Analysis of thunderstorm and lightning activity associated with sprites observed during the EuroSprite campaigns: Two case studies

Abstract

During the summers of 2003 to 2006 sprites were observed over thunderstorms in France by cameras on mountain tops in Southern France. The observations were part of a larger coordinated effort, the EuroSprite campaigns, with data collected simultaneously from other sources including the French radar network for precipitation structure, Meteosat with images of cloud top temperature and the Météorage network for detection of cloud-to-ground (CG) flash activity. In this paper two storms are analyzed, each producing 27 sprite events. Both storms were identified as Mesoscale Convective Systems (MCS) with a trailing stratiform configuration (ST) and reaching a maximum cloud area of~120,000 km 2 . Most of the sprites were produced while the stratiform area was clearly developed and during periods of substantial increase of rainfall in regions with radar reflectivity between 30 and 40 dBZ. The sprite-producing periods followed a maximum in the CG lightning activity and were characterized by a low CG flash rate with a high proportion of +CG flashes, typically around 50%. All sprites were associated with +CGs except one which was observed after a −CG as detected by the Météorage network. This −CG was estimated to have −800 C km charge moment change. The peak current of spriteproducing + CG (SP + CG) flashes was twice the average value of +CGs and close to 60 kA with little variation between the periods of sprite activity. The SP + CG flashes were further characterized by short time intervals before a subsequent CG flash (median value b 0.5 s) and with clusters of several CG flashes which suggest that SP + CG flashes often are part of multi-CG flash processes. One case of a lightning process associated with a sprite consisted of 7 CG flashes.

A gigantic jet event observed over a thunderstorm in mainland China

“…Figure 5(a) shows that both of +CGs and -CGs reached a peak at 20:35, which resulted from the storm intensification that could be seen clearly from Doppler radar reflectivity image. The decrease of negative CGs and increase of positive CGs shown in Figure 5(b) during the sprite time period was consistent with previous studies [14,26].…”

“…The decrease of cloud-top temperature after 22:00 may be due to the moist warm air from the Huanghai Sea which reactivated the storm convection (the storm moved toward the Huanghai Sea), leading to the decrease of cloud top brightness temperature. The lowest cloud top brightness temperature was 75°C in the sprite time period, a little lower than that of the previous studies [14,26]. Figure 3 [18], indicating convection in storm A at this time was very strong and in good agreement with previous studies [17,18].…”

Relativistic electron beams above thunderclouds

“…Thunderstorms and lightning activities in southern Europe have recently attracted special interest because numerous sprites are observed with video cameras above thunderclouds which regularly develop during the summer months from the beginning of May to mid-September (Soula et al, 2009;Neubert et al, 2008 The sprite discharge consists of the main body of the sprite surrounded by three columniform sprites at distances up to ∼20 km. The main body of the sprite extends upwards from ∼60 km to ∼85 km height as triangulated by use of the two video cameras.…”

Ground-based observations of the relations between lightning charge-moment-change and the physical and optical properties of column sprites

“…We used a standard commercial CCD camera-Watec 902H2 Ultimate operating with a frame rate of 33ms/frame, that is commonly used by other TLEs research groups in Europe and in Japan [Bor et al 2009, Soula et al, 2009 (575-1187nm). The filter transmittance, the quantum efficiency of the camera, atmospheric transmittance and sprite spectrum [Hampton et al 1996] are shown in Figure 2.…”