Temperature Anomaly in the Tokyo Metropolitan Area during the COVID-19 (coronavirus) Self-Restraint Period

Japan underwent a nationwide self-restraint of human activities in spring 2020 to prevent the spread of the COVID-19 infection. In order to evaluate the effect of suppressed human activities on temperature in the Tokyo Metropolitan area, a statistical analysis was made for temperature anomalies during the self-restraint period using hourly data on the AMeDAS network. The temperature anomaly was defined by the departure from the value that would have been observed without self-restraint, estimated from regression analysis for temperatures at surrounding non-urban stations. It was found that the temperature in central Tokyo (Kitanomaru Park) had a negative anomaly of -0.49 degrees C with a 95% confidence range of +/- 0.19 degrees C on the average over the strong self-restraint period from April to May. The anomaly was larger in the nighttime than in the daytime, and was found in an area spreading for several tens of kilometers, with a decreasing magnitude according to the distance from Tokyo. These facts indicate a possibility that the reduction of anthropogenic heat release during the self-restraint period resulted in substantial decrease of temperature in the Tokyo Metropolitan area.