The Impact of COVID‐19 on Weather Forecasts: A Balanced View

Aircraft reports are an important source of information for numerical weather prediction (NWP). From March 2020, the COVID‐19 pandemic resulted in a large loss of aircraft data but despite this it is difficult to see any evidence of significant degradation in the forecast skill of global NWP systems. This apparent discrepancy is partly because forecast skill is very variable, showing both day‐to‐day noise and lower frequency dependence on the mean state of the atmosphere. The definitive way to cleanly assess aircraft impact is using a data denial experiment, which shows that the largest impact is in the upper troposphere. The method used by Chen (2020, https://doi.org/10.1029/2020gl088613) to estimate the impact of COVID‐19 is oversimplistic. Chen understates the huge importance of satellite data for modern weather forecasts and raises more alarm than necessary about a drop in forecast accuracy. Plain Language Summary Aircraft reports are important for weather forecasting, but satellite data are more important and satellite data have continued as normal during the hiatus due to COVID‐19. The signal from loss of aircraft data is not clear above the noise from random variations in forecast skill and longer‐term trends. One of the strengths of modern weather forecasting is its robustness arising from the large range of observations used. Key Points Aircraft meteorological observations have been badly affected by the pandemic but satellite observations have continued unaffected Tests show that the largest impact of aircraft observations is at 10–12 km altitude at short range There is no obvious degradation of forecast accuracy in 2020; variations in predictability and addition of other observations play a role