Fig. 1: Climatology and changes of SO2 emissions and lightning density.
a Topography (m) and climatology (2012–2022) of sea surface temperature (SST; K) and circulations (m s−1) at 850 hPa. b, d SO2 emission rate (tons km−2 yr−1) from international shipping and lightning density (strokes km−2 yr−1) averaged over 2012–2019. c, e Differences in SO2 emission rates and lightning density during 2020–2022 vs. 2012–2019. The percents in panels (c) and (e) indicate the area-averaged changes of SO2 emissions and lightning density within the shipping lane (i.e., black polygon). Circles in panel e indicate grid cells with statistically significant differences at 95% confidence level. The SST and circulation data are from ERA5; SO2 emission and lightning data are from CEDS and WWLLN. The blue box represents the domain of interest. The grid cells enclosed by the black polygon are defined as the shipping lane and the remaining grid cells within the blue box are defined as the reference lane. The red box in the inset map shows the location of the study domain over the Bay of Bengal. For more details, please refer to the Methods section. The figure was created using Matplotlib Python package.
