Fig. 4: Observed air quality response to sudden stratospheric warming events (SSWs).
a Regression of anomalous sea level pressure (SLP) (from the MERRA2 reanalysis) onto the station measurements of daily time-series of surface inhalable particulate (PM10) concentrations from Finokalia, Greece. Warm and cold shadings indicate positive and negative anomalies that are statistically significant at the p < 0.10 level based on a Student’s t-test, respectively. Histogram of b the level of PM10 concentrations (units: μg m−3) at Finokalia, Greece and c, d the expected number of poor air quality days per 30-day period for two air quality standards (AQS), during 1000 sets of non-SSW episodes (colored bars, see Methods). Thick vertical colored line indicates the non-SSW mean; gray shading indicates the 5th–95th percentile confidence interval derived from the non-SSW spread. Thick vertical black line indicates the SSW composite. In panels c, d, poor air quality days are defined when the daily-mean PM10 concentrations exceed the daily limit of c 50 μg m−3 and d 260 μg m−3, respectively. e–h The same as a–d but for station observations of surface PM10 concentrations from M'Bour, Senegal. Made with Natural Earth. Free vector and raster map data @ naturalearthdata.com.
