Analysis of cloud-to-ground lightning and its relation with surface pollutants over Taipei, Taiwan

Abstract

Premonsoon (March–April) cloud-to-ground (CG) lightning activity over Taipei, Taiwan, is analyzed in relation to surface pollutants like particulate matter (PM10), sulfur dioxide (SO2), nitrogen oxides (NOx) and ozone (O3) concentration for a period of 6 years (2005–2010). Other surface parameters like aerosol optical depth and cloud top temperature are also investigated taking data from Moderate Resolution Imaging Spectroradiometer satellite products. Results reveal that SO2 is more strongly associated with CG lightning activity compared to PM10 concentration. Other surface pollutants like NOx and O3 also show strong linear association with CG lightning flashes. Additional investigations have also been performed to extreme lightning events, particularly to a few long-lasting lightning episodes considering the concentrations of NOx and O3 found on days with no lightning activity as representative of the background concentration levels of the said two parameters. Results indicate that the NOx concentration on days with lightning activity is more than 2-fold compared to the non-lightning days while the O3 concentration is increased by 1.5-fold. Such increase in NOx and O3 concentration on days with lightning strongly supports the transport phenomena of NOx and O3 from the upper or middle troposphere to the lower troposphere by downdraft of the thunderstorm during its dissipation stage. Overall, studies suggest that enhanced surface pollution in a near-storm environment is strongly related to the increased lightning activity, which in turn increases the surface NOx level and surface O3 concentration over the area under study.