Eclipse across America: Citizen Science Observations of the 21 August 2017 Total Solar Eclipse

On 21 August 2017, North America witnessed a total solar eclipse, with the path of totality passing across the United States from coast to coast. The major public interest in the event inspired the Global Learning and Observations to Benefit the Environment (GLOBE) Observer to organize a citizen science observing campaign to record the meteorological effects of the eclipse. Participants at 17 585 observing sites collected 68 620 temperature observations and 15 978 cloud observations. With 7194 sites positioned in the path of totality, participants provide a nearly unbroken record of the cloud and temperature effects of the eclipse across the contiguous United States. The collection of both temperature and cloud observations provides an opportunity to quantify the cloud-temperature relationship. The unique character of citizen science, which provides data from a large number of observations with limited quality control, requires a method that leverages the large number of observations. By grouping observing sites along the path of totality by 1 degrees longitude bins, the errors from individual sites are averaged out and the meteorological effects of the eclipse can be determined robustly. The data reveal a distinct relationship between prevailing cloud cover and the eclipse-induced temperature depression, in which overcast conditions reduces the temperature depression by about one-half of the value from clear conditions. A comparison of the GLOBE results with mesonet data allows a test of the robustness of the citizen science results. The results also show the great benefit that research using citizen science data receives from increased numbers of participants and observations.