Nocturnal urban heat island in Lisbon (Portugal): main features and modelling attempts

Abstract

In recent years, several studies have examined the Lisbon urban climate. A central conclusion is the existence of a nocturnal urban heat island (mean ΔTu−r = 2.5 °C). The aim of this paper is to summarise several attempts carried out in the last decade to interpolate nocturnal air temperatures across Lisbon, in order to be able to draw thermal maps as accurately as possible. This study refers only to clear nights. Stepwise multiple regression and a Geographic Information System were used to model the relation between air temperature and parameters related to land-use and topography. The different regression models (coefficients of determination between 0.68 and 0.92) show that canopy layer air temperature depends on sky-view factor, building height and percentage of built-up area, but also to a great extend on mesoclimatic geographic factors such as altitude, topography and distance from the Tagus River. Examples of four frequently encountered nocturnal air temperature patterns are presented, each corresponds to a different weather type. This method employed could prove useful in drawing climatic maps that may be of use in master plans of urban municipalities.