Decreases in the urban heat island effect during the Coronavirus Disease 2019 (COVID‐19) lockdown in Wuhan, China: Observational evidence

Abstract

The Coronavirus Disease 2019 (COVID-19) lockdown in early 2020 reduced human activities in Wuhan, China, thereby altering the urban heat island (UHI) effect. The epidemic period (EP) during January 1, 2020-May 31, 2020 is divided into four stages, including pre-lockdown, first (EP_LS1) and second (EP_LS2) lockdown, and after-lockdown (EP_ALS) stages, which are identified according to different antivirus measures in early 2020 and confirmed by comparing the daily electricity consumption over the Wuhan metropolitan area during 2020 and 2019. Then, the Wuhan UHI intensity (UHII) during each stage is compared to that during the baseline period of 2016-2019 and 2021. Daytime, night-time, and daily UHIIs are reduced; the larger decrease is during EP_LS1 and EP_LS2, of which EP_LS1 with the strictest antivirus measures shows a significant decrease (<−0.12 C or <−36%), especially during night-time with −0.23 ± 0.05 C (or −47 ± 9%). The declined UHII persists in all stages (excluding EP_ALS), even after removing the natural variability of the air temperature; EP_LS1 still exhibits the largest and significant decrease (<−0.18 C or <−52%).To remove possible impacts of the local weather conditions, the UHII changes are recalculated by randomly sampling the 90, 80, 70, and 60% data points in each stage of EP with 1,000 repetitions. Results suggest limited influence of the local weather conditions, and then validate our findings. This study provides an important observational evidence of human-induced control on urban climate, and further confirms the necessity to include human dynamics in climate/earth system models for better simulating and predicting urban climate.

Spatiotemporal Analysis of Urban Heat Islands and Vegetation Cover Using Emerging Hotspot Analysis in a Humid Subtropical Climate

“…For several reasons, understanding temporal and spatial variations in urban heat islands (UHI) is critical [1]. First, the UHI effect is a phenomenon in which metropolitan regions have greater temperatures than surrounding rural areas due to human activities such as transportation, industrial processes, and building materials [2].…”

Study on the Impact of Urban Morphologies on Urban Canopy Heat Islands Based on Relocated Meteorological Stations

“…The CUHII is commonly defined as the difference in near-surface temperature between urban and rural stations or regions. The classification of meteorological stations is typically based on various criteria, population [13][14][15], land cover/land use (LCLU) [16][17][18], and spatial location [19]. Using population as an example, Liu et al [15] classified meteorological stations with a population of fewer than 40,000 as reference stations.…”

“…In terms of land use criteria, Ren et al [16] considered a station as a reference station if the area within a 2 km radius centered on the station had less than 33% artificial construction. Sun et al [17] identified a rural site as one where the percentage of built-up land areas within 1-5 km and 7-78 km buffer zones was less than 3% and 15%, respectively.…”