: Received 7 May 2013 Received in revised form 24 October 2013 Accepted 4 November 2013 Keywords: Physiologically equivalent temperature Urban planning Replanning Stuttgart ENVI-met RayMan a b s t r a c t Adaptation and mitigation measures, which could be utilized in urban planning, were quantified in regard to their influence on thermal conditions for humans. The effects of city-planning redesign on ther- mal human-biometeorological conditions are analysed in an urban quarter in Stuttgart, Germany. Two micro-climate models are applied to receive quantitative information about mitigation and adaptation measures. The Physiologically Equivalent Temperature (PET) was simulated by RayMan and ENVI-met 3.5 to assess thermal human-biometeorological conditions of the current urban environment. The planned residential area and different green space scenarios are analysed and their thermal conditions are com- pared. In addition, different orientations and aspect ratios in street canyons were analysed. Aim was to find out how heat stress during summer can be minimized and to optimize thermal comfort and solar access for mid-latitude cities during the whole year. PET was found to be around 10 ◦ C lower under trees compared to green areas (38 ◦ C) and at least 25 ◦ C lower than over sealed areas (48 ◦ C). This result cor- responds to an increase of heat stress of three thermophysiological assessment classes for PET. Thermal stress can be reduced in a street canyon with a northwest-southeast orientation combined with an aspect ratio of at least 1.5. This configuration allows nevertheless solar access during winter and maximizes the frequency of thermal conditions during the whole year. © 2013 Elsevier B.V. All rights reserved. 1. Introduction As heat stress is expected to occur more frequently, more intense and long-lasting in Middle Europe in the 21st century (Meehl & Tebaldi, 2004; Schär et al., 2004), measures for the improvement of urban climate are indispensable to enhance health and well-being of city dwellers (Matzarakis & Nastos, 2011). Therefore, the consid- eration of climatic aspects of urban structures for city planners is essential (Eliasson, 2000). One facing target, not only for anthro- pogenic climate change issues, is to create appropriate climatic ∗ Corresponding author. Tel.: +49 761 203 6925; fax: +49 761 203 6922. E-mail addresses: Christine.Ketterer@meteo.uni-freiburg.de (C. Ketterer), Andreas.Matzarakis@meteo.uni-freiburg.de (A. Matzarakis). 1 Tel.: +49 761 203 6921; fax: +49 761 203 6922. conditions by means of vegetation (Matzarakis & Endler, 2010; Shashua-Bar & Hoffman, 2004). As human beings experience the integral effect of the mete- orological conditions that include air temperature, air humidity, wind velocity and radiation fluxes, all these parameters have to be considered in an assessment of the thermal environment (Fanger, 1972). Since other experimental studies did not find significant micro-scale stratifications of air temperature within a street canyon (Bourbia & Awbi, 2004; Santamouris, Papanikolaou, Koronakis, Livada, & Asimakopoulos, 1999), an analysis based on air tem- perature alone is therefore not appropriate (Thorsson, Lindberg, Björklund, Holmer, & Rayner, 2011). Experimental studies are mostly limited to existing urban morphology and single point mea- surements. However, micro-scale models, e.g. ENVI-met (Bruse & Fleer, 1998; Huttner, 2012), SOLWEIG (solar and longwave environ- mental irradiance geometry; Lindberg, Holmer, & Thorsson, 2008) and RayMan (Matzarakis, Rutz, & Mayer, 2007, 2010) are more 0169-2046/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.landurbplan.2013.11.003