Fig. 3: Distributions of potential vorticity (PV) and ozone over northern China based on MERRA-2 data.
From: Stratospheric influences on surface ozone increase during the COVID-19 lockdown over northern China
a Horizontal distribution of PV (color shaded, unit: PVU, 1PVU = 10−6 m2 s−1 K kg−1) at 500 hPa over northern China at 08:00 local time on February 15, 2020. Dry regions with low RH (5% and 20%) at 850 hPa are marked by magenta lines. Regions with downward air motions (ω = 0.3 pa s−1) are marked by blue lines. b Vertical cross-section of PV (color shaded) and ozone concentrations (magenta lines, unit: ppbv) along the black dashed line shown in (a). The names of the cities in (a) are abbreviated from their corresponding full names, listed in Table 2.
