Contents lists available at ScienceDirect Urban Climate journal homepage: www.elsevier.com/locate/uclim Between aspiration and actuality: A systematic review of morphological heat mitigation strategies in hot urban deserts Saud AlKhaled a,⁎ , Paul Coseo b,c , Anthony Brazel c,d , Chingwen Cheng b,c , David Sailor c,d a College of Architecture, Kuwait University, Adailiya, Kuwait b The Design School, Herberger Institute for Design and the Arts, Arizona State University, 1001 S Forest Mall, Tempe, AZ 85287, USA c Urban Climate Research Center, Arizona State University, PO Box 85287-5302, Tempe, AZ 85287-5302, USA d School of Geographical Sciences and Urban Planning, Arizona State University, 975 S. Myrtle Ave., Tempe, AZ 85287, USA ARTICLE INFO Keywords: Heat mitigation Urban desert Heat vulnerability Urban morphology Urban materials Urban landscapes ABSTRACT The rising risks of thermal extremes are among the largest global threats. They are significant in hot urban deserts (HUDs) given the already high air temperatures, urban-induced heating, and vulnerability of residents. The challenge compounds as localities combat urban heating with mitigative approaches unmindful of on-ground constraints in hot desert environments. Based on a systematic literature review, this study investigates the current state of knowledge of mor- phological heat mitigative interventions in HUDs. First, metrics, measurements, and methods were extracted to examine the applicability of different interventions. Then, a content synthesis identified the levels of strategy success. Lastly, challenges and uncertainties were identified to compare mitigation aspirational aims from their actualities. For hot urban deserts, the results indicate opportunities to use seldomly investigated morphological metrics such as the length of contiguous vertical facets and intermediate orientations of canyons to mitigate urban-induced heating. In addition, this study reports the methodological challenges in metric computations across scales. It revealed the impact of coupling effects and measurements approaches in defining the success of morphological mitigative interventions. The review illustrates the need to unpack complex relationships between mitigation interventions and thermal stimuli both spatially and temporally to optimize benefits and minimize tradeoffs of mitigation strategies. 1. Introduction In hot urban desert regions (HUDs), urbanization processes have combined with thermally extreme bioclimatic dynamics to create today's magnitude, frequency, and distribution of urban-induced warming. Urban-induced warming was documented first in London and then in other industrial cities (Howard, 1833; Kratzer, 1937; Oke, 1968). This urban-induced warming is also known as the urban heat island (UHI) effect. Discovery of UHI accompanied findings that associated changes in carbon dioxide concentrations with human-induced global climate change, commonly known as greenhouse gas forcing (Arrhenius and Holden, 1897). Today, urban- induced warming and greenhouse gas forcing work in parallel to produce dangerous, localized heat episodes that may last from days to months. In particular, cities in hot desert regions are especially vulnerable to sustained, dangerous, and increasingly perilous thermal conditions (Pal and Eltahir, 2015). https://doi.org/10.1016/j.uclim.2019.100570 Received 30 April 2019; Received in revised form 17 September 2019; Accepted 1 December 2019 ⁎ Corresponding author at: College of Architecture, Kuwait University, Adailiya, Kuwait E-mail address: saud.alkhaled@ku.edu.kw (S. AlKhaled). Urban Climate 31 (2020) 100570 2212-0955/ © 2019 Elsevier B.V. All rights reserved. T