Tuesday, 22 January 2008: 9:30 AM
Global studies of tropical cyclones using the World Wide Lightning Location Network
222 (Ernest N. Morial Convention Center)
The lightning activity generated by tropical cyclones is not well understood, mainly because these storms occur over the ocean away from land-based regional lightning networks. Recent studies have used satellite-based lightning detection (e.g. TRMM and FORTE) and extended regional networks (e.g. LR-NLDN) to investigate lightning activity in tropical cyclones well before they reach landfall. However, these satellites can only detect lightning from a particular storm for a few minutes each day and these extended networks only cover a limited global region. In this paper, we use the World Wide Lightning Location Network (WWLLN), the only real-time network that covers the entire globe, to analyze the change in lightning activity during the evolution of tropical cyclones. We present case studies of tropical cyclones in different global regions, such as the western Pacific and the Atlantic basin, to investigate whether lightning activity can be used as a proxy for convection evolution and organization. For each case study, we discuss where the lightning activity occurs, such as in the eyewall and rainband regions, during different stages of storm evolution. These case studies will be compared to the previous work of Molinari et al., 1999, Monthly Weather Review, 127 (4), 520-534, which suggests that eyewall lightning intensifies before eyewall replacement cycles during Atlantic basin hurricanes. These eyewall cycles are often covered by thick cirrus overcast and thus can typically only be observed using in situ aircraft measurements. Hence, we examine whether lightning activity can remotely identify the eyewall replacement process. Additionally, to investigate how tropical cyclones sometimes intensify or weaken just before making landfall, we study the lightning activity as the storms approach and hit land. Using the knowledge gained through these case studies, we are presently developing a statistical analysis of lightning activity in all tropical cyclones globally since 2004. We present the preliminary results of this statistical investigation and discuss whether monitoring lightning activity during tropical cyclones can lead to better forecasting and nowcasting of storm evolution, especially where aircrafts measurements are not typically feasible.