Analysis of cloud-to-ground lightning and its relation with surface pollutants over Taipei, Taiwan
Premonsoon (March–April) cloud-to-ground (CG) lightning activity over Taipei, Taiwan, is analyzed in relation to surface pollutants like particulate matter (PM 10), sulfur dioxide (SO 2), nitrogen oxides (NO x) and ozone (O 3) 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 SO 2 is more strongly associated with CG lightning activity compared to PM 10 concentration. Other surface pollutants like NO x and O 3 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 O 3 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 O 3 concentration is increased by 1.5-fold. Such increase in NO x and O 3 concentration on days with lightning strongly supports the transport phenomena of NO x and O 3 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 O 3 concentration over the area under study.