Urban Heat Island and Park Cool Island Intensities in the Coastal City of Aracaju, North-Eastern Brazil

Max Anjos,António Lopes

doi:10.3390/su9081379

Abstract

In this study, an evaluation of the Urban Heat Island (UHI) and Park Cool Island (PCI) intensities in Aracaju, North-Eastern Brazil, was performed. The basis of our evaluation is a 2-year dataset from the urban climatological network installed with the principles and concepts defined for urban areas related to climatic scales, sitting and exposure, urban morphology, and metadata. The current findings update UHI intensities in Aracaju refuting the trend registered in previous studies. On average, the UHI was more intense in the cool season (1.3 °C) than in hot season (0.5 °C), which was caused by wind speed decrease. In relation to the PCI, mitigation of high air temperatures of 1.5–2 °C on average was registered in the city. However, the urban park is not always cooler than the surrounding built environment. Consistent long-term monitoring in the cities is very important to provide more accurate climatic information about the UHI and PCI to be applied in urban planning properly, e.g., to provide pleasant thermal comfort in urban spaces.

Highlights

The Urban Heat Island (UHI) is one of the most well-known thermal patterns in settlements
In Aracaju, the UHI has proven to be more intense during the cool season than in the hot season
The results have shown that during cool afternoons UHI intensity averages increased with a peak of 1.3 ◦C at 15:00 caused by the overall average wind speed decrease compared to the hot season, whereas in this season the average daily UHI intensity was of about 0.5 ◦C, which is considered a case of the near-absence of UHI

Summary

Introduction

The Urban Heat Island (UHI) is one of the most well-known thermal patterns in settlements. The UHI refers to the generally warmer urban atmosphere when compared with the surrounding non-urban areas. UHI intensity is defined as the maximum temperature difference between urban and rural areas (∆Tu=urban-r=rural). The first approach (∆Tu-r) compares the temperature of the warmest location in the urban area with the temperature of a location in the rural area that is seen as the coolest. Brazilian cities are characterized by complex urban morphologies, and defining what is ‘urban’ and ‘rural’ is not an easy task [1], since those adjectives may have different connotations. There may be urban areas that are not the warmest, and the heating of non-urban areas cannot be disregarded from the analysis

Results

Discussion

Conclusion