The origins of modern urban climate science: reflections on 'A numerical model of the urban heat island'

Modern urban climatology is a part of boundary-layer climatology with a focus on the urban effects on the atmosphere. The best known of these effects is the urban heat island (UHI), which has been a subject of study for more than 200 years and may be categorised into air, surface and substrate types. Progress on this topic has occurred in various phases associated with theoretical developments, improvements in technology (instruments and computing) and study design, to isolate the causative drivers. The history of the field can be categorised into response-based (descriptive) and process-based (analytic) periods associated with hypothesis generation and testing, respectively. Myrup's paper on simulating the UHI, published in 1969, is at the forefront of this shift in approach and is the first application of numerical modelling to the topic. Its computational methods place the UHI within the context of the surface energy budget and the exchanges of energy, urban characteristics, and the substrate as well as overlying air. The paper is a classic that had considerable impact on the approach that geographical climatology took to examining the UHI; however, it is not without its limitations Careful reading of Myrup's work provides insights into how the field has evolved in the last 50 years. In particular the recurring issues associated with conceputalising the urban thermal effect and challenge of comparing models results with field observations. Remarkably, key urban climate questions on how to cool cities, how to plan cities for future climate, and the factors that impact UHI are still being studied, albeit with more sophisticated models. A numerical model of the urban heat island is part of a rich literature on the UHI that illustrates the development of the urban climate science that deserves to be read and cited.