Evolution of the impacts of the 2009–10 El Niño and the 2010–11 La Niña on flash rate in wet and dry environments in the Himalayan range

Abstract Impacts of the 2009–2010 El Nino and the 2010–2011 La Nina events on the lightning activity in the climatologically dry and moist regions of the Himalayan range are studied from the 18-year (1995–2012) data obtained from the combination of Optical Transient Detector and Lighting Imaging Sensors on the TRMM satellite. Average flash rates in both regions are higher than the 18-year normal during both El Nino and La Nina events. Our results suggest that the impacts of El Nino and La Nina need to be examined season-wise separately in moist and dry regions. During El Nino, the flash rate increases from the month of February into the pre-monsoon season but has no significant effect in the monsoon and post-monsoon seasons in the moist region. On the contrary, flash rate does not change during the pre-monsoon but is higher than normal in the monsoon and lower than normal in post-monsoon season in the dry region. During La Nina, it does not change from its normal value in any season of the moist region and even in pre-monsoon season of dry region. However, it is higher than normal in the monsoon and post-monsoon seasons of the dry region. In the dry region, while flash rate is highly correlated with convective available potential energy (CAPE), surface temperature, and convective rain fall, it is highly correlated only with CAPE in the moist region during La Nina events. Moist convection and aerosols appear to be important parameters for production of lightning in moist and dry regions, respectively. Progress of the monsoon current dramatically affects the lightning activity in both moist and dry regions.