Evolution of lightning activity observed during rapid intensity changes of tropical cyclones

Abstract

<p>We study evolution of lightning activity accompanying rapid intensity changes of tropical cyclones worldwide. We use a dataset of 400 tropical cyclones occurring between 2012 and 2017. We use the cyclones tracks from the International Best Track Archive for Clime Stewardship. The lightning data are provided by the World Wide Lightning Location Network (WWLLN). We inspect the lightning activity and median stroke energies accompanying rapid intensifications (RI) of cyclones, defined as increases of the wind speed by more than 30 kt in 24 hours, and their rapid weakenings (RW), defined as decreases of the wind speed by more than 40 kt in 24 hours.</p> <p>In an area of radial wind maximum (RWM), we observe a stroke density of 15.1 strokes/(100 km)<sup>2</sup>/hour for RI and 21.8 strokes/(100 km)<sup>2</sup>/hour for RW, respectively, which is much higher than average RWM density 7.9 strokes/(100 km)<sup>2</sup>/hour over the duration of the cyclone. A median stroke energy is 0.3 kJ during RI and 0.7 kJ during RW. It means that during rapid intensification of cyclones, there are less strokes with slightly higher energies and during rapid weakening there are more strokes with slightly lower energies. When analyzing the cyclones in both hemispheres separately, we obtain 0.3 kJ for RI and 0.6 kJ for RW in the northern hemisphere, and 0.8 kJ for RI and 0.9 kJ for RW in the southern hemisphere. The difference in the stroke density during RI and RW was observed larger in the northern hemisphere (19.7 vs 34.1 strokes/(100 km)<sup>2</sup>/hour), when in the southern hemisphere the stroke density is much lower and differs less (4.4 strokes/(100 km)<sup>2</sup>/hour for RI and 5.1 strokes/(100 km)<sup>2</sup>/hour for RW).</p> <p> </p>