Ground Observation of Negative Sprites Over a Tropical Thunderstorm as the Embryo of Hurricane Harvey (2017). Issue 14 (28th July 2021)

• Record Type: Journal Article
• Authors: Wang, Yongping; Lu, Gaopeng; Cummer, Steven A.; Lucena, Frankie; Cohen, Morris B.; Ren, Huan; Li, Jiagen; Cheng, Zhengwei; Zhang, Shoubao
• Is Part Of: Geophysical research letters. Volume 48:Issue 14(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-07-28
• Subjects: negative sprite -- oceanic thunderstorm -- charge structure; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2021GL094032
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: We report on the observation of six red sprites produced by negative cloud‐to‐ground (CG) lightning strokes in a tropical thunderstorm that later evolved into Hurricane Harvey (2017). Most of these sprites conformed to the morphological characteristics of typical negative sprites previously observed over continental thunderstorms. The sprite‐producing CG strokes were located in or near the deep convection region and their impulse charge moment changes all exceeded −500 C‐km. During the sprite generation stage, the CG lightning stroke rate declined and the tropical thunderstorm structure appeared stable. Our analysis suggests that tropical marine meteorological systems, such as tropical disturbances, depressions, and thunderstorms are more likely to be main production systems of negative sprites. The frequent occurrence of 18 gigantic jets produced by the same thunderstorm further indicates that the thundercloud charge structures of sprite‐producing oceanic thunderstorms are significantly different from that of continental thunderstorms. Plain Language Summary: The space‐borne observations from the ISUAL indicate that there could be a very high proportion (nearly 20%) of negative sprites produced in the ocean. Our previous observations of sprites over Hurricane Matthew (2016) found that all the sprites were produced by positive cloud‐to‐ground lightning strokes. However, only a few dozen hurricanes occur in the North Atlantic every year. In this paper, we report the observation of six negative sprites over a tropical thunderstorm that is more representative to the typical thunderstorms in the ocean. We speculate that this may be due to that the dynamic structure of the outer rainband of hurricanes is similar to the trailing stratiform of the mesoscale convective systems, while the ordinary oceanic thunderstorms with deep convection cores (as inferred from cold cloud tops and high lightning density) are similar to the continental convective meteorological system. Also, the phenomenon of frequent occurrence of gigantic jets indicates that there was an extensive distribution of middle negative charge in the thundercloud. Therefore, the charge structure is different between oceanic thunderstorms and continental thunderstorms and is likely to play an important role in the production processes of sprites with different polarities. Key Points: All the negative sprites were produced over the deep convection region with cold cloud tops and high lightning density in a tropical storm The polarity paradox of sprites may be attributed to the charge structure in the thundercloud and the type of parent lightning The frequent occurrence of gigantic jets implies the presence of an extensive negative charge layer in the thundercloud