Quantifying the contribution of tropical cyclones to lightning activity over the Northwest Pacific

摘要

This study quantifies the impacts of tropical cyclones (TCs) to the geographical and seasonal lightning activity over the northwest Pacific (5 degrees-35 degrees N, 100 degrees-160 degrees E), and examines the connection between the occurrence of TC lightning and El Nino-Southern Oscillation (ENSO). Lightning data from the World Wide Lightning Location Network (WWLLN) and best-track data from the China Meteorological Administration are used to investigate 263 TCs for TC seasons (Jun-Nov) in the years 2005-2017. Results show that, on average, TCs account for about 4.9% of all lightning in the domain. The highest contributions occur in the northern South China Sea and the ocean northeast of the Philippines. The monthly TC contribution varies from 2.6% to 6.1% with the greatest in July and the lowest in June. The peak location of lightning center contributed by TCs are observed a poleward shift from early summer (Jun-Jul) to late summer (Aug-Sep), and an equatorial shift from late summer to autumn (Oct-Nov). In terms of TC intensity, tropical storm strength TCs are the dominant lightning contributor (2.0%) over the northwest Pacific. A greater likelihood of lightning activity in tropical storms than in typhoons is observed during the landfall, especially within the inner core region. Super typhoons produce lightning in more eastward longitude and more equatorward latitude than weaker strength TCs. The relationship between TC lightning and ENSO reveals that TCs contribute greater lightning during La Nina periods (5.0%) than El Nino periods (3.2%) over the northwest Pacific. In El Nino years, super typhoons contribute the greatest lightning amounts (1.8%), while in La Nina years tropical storms contribute the greatest (2.2%). Infrared satellite observations indicate that the high contribution of lightning in tropical storms is due to the large occurrence of very deep convection in these storms during their landfall.