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 (NO_x) 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 NO_x 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 NO_x 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 NO_x 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 NO_x and O₃ concentration on days with lightning strongly supports the transport phenomena of NO_x 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 NO_x level and surface O₃ concentration over the area under study.