Impact of aircraft and Aeolus data in ECMWF forecasts before and after the COVID-19-related reduction in air traffic. Forecast Sensitivity to Observation Influence (FSOI) measures how various observing systems influence the ECMWF numerical weather forecast quality. The figure shows the total impact [Mega J/kg] of aircraft data and Aeolus data for two weeks before and after the reduction in aircraft data owing to COVID-19. The impact of Aeolus has increased by 23%. This is impressive considering that the number of Aeolus observations are considerably lower than the number of aircraft observations, as can be seen in the plot linked here.
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