Relationship between the COVID-19 Outbreak and Temperature, Humidity, and Solar Radiation Across China

Novel coronavirus (COVID-19)-infected pneumonia appeared in Wuhan City, Hubei Province, China in early December 2019. Since then, COVID-19 cases have appeared in many provinces in China. While the incidence of many infectious diseases, including that of coronavirus, shows seasonal patterns, our understanding of this phenomenon is still incomplete. We used fifth-generation re-analysis data (ERA-5) released by the European Center for Long-Term Weather Forecast (ECMWF), counted the cumulatively confirmed cases in each province from January and February 2020, and analyzed the data after the outbreak of COVID-19 from early December in China. The relationship between the number of cases and the monthly average temperature, specific humidity, and downward short-wave ultraviolet (UV) radiation in each province of China, showed that COVID-19 cases were concentrated in the provinces with temperatures in range of 0–10 °C. The downward short-wave UV radiation in these areas was below 1.5 MJ·m-2·d, while the specific humidity range was between 2–6 g/kg. These meteorological and environmental factors may be the most suitable environments for potential transmission of the virus. A further understanding of the environmental factors that are prevalent in the development of COVID-19 will help predict the potential risks of the global spread of this disease, and provide support for the prevention and surveillance of countries around the world.