Scott Krayenhoff has led an effort to conduct a systematic review of the numerical modeling literature to understand the potential of mitigation strategies to cool cities. This study, co-authored by Broadbent, Zhao, Georgescu, Middel, Voogt, Martilli, Sailor, and Erell seeks to contextualize and assess reliability of published studies. Using 25 criteria, this study assesses methods and results from 146 studies published from 1987 to 2017. As noted by Krayenhoff, the study’s two key findings are:
1) The ability of numerical models to quantify the amount of cooling provided by urban heat reduction strategies like green roofs or street trees needs to be tested. Currently, such models are often evaluated based on their ability to represent meteorological conditions prior to implementation of the cooling strategy (e.g., tree planting, green roofs, or cool pavements or roofs).
2) The numerical modeling field is getting closer to consensus cooling effectivenesses of these strategies for clear sky summer or heat wave conditions, when the cooling is needed most. Green infrastructure and reflective materials demonstrated broadly similar ability to cool urban air temperatures per area application: approximately 0.3 degrees per 10% land area for strategies such as street trees and reflective materials. Of course there is a lot of variability around that number depending on location, weather, details of the cooling strategy, etc.
See the full paper here.