"This application provides visualizations of data related to the COVID-19 virus spread along with climate information from the C3S Climate Data Store. An interactive world map shows time averages of air temperature and humidity over selectable predefined periods. Circles, representing the number of deaths related to COVID-19, are placed on regions where the virus has spread. Clicking on each circle, the time evolution of the number of fatalities in the corresponding region is shown, together with information on the local temperature and humidity for the selected period.

This application is inspired by a series of research studies exploring the diffusion efficiency of the COVID-19 and the Influenza virus in different atmospheric stable conditions (e.g., see Sajadi et al., 2020; Lowen et al., 2007; Tamerius et al., 2013). Given the novelty of the COVID-19 virus and the lack of confirmed relationships between the infection and the relevant climate variables, the application should only be considered as an exploratory tool.

For simplicity, the map shows meteorological variables averaged over the same periods which fatalities numbers refer to, without taking into account any delay between infection and eventual death. While the white regions in both the map and the time series correspond to the values identified in Sajadi et al. (2020) as the most favorable ones for the spread of the virus, the other ranges used for the color palettes have been chosen arbitrarily. The number of fatalities has been chosen as indicator for the virus spread given its robustness with respect to the other available data (number of confirmed cases and number of recovered patients). The values represented in the meteorological time series refer to single points located approximately at the center of each circle.

COVID-19 related data are provided by Johns Hopkins University Center for Systems Science and Engineering (JHU CSSE), and are available at the following GitHub repository. These are used in the application without any prior quality control by C3S. Meteorological data are from ERA5 reanalysis: hourly data on single levels and pressure levels and monthly averages on single levels and pressure levels.

The designations employed and the presentation of material on the map do not imply the expression of any opinion whatsoever on the part of the European Union concerning the legal status of any country, territory or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.

List of user-selectable parameters

Variable: temperature and humidity;
Month;

Description of the graphical output

The application presents an interactive world map showing time averages of one variable, selectable via a drop-down menu, between air temperature and specific humidity. The averaging month can be selected: for months since the beginning of 2020, values for 2020 are shown; for the remaining months of the year, a climatological average (2000-2019) is presented. On the map, circles are placed in the centre of regions where the virus has spread; their size is proportional to the number of the deaths related to COVID-19 occurred in that region during the selected month. Clicking on a circle, a side window appears showing a plot of the daily time evolution of the local number of fatalities attributed to the virus, and plots of air temperature and specific humidity at a grid-point close to the centre of the circle, for the same time steps."