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

Abstract

AbstractThe 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.