Synergies between urban heat island and heat waves in Seoul: The role of wind speed and land use characteristics.

Inhan Kim,Jack Ngarambe,Geun Young Yun,Jacques Nganyiyimana,Jun Yang,Mat Santamouris

doi:10.1371/journal.pone.0243571

Abstract

The effects of heat waves (HW) are more pronounced in urban areas than in rural areas due to the additive effect of the urban heat island (UHI) phenomenon. However, the synergies between UHI and HW are still an open scientific question and have only been quantified for a few metropolitan cities. In the current study, we explore the synergies between UHI and HW in Seoul city. We consider summertime data from two non-consecutive years (i.e., 2012 and 2016) and ten automatic weather stations. Our results show that UHI is more intense during HW periods than non-heat wave (NHW) periods (i.e., normal summer background conditions), with a maximum UHI difference of 3.30°C and 4.50°C, between HW and NHW periods, in 2012 and 2016 respectively. Our results also show substantial variations in the synergies between UHI and HW due to land use characteristics and synoptic weather conditions; the synergies were relatively more intense in densely built areas and under low wind speed conditions. Our results contribute to our understanding of thermal risks posed by HW in urban areas and, subsequently, the health risks on urban populations. Moreover, they are of significant importance to emergency relief providers as a resource allocation guideline, for instance, regarding which areas and time of the day to prioritize during HW periods in Seoul.

Highlights

The world has seen recent increases in temperature that are, arguably, attributable to climate variability and increased greenhouse gas emissions that intensify radiative forcing [1]
This finding suggests that the frequency of heat waves (HW) and the intensity of urban heat island (UHI) both flourish under the same synoptic weather conditions, notably reduced wind speeds are the likely reason for the differences in UHI levels between HW and non-heat wave (NHW) periods observed in Seoul city
We explored the synergistic interactions between HW and UHI in Seoul city

Summary

Introduction

The world has seen recent increases in temperature that are, arguably, attributable to climate variability and increased greenhouse gas emissions that intensify radiative forcing [1]. This increase in global temperature results in adverse effects on the ecosystem, food security, water supply, human health, and well-being. One of the consequences of increased temperatures with definitive and detrimental effects on human health is the occurrence of heat waves (HW). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Methods

Results

Discussion

Conclusion